♦ * ORGANIC CHEMISTRY. A TEXT-BOOK OF ORGANIC CHEMISTRY. BY A. BERNTHSEN, Ph.D., Director of the Scientific Department in the Chief Laboratory of the Baden Aniline and Alkali Manufactory, Ludwigshafen-am-Rhein; formerly Professor of Chemistry in the University of Heidelberg. TRANSLATED BY GEOEGE M^GOWAN, Ph.D., Demonstrator in Chemistry, University College of N. Wales, Bangor. THE ORIGINAL TEXT SPECIALLY BROUGHT UP TO DATE BY THE AUTHOR FOR THIS EDITION. 0 , IaJ ■ (RJU^^u^ LONDON: BLACKIE & SON, Limited; NEW YOKK: D. VAN NOSTEAND COMPANY. 1892. S41 AUTHOR'S PREFACE TO THE GERMAN EDITION. In lecturing upon Organic Chemistry in the University of Heidelberg, I have felt more and more each session the desira- bility of being able to place in the hands of my students a small text-book, which, while not exceeding some thirty sheets in size, and of which the descriptive portion was condensed as far as practicable, should yet be of a strictly scientific charac- ter; a book which, beginning with homologous series, should lay especial emphasis upon summarizing the characteristics of each class of compounds, and, wherever possible, upon the inductive development of the theoretical relations existing between them. The following text-book of Organic Chemistry is an attempt to fulfil these requirements. Excepting in a few cases, where another arrangement appeared to be more suitable, there is given here for each class (after a short general description) a concise statement of the occurrence, general modes of forma- tion, constitution and isomerides, and behaviour of the com- pounds in question. The choice of the compounds described has been practically determined by the requirements of teach- ing. A number of tables are incorporated, which I have already found useful in my lectures, and which are of service for summarizing. The treatment of the theoretical matter is, especially in the first half of the book, purely inductive; the isomeric relations of the parafiins, for instance, are first referred to under butane, 64643 vi author's preface. and no constitutional formula of any important compound is given without the grounds for it being indicated. The induc- tive method is also retained even where, as in the case of the theory of the benzene derivatives, the historical development has run on other lines. In accordance with this the class definitions are based not on theoretical but on actual relations. Type of two sizes has been employed in the book, in order that the matter which is of the greatest importance, either in itself or for the purposes of a general review, may be readily distinguished. I have deemed it advisable to give a number of references with regard to points which have a particular historical value, and also to some of the more important recent researches, especially where space did not allow of these being treated in detail. Special pains have been taken to make the index complete. I trust, therefore, that the book will be found useful, not only to the student of chemistry proper on his entering upon the study of Organic Chemistry, but also to students of medi- cine and pharmacy, whose requirements have been carefully borne in mind. It should also prove of service to chemists engaged in technical work, who may wish to obtain a short survey of the present state of our science. I should feel greatly obliged, if my readers would kindly draw attention to any inaccuracies of statement or errors of print which may have crept into the work. (Signed) A. BERNTHSEN. Heidelberg, Ajpril^ 1887. AUTHOR'S PREFACE TO THE ENGLISH EDITION. The translation of this book has been carried out by Dr. M'Gowan, who has reproduced the meaning of it so thoroughly that I feel myself bound to acknowledge in an especial manner the accuracy of the work, and to express my warm thanks to him for the same. The large amount of new and important matter in the domain of Organic Chemistry, which has appeared since the German edition of this book was published, has been specially gone over for this edition, and at the same time the original text has been carefully revised. (Signed) A. B. Mannheim, March, 1889. TEANSLATOR'S PREFACE. In introducing the English edition of this text-book, almost nothing remains to be added to what Professor Bernthsen has said in his prefaces. The proof slips had the great advantage of being carefully revised by himself after my own corrections had been made, which should ensure the accuracy of the work. The book has been very well received in Germany, and will, I trust, be found equally acceptable here. GEORGE M^GOWAN. University College of N. Wales, Bangor, May, 1889. TABLE OF CONTENTS. INTRODUCTION. Page Qualitative Analysis, 2 Quantitative Analysis, 4 Calculation of the Formula, 7 . Determination of Molecular Weight, ------ 8 Modes of determining Vapour Density, - - - - - 11 Polymerism and Isomerism, . - - - - - - - - 13 Chemical Theories, - - - - - - - - - -13 Explanation of Isomerism; determination of the Constitution of Or- ganic Compounds, - - - - - - - - - 16 Rational Formulae, 19 Homology, .-----..---20 Radicles, 22 Classification of Organic Compounds, 23 Physical Properties of Organic Compounds, . . - - 24-32 Fractional Distillation, 27 Class I.— METHANE DERIVATIVES. I. Hydrocarbons, 34 A. Saturated Hydrocarbons, CnH2a+2) 34 Isomerism, Nomenclature, Constitution, - - - 41 B. defines, CnH2n, 46 Appendix; Hydrocarbons, CnH2a, with closed chain, - 52 c. Acetylene Series, CnH2n_2, 53 D. Hydrocarbons, CnH2a_4 and CnH2a-65 - - - - 57 II. Haloid Substitution Products of the Hydrocarbons, - 58 A. Of the Saturated Hydrocarbons, 58 B. Of the Unsaturated Hydrocarbons, 69 III. MoNATOMic Alcohols, 70 A. Monatomic Saturated Alcohols, CnH2a-f-iOH, - - - 71 Primary, Secondary and Tertiary Alcohols, - - - 73 (506) ^2 X CONTENTS. Page B. Monatomic Unsaturated Alcohols, CnH2n-i OH, - - 86 C. Monatomic Unsaturated Alcohols, CnH2n-3 0H, - - 88 IV. Derivatives of the Alcohols, 88 A. Ethers Proper (Alcoholic Ethers), 88 B. Thio-alcohols and -ethers, ...... 93 c. Ethers of the Alcohols with Inorganic Acids, and their Isomers, ......... 97 1. Ethers of Nitric Acid, 99 2. Derivatives of Nitrous Acid : a. Ethers, 100 (3. Nitro-derivatives of the Hydrocarbons, - - - 100 3. Derivatives of Hyponitrous Acid, 103 4. Ethers of the Chlorine Acids, 103 5. Ethers of Sulphuric Acid, 103 6. Derivatives of Sulphurous Acid : a. Ethers, 104 ^. Sulphonio Acids, 105 7. Ethers of Tri- and Polybasic Acids, - - - - 106 8. Alcoholic Derivatives of Hydrocyanic Acid: tt. Nitriles, 107 Iso-nitriles, - - - - - - - - 109 D. Nitrogen Bases of the Alcohol Radicles, - - - - 110 Appendix: Hydrazines, 117 E. Compounds of Phosphorus, Arsenic, &c., v^^ith Alcohol Kadicles : 1. Phosphorus Compounds, - - - - - - 119 2. Arsenic Compounds, 122 3. Antimony, Boron and Silicon Compounds, - - - 125 F. Metallic Compounds of the Alcohol Radicles, - - - 126 V. Aldehydes and Ketones, - 128 A. Aldehydes, 129 B. Ketones, - 138 VI. Monobasic Eatty Acids, 146 A. Saturated Acids, C^HonO-i, 146 B. Unsaturated Acids, Cn Hon-o 0-2, 164 CONTENTS. xi Page c. Propiolic Acid Series, CnH2n-4 02, 167 D. Substitution Products of the Monobasic Acids, - - 168 VII. Acid Derivatives, 173 A. Ethers of the Patty Acids, 174 B. Chlorides of the Acid Kadicles, 176 c. Acid Anhydrides, 178 D. Thio-acids and Thio-anhydrides, 179 E. Amides, 180 F. Amido- and Imido-chlorides, 183 G. Thiamides and Imido-thio-ethers, 184 H. Amidines, - 185 Amidoximes, 186 viii. Polyatomic Alcohols, 187 A. Glycols, ... 187 Derivatives, - - - - - - - - -187 Amines of the Diatomic Alcohols, 193 B. Triatomic Alcohols, - - - - - - - - 198 c. Tetra-, Penta- and Hexatomic Alcohols, - . - - 202 Oxidation Products of the Polyatomic Alcohols, - - 204 IX. Polyatomic Monobasic Acids, 206 A. Diatomic Monobasic Acids, 206 Amido-acids, 212 Lactic Acids, 214 Appendix: Lactones, - - • - - - 218 b. Tri- to Hexatomic Monobasic Acids, - - - - 219 C. Aldehyde-alcohols, 220 D. Ketone-alcohols, 221 E. Diatomic Aldehydes, 221 F. Diatomic Ketones, 221 G. Ketone-aldehydes, 222 H. Monobasic Aldehyde-acids, 222 I. Monobasic Ketonic Acids, 222 X. Dibasic Acids, 227 A. Saturated Diatomic Dibasic Acids, 228 b. Unsaturated Diatomic Dibasic Acids, . - - . 236 xii CONTENTS. Page c. Triatomic Dibasic Acids, - - - - - - - 238 D. Tetratomic Dibasic Acids, ------ 240 E. Penta- and Hexatomic Dibasic Acids, . - . - 243 F. Dibasic Ketonic Acids, 244 XI. Tri- to Hexabasic Acids, 245 A. Triatomic Tribasic Saturated Acids, . . . . 245 B. Unsaturated Acids, -------- 246 c. Tetratomic Tribasic Acids, • - 246 D. Pentatomic Tribasic Acids, ------ 247 E. Tetra-, Penta- and Hexabasic Acids, . . - - 247 XII. Cyanogen Compounds, 248 A. Cyanogen and Hydrocyanic Acid, - - - - . 249 B. Halogen Compounds of Cyanogen, . - - - - 257 C. Cyanic and Cyanuric Acids, - - - - - - 257 D. Thiocyanic Acid and its Derivatives, - - - - 261 E. Cyanamide and its Derivatives, - - - - - 264 r. Appendix : Theoretical Considerations as to Isomerism in the Cyanogen Group, - - - - - - - 265 XIII. Carbonic Acid Derivatives, 266 A. Ethers of Carbonic Acid, 267 B. Chlorides of Carbonic Acid, 268 c. Amides of Carbonic Acid, - - - . 269 Ureides, 272, 279 D. Sulphur Derivatives of Carbonic Acid, - - - - 274 E. Amidines of Carbonic Acid, ------ 277 F. Uric Acid Group, - - - 279 XIV. Carbohydrates, 285 A. The Grape Sugar Group, 285 B. The Cane Sugar Group, 289 C. The Cellulose Group, 292 XV. Transition to the Aromatic Compounds, - - - - 295 A. Tri-, Tetra- and Penta-methylenes, ----- 295 B. Furfurane, Thiophene and Pyrrol, - - - - - 297 c. Pyrazols and Thiazols, - - 302 CONTENTS. xiii Class II.— BENZENE DERIVATIVES. Page XVI. Summary, 303 Differences between the Benzene and Fatty Hydrocarbons, 306 Isomeric Relations, 307 Proof of the Equal Value of the Six Hydrogen Atoms, - 307 Proofs, that for every H-atom (a), two other pairs of symmetrically linked H-atoms exist, - - - - 308 Constitution of Benzene, - - - - - - - 311 Determination of Position, - - - - - - 313 Special Benzene Formulae, - - - - - - 316 Laws Governing Substitution, - - - - - - 317 Further Isomerism, - - - - - - - - 318 Occurrence of the Benzene Derivatives, - - - - 319 Modes of Formation of the Benzene Derivatives, - - 320 XVII. Benzene Hydrocarbons, 323 A. Saturated Hydrocarbons, 323 B. Unsaturated Hydrocarbons, ------ 331 xviii. Haloid Substitution Products, 332 XIX. Nitro-substitution Products, 336 XX. Amido-derivatives, 340 A. Primary Monamines, 342 B. Secondary Monamines, 346 c. Tertiary Monamines, 348 D. Quaternary Bases, - - - - - - - 348 E. Diamines, Triamines, &c., 349 Aniline, 350 Substitution Products of Aniline, - - - - 352 Alkylated Anilines, 353 Di- and Tri-phenylamines, 355 Colour Derivatives of Diphenylamine, - - - 355 Anilides, 357 Homologues of Aniline, ------ 358 Diamines, Triamines, &c., 359 xiv CONTENTS. Page XXI. DiAZO- AND AZO-COMPOUNDS ; HYDRAZINES, - - 360 A. Diazo-compounds, - - - - - - - 360 B. Diazo-amido-compounds, 364 C. Azo-compounds, 366 1. Azoxy-compounds, - 366 2. Hydrazo-compounds, - - - - - - 367 3. Azo-compounds, 367 4. Amido-azo- and Oxy-azo-compounds, - - - 368 D. Hydrazines, 372 XXII. Aromatic Sulphonic Acids, 373 XXIII. Phenols, 376 A. Mon atomic Phenols, - 378 Phenol, - 381 Derivatives of Phenol, 382 Homologues of Phenol, - - - - - - 387 B. Diatomic Phenols, - 388 c. Triatomic Phenols, 391 D. Tetra-, Penta- and Hexatomic Phenols, - - - 392 E. Quinones, 392 F. Quinone Chlor-imides, - - 395 XXIV. Aromatic Alcohols, Aldehydes and Ketones, - - 395 A. Aromatic Alcohols, - - - - - - - 395 . B. Aromatic Aldehydes, 398 c. Aromatic Ketones, - - - - - . 399 D. Oxy-alcohols and -aldehydes; Ketone-alcohols, - - 400 XXV. Aromatic Acids, - - 401 Summary, 401 A. Monobasic Aromatic Acids, ------ 409 1. Monatomic Saturated Acids, - - - - - 412 Benzoic Acid, 412 2. Monatomic Unsaturated Acids, - - - - 417 3. Diatomic Saturated Phenolic Acids, - - - 419 4. Alcohol- acids and Ketone-acids, - - - - 422 5. Tri- and Polyatomic Phenolic Acids, - - - 425 6. Unsaturated Phenolic Acids, 427 CONTENTS. . XV Page B. Dibasic Acids, ... ^ - - - - 428 c. Tri- to Hexabasic Acids, 430 XXVI. Indigo (or Indole) Group, 431 Indigo, 431 Derivatives of Indigo, - - 433 Indole, 436 XXVII. DiPHENYL Group, 438 Diphenyl, 438 Diphenyl Derivatives, 439 XXVIII. DiPHENYL-METHANE GROUP, 442 Diphenyl-methane, 442 Benzophenone, 444 Homologues of Diphenyl-methane ; Fluorene, - - - 445 XXIX. Triphenyl-methane Group, 446 Triphenyl-methane, 446 Triphenyl-methane Dyes, 448 1. Diamido-triphenyl-methane Group, - . - - 449 2. Eosaniline Group, 450 8. Trioxy- triphenyl-methane Group, - - - - 454 4. Triphenyl-methane-carboxylic Acid (the Eosin Group), 455 XXX. DiBENZYL Group, 457 Appendix: Diphenyl-diacetylene, 459 COMPOUNDS WITH CONDENSED BENZENE NUCLEI. XXXI. Naphthalene Group, 460 Naphthalene, 460 Derivatives of Naphthalene, 463 Homologues; Carboxylic Acids, . . - . - 457 Appendix: Indonaphthene; Thiophthene, - - - - 468 XXXII. Anthracene and Phenanthrene Groups, - - - 469 a. Anthracene, 469 Derivatives of Anthracene, - - - - - - 471 Alizarin, 474 xvi CONTENTS. Page B. Phenanthrene, - - - - - - - - 475 c. Hydrocarbons of more Complex Nature, - - - 477 Eluoranthene; Pyrene; Chrysene; Ketene, - - - 477 PYRIDINE DERIVATIVES, ALKALOIDS AND COMPOUNDS RELATED TO THEM. General Characters; Summary, 478 xxxiii. Pykidine Group, 481 Pyridine, 485 Homologues of Pyridine, ------- 486 Pyridine-carboxylic Acids, 487 Hydro-derivatives, 488 Appendix; Pyrone Group; Ketines, 491 XXXIV. QUINOLINE AND ACRIDINE GROUPS, 491 A. Quinoline Group, 491 Quinollne, 495 Homologues; Condensed Quinolines, - . - . 496 Quinoline-carboxylic Acids, 497 Bases related to Quinoline, 497 B. Acridine Group, 498 c. Alkaloids of Unknov^rn Constitution, - - - - 499 {a) Opium Bases, 499 (6) Cinchona Bases, 500 (c) Strychnine Bases, 500 {d) Solanine Bases, - - - - 1. . . 501 D. Phenazine Group, 501 Phenazine, 501 Toluylene Red, 502 Safranines, 503 Appendix; Dyes of Unknown Constitution, - - 503 XXXV. Terpenes and Camphors, 504 Ethereal Oils, 504 A. Terpenes, 504 B. Camphors, - 509 CONTENTS. xvii Page XXXVI. Eesins; G-LucosiDES; Vegetable Substances (of Un- known Constitution), - 511 A. Resins, - - - - - - - - - 511 B. Glucosides, 512 c. Vegetable Substances of Unknown Constitution, - - 513 XXXVII. Albuminous Substances; Animal Chemistry, - - - 514 A. Albumens, 515 B. Albumenoids, - - - - - - - - 517 C. Compounds of a Higher Order than Albumen, - - 519 D. Substances produced during Metabolic Processes, - - 519 INDEX, . - 521 ADDITIONS AND COREEOTIONS. Page 15, line 8 from foot. In case the above sentence should have the effect of unintentionally causing the reader to undervalue the work of Kolbe and FranJcland on this subject, I would (with the author's concurrence) refer him for further details to Kopp^s " Entwickelung der Chemie in der neueren Zeit" (Miinchen, 1873), and to ^. Meyer^s "Geschichte der Chemie" (Leipzig, 1889). —Trans. Page 86, line 1. For " Methyl-ethyl-caebinol " read " Methyl-ethyl-carbin- CARBINOL." Page 221, after line 4 from foot: "Diaterebic acid is unknown in the free state. Its lactone is Terebic acid, C7H10O4, which results from the oxidation of oil of tur- pentine with chromic acid mixture." Page 222, after line 18 read: Pyroracemic aldehyde, CH3 - CO - CHO, can be prepared from isonitroso-acetone, just as di-acetyl can from methyl-isonitroso-acetone. Page 274, foot of. The names of the compounds in this table are as nearly as possible literal translations from the German. Page 281, line 5 from foot. After ''Parabanic acid" read oxalyl urea.''^ Page 403, after line 9 read : e.g. CeHs - CH = CH - CO2H CsHs - C = C - COoH Cinnamic acid. Phenyl-propiolic acid. Page 482, after line 23: '^Piperidine is therefore also termed Pentamethylene-imine." ABBREVIATIONS. A. — Liebig's Annalen der Chemie. Ann. Chim. Phys. = Annales de Chimie et de Physique. Arch. f. Phys. — Archiv f tir Physiologie. B. = Berichte der Deutschen Chemischen Gesellschaft. Ch. Soc. J. = Journal of the Chemical Society. J. pr. Ch. — Journal fur Praktische Chemie. Monats. f. Chemie = Monatshefte fiir Chemie und verwandte Theile anderer Wissenschaften. Z. Anal. Ch. = Zeitschrif t fiir Analytische Chemie. ( °) or B. Pt.=: Boiling Point. [ °] or M. Pt. = Melting Point. OEGANIC CHEMISTRY. INTRODUCTION. ^ Organic Chemistry is the Chemistry of the Carbon Com- pounds. Formerly those compounds which occur in the organic, i.e, the animal and vegetable, worlds were classed under Organic, and those which occur in the mineral world under Inorganic Chemistry, the first to adopt this arrangement having been Lemery in his Cours de Chimie (1675). After the recognition of the fact that all organic substances contain car- bon, it was thought that the difference between organic and inorganic compounds could be explained by saying that the latter were capable of preparation in the laboratory, but the former only in the organism, under the influence of a particular force, the life force — vis vitalis — (Berzelius). But this assump- tion was rendered untenable when Wohler in 1828 synthetically prepared urea, CONgH^, a typical secretion of the animal organism, from cyanic acid and ammonia, two compounds which were at that time held to be inorganic; and when, shortly afterwards, the synthesis of acetic acid, by the use of carbon, sulphur, chlorine, water and zinc, was effected. Since then so many syntheses of this kind have been achieved as to prove beyond doubt that the same chemical forces act both in the organic and inorganic worlds. The separation of the two branches. Organic and Inorganic Chemistry, from each other is, however, still retained for con- venience sake, although the original reasons for this separation, which at the time was more or less a matter of necessity, have since been found to be erroneous. In consequence of the great capability for combination which carbon possesses, the number of organic compounds is extraordinarily large, and in order to (506) A 2 INTRODUCTION. be in a position to study them, it is necessary to have a know- ledge of the other elements, including the metals. The carbon compounds, many of the most important of which contain only carbon and hydrogen, or carbon, hydrogen, and oxygen, also stand in a closer relationship to each other than do the com- pounds of the other elements. Partly upon grounds of con- venience, carbon itself and some of its principal compounds, such as carbonic acid, which is so widely distributed in the mineral kingdom, are treated of under Inorganic Chemistry. One must not confound the terms "organic" and '^organized" bodies; the latter, e.g. leaves, nerves and muscles, and also the life-processes which go on in the interior of the organism, are treated of under Physiology and Physiological Chemistry. Constituents of the Carbon Compounds. Many organic substances are made up of carbon and hydro- gen alone, such being termed hydrocarbons, for instance, ethy- lene, benzine, petroleum, benzene, naphthalene, and oil of tur- pentine; a vast number consist of carbon, hydrogen, and oxy- gen, for instance, wood spirit, alcohol, glycerine, aldehyde, oil of bitter almonds, formic acid, acetic acid, stearic acid, tartaric acid, benzoic acid, carbolic acid, tannic acid, and alizarin; many (chiefly basic) compounds contain carbon, hydrogen, and nitrogen, for instance, prussic acid, aniline, and conine; as examples of compounds containing carbon, hydrogen, nitrogen, and oxygen, may be taken urea, uric acid, indigo, morphine, and quinine. In addition to these, sulphur, chlorine, bromine, iodine, phosphorus, and, generally speaking, the larger number of the more important elements, are also frequent constituents of the carbon compounds. Qualitative Analysis of Organic Compounds. The presence of Carbon in a compound is often proved by the "carbonization" of the latter, e.g. starch, sugar, &c., when heated in a glass tube, or when concentrated sulphuric acid is poured over it. Those compounds which boil without decom- QUALITATIVE ANALYSIS. 3 position deposit carbon when their vapours are led through a red-hot tube. But the best proof of the presence of carbon is obtained by completely oxidizing the organic compound by either heating it with copper oxide (see below), or by leading its vapour over the glowing oxide. The carbon present is thus converted into carbon dioxide, and the Hydrogen into water. Nitrogen in organic compounds is recognized — (a) Frequently by a smell resembling that of burnt hair, upon heating; (h) Frequently by the presence of red fumes, or by explosion, upon heating (nitro- and diazo-compounds) ; (c) In most cases by the liberation of ammonia upon heating with soda-lime (/FoA/gr); {d) In all cases by heating with potassium (and in most cases with sodium), and testing the metallic cyanide formed — (see Cyanogen Compounds) — by dissolving the melted mass in water, adding alkali and a few drops of ferrous sulphate and ferric chloride solutions, boiling, and saturating with hydro- chloric acid (formation of Prussian Blue); or by converting the cyanide into sulphocyanide, and proving the presence of the latter by means of the blood-red coloration with ferric chloride. [See tests for hydrocyanic acid (Lassaigne).] If sulphur be likewise present, iron filings must be added. Testing for the Halogens. Direct addition of nitrate of silver is usually not practicable; thus, no chlorine can be detected in chloroform even upon boiling it with AgNOg. The halogens are therefore tested for: (a) By heating the substance on a platinum wire with cupric oxide in the Bunsen flame, or by causing the vapour of the compound to pass over glowing copper gauze; in this way chlorine gives first a blue and then a green flame coloration, and iodine a green (Beilstein); (b) By heating the substance strongly with pure lime, and testing the haloid calcium salt produced with silver nitrate, (c) By heating in a sealed tube with fuming nitric acid and nitrate of silver, when the haloid silver salt is produced (Carius), 4 INTRODUCTION. Testing for Sulphur: (a) In many cases, upon boiling with an alkaline solution of lead oxide, brown sulphide of lead is formed {e.g. white of egg); (h) By heating with sodium, and testing the sodium sulphide formed with water upon a silver coin (black stain); or by means of sodium nitroprusside (purple -violet coloration), (Schonn) ; (c) By complete oxidation in the dry way, by fusing with potassium hydrate and nitre, or by heating with mercuric oxide and sodic carbonate; or in the wet way, by fuming nitric acid (Carius), and testing the sulphuric acid produced, by chloride of barium. In like manner Phosphorus is converted by complete oxida- tion into phosphoric acid; or, upon heating with powdered magnesia, and moistening the resulting mass with water, the presence of phosphu retted, hydrogen can be recognized (Schonn). All the other Elements are tested for, after complete oxida- tion of the compound (preferably by Carius^s method), in the usual way. Quantitative Organic or Elementary Analysis. A. Estimation of Carbon and Hydrogen (Combustion). The substance is oxidized by heating it to redness with cupric oxide {Liehig)y or with other substances which readily give up oxygen, such as lead chromate, platinum asbestos and oxygen (Kojyfer), &c., in a tube of difficultly fusible glass, which is open either at one or at both ends. The carbon dioxide, thus produced by the oxidation of the carbon, is absorbed by a moderately concentrated solution of caustic potash contained in specially shaped bulbs (Llebig, Mohr, MitsclierUch, JVinJder, &c.), and the water, produced by the oxi- dation of the hydrogen, in a U-shaped chloride of calcium tube, both tubes being weighed before and after the combustion. If the substance — (0*2 to 0*3 grm.) — is solid, it is either mixed with tine copper oxide (Liebig, Bunsen,) or placed in a porcelain ELEMENTARY ANALYSIS. 5 or platinum boat and burnt in a stream of air or oxygen (open tube). Liquids are weighed out in small thin sealed glass bulbs. When nitrogen is present, a spiral of copper-foil is placed in the front part of tlie combustion tube and heated to redness, in order to reduce any oxides of nitrogen which may be formed in the subsequent combustion. In the presence of sulphur or of the halogens, lead chromate, which has been fused and then powdered, is used instead of copper oxide, so as to convert any CI, SO2, &c., into Pb CI2, Pb SO^, &c., and so to prevent them from passing into the potash solution. When only halogens, without sulphur, are present, the combustion is carried out with copper oxide, a copper, or still better a silver spiral, which is kept cool, being placed in the fore-part of the tube to retain the halogens. In the presence of alkalies or alkaline earths (which would retain carbon dioxide), lead chromate mixed with y^^h of its weight of potassic bichromate is used; the chromic acid then expels all the carbonic acid. Explosive compounds must be burnt in a vacuum. From the weights of carbon dioxide and water found, the percentages of C and H are readily calculated: B. Estimation of Nitrogen. This estimation is either rela- tive or absolute. In the former case the proportion between the nitrogen and the carbonic acid evolved is determined (Liehig, Bunsen); in the latter the nitrogen is either estimated as such volumetrically, or as ammonia. The conversion into Ammonia is effected by heating the substance strongly with soda-lime (Will, Varrentrap), or by treating it with strong sulphuric acid and permanganate of potash (Kjeldahl; Z. Anal. Ch. 22. 366; also B. 19, R. 852). The ammonia is then either titrated directly, or transformed into the double chloride of ammonium and platinum (NH^ Cl)2 Pt CI4, which is then weighed, or else ignited, and the weight of the residual metallic platinum noted. 6 INTRODUCTION. In the Volumetric Estimation of Nitrogen the substance is mixed with copper oxide, a copper spiral being also used, and the combustion is carried out in the usual way, but in a stream of carbonic acid; the CO^ is either generated from magncsite in the tube itself, or led through it. The nitrogen is collected over mercury and aqueous caustic potash (Dumas), or directly over potash (Zulkowsky, Schwarz, Schiff, &c.). Its percentage is got from the formula — N (per cent.) = V • • • 0-001256 • ^ where V = the volume of the nitrogen, b = the barometric pressure t = the temperature, w = the tension of the water vapour, 0'001256 = the weight of a normal cubic centimeter of nitrogen, and g = the weight of the substance taken The volumetric method is available in every case, but the other (ammonia) method not always, not, for instance, in the case of nitro-compounds, of many organic bases, &c., the nitro- gen of these not being completely transformed into ammonia upon heating with soda-lime. For the simultaneous determination of carbon, hydrogen, and nitrogen, the combustion must be carried on in a stream of pure oxygen, the mixture of gases escaping from the potash bulbs being collected over a solution of chromous chloride, which absorbs the oxygen but not the nitrogen (B. 19. R 710). C. Estimation of Sulphur and Phosphorus. The Sulphur is estimated as sulphuric acid, being converted into this — (a) in the wet way, by heating the substance with fuming nitric acid to 150°-250° in a sealed tube (Carius), or in a mixed stream of nitric oxide and oxygen or nitric acid vapour in a combustion tube (Claesson); (h) in the dry way — (and this method is only available in the case of the less volatile compounds) — by fusing the sub- stance with potassic hydrate and nitre, or with soda and CALCULATION OF KORMUL^E. 7 chlorate or cliromate of potash, also by heating with soda and mercuric oxide, or with lime in a stream of oxygen, and so on; (c) by burning in a stream of oxygen and collecting the SO2 formed in hydrochloric acid containing bromine {Sauer). Phosphorus is estimated by analogous methods. D. Estimation of the Halogens. Here also the organic sub- stance is completely decomposed — (a) after Carius, as above, in a sealed tube, with addition of silver nitrate, by which means the halogen is converted into its silver salt; (b) by heating the compound strongly with pure lime in a hard glass tube, or in two crucibles, one of which is inverted in the other, or with sodic carbonate and nitre in a tube. The chloride formed is precipitated with silver nitrate in the usual way; (c) by the action of nascent hydrogen (sodium amalgam), the halogen in the organic substance can frequently be converted into its hydrogen compound {KekuU), E. Inorganic Bases and Acids, contained in organic salts, can often be estimated directly by the usual methods. F. Oxygen is almost invariably determined by difference ; direct methods of estimation have been proposed by Baumhauer, Ladenhurg, Stromeyer, and others. The limit of error in an estimation of carbon is about 0*05 to 0*1 p.c, in one of hydrogen + 0*1 to 0*2 p.c, while in the volumetric estimation of nitrogen several tenths p.c. too much are easily found. The Calculation of the Formula. The same principle applies here as in the case of inorganic compounds, i,e, the percentage numbers found are divided by the atomic weights of the respective elements, the relative pro- portions of the quotients obtained being expressed in whole numbers. For instance, acetic acid being found to contain 40*11 p.c. carbon, 6*80 p.c. hydrogen, and, consequently, 53*09 8 INTRODUCTION. p.c. oxygen, the quotients are to each other as 3*34 : 6*80 : 3*32 = 1:2:1. The simplest analysis-formula of acetic acid would therefore be CHgO. Sometimes figures are obtained which correspond with equal nearness to different formulae, between which it is therefore impossible, without further data, to choose. For instance, a sample of naphthalene yields on analysis 93*70 p.c. carbon and 6'30 p.c. hydrogen; the quotient proportion here is 7*81 to 6*30 = 1*239 : 1, which corresponds equally well with the numbers 5 : 4 or 11 : 9. The formula C5H4 requires 93*75 p.c. carbon and 6*25 p.c. hydrogen, and the formula CnHo, 93*62 p.c. carbon and 6*38 p.c. hydrogen, the deviations from the actual numbers found being in both cases within the limits of experimental error. Therefore other considerations must be taken into account here, in order to decide between the two formulae. Even in simple cases, such as that of acetic acid, the formula found (CH2O) is not to be taken as the molecular formula without further proof; it only expresses the atomic number proportions. The molecular formula has to be determined according to special principles. Determination of Molecular Weight. Our chemical formulae {e.g. CH2O) express not merely a percentage relation, but at the same time the smallest quantity of the compound which is capable of existing as such, i.e. a molecule of it. This molecule is ideally no longer divisible by mechanical means, but only by chemical, and then into its con- stituent atoms. If the formula CH^O were the correct one for acetic acid, then the amount of oxygen (or carbon) contained in a molecule would be indivisible, and that of hydrogen divisible only by 2. Since, however, it has been observed that one-fourth of the total hydrogen in acetic acid is replaceable, e.g. by a metal, with the formation of a salt, it is obvious that the quan- tity of hydrogen in the molecule must be divisible by 4, and so the formula must contain at least 4 atoms of hydrogen, and must therefore be C^f>^, or some multiple of it. This is, in fact, the case. Acetate of silver contains 64*67 p.c. silver, and therefore 35-33 p.c. of the acetic acid radicle; or, to 1 atom of silver =108 parts by weight, there are 59 parts by weight of the acid radicle. This 59, together with 1 atom of hydrogen = 1, DETERMINATION OF MOLECULAR WEIGIir. 9 makes the molecular weight of acetic acid 60, = 2 x 30, This is a determination of molecular weight by chemical means. Such determinations are carried out in the case of acids generally by means of their silver salts, which are usually constituted normally, are easy to purify, are almost always free from water of crystallization, and are readily analysed. One only requires to know here whether the acid is mono- or polybasic. In the case of a di-, tri-, &c., basic acid, the above calculation must be made with reference to 2, 3, &c., atoms of silver, whereas acetic acid^ — being monobasic — contains only one replaceable atom of hydrogen, which is therefore exchanged for one atom of silver. Consequently, its formula cannot be a multiple of C2H^02. In the determination of the molecular weight of Bases, their platinum salts are similarly made use of, these being almost always constituted on the type of platinum-ammonium chloride : (]SrH^Cl)2, PtCl^: i.e. they contain two molecules of hydro- chloric acid and one molecule platinic chloride to every two molecules of a mono-acid, or to one molecule of a di-acid base. To determine the molecular weight of Indifferent Com- pounds, derivatives must be prepared and examined for the proportion of the total hydrogen which is replaceable, e.g., by chlorine. For example, by the action of chlorine upon naph- thalene, there is first formed the substance mono-chloro-naph- thalene, which contains 73-8 per cent. C, 4*3 per cent. H, and 21-9 per cent. CI, these numbers giving the formula C^qH^CI. In the same way benzene yields the compound C^H^Cl. In both these cases the halogen acts by replacing hydrogen, and at least one atom of the latter in the molecule must be replaced^ since fractions of an atom are necessarily out of the question. If, then, the compound obtained has the formula C^oH^:Cl, it follows that l^th of the H present has been replaced by CI, and there must consequently be 8, 8 x 2, or 8 x 3, &c., atoms of hydrogen in the compound, and likewise 10 atoms, or some multiple of 10, of carbon. But a multiple of 8 or 10 may be rejected, since no compounds have been observed which would 10 INTRODUCTION. indicate the replacement of y^th of the total hydrogen. This leads to the formula C^oHg for naphthalene, the other possible formula got by analysis, viz., C^^Hg (see p. 7), being now untenable. In a similar way the formula of benzene is found to be CgHg. These molecular weight determinations by chemical methods find their strongest support in Determinations of molecular weight by physical methods. According to the law of Avogadro (1811), and Amjphre (1814), all gases under similar conditions, i.e, in the perfectly gaseous state and under the same temperature and pressure, contain in equal volumes equal numbers of molecules. It follows from this that the weights of equal volumes of different gases are proportional to the weights of equal numbers of their con- stituent molecules, in other words, the molecular weight is proportional to the specific gravity of the gas. Thus, if be the molecular weight of any given substance required, Mh that of hydrogen, S the specific gravity of the former as com- pared with air, and 0*06926 the corresponding specific gravity of the latter, then M,:Mh = 8:0-06926. And since Mh = 2, M, = ^^'^^ =8.28-87. 0-06926 To determine, therefore, the molecular weight of a gas, one has only to find its specific gravity, (air = l), and to multiply this by 28-87. To take an example, the specific gravity of acetic acid vapour being found to be 2-078, then M = 2-078 X 28-87 = 60, and the molecular formula is CgH^Og = 60. In like manner, the specific gravity of naphthalene vapour is 4*33 and the molecular weight 128 = C^QHg; the specific gravity of benzene vapour 2-702 and the molecular weight 78 = CoHg. It is essential to the application of this method that the temperature of the vapour shall be so high above the boiling DETERMINATION OF VAPOUR DENSITY. 11 temperature of the substance that the latt(^r is in the perfectly gaseous state, remaining at the same time undecomposed. Another mode of determining molecular weight by physical methods has been devised by Raoult (Ann. Chem. Phys. 1883). It depends upon the measurement of the lowering of the solidi- fying temperature of a solvent, e.g. water, benzene, or glacial acetic acid, which is produced by a given weight of the sub- stance dissolved ; from this value, which is a function of the molecular weight of the substance in question, the latter is deduced. This method is of value, since it allows of the determination by physical means of the molecular weight of substances which cannot be vaporized without decomposi- tion. (Cf. V. Meyer, B. 21, 536; also B. 21, 701, 767, 860, E. 165, etc.) Appendix: Determination of the Specific Gravity of Gases and Vapours. (Vapour Density.) A. By estimating the weight of a given volume of the gas or vapour. 1. Bunsen^s method. Three glass balloons of approximately equal size and weight are used, the first being pumped empty of air, and the second and third filled respectively with air and with the gas in question in a thermostat at a constant temperature. The respective weights of the balloons being p-^^ Vz^ specific gi;avity = 2. Dumas' method. 10 to 20 grm. of the substance are heated to boiling in a round glass balloon with a narrow neck, immersed, e.g.^ in an oil-bath. After the temperature has remained constant for a con- siderable time, the point of the neck is closed by the blowpipe, and the balloon weighed ; it is then opened over mercury and weighed again. Both of the above methods require a large quantity of material and, further, if the substance be not absolutely pure, the last-mentioned method will be liable to the error caused by the vapour of the more difficultly volatile constituent remaining in large quantity in the balloon. Troost and Hautefeuille have modified the method for higher tempera- tures, using a porcelain balloon. B. By estimating the volume of vapour from a given weight of substance. 12 INTRODUCTION. 1* . Gay Lussac's method. The substance, weighed in a small bulb, is introduced into a glass cylinder filled with mercury. This cylinder is surrounded by a glass mantle, the lower end of which also dips into mercury, and which is filled with a hot liquid, such as water, aniline, etc. The whole apparatus is warmed and, after the substance in question has been completely vaporized, its volume at the temperature f is determined. P. A. W. Hofmann's method. The substance is introduced into a barometer tube surrounded by a wider cylinder, through which the vapour of a suitable heating liquid (water, aniline, diphenylamine, etc.) is led. The cylinder can itself act as a reflux condenser. One advantage of this method is that, by the use of a partial or even complete vacuum, the boiling point of the substance in question is lowered, and thus the vapour density of compounds which decompose on being gasified under the ordinary atmospheric pressure can be determined. 2. V. Meyer's air-displacement method. The small tube containing the substance is dropped into a perpendicular glass tube, the lower and wider part of which is cylindrically shaped and sealed. This is kept warm at a constant temperature, being surrounded by a long glass mantle in which a suitable liquid boils, the upper part of the mantle itself serving for the condensation of the vapour. The displaced air alone escapes, and is collected over water and measured. No determination, therefore, of the temperature of the vapour of the substance in question is required. Both of the above methods require only up to O'l grm. substance. In all cases s=? V where g = the weight of the vapour, and v = the weight of an equal volume of air. Thus by the air-displacement method 8=^^ ^ {h-w)^ 273 760 21Z + t 773 where n — Vae number of cubic centimetres of displaced air, 1 c.c. of air weighing -A^ of a gramme. The other figures have the same meaning as on p. 6. CHEMICAL THEORIES. 13 Polymerism and Isomerism. The determination of molecular weight is of the first im- portance, because different substances very frequently have the same percentage composition and therefore the same empirical analysis-formula, and yet are totally distinct from one another. This difference is often found to arise from difference in the size of the molecule. Thus formic aldehyde, CH2O, acetic acid, C2H4O2, lactic acid, CgHgOg, and grape sugar, CgH^gOo' have all the same percentage composition, as have also ethy- lene, C2H4, propylene, CgH^, and butylene, C^Hg. Compounds standing in such relation to each other are termed polymers. Very frequently, however, substances which are totally dis- tinct from each other possess both the same percentage com- position and the same molecular weight ; that is to say, these substances are made up not only of the same atoms, but also of an equal number of these atoms ; such instances are termed isomers or metamers. (See Ethers.) Thus, for instance, common alcohol and methyl ether, the latter of which is obtained by heating methyl alcohol with sulphuric acid, have one and the same molecular formula, C^Ilfi. The striking phenomenon of isomerism is only explicable on the assumption that the grouping of the constituent atoms of the molecule is different in the two cases. This difference in grouping may be considered as being due to a difference in the linking powers of the atoms, as is indicated by the dissimilar chemical behaviour of isomers, and explained by the theory of valency. Chemical Theories ; the Theory of Valency. After the fall of the Electro-Chemical theory, unitary formulae — in contradistinction to the earlier dualistic formulae — were much used ; thus alcohol had the formula C4Hg02 (using the old equivalent weights). The necessity for comparing substances of complicated composition with simpler ones, taken as " Types," had already repeatedly led to the pro- pounding of new theories for representing the constitution of organic compounds, e.g. the older Type theory (Dumas), and the Nucleus theory (Laurent), 14 INTRODUCTION. This obtained a firmer basis through Gerhar city's Theory of Types, which received support more especially from the discovery of the acid anhydrides, the proper interpretation of the formulae of the ethers (see these), and the discovery of ethylamine and other ammonia bases by Gerhardt (1851), Williamson (1850), Hofmann (1849 and 1850), and Wurtz (1849). All compounds, inorganic as well as organic, were in this way compared with simpler inorganic substances taken as "Types," of which Gerhardt named four, viz. — H HI HI HI CI I N The first two of those really belong to the same type. Thus the fol- lowing formulae, for example, were arrived at — Clj Clj CI / Potassium chloride. Ethyl chloride. g}0 g}0 NO.}o Potassium hydrate. Nitric acid. Potassium oxide. Nitric anhydride. Alcohol. Ether. H [^N hJ C2H5 H H N CI / Acetyl chloride. Acetic acid. Acetic anhydride. C2H3O ) H f N H Ethylamine. Acetamide. etc., etc. Organic compounds could thus, like inorganic, be referred to inorganic types by assuming in them the presence of Radicles (e.g. ethyl, C2H5 ; acetyl, CgHgO, etc.), i.e. of groups of atoms which play a role analogous to that of an element, and which can be transferred by double decomposition from one compound to another. Thus ethyl chloride, C2H5CI, alcohol, CgHgO, ethylamine, CgH^N, ether, Q^^qO, etc., received the same radicle CgHg, ethyl, this showing the close relationship existing between these compounds, a relationship which now found in this way expression in writing. Sulphuric acid, H2SO4, was derived from the double water type, thus — and chloroform, CHCI3, and glycerin, C3H8O; chloric acid and water types — CI3/ CI3 / ' "3^ ' ^^3 the assumption being made that the radicles (C2H5), (SOj)", (CH)' (SO2)" ^ from the triple hydro- H3/"3 H3 |03, , and THKORY OF VALENCY. 15 (C^Hg)"' could replace a number of hydrogen atoms corresponding to the number of accents (') marked upon them, i.e. that they were mon- atomic, diatomic, etc. To the above three types KekuU afterwards added a fourth, of especial importance as regards the carbon com- pounds, viz. — It was then found that many compounds could be referred equally well to one or another of these types, methylamine, for instance, either to CH4 or to NHq, thus — The assumption, already mentioned, of the atomic groups (radicles) which in these types replaced hydrogen, led further to more exact investigations of the chemical value, i.e. the replaceable value, of those groups as compared with that of hydrogen. In this way one learnt to distinguish between mono-, di-, tri-, etc., valent groups, and, generally speaking, to pay more attention to equivalent proportions. Out of this there grew the conviction that a more profound idea (the ' * Type idea ") lay at the root of the types themselves — viz., that there are mono-, di-, tri-, and tetra valent, etc., elements, which possess a corresponding replacing or combining value as regards hydrogen {Kekul4, 1857 and 1858, A. 104, 129, and 106, 129), and that therefore H is monovalent, 0 divalent, N trivalent, C tetravalent, and so on. The principles of the theory of Valency or theory of Chemical Values are in this book assumed to have been already learnt from inorganic chemistry. With the setting up of the type CH4 by KekuU, and the knowledge of the tetravalent nature of carbon accompanying this, were connected the endeavours of Kolbe to derive the constitution of organic compounds from carbonic acid, (according to Kolbe C2O4, C=6, 0 = 8), but from an incomplete grasp of the subject of equivalent proportions a clear insight into this was not arrived at. (See note on page xix. ) The question of the valency of elements, a point which it is often difficult to decide in inorganic chemistry, is infinitely easier of determination in the case of the carbon compounds, because carbon shows itself tetravalent towards hydrogen as well as towards chlorine and oxygen. Since now hydrogen as the unit of valency is monovalent, and, further, since the divalence of oxygen cannot reasonably be doubted, the valency 16 INTRODUCTION. of the three " organic " elements H, 0, and C may be considered as resting upon a sure basis, as may also the conclusions drawn therefrom, and this all the more since the most important carbon compounds are made up of those three elements. Explanation of Isomerism ; Determination of the Constitution of Organic Compounds. The theory of valency makes the phenomenon of Isomerism easy to understand. That this depends upon the different grouping or combination of the atoms in the molecule follows from the fact that isomeric bodies, upon chemical transforma- tion, break up into or exchange perfectly different atomic groups or atoms. We now arrive at the task of determining the different modes of combination of the atoms in the molecule, i.e., the chemical constitution of the carbon compounds. This is in every case only possible and permissible for com- pounds whose chemical behaviour in the most dissimilar directions is known. The points of view which determine this can best be explained by giving an example. When an ethereal solution of methyl iodide, CH3I, is treated with sodium, there is first formed the group CHg, methyl, which — from carbon being tetravalent — must have a " free affinity (^) — \H The determination of the molecular weight of the gaseous compound ethane, formerly called methyl, which is thus pro- duced, shows however that it has the formula C^B.^^^^ ^C^Hg). The two methyl groups have therefore combined together, and it cannot well be doubted that this combination is effected by their free affinities. Ethane therefore receives the constitu- tional formula — C=H3 H3C— CH3;= I j C=H, DETERMINATION OF CONSTITUTION. 17 or, more shortly, CH3 /CH3\ This ethane can also be prepared from common alcohol. By the action of a halogen-hydride upon alcohol, one atom of oxygen and one of hydrogen together are exchanged for an atom of the halogen with formation, for example, of C^H^Cl, ethyl chloride ; then nascent hydrogen, acting upon this chloride, replaces the halogen, thus, C^HgO + HCl = C2H5CI + H2O ; C2H5C1 + H2 = C2H, + HC1. Conversely, by treating ethane with chlorine, ethyl chloride, C2H5CI, can be formed, and from this latter compound, alcohol. (See Special Part.) Thus, one atom of oxygen and one of hydrogen have here replaced one atom of chlorine, from which it follows that the two first-named together form the monovalent residue — (0 — H), hydroxyl. It is also evident from this reaction that one atom of hydrogen in alcohol behaves differently to the other five, and must con- sequently be difi*erently bound. Thus it is, for instance, re- placeable by metals, acid radicles, etc., and, when the oxygen is removed from the compound, it is removed also, whereas the other five hydrogen atoms are not affected. It is especially to be noted that the relation of the two carbon atoms to one another is not altered by the removal of the oxygen. All these facts lead to the constitutional formula for alcohol : CHo— CH2OH or /H. C— H \0— H In methyl ether, C2HgO, which is isomeric with this alcohol, no one of the six hydrogen atoms shows any difference to the others ; and, further, when its oxygen is removed, say by the action of hydriodic acid, the connection between its two carbon atoms is broken, with the formation of products which contain (506) B 18 INTRODUCTION. only one atom of carbon in the molecule, these products being, according to the conditions, — either one molecule methyl iodide and one molecule methyl alcohol or two molecules methyl iodide, thus — CgHgO + HI = CH4O + CH3I, or, O^HgO + 2HI - 2OH3I + H^O. From this it is to be concluded that in methyl ether the two carbon atoms are not bound directly to one another, but only by interposition of the oxygen. These conditions find expres- sion in the following constitutional formula — C=H3 I CH3— 0— CH3 ; or 0 C^H3 In a precisely analogous manner we obtain for acetic acid the constitutional formula — H , O i^OH; or H- -U- i- H 0— H On account of the innumerable cases of isomerism which have been observed, empirical formulae alone are in most cases insufficient for the discrimination of organic compounds ; it generally requires the constitutional formulae to give a clear idea of their behaviour and of their relations to other sub- stances. Careful study has made it possible within the last few decenniums to find out the mode in which the atoms are combined in the molecule of most organic compounds, and from this to deduce new methods for their preparation. The theoretical views and the knowledge thereby gained of the nature of carbon may be expressed somewhat as follows — 1. Carbon is tetravalent. 2. Its four valencies are all equal ; there is only one mono- substitution product of methane. 3. The atoms or atomic groups which are held bound by thetie four valencies cannot directly exchange places with RATIONAL FORMULAE. 19 each other. Proof: there are in every case two physically different tetra-substitution products C, a, b, c, d of methane (see p. 23). 4. Several carbon atoms can be connected together by either one, two, or three valencies. 5. Those compounds form either open or ring-shaped closed chains. One may picture the carbon atom in one's own mind as a tetrahedron, the four corners of which represent the affinities or affinity -directions, and which is regular if the carbon atom is combined with four atoms similar to each other, but of less symmetrical form in other cases. One has thus to think of two carbon atoms, connected by a single bond, as colliding at an angle of the tetrahedron, but free to move round each other ; of two carbon atoms, connected by a double bond, as joined together at an edge of the tetrahedron, but no longer free to revolve round each other; and of two carbon atoms, connected by a triple bond, as joined by two sides of the two tetrahedrons. Such conceptions have proved of great value in the investigation of the finer cases of isomerism, on the one hand, as regards the optical dififerences of substances which are chemically identical, (e. g. the lactic and the tartaric acids), and on the other as regards many differences, hitherto unexplained, between bodies which appear to possess the same chemical constitution, especially such as contain a double carbon bond in the molecule, {e.g. fumaric and maleic acids, p. 218). (Cf. Van H Hoff, "Dix Annies dans I'histoire d'une theorie," Rotterdam, 1887 ; Wislicenus, " Raumliche Anordnung der Atome, etc," Leipzig (Hirzel)^ 1887, referred to in B. 20, R. 448 ; Baeyer, B. 18, 2277 ; A. 245, 103 ; V. Meyer, B. 21, 784, 946). Rational Formulae. Great latitude is permissible as regards the mode of writing constitutional formulae, according to the particular points which it is desired to emphasize. The symmetrical arrange- ment or otherwise of the formula on paper is of no consequence, because the prevailing theories have regard almost alone to the mode of combination, and not to the actual positions of the atoms. Upon this latter point, experiment can yield almost no data. A shortened constitutional formula, which indicates more chemical relations than an empirical one does, is called a rational formula; g.^., CgH^OH, alcohol; (0113)20, methyl ether. 20 INTRODUCTION. For acetic acid, instead of the constitutional formula already given on page 18, the following rational formula may be used — ■ CH3— CC <^ or C— C— C<^ The first of these hydrocarbons, with a non-branching chain, are termed the normal hydrocarbons ; the last, the iso-hydro- carbons. (See p. 41.) The principles by which such constitutional formulae are arrived at will be explained under Butane and Pentane. Only those homologues are comparable whose constitutions are similar, as in the case of the normal hydrocarbons. Occurrence. — The hydrocarbons of the paraffin series occur naturally in great variety. Thus, methane is exhaled from 0(UinRl{KN(!K ; MODKS OK FOPvMATION. 37 the earth's crust, .is i)it gas and as marsh gas. The next higher liomologucs are found dissolved in petroleum, which also contains the higher hydrocarbons in large amount. Solid hydrocarbons occur as ozokerite or earth wax. By the frac- tional distillation of petroleum, a large number of these com- pounds have been isolated. Heptane and hexadecane are also found in the vegetal)le kingdom. Modes of formation. — A. The gaseous as well as the liquid and solid members of this series are obtained by the distilkition of lignite (Boghead-, Cannel coal), wood, bituminous shale, and, in very much smaller quantity, from pit coal. Paraffins are also got by dissolving carbide of iron in acids, and by heating wood, lignite, and coal, but not graphite, with hydriodic acid. B. From substances containing an equal number of carbon atoms in the molecule. 1. From the halogen alkyls,"^ C^Hga+iX, and, generally speaking, from the substitution products of the hydrocarbons by exchange of the halogen for hydrogen, (backward substitu- tion). This is effected by the action of sodium amalgam, or of zinc and hydrochloric acid, by heating with water and zinc to 160°, (Frankland), or with fuming hydriodic acid, which last is a most energetic reducing agent, especially in the presence of red phosphorus ; and so on. Heating with anhydrous chloride of aluminium has a similar effect. ^ 02H6l + HH = C2Hfi + HI. CH3I + HOH + Zn = CH4 + Zn | C2H5I + HI = C^H, + 1^. ^ -r^^ . . ^ ^ ^ o z Basic iodide of zinc. 2. From the monatomic alcohols, C^Hgn+iOH. a. By first converting them into the corresponding halogen compounds, e.g, by means of halogen hydride, and then trans- forming those, according to 1, into the paraffins. Kmfft has prepared the higher normal paraffins from these *The monovalent residues, CnH2ii4-i, methyl, ethyl, etc., which are at the same time the radicles of the monatomic alcohols, CnH2n+iOH, are frequently termed alkyls. 38 I. HYDROCARBONS. lialogen-alkyl compounds, by splitting off the halogen hydride and heating the residual C,,Ho,, with HI. (B. 16, 1714.) h. By heating directly with hydriodic acid — C^H.OH + 2HI - C^H.I + H^O + HI = C^H, + H^O + 1^, 3. Also by heating polyatomic alcohols, such as glycerine, with hydriodic acid to a high temperature. 4. From compounds richer in oxygen, such as aldehydes, ketones and acids, by heating them to a high temperature, e.g. 280°, with hydriodic acid saturated at 0° and amorphous phosphorus. The above compounds are frequently converted in the first instance into the cor- responding chlorides by means of phosphorus pentachloride. ' 5. From hydrocarbons poorer in hj^drogen, i.e. unsaturated hydrocarbons (see these), by the addition of nascent hydrogen ; e.g. ethane from ethylene or acetylene and hydrogen, either in presence of platinum black or by heating the mixture of gases to 400''-500°. Also by heating with hydriodic acid, (see above, 3), or by addition of halogen or halogen hydride, and exchange of the halogen for hydrogen, according to 1. ^^^^^ ' CgH^ + H9 = ^2^6^ ( C^H, + HBr = CgHgBr, tc,H,Br + H2 = C,H, + HBr. C. From acids containing more carbon, with separation of carbon dioxide. Thus, by heating acetate of calcium with , soda-lime, methane and carbonic acid are formed : CHgCOONa + NaOH = CH^ + Na^COg. D. By the combination of two radicles containing a smaller number of carbon atoms. 1. By the action of sodium upon the alkyl iodide in ethereal solution, {FTurtz), see p. 16 ; or by heating with zinc in a sealed tube, (FranJdtmd) : pXT T CJHg PH^ + Na2= r +2NaI. By this method also two different radicles can be combined, e.g. CoH.I + C^HjjI give C^H^ + CJi^ = C^Hi^, ethyl-butyl, (JFurtz' Mixed Radicles''). MCTIfANl^]. 39 2. By the action of halogen alkyl upon zinc alkyl, whereby dissimilar radicles may also be united — 2^-" = Znl2 + 2CH3.CH3. 3. By the electrolysis of acids of the acetic acid series, (Kolbe, 1848) : CH3-COOH __^^3 -p. CH3-COOH -^jj +^^^2+^2- The hydrogen is here evolved at the negative pole, and the hydrocarbon and carbon dioxide at the positive. Methane, (Fl^te, 1778). Occurrence. As an exhalation from the earth's crust, more especially at Baku in the neigh- bourhood of the Caspian Sea (the Holy Fire " of Baku) ; on the peninsula of Apscheron, where it is used for heating pur- poses in the Tartar village of Balachana ; in North America, e.g. from the large gas wells at Pittsburg, such as the Burns well (see Ethane) ; in Italy ; near Glasgow ; in the exhalations from mud volcanoes, for instance, at Bulganak in the Crimea, where the gas is almost pure methane, (JBunsen), and so on. As pit gas in mines, where it causes explosions. As marsh gas, produced along with CO^ and N by the decomposition of organic substances under water ; further, by the fermentation of cellulose, e.g. by river mud (by means of Bacillus amylobacter "). It is also found in rock salt (the Knistersalz of Wieliczka), and in the human intestinal gases, (up to 57 per cent. CH^ after eating pulse). The illuminating gas obtained by the destructive distillation of coal contains about 40 per cent, methane. Modes of preparation. 1. Methane is formed synthetically in an indirect manner by the union of carbon and hydrogen to acetylene at the temperature of the electric arc, the subsequent transformation of this into ethane, and of the latter into methane at a red heat, {Berthelot), thus : C2H2 + 2H2 = C2He ; C2Hg = CH^ + C + Hg. 2. From carbon monoxide and hydrogen under the influence of electricity ; CO + 3FI,^ - CH^ 4- Kp. 40 1. HYDROCARBONS. 3. By leading sulphuretted hydrogen and carbon bisulphide over red- hot copper ; CS^ + 2H2S + 8Cu = CH4 + 4Cih,S. 4. Preparation from acetic acid, (Bunsen). Sodium acetate is heated with baryta or, less advantageously, with soda-lime ,(cf. p. 38), ethylene, CgH^, and hydrogen (up to 8 per cent.), being formed at the same time. Acetic acid may also be made to yield methane by a process of fermentation. 5. Methane is obtained chemically pure from zinc methyl and water ; also (see B, 1) by the reduction of methyl iodide, CH3I, e.g. in alcoholic solution by means of zinc in the presence of precipitated copper, (the Gladstone-Tribe Copper- zinc Couple ") ; ^ also by the backward substitution of chloro- form, CHCI3, or carbon tetrachloride, CCL. 1 6 Properties. Gas, Sp. Gr. 0*559 ( = §8^' ^' ^^^^ condensable under a pressure of 140 atmospheres at 0°. Boils at -164°, and solidifies at -186°. Absorption coefficient in cold water about 0*05, in cold alcohol 0*5. Burns with a pale and only faintly luminous flame. Is decomposed by the electric spark into carbon and hydrogen. Splits up for the most part into its elements on being led through a red hot tube, but there are formed at the same time CgH^^, CgH^, ^2^2^ and, in smaller quantity, CgHg, benzene, C^oHg, naphthalene, and other products. The first three hydrocarbons just men- tioned, ethane, etc., behave similarly. Ethane, G^^cy Occurrence. In crude petroleum. Con- stitutes, for example, the gas of the Delamater gas well in Pitts- burg, and is there utilized for technical purposes. Preparation. By the electrolysis of acetic acid, {Kolhe, 1848), and therefore formerly called methyl " ; also from ethyl iodide, alcohol, and zinc dust, or from zinc ethyl, (Frankland), hence the name ethyl hydride." " Ethyl hydride " and methyl," which were formerly supposed by Frankland and Kolhe to be different substances, were proved to be identical by Schorlemmer in 1863 by their conversion into C2H5CI. ^ This is a special preparation of zinc coated with copper precipitated from a solution of copper sulphate, which acts much more energetically than zinc alone. (Ch. Soc. J. 1884, 154.) KTTTANK, ETC. ; TSOMERTSM. 41 Properties. Gas, c()n(lcnsal)lc under a prcssuro of 40 atmos- pheres at 4°; soiTiovvhat more soluble than nietliane in water and alcohol. Burns with a faintly luminous flame. Propane, CgHg. Present in crude petroleum, and liquid below - 17°. Preparation. By the action of hydriodic acid on acetone or glycerine (Berthelot), thus : C3H^ + 2H, = C3H8 + H20; Acetone. C3H303 + 3H2 = C3H3 + 3H20; Glycerme. or from isopropyl iodide with zinc and hydrochloric acid. Butane, C^H^q. Two isomeric butanes exist. Normal butane boils at +1°, and has the Sp. Gr. 0*60 at 0° ; isobutane boils at - 17°. Normal butane, which is also present in petroleum, can be prepared by the action of sodium amalgam or zinc upon ethyl iodide, C2H5I, (Frankland), and has therefore the following constitution : CH3— CH2— CH2— CH3 (di-ethyl) : CH3— OH2I , _ CH3— CH2 2NaT + CH3— CH2I + ^^^2 - CH3— CH2 ^ Isobutane is formed from isobutyl iodide, C^Hgl, {Wurtz), according to B, 1, and also by the action of zinc and water upon tertiary butyl iodide, (which see), (Butlerow). Isomerism, Nomenclature, Constitution. The Isomerism of the two butanes is explained on the assumption that in isobutane the carbon atoms are not com- bined witli one another in a " continuous straight line " but in a branching " one, according to the formula : CH3 I CH— CH3, = CII(CH3)3, CH3 42 I. IIYDTiOCARBUNS. which corresponds with the name tri-ra ethyl-methane. (See below.) The evidence for this rests upon the proof of the constitution of tertiary butyl iodide, C^B^)!. (Cf. p. 43.) These two butanes are theoretically the only possible ones of the formulae C^H-^q. All the succeeding hydrocarbons can, according to theory, exist in various isomeric modifications. Thus theoretically three pentanes should exist, and as a matter of fact three are known. Of hydrocarbons with six carbon atoms, five isomers are possible, and they are all known. Of the nine possible heptanes, CyH^^., the existence of five has already been proved. The number of theoretically possible isomers increases very rapidly with increasing carbon, so that, according to Cayley, 802 isomeric hydrocarbons of the formula G^^^^ are possible. Of these isomers only one can be normal, i.e. can have a carbon chain in a continuous straight line (p. 36), in which each of the two carbon atoms at either end are combined with three atoms of hydrogen, and all the middle ones with two, according to the formula : CH3 — (CHa)^ — CH3. A convenient Nomeiiclature for the more complicated paraffins is arrived at by making methane the starting point for all of them, that carbon atom from which the branching chain emanates being considered as originally belonging to in which the hydrogen atoms are supposed to be wholly or partially replaced by hydrocarbon radicles, thus : /CHo CH^CH3 = Dimethyl-ethyl-methane. The names of the well known lower hydrocarbon radicles (alkyls) are also frequently used as a basis ; for instance, the group (CH3)2CH is termed isopropyl, (see Iso-propyl Alcohol), hence the compounds : ^j[j3\>CH— CH2— CH3 : Ethyl-isopropyl. ^ JJ^>CH— CH<^ . Di-isopropyl. NOMIONCLATIJKK ; ( ;( JNSTITU'J'K )N. 43 Schorlemmer diistiu'^'uishes between tlie following four ekisses of paraffins : — 1. Normal paraffins. 2. Iso-paraffins, in which one assumes a single branching in the molecule. 3. Meso-paraffins, with several of such branchings. 4. Neo-paraffins, containing one carbon atom to which four others are united. The boiling points of the normal hydrocarbons are always higher than those of the isomers ; indeed the boiling point becomes lowered continuously the more the carbon atom chain is branched, i.e. the more methyl groups arc gathered together in the molecule. The Constitution of the higher paraffins can in most cases only be arrived at with certainty from their synthetical formation, (e.g., normal butane and hexane), or from their chemical relation to oxygenated derivatives whose constitution is already known, especially to the ketones and acids. (See Ketones.) If, for instance, by the action of PCl^ upon acetone, for which the constitution CH3 — CO — CH3 is proved, the sub- stance (CH3)2CCl2, = CH3 — CClo — CH3 (acetone chloride) be formed, and this be then treated with zinc methyl, the resulting hydrocarbon, a pentane, will have the constitution (0113)^0 : gi;>cZB = ^i;>c<^i;+znci. The same hydrocarbon, tetra-methyl-m ethane, is also pro- duced by the action of zinc methyl on tertiary butyl iodide, (see this and also p. 42), from which it follows that the con- stitution of the last-named compound is (0113)301 : OHgx * OHgx CHg-^OI -1- znOHo = 0H3-^0— OH, + znl. OH3/ OH3/ And, since tertiary butyl iodide is converted by nascent hydrogen into isobutane, the formula of the latter is thus proved to be (OH3)30H. The same constitution-formula for tertiary butyl iodide is arrived at from that of tertiary butyl alcohol. (See these.) 44 I. HYDROCARBONS. Pentanes. According to theory, and also in reality, three isomeric pentanes exist. (See table.) 1. Normal pentane, CH3 — CR^—CU^ — CHg— CH3. 2. Isopentane, ethyl-isopropyl,'' (CH3)2=CH — CHg — CH3, (from iso-amyl iodide.) 3. Tetra-methyl-methaney G(GIi^)^. The two first are contained in petroleum. (That portion of the petroleum distillate which boils under 0° is used as an anaesthetic under the names rhigolene and cymogene, and also in the preparation of ice.) Isopentane is formed from amyl-iodide, according to B, 1. For tetra-methyl-methane, see above. Hexanes, CgH^^. The five hexanes known boil between 46° and 71°. Normal hexane is produced, among other methods, by the action of hydriodic acid upon mannite, CqR^JJq, and also upon aniline, CgH^N. Its constitution follows from its formation from normal propyl iodide, CH3.CH2.CH2I, and sodium, in a manner analogous to that of normal butane. Normal heptane, C^H^g, B.Pt. 98°, is present, for instance, in the ethereal oil of Pinus Sabinia, the Californian nut pine. It has a strong smell of oranges and produces insensibility when breathed. From petroleum have been separated the two first- mentioned pentanes, also normal hexane and an isomer, both being pre- sent in the so-called " gasoline," which is obtained by the distillation of petroleum, and is used for carbonizing coal gas ; further, normal Heptane, n-Octane,^ n-Nonane, and n-Decane, besides an isomer of each, and in addition to these (as also from the distillation of cannel and Boghead coal), a large number nominally of the higher hydrocarbons, (CahourSy Pelouze^ Warren, Schorlemmer). In all probability these products are not chemical individuals but an inextricable mixture of homologues and isomers stand- * The petroleum ether and ligroin of commerce consist principally of the hydrocarbons C(jHi4, CyH^g, and CgHig. TIIK IlKJIIiai JIYDllOCAUliUNS. 45 iiig very near to each other, as is sliowii by a comparison with the artificially prepared normal hydrocarbons. (See below.) F. Kraft has prepared the whole series of normal hydro- carbons (see table), from to C25Hr,2i and also those with 27, 31, and 35 atoms of carbon, from the acids C^g' ^14? ^10 and C^g of the acetic acid series, (see these), for which the normal constitution, i.e. non-branching carbon chain, has been demonstrated ; and also from the ketones, CnHgnO, which are obtained by subjecting the barium salts of these acids to dry distillation, either alone or together with acetate or lieptoate of calcium, and which, as a consequence of their mode of for- mation, yield normal hydrocarbons. (See Ketones.) These are, from about G^Ji^^^ (M. Pt. 18°) on, solid at the ordinary temperature. Upon distillation under the atmospheric pressure, the higher hydrocarbons partially decompose into lower ones of the formulae GJi2n+2 and CnHgn^, but they may be distilled in a vacuum, whereby their boiling points are reduced by 100° or more. (See table.) Petroleum, Earth Oil — This is produced by the decomposition of animal organisms {EngUr). It is found between Pittsburg and Lake Erie in America ; between Lake Erie and Lake Huron in Canada ; in Hanover, Holstein, and Elsass in Germany ; in Boryslaw by Dro- hobycz in GaHcia ; in the Crimea ; in the Caucasus, where the oil fountains rise to a height of 9 metres in summer ; etc. The specific gravity of the Pennsylvanian oil, after purification by treatment with caustic soda and sulphuric acid and subsequent distilla- tion, is 0-79 to 0-81, and its boihng point 200°-300°. The Canadian oil has a higher specific gravity, and contains substances of a very un- j)leasant odour. Petroleum has been a commercial product since 1848. It must not be forgotten that all earth oils do not possess a similar composition. While the American oil consists almost entirely of paraffins, recent investigations have shown that petroleums from other sources, especially those from the Caucasus and Galacia, contain for the most part other hydro- carbons, a mixture of " naphthenes " {GJl^n^ see olefines and hexa-hy dro-benzene) . Paraffin, obtained by Beichenhach in 1830 from wood tar, is got by * The hydrocarbons undergo a similar decomposition upon treatment with AlgBrg + HI ; e.g. CqRu yields C4H8 and OaHgBr. 46 I. HYDROCARBONS. the distillation of lignite or peat. It also is a mixture of many hydro- carbons, about 40 per cent, of it consisting of the compounds C22H4g, ^24^50 5 CogHgo, and C28H58. Liquid Paraffin {ReichenhacK' s Eupion ") and the butter-like Vase- line are high-boiling distillation products of lignite or petroleum, and the same applies to many lubricating oils. Ozokerite, green, brown, and red, and of the consistency of wax, melting point 60°-80°, is a natural paraffin found at Boryslaw in Galicia, at Tscheleken near Baku (also called Neftgil), on the Caspian Sea, and forms the ceresine of commerce when bleached. From it there has been isolated a hydrocarbon *'lekene" containing 24 atoms of carbon. Asphalt, or Earth Pitch, found in India, Trinidad, Java, and Cuba, is a transformation product of the higher-boiling earth oils, produced by the action of the oxygen of the air, just as paraffin absorbs oxygen and becomes brown upon prolonged heating in the air. It is used for cements and salves, and in asphalting, photo-lithography, etc. B. Olefines or Hydrocarbons of the Ethylene Series (Alkylenes) : GJl^^. Summary. M. Pt. B. Pt. M. Pt. B. Pt. Ethylene, Propylene, Butylene (3), Amylene (5), Hexylene, Heptylene, Octylene, Nonylene, Decylene, Undecylene, C2H4 C4H3|^ C7H14 C'loH20 CnH22 - 160° -103° Gas -5° + r -6° + 39° G8° 98° 125° 153° 175° 195° Dodecylene, Tridecylene, Tetradecylene, Pentadecylene, Hexadecylene, \ Cetene, j Octadecylene, Eicosylene, Cerotene, Melene, ^^12^24 ^141^28 ^16^32 ^201140 C27H54 -31° -12° + 4° 18° 58° 62° \ 96°+ 233° {127° 247° {179° A Methylene, CH^^, does not exist ; when it should result, ethylene, CgH^, is formed instead, (Perrot, Butlcrow). Thus : 2CH3CL - 2IIC1 = C^H^. ^The melting and boiling points given from C5H1Q on, are those of the normal hydrocarbons. + { Signifies boiling point under 15 m.m. pressure. OLEFINES. 47 The inembers of this second series of hydrocarbons differ from tlie paraffins by containing two atoms of hydrogen less than these. In their physical properties they resemble the methane homologues very closely. C2H4, CgH^., and C4Hg are gases, C^Hjo a volatile liquid, the higher members liquids with rising boiling point and diminishing mobility, while the highest are solid and similar to paraffins. The boiling points of members of both series containing the same number of carbon atoms, and whose constitutions are comparable, lie very close together, but the melting points of the olefines are somewhat the lower of the two; e.g. CigHg^, M. Pt. 21°, B. Pt. {157°, and G^^YL^^, M. Pt. 4°, B. Pt. {155^ Most of the olefines are easily soluble in alcohol and ether, but insoluble in water, only the lower members dissolving slightly in the latter. The specific gravities of the normal olefines, measured at the melting points, rise from about 0'63 upwards, and approach with increasing carbon to a definite limit, viz., about 0*79. In their chemical relations, the olefines differ materially from the paraffins : (a) By additive reactions. They combine readily with nascent hydrogen, with hydrochloric, hydrobromic, and hydri- odic acids, with chlorine, bromine, iodine, fuming sulphuric acid, hypochlorous acid, nitrous acid, and, generally speaking, with two monad atoms or monovalent groups, whereby members of the methane series or their derivatives ensue; hence their name of " Unsaturated Hydrocarbons." Combination with hydrogen is sometimes effected, e.g. in the case of ethylene, by the aid of platinum black at the ordinary temperature, or by raising to a red heat, or by heating the olefines or their di-chlor-, etc., addition products with fuming hydriodic acid and phosphorus. (Cf. modes of formation of the saturated hydrocarbons B 1 and 5.) C2H4 + H2 C2H4 + CI2 C^H, + HI C2H4 + H2SO4 C,H,(SO,H). 48 I. HYDROCARBONS. Ethylene chloride, CgH^Clg, obtained by the combination of ethylene with chlorine, was formerly called the oil of the Dutch chemists, hence the name of " defines " for the whole class of hydrocarbons C^jHan, {Guthrie). Chlorine adds itself on more easily than iodine, but hydro- chloric acid with more difficulty than hydriodic, bromine and hydrobromic acid standing mid-way. When a halogen hydride is used, the halogen attaches itself to that carbon atom which is combined with the least hydro- gen. (Of. Substitution Products.) Particular olefines, e.g. isobutylene, also combine slowly with water to alcohols under the influence of dilute acids. Ethylene combines with fuming sulphuric acid at the ordin- ary temperature, and with the English acid at 160°-170°. {h) By their capability of polymerizing, especially in presence of sulphuric acid or zinc chloride. In this way are formed from amylene, C5H10, in presence of sulphuric acid, the polymers CjoHgo, CjgHgo, and C20H4Q, and from butylene similar compounds. (c) By their behaviour upon oxidation. They are easily oxidized by KMnO^ or CrOg, but not by cold HNO3. By this reaction, either oxidation products — (acids) — containing less carbon are formed, by the breaking up of the double carbon bond, (see p. 49, also A. 197, 243) ; or, when KMn04 is employed, no carbon atoms are separated, but two hydroxyls are introduced, with formation of a diatomic alcohol. (See p. 187 ; cf. B. 21, 1230, etc.) Modes of Formation, (a) Together with paraffins by the destructive distillation of many substances, such as wood, lignite and coal, and also by the distillation of the paraffins (cf. p. 37) ; illuminating gas consequently contains the olefines ^^2^4) CgHg, C^Hg, etc, (h) By abstraction of water from the alcohols, C^Hsn+iOH, by heating them with sulphuric acid, phosphorus pentoxide, zinc chloride, etc. When sulphuric acid is used, an alkyl-sulphuric acid, e.g. ethyl-sulphuric acid, CgHj^SO^H, is first formed, and this decomposes upon further warming into alkylene and sul- phuric acid. This method is especially applicable in the case of the lower homologues. Many alcohols split up into olefine FOUMATION ANJJ CONSTITUTION OF THE OIJ^^FINES. 41) and Wiiter, even when only strongly liciitcd alone, e.g. secondary butyl alcohol at 240°. A convenient method of obtaining the higher olefines is to distil the pahiiitic ethers of the higher alcohols under somewhat diminished pres- sure, when the corresponding olefines and palmitic acid are produced. {c) By heating the halogen compounds C^Hsn+iX with alcoholic potash, or by passing their vapour over red-hot lime or hot oxide of lead, etc.; sometimes by distillation alone : + KOH --^ C,Hi, + KI + H,0. The bromine com])ounds are particularly suited for this. {(1) Sometimes from the haloid compounds CuHjuXo by abstraction of the halogen, e.g. ethylene from ethylene bromide by treatment with zinc : C2H4Br2 + Zn = C2H4 + ZnBrg. (e) By the electrolysis of dibasic acids of the succinic acid series ; thus succinic acid itself yields ethylene : C2H4(COOH)2 = + 2CO2 + H2. Other modes of formation correspond with these under D 1 and 2 for the paraffins. Constitution of the Olefines. For ethylene, produced by the abstraction of two atoms of hydrogen from ethane, the following formulae may be given : CH3 CHo — CHo I. I • 11. I III. II CH= CH2— CH2 In the formulae I. and II., two free carbon affinities are assumed in the ethylene molecule. Formula III. follows from the assumption that the affinity which becomes free at each of the two carbon atoms, upon abstraction of the hydrogen, is employed in creating a " double bond " between them. Upon the taking up again of two atoms of hydrogen or halogen, the two free affinities in I. and 11. would become bound by them, while in III. the double bond would be changed into a single one, and the free affinity of either carbon atom would be employed in binding the two new hydrogen (or other) atoms. Now the ethylene bromide which is formed by the addition of bromine to ethylene has, for reasons which will be given under that compound, the constitution CH^Br — CH^Br, and ( 506 ) D 50 I. HYDROCARBONS. likewise the compound obtained by the addition of ClOH, i.e. CI and OH, viz. glycol chlorhydrin, the constitution CHgCl — CH2OH; consequently formula I., according to which these substances would have the constitutions CH3 — CHBrg and CH3— CHCl(OH), is excluded. Formula III. is more probable than formula II. : — (a) On account of methylene, CH2=, being incapable of existence; all attempts to isolate it have only yielded ethylene, C2H4 (see p. 46), so that free affinities probably cannot exist in the carbon atom. (b) Because one would -otherwise expect to have two isomeric ethylenes, but all endeavours to prepare an isomer have proved fruitless, (ToUens and L. Meyer) ; and further because more isomers of the next higher homologues, propylene and butylene, should exist than can actually be prepared. (c) Because the free affinities to be assumed according to II. are never found singly, (which should in that case be possible), but invariably in pairs only, and indeed only on neighbouring carbon atoms. This is proved from the constitution of the compounds obtained by the addition, for instance, of Brg. It is therefore to be concluded that in ethylene and its homologues a double carbon bond, corresponding to formula III., exists. By this term double bond" is not, however, to be understood a closer or more intimate combination. The olefines, on the contrary, are more readily oxidized than the paraffins, being thereby attacked at the point of the double bond. Other properties, especially physical ones, also give indications that a double bond between two carbon atoms is looser, and therefore more easily broken than a single one. (Of. Briihl, A. 211, 162). As soon as a hydrocarbon, CnH2n+2) contains not less than three carbon atoms, the elimination of two atoms of hydrogen, with formation of a hydrocarbon, On Hon, can also be brought about by a method other than the formation of a double bond, viz. by the "closing of the carbon chain." The compounds in which this is to be assumed are sharply distinguished from the olefines, and are not to be included among them. Ethylene, elayl, oil-forming Gas, CgH^, = CHg^CHg. KTIIYIJONE, ETC. 51 This compoiiiid was discovered in 1795 by four Dutch chemists. Its forniuLa wlis established by JJal/ou. Formation — see above, lllnmiiiating gas generally contains 4 to 5 p.c. of ethylene. The latter is usually prepared by heat- ing alcohol with excess of concentrated sulphuric acid, with addition of sand, a mixture of equal portions of the two liquids being subsequently dropped into the evolution flask. Sulphur dioxide, etc., are produced at the same time by secondary reactions. Small quantities can be conveniently prepared from ethylene bromide and zinc. It is further formed (instead of its hypothetical isomer indicated above) by heating ethylidene chloride, CHg — CHCI2, with sodium. Liquid at 0° under 44 atmospheres pressure. B. Pt. 103°. Very slightly soluble in water and alcohol. Burns with a luminous flame, and forms an explosive mixture with oxygen. When rapidly mixed with two volumes of chlorine and set fire to, it burns with a dark red flame, with formation of hydrochloric acid and deposition of much soot. It is con- verted at a red heat into methane, CH^, ethane, CgHg, acety- lene, C2H2, etc., with separation of carbon. (See p. 40.) It combines with hydrogen in presence of spongy platinum to ethane, C^Hg. Propylene, CgH^, = CH2=CH— CH3. Only one propyl-, ene belonging to the olefine group is theoretically pos- sible and only one is known, viz., a methylated ethylene, (see p. 52.) (On the assumption of two free affinities instead of a double bond, four isomeric propylenes would be possible.) It can be prepared from isopropyl iodide and caustic potash, or by heating glycerine with zinc dust. It is still a gas at - 40°. Butylene, C4H8. Three butylenes are possible according to theory, and three are known. All of them are gaseous, their boiling points lying between - 6° and + 1°. Butylene and pseudo-butylene are derived from normal butane, while isobutylene comes from isobutane, since they severally combine with to form these hydrocarbons. The first, a-butylene, is prepared from normal ; the second, /3-butylene, from secondary ; and the third, 7-butylene, from tertiary butyl iodide by the action of caustic potash upon these ; the last can also be got from isobutyl alcohol and sulphuric acid. The isomerism of the two butyl- 52 J. HYDROCARBONS. enes derived from normal butcane is explained by the assumption of a double bond at different points, thus : a-butylene, CH3— CH2— CH--CH2 ; i8-butylene, CH3— CH^CH— CII3. Isobutylene has the formula (0113)2 = C = CHg. The behaviour of these isomers upon oxidation is in accordance with the above formulae, the oxidation always taking place at the point of the double bond. Amylene, C^H^q. A large number of isomeric amylenes are known, among them being Iso-amylene, obtained from ordinary amyl iodide and caustic potash, and for which the constitutional formula (CH3)2CH — CH=CH2 (isopropyl-ethylene) is assumed. The higher Olefines of normal constitution, with 12, 14, 16, .and 18 atoms of carbon, have been prepared by Kmfft accord- ing to method h. Cerctene and Melene (M. Pt. 60°) are obtained by the distillation of Chinese and bees' wax. They are like paraffin in appearance, and are but slightly soluble in alcohol. Appendix. For the hydrocarbon, CyHg, there is still another constitutional formula possible, viz. — \ / Trimethylene (I.). CH, CHg — CHg Similarly for C^Hg : | | Tetramethylene (11.). CH2 — CH2 — CH2 And for CgH^2 • I I Hexamethylene (HI.)- CH2 — CH2 — CH2 The carbon atoms in these formulae do not form open " but closed " chains, or quasi " rings." There are many grounds for supposing that such closed chains exist in certain com- pounds, (see p. 50). Thus, a gas isomeric with propylene is known, which appears to correspond with formula L, and is therefore called tri-methylene. It is formed by heating trimethylene bromide, CH2Br--CH2 — CH2Br, with sodium, {Freiuid, J. pr. Ch. [2] 26, 367.) It combines with bromine only with difficulty, but more easily with hydriodic acid to normal propyl iodide, C3H7I, and, unlike propylene, it is not altered by KMnO^. (See Trimethylene and Tetramethylene Derivatives.) 53 Fni'tlier, a whole Rcrics of liydrocai hoiis, l)Oginnii\ij; with C(.TIj2' known, which are obtained by the achlition of hydrogen to benzene and its homologues, eg. hexa-liydro- benzene, C^H^2- These do not belong to the olcfines, but most probably contain closed carbon chains, according to formula III. (See Aromatic Hydrocarbons.) Identical with these are — according to Markownihoff and Spady- the hydrocarhons, CuHgu, mentioned on p. 45, the " naphthenes, " which are contained in certain petroleums (in the Caucasian, BeilsfpJn, Kur- hatow, and in very small quantity in the American). Unlike the olcfmes, these are not dissolved by sulphuric acid, but they are trans- formed .by nitric-sulphuric acid or by heating with sulphur into deriva- tives of aromatic hydrocarbons, or into the hydrocarbons themselves (see these). Bromine does not give addition products with them, but acts as a substituent. Those already described are " Octo-naphthene," C'stiiS' " ^^^ono-naphthene," CgHig, and the homologues up to C15H3Q. (Cf. B. 16, 2663; 18, 2234, R. 662; 20, 1850). O. Hydrocarbons, C,,H2,,_2: Acetylene Series. Summary. B. Pt. M. Pt. B. Pt. i r Acetylene \ \ (Ethine),/ Gas. ^12^22 /Dodecylidene \ \ (norm.), j -9° {]05°t C3H4 Allylene (Allene), r Crotonylene, \ \ etc. (Butine), j / Valerylene, etc. \ \ (Pentine), / Diallyl (Hexine), 51° /59° /Tetradecylidene \ \ (norm.), / fHexadecylidene \ \ norm.) I y (Cetylene), J /Octadecylidene \ \ (norm.), j + 6° 20° 30° {134° {l60° {l84° Heptine, etc., 108° Eicosylene (norm.). liquid 314° * The boiling points from C4 on, are those of the normal compounds, t Boiling point under 15 m.m. pressure. The hydrocarbons of this series again differ from those of the 54 I. HYDROCARBONS. preceding by containing two atoms of hydrogen less. In physical properties they closely resemble both the latter and those of the methane series ; thus the lowest members up to CJIq are gaseous, the middle ones liquid, and the highest solid, and in their melting and boiling points they do not differ to any extent from those of the other series with an equal number of carbon atoms. The specific gravities of the normal hydrocarbons C^g? ^iv ^i6' ^^is' melting point, gradually approach with increasing carbon to a definite limit (0*80), and are somewhat higher than those of the corresponding members of the ethylene series throughout. In their chemical relations the acetylenes stand nearer to the olefines than to the paraffins, in so far that they are un- saturated and therefore capable of forming addition products. 1. They combine either with two atoms of hydrogen or halogen, or with one molecule of halogen hydride to olefines or their substitution products, thus : CgHg + = CgH^. C2H2 + HBr = C^HgBr (vinyl bromide) ; or with four atoms of hydrogen or halogen, or two molecules halogen hydride to paraffins or paraffin substitution products, thus : C2H2 + = (^2^6 (^^ presence of platinum black). C2H2 + 2HBr--=C2H4Br2. C2H2 + 2Br2 =C2H2Br,. Like many of the olefines, various members of this series combine with water under the influence of dilute acids, thus allylene, C3H4, gives acetone, CsHgO ; and acetylene, C2H2, gives crotonic aldehyde, with intermediate formation of acetic aldehyde ; and, as in the case of the oletines, ether -sulphuric acids are to be assumed here as inter- mediate products. HgClg and other mercury salts also induce such hydration : C2H2 + H2O = C2H4O (aldehyde). C3H4 + H2O = CyHgO (acetone). 2. The capability of undergoing polymerization is also peculiar to several of the acetylene hydrocarbons ; thus, acetylene is transformed into benzene upon being led through a red-hot glass tube. This is an important synthesis of benzene : ^CgHg = CjjHg. 6 CONSTII'II'I'ION OF TlIK OT.KnNKS. 55 At the same time the compounds CgH^, C^^^Hg, etc., are formed. Similarly allylcne, C3H4, gives mcsitylene, GgR^^^ upon treatment with sulphuric acid and a little water. (See Benzene Derivatives.) 3. Acetylene and some of its homologues react even at the ordinary temperature, in a manner which is peculiar to them, with an ammoniacal solution of cuprous or argentic oxide, to form reddish-brown or yellow-white precipitates, e.g. C2CU2 + ; CgAgg 4- H2O, which are explosive, and which are decomposable by acids, such as HCl, with regenera- tion of the hydrocarbon. The hydrogen of acetylene can be replaced by potassium or sodium ; thus, upon heating the former with sodium, the com- pounds C2HNa and C2Na2 are obtained. These are decom- posable by water or acids with separation of acetylene. All the hydrocarbons CnH2n_2 do not, however, give such metallic compounds, but only the true homologues of acetylene, i.e. those which contain a triple bond. (See below.) Constitution. Upon grounds similar to those which have already been explained under ethylene, the constitutional formula for acetylene, C2H2, is assumed to be CH=CH, according to which the carbon atoms are joined together by a triple bond. For a compound C3H4, there are therefore possible the two following constitutional formulae : CH=C— CH3 and CH2=C=CH2. AUylene. Allene. As a matter of fact two hydrocarbons C3H4 do exist, only one of which, allylene, yields metallic compounds. It is therefore to be considered the true homologue of acetylene, containing a triple bond, according to the first of the two above formulae, while to allene the second formula, with the two double bonds, is to be ascribed. The constitution of the tetra-bromo-propanes, which are formed from these by the addition of Br^, agrees with this conception. The capability of yielding metallic compounds is therefore contingent upon the presence of the group — C=CH. 56 I. HYDROCARBONS. In the case of the higher homologues isomerism may be due cither to the difference in position of the triple carbon l)ond in the molecule, or to the presence and different positions of the two double bonds. The constitution of a compound is fixed by the formation or otherwise of metallic derivatives, and by its behaviour upon oxidation. (See Oxida- tion of the Butylenes, p. 52. ) Modes of formation. 1. Along with the hydrocarbons already described, by the distillation of wood, lignite, coal, etc. ; thus illuminating gas contains acetylene, allylene, and crotonylene. 2. By treating the haloid, preferably the bromine, com- pounds CnHsnXg and GJrL^a-^^ with alcoholic potash : C^H^Br^^C^HgBr + HBr. CsHgBr =C2H2 +HBr. Further, from the unsaturated alcohols CnHgnO. (See p. 48 (b). 3. By electrolysis of the acids of the fumaric acid series, [KelcuU). Acetylene is further formed : 4. From its elements, when an electric arc is caused to pass between two carbon poles in an atmosphere of hydrogen. 5. By decomposing CgCa or CgKg by water. 6. By the incomplete combustion of many carbon com- pounds, for instance, when the gas in a Bunsen lamp burns below. 7. From chloroform and sodium (or red-hot copper) : 2CECl3-f3Na2 = CH=CH -I- 6NaCl. 8. From ethane, ethylene and methane at a red heat, or by the action of the induction spark. (See pp. 40 and 51.) 9. By heating with dry potash on the one hand, and with sodium on the other, certain acetylene hydrocarbons are transformed int > isomers. Acetylene, C2H2. — Was first obtained impure by E. Davy horn CaCg in 1839, and pure by Berthelot in 1849. Illuminating gas contains 0*06 per cent. Is best prepared from ethylene bromide. It becomes liquid at 1° under a pressure of 48 atmospheres, burns with a luminous and very sooty flame, and has a peculiar disagreeable smell. Dissolves in its own volume of water and in ^th of its volume of alcohol. Is 57 poisonous, combining with the liacnioglolnn of the blood. It is decomposed into its elements with detonation by explosive fulminate of silver, and also by the electric spark. It combines with hydrogen to ethane, upon being heated with the latter in presence of platinum black, or to ethylene, upon treating its copper compound with zinc and ammonia. A mixture of acetylene and oxygen explodes violently when a light is applied to it. Chromic acid oxidizes acetylene to acetic acid, and permanganate of potash to oxalic acid. It combines with nitrogen under the influence of the induction sp;irk to hydrocyanic acid (see this), and detonates upon being mixed with chlorine, but additive products, e.g. C2H2CI2, can however be prepared. As little as -^^-^ milligramme of it can be detected by the formation of the dark-red copper compound C2CU2 + H2O, perhaps CgH — Cu — Cu(OH). This latter explodes when struck, or when heated to a little over 100°. AUyleiie, C3H4, = CH3— C = CH, can be prepared from propylene bromide, CsHgBrs, = {CH3— CHBr- CHsBr). AUene, C3H4, = CH2=C=GH2, is obtained by the electrolysis of itaconic acid. Crotonylene or Butine, CH2=CH — CH=CH2, is contained in illumi- nating gas, and can be prepared by the action of hydriodic acid upon erythrite ; it is isomeric with Caoutchin (obtained by the dry distillation of caoutchouc). Pyrroly- lene, C4Hg, from pyrrolidine, is probably identical with the butine from erythrite. (See Pyrrolidine, and also B. 18, 2077.) Piperylene, CgHg, = CH2 = CH — CHq— CH^CHg, is a hydrocarbon obtained from piperidine. (B. 16, 2059.) Isoprene, Hemi-terpene, Valerylene, CgHg, B. Pt. 38°, is another hydrocarbon closely related to the terpenes, into which it goes by polymerization. (See limonene.) Di-allyl or Hexine, C^E^o, = CH2 = CH— CHo— CH2— CH^CH.,, is got from allyl iodide and metallic sodium; B. Pt. 59 . Has a penetrating ethereal and radish-like odour. Gives no metallic compounds. Conylene, C8H14, (probably Iso-propyl-piperylene), B. Pt. 125"^, is pre- pared from Conine. (B. 14, 710.) The higher hydrocarbons of this series, containing 12, 14, 16, and 18 atoms of carbon in the molecule, have been prepared by Krajft from the corresponding olefines, according to method 2. Isomeric with these hydrocarbons are certain hydro-derivatives of aromatic hydrocarbons, e.g. tetra-hydro-xylene, C8FT14 ; deca-hydro- naphthalene, CjoHig. (See Aromatic Compounds.) D. Hydrocarbons, C,,!!^,,.^ and C^Ho,,.^. Among the hydrocarbons still poorer in hydrogen may be mentioned — 58 II. HALOID SUBSTITUTION PI101)U(JTS. a. CnH2n-4: Pirylene, Cr^U^ (from pipcridine. B. 15, 1024.) The homologues of this have received the termination "one," e.g. Hexone. GJI^n-e' Di-acetylene, C4H2, = CH=C— C=CH. This is prepared by heating the ammonia salt of di-acetylene-di- carboxylic acid, (see this), with ammoniacal copper solution, whereby it is transformed into the Cu-com pound of di- acetylene, and then warming this with potassium cyanide. It is a gas of a peculiar odour, which yields a violet-red copper compound and a yellow silver one, the latter exploding upon bein^ rubbed, even when moist. {Baeyer^ B. 18, 2269.) Di-propargyl, C,H„ - CH=C— CH^— CH^— C=CH, is obtained by the addition of bromine, 2Br2, di-allyl, CgH^Q, 4 molecules HBr separating; B. Pt. 85°. It gives copper and silver compounds, and takes up 8 atoms of bromine, etc. It possesses an especial interest from being isomeric with benzene. Likewise isomeric with the latter is the hydrocarbon CH3— C=G— Ce^C— CH3. (B. 20, R. 564). TropiUdene, C7H8, B. Pt. 114", from Tropine. (A. 217, 133.) II. HALOID SUBSTITUTION PRODUCTS OF THE HYDROCARBONS. (See p. 20 and Table, p. 60.) A. Halogen Derivatives of the Paraffins. General Properties. — Only a few of these compounds, e.g, CH3CI, C2H5CI, and CHgBr are gaseous at the ordinary tem- perature, most of them being liquid, and those with a very large number of carbon atoms in the molecule solid. Such also as contain a large number of halogen atoms, e.g. CI4, CgClg, are solid ; among these come first the iodine compounds which, under similar conditions, also possess considerably higher boiling points than the analogous bromine compounds, and these again higher than the chlorine ones ; for instance, C2H5I, B. Pt. 72^ C^H.Br, B. Pt. 39°, and C^H.Cl, B. Pt. \2\ Under comparable conditions, the boiling points of the iodides lie, for each atom of halogen, about 50°, (40°-60°), and those of the bromides about 22°, (20°-24°), above those of the chlorides. The lowest members of the series have, in the liquid form, TT. ITALOTD SUr.STI'rU'l l( )N IMIODIKJTS. 59 at first a higher specific gravity than water, ejj, Cll.jl, Sp. Gr. 2-2, C^ti'jl^'^*? ^P- With increasing carbon, however, they become more Hke the paraffins, the influence of the halogen diminishing, and consequently lighter than water. The halogen substitution products of the hydrocarbons are almost or quite insoluble in water, but easily soluble in, and therefore miscible to any extent with alcohol and ether, and also soluble in glacial acetic acid. They often possess a sweet ethereal odour, but this becomes less marked with diminishing volatility. Most of them are combustible ; thus methyl- and ethyl chloride burn with a green-bordered flame, while ethyl iodide and chloroform can only be set fire to with difficulty. Many members of the series containing 1 or 2 atoms of carbon produce insensibility and unconsciousness when inhaled, e.g. CHCI3, C^HgClg, C^H^Br, and C^HCl,. In all these compounds the halogen is more firmly bound than in inorganic salts, so that, for instance, when silver nitrate is added to an alcoholic solution of the chlorine com- pound, e.g. chloroform, it causes no precipitation of AgCl. Nevertheless, the halogen is in most cases easily exchangeable for other elements or groups, a circumstance of the utmost importance for many organic reactions. This is especially true for the iodine and bromine compounds, wliich react more readily than the chlorides, and, on account of their lesser volatility, are easier to work with ; thus CgH^Br reacts with AgNOg at the boiling temperature, and CgH^I in the cold even. In all halogen compounds, the halogen can be again replaced by hydrogen by backward substitution, e.g. by Na amalgam, by zinc dust and hydrochloric or acetic acid, or by heating with hydriodic acid. (See p. 37, B, 1.) Of fluorine compounds, only a few are known as yet ; CH3F and C2H5F are gases. Modes of formation. — 1. By Substitution. Chlorine and bromine act for the most part as direct substituents, (see p. 35.) With the gaseous hydrocarbons their action even in the cold is an extremely energetic one, {e.g. chlorine mixed with methane easily causes an explosion, so that dilution with COg is necessary) ; the higher members require to be heated. 60 II. ILVLOIB SUJISTITUTJON PRODUCTS. m O < o o p:^ ft >H M W H O H O P O o H H O ^ .2^1 <1 .2:3 S 3 O OO pq p^ pq Ph pq 6 o .J^' .O S Q pq o Wi-H h-i " l-H HH O OOO^ o S 3 2 O CI Oi S g OS- ^ ^ riO o ooooo (M T# tH (M Ci (Ml-* r-H CO I ^ p 3 _0 ^ ^^^^^ O M hH « CO W M W ooo 3 -^^ ^ M W W CI CI c^ 000 — ' — ^ - ., e.g, nary, itylj op 0 0 Ph ^ 0 m ^ >,cq , isomers of Normal iodide, Iso-prop^ isomers of 1. Norma 2. Iso-pri 3. Second 4. Tertiai iodide, 0 1 07 r 0 1 Q I o ?i S ^ V d X O . CD M C M HH 03 l-H Ol-H^O 00 o MODKS OF FORMATfON. 6] The first halogen atom enters most easily into the compound, the substitution becoming more diliicult as the number of those atoms present increases. In the case of the higher hydrocai'bons there usually result two isomeric mono-substitution products. The action of the halogens is further facilitated by sunlight, and by the presence of iodine, this latter acting as a carrier of chlorine by the alternate forma- tion of ICI3 and ICl, thus: IClg^ICl + Clg. Antimony pentachloride and similar chlorides act in the same way, and also ferric chloride, this last being eminently suitable for brominating or iodating. (B. 18, 2017 ; A. 231, 195.) When it is wanted to chlorinate completely, the sub- stance in question is repeatedly saturated with chlorine in presence of iodine, and heated in a tube to a high temperature. From methane are formed the whole series of substitution products up to CCI4. Ethane first yields ethyl chloride, CaHgCl, then ethylidene chloride, C2H4CI2, and so on up to C2CI6. From propane is first produced normal propyl chloride, C3H7CI, and finally CgOg. The latter decomposes, upon vigorous chlorination, first into CgCle and CCI4, and the perchloro -ethane subsequently into 2 molecules CCI4. On chlorinating butane and the higher hydrocarbons strongly, an analogous splitting up of the molecule is effected. CBr4 and other similar compounds are transformable into bromo -derivatives of benzene. Iodine seldom acts as a direct substituent, since by this reaction hydriodic acid would be formed, which would then substitute backwards. (See p. 37.) To induce the action therefore, the HI formed must be removed by HIO3 or HgO. The iodine substitution products of the hydrocarbons are usually prepared indirectly, (according to 2 or 3). 2. From Unsaturated Hydrocarbons. These combine readily with halogen or halogen hydride. (See p. 47.) It stands to reason that no methane derivatives can be formed in this way. Ethylene gives with hydrochloric, hydrobromic, and hydri- odic acids, ethyl chloride, etc., i.e. mono-substitution products of ethane; with chlorine, etc., it gives di-substitution products. The compound C2H4CI2, obtained by the action of chlorine, is called ethylene chloride, and is isomeric with the ethylidene chloride got by the further chlorination of C2H^C1. (For an explanation of this isomerism, see p. G7.) Propylene combines with hydriodic acid to isopropyl 62 II. HALOID SUBSTITUTION PRODUCTS. iodide, CyH-I, which is reconverted into propylene by separa- tion of HI. But the same propylene results from a compound isomeric with isopropyl iodide, viz., normal propyl iodide, (and also, of course, from the above mentioned normal propyl chloride), by the splitting off of hydriodic (or hydrochloric) acid, so that by this reaction normal propyl iodide can be transformed into isopropyl iodide. (See p. 65.) From the three butylenes there result similarly two butyl iodides, viz., secondary and tertiary, which, as well as the two other exist- ing butyl iodides, yield these butylenes again with alcoholic potash ; in this way the two last-mentioned butyl iodides are convertible into their isomers, the two first, (see p. 66). A study of the constitution of the compounds formed, shows that in these addition reactions the halogen invariably affixes itself to that carbon atom with which are combined the smallest number of hydrogen atoms, e.g, CH3— CH=CH2 + HI = CH3— CHI— CH3, {not CH3— CH2— CH2I) ; from C3H^X onwards therefore, there result only ^' secondary " and tertiary " ^ compounds. 3. From Compounds containing oxygen. (a) From the alcohols C^Han+iOH. In these the OH is readily exchangeable for chlorine, bromine, or iodine by the action of halogen hydride,! thus : C2H5OH + HBr = CaH^Br + HgO. In the action of these acids a state of equilibrium is reached, since the above reaction can go on in exactly the opposite direction ; it is therefore necessary either to use a large excess of halogen hydride, (e.g. to saturate with the gas or to heat in a sealed tube), or to remove the water formed, by sulphuric acid, zinc chloride, etc. * The names "primary," "secondary," and "tertiary" compounds are founded upon those of the alcohols— primary, secondary, or tertiary — in question, from which they can be prepared according to method 3. t In such exchange the halogen takes the place of the hydroxy], so that the constitution of the haloid product corresponds with that of the alcohol used. MODES OF FORMATION. G3 Methyl- and ethyl chlorides are easily prei)ared by distil- ling the corresponding alcohol with common salt and snlpl)uric acid, or by leading hydrochloric acid gas into the warmed alcohol containing half its weight of zinc chloride in solution, [Groves), The chlorides of phosphorus are also applicable for the sub- stitution of OH by 01, since they react in the same way with alcohols as with water, thus. : POI3 + 3HOH = P(OH)3 + 3H01. POI3 + 3O2H5OH = P(OH)3 + 302H50h Phosphorus pentachloride is most frequently used for this purpose, going as a rule into the oxychloride : POI5 + O2H5OH = C2H5OI + HOI + POOI3. Phosphorus oxychloride itself is also sometimes employed. Of especial importance here is the application of the halogen compounds of phosphorus in the production of bromine and iodine compounds. The former need not be prepared before- hand, the end being achieved by gradually bringing phosphorus and iodine or bromine together in presence of the alcohol : 3OH3OH + P -1- 31 - 3OH3I + H3PO3. (&) From the polyatomic alcohols, halogen substitution pro- ducts are also obtained, e.g. tri-chlorhydrin, O3H5OI3, from glycerine, 03H5(OH)3, and POl^; isopropyl iodide, OgH^I, or allyl iodide, O3H5I, from glycerine and HI, i.e. I and P, according to the conditions of the experiment (see p. 65) ; hexyl iodide, OgH^gl, from mannite, 0(5Hg(0H)g and HI, the latter acting here as a reducing agent also. (c) From aldehydes and ketones, (see these), j^i-chloro-substitution products result by the action of FClg, e.g. ethylene chloride, C2H4CI2, from aldehyde, C2H4O ; acetone chloride, CgHgClg, from acetone C^H^O. Halogen substitution products are also occasionally prepared from acids by the exchange of 0 and OH for three CI atoms. 4. Ohlorine and bromine compounds are frequently formed from the corresponding iodine or bromine ones by driving out the weaker halogen from its combination by the stronger one, e.g. isopropyl bromide from the iodide, or methylene bromide from methylene iodide. Oonversely the chlorine and bromine 64 II. HALOID SUBSTITUTION PRODUCTS. compounds may be transformed into the iodine ones by heating with sodium iodide (in alcoholic solution, see B. 18, 519), potassium iodide, dry calcium iodide (B. 16, 392), or with fuming hydriodic acid. 5. For special modes of formation, see the compounds CH3CI, CHClo, and CHI3. Mono-substitution Products. Methyl chloride, CH3CI, {Dumas and Feligot, from CH^O, 1836). Prepared from methyl alcohol, ZnCl2, and HCl (see p. 62); also by distilling the "vinasse'' of the sugar manu- factories, and heating the tri-methylamine hydrochlorate obtained to 360°, (Vincent). Colourless gas with an ethereal odour. B. Pt. 23°. Slightly soluble in water (4 volumes in 1 volume water), but more easily in alcohol. Is used for the production of artificial cold, for extracting perfumes from flowers, and for methylating dyes in the colour industry. Burns with a green-bordered flame. Methyl bromide, CHgBr, (Bunsen, from cacodyl compounds, 1844). Prepared from methyl alcohol, P and Br. B. Pt. + 4*5° ; Sp. Gr. 1*73 at 0° ; has a pleasant ethereal odour similar to that of methyl chloride and of chloroform and a burning taste, and burns with difficulty, with a greenish-brown flame. Methyl iodide, CH3I, (Dumas and Peligot), Prepared from methyl alcohol, P and I. B. Pt. 44° ; Sp. Gr. 2-27 at 25°. Is not easily set fire to. When it is heated with 16 volumes of water to 100°, methyl alcohol and hydriodic acid are pro duced. Ethyl chloride, G^fj\ (Basilius Valentinus : " Spiritus salis et vinis," or sweetened alcohol"). Prepared by the action of CI on CgHg, (Schorlemmer ; cf. p. 40). For Groves' method (1874), see p. 63. Is formed as a bye-product in the manufacture of chloral. Easily compressible gas; B. Pt. + 12°. Burns with a green-bordered flame. Can be easily preserved in alcoholic solution (1 : 2). Ethyl bromide, C^H^Br, (SeruUas, 1827). Prepared from METHYL AND ETHYL CHLORIDES, ETC. 65 alcohol with P and Br, or with KBr + H2SO4. Burns with a beautiful green smokeless flame, emitting bromine vapours. Ethyl iodide, C2H5I, (Gay-LussaCj 1815). Is best prepared from 90 per cent, alcohol, P and 1. Colourless liquid with a peculiar ethereal smell, somewhat resembling that of leeks. B. Pt. 72° ; Sp. Gr. 1-94. Almost insoluble in water, but mis- cible with alcohol and ether, and difficult of ignition. Heated with water to 100°, it is converted, analogously to methyl iodide, into C2HgO and HI. Chlorine converts it into C2H;^C1, and bromine into C2H5Br. When exposed to light, iodine separates with formation of C4H^q. It is used for inhalation in cases of asthma. Of Propyl chloride, -bromide, and -iodide, CgH^X, two isomers each exist, the normal propyl and the isopropyl com- pounds, the former boiling at a somewhat higher temperature than the latter. To the normal compounds the constitutional formula CH3 — CHg — CHgX is ascribed, and to the iso-com- pounds the formula CH3 — CHX — CH3, since they are derivable respectively from normal propyl alcohol and from isopropyl alcohol or acetone, substances whose constitution is easily arrived at. According to theory only these two cases are possible, since propane contains but two kinds of hydrogen atoms, viz.: — (1) six combined with the end carbon atoms, and (2) two combined with the middle ones. For the transformation of the normal into the iso-compounds, see p. 62. Normal propyl chloride, see p. 61, also table, p. 60. Normal propyl bromide only goes partially into isopropyl bromide at 280°, but when heated with AlgBr^ the transfor- mation is direct, an intermediate Al-compound being formed [KekuUy Schr otter). Isopropyl iodide is prepared from glycerine, phosphorus, and iodine (see p. 63) ; allyl iodide is formed as intermediate product, and at the same time some propylene : C3H,(OH)3 + SHI = = C^H,! + 1^. C3H5I + HI =C.^, + \. C8H5l + 2HI = CyHjI + i2. (600 ) E 66 II. HALOID SUBSTITUTION PRODUCTS. Normal propyl iodide is got from the alcohol. The Butyl-haloid compounds, O^H^X, are already known each in four isomeric forms, which in part differ materially from one another in boiling point, (up to 30°). As a matter of fact four isomers are theoretically possible. Thus from normal butane are derived : (a) CH3-CH2— CH2— CH2I, and {b) CH3— CHg— CHI— CH3. Normal butyl iodide. Secondary butyl iodide. In these hydrocarbons also there are two kinds of hydrogen atoms, [a) those connected with the end, and {b) those with the middle carbon atoms. From tri-methyl-methane, CH = (0113)3, are similarly derived The constitution of these four compounds follows, among other reasons, from those of the four corresponding butyl alcohols, (p. 84), from which they can be prepared by the action of halogen hydride (HI). As regards the transformation of a into its isomer b, and of c into d, see p. 62. Isobutyl bromide changes into the tertiary compound by simple heating to 230°-240°, which is to be explained by the inter- mediate formation of butylene. The Isobutyl compounds are the easiest to prepare, (from isobutyl alcohol). The Tertiary readily react with HgO to form the alcohol and halogen hydride, this taking place even in the cold in the case of the iodide. For the constitution of tertiary butyl iodide, see also p. 43. Of the Isomers, CgHi^X, e.g. amyl chloride, eight are theoretically possible. Six chlorides are actually known. Of special interest are iso-amyl chloride, bromide, etc., compounds which are obtained from iso-amyl alcohol, and to which the constitution (CH3)2=CH — CHg — CH2X is assigned. Further, analogous compounds with from 6 to 12 and even more, e.g. 16 and 30, carbon atoms are known. A secondary hexyl iodide, CH3 — (CH2)3 — CHI — CH3, is got from mannite or dulcite with HI and P. Cetyl bromide and -iodide, CjgHggBr and C16H33I, are liquids which solidify at a moderate temperature. {Linnemann,) (c) ^^s^cH-CH^X, Isobutyl iodide. (Wurtz.) and 2. Di-substitution Products. Methylene chloride, CHgClg, Methylene bromide, CHgBrg, and Methylene iodide, CH2I2, are colourless liquids which one obtains either from the tri-haloid substitution products ETHYLENE AND ETHYLIDENE COMPOUNDS. 67 by backward substitution, or from the mono-substitution products by the introduction of more halogen. (See table, p. 60 ) The compounds C2H4X2 are known in two isomeric forms, to which are assigned the constitutional formulae : CH^X— CH^X and CH3— CHX^. Ethylene compounds. Ethylidene compounds. The former result from the addition of halogen to ethylene, or from the action of halogen hydride or halogen phosphorus upon glycol, C2H4(OH)2, (see this). Ethylene chloride, C2H4CI2, (oil of the Dutch chemists, 1795), B. Pt. 84\ Ethylene bromide, G^R^Br^, (Balard), is prepared by lead- ing ethylene into cold bromine, and has a pleasant odour like that of chloroform. M. Pt. +9° ; B. Pt. 131° ; Sp. Gr. > 2. CrystaUizes in the cold. Yields glycol, C2H4(OH)2, upon prolonged heating with excess of water to 100°, or with K2CO3. Ethylene iodide, C2H4I2, is solid and easily decomposable. These compounds yield acetylene with alcoholic potash, and are transformed into glycol by exchanging their halogen atoms for hydroxyl. Now, from the relation of the latter to glycol chlorhydrin and mono-chloracetic acid, it has the con- CH2— OH stitution • ; consequently in ethylene chloride, etc., CHg — OH the two halogen atoms are combined with different atoms of carbon. The following forms more special proof of the above statement : Ethylene chloride can, by exchange of CI for OH, be transformed into glycol chlorhydrin, (which is also formed from glycol and HCl), and this can then be oxidized to mono-chloracetic acid, C2H3CIO2 = CH2CI— COOH, (see this). Since in the latter the OH and CI are bound to different carbon atoms, the same must be the case in glycol chlorhydrin, and also, for the CI atoms, in ethylene chloride. The Ethylidene compounds are obtained from aldehyde, (para-aldehyde), by exchange of the oxygen for halogen by maans of phosphorus chloride, etc. 68 II. HALOID SUBSTITUTION PRODUCTS. Ethylidene chloride, also called ethidene chloride, is, how- ever, most conveniently prepared with phosgene, COCI2, thus : CH3— CHO + COCI2 = CH3- CHCI2 + CO2. It is also formed by the further chlorination of C2H5CI, and is a bye-product in the manufacture of chloral. Its boiling point (57°) is lower than that of ethylene chloride (84°). It is an anaesthetic. Propylene chloride, etc., CgHgClg, -Brg, -I2, are likewise known. They result partly upon the addition of halogen to propylene, and have then an unsymmetrical constitution, e.g. propylene chloride, CH3— CHCl— CH2CI. Isomeric with them are the symmetrically constituted Trimethylene derivatives, of which tri-methylene-bromide, CIl2Br — CHg — OHgBr, results from the addition of hydrobromic acid to allyl bromide : CHa^CH— CHgBr 4- HBr = CHaBr— CHg— CHaBr. 3. Tri-substitution Products. Chloroform, CHCI3, (Liehig and Soubeiran, 1831 ; formula established by Dumas ^ 1835.) Formation. 1. From methane and methyl chloride, (see p. 59). 2. By heating alcohol with chloride of lime and water. 3. Along with alkaline formate by warming chloral or chloral hydrate with aqueous alkali : CCI3— CHO + NaOH = CHCI3 + HC02Na. This last method of formation is the best for the obtaining of pure chloroform. Its formation from alcohol and bleaching powder, i.e. by the action of chlorine upon alcohol, may be considered to rest upon the intermediate production of chloral. Properties. Colourless liquid of a peculiar ethereal odour and sweetish taste. Hardly soluble in water. Solid below -70°. B. Pt. 61-2°. Sp. Gr. 1*527. Dissolves fats, resins, caoutchouc, iodine, etc. Is a most valuable anaesthetic, {Simpson, Edinburgh, 1848). The carbamine reaction (see Iso-nitriles) furnishes a delicate test for the presence of chloroform. BTIOMOFOIIM ; lODOFOIlM. 69 Beactionft, Alkaline cliroinatc; produces phosgene. Potassium amal- gam induces the formation of acetylene. Potash decomposes it to formate and chloride, thus : CHCI3 + 4K0H = HCO2K + 3KC1 + B.fi. Ammonia at a red heat produces hydrocyanic and hydrochloric acids: CHCI3 + NH3 =: HCN + 3HC1. Bromoform, CHBrg, is sometimes present in commercial bromine. Iodoform, CHI3, (SeruUas, 1822 ; formula established by Dumas), is prepared by warming alcohol with iodine and alkali or alkaline carbonate : C2H5OH + + 6K0H = CHI3 + HCO2K + 5KI + 5H2O. It can also be got in the same way from acetone, aldehj^de, lactic acid and, generally, from compounds which contain the group CH3— CHOH— C, or OH3— CO— C, (Lieben). Yellow hexagonal plates. M. Pt. 119° Contains only 0 25 per cent. H, which at first caused the presence of the latter to be overlooked. Has a peculiar odour, and is volatile with steam. Important antiseptic. Methyl- chloroform, CH3 — CCI3. This compound, the trichloride of acetic acid, also acts as an anaesthetic. Glyceryl chloride, t/ri-chlorhydrin, C3H5CI3, is obtained from glycerine and PCl^ (p. 63). B. Pt. 158°. The corre- sponding bromine compound is also known, but not the iodine one, C3H5I3, which decomposes in the nascent state (i.e. when glycerine, phosphorus, and iodine react together), into allyl iodide, C3H^I, and I2. (See pp. 63 and 65.) 4. Hig'her Substitution Products. Carbon tetra- chloride, CCI4. Can be prepared from chloroform or carbon bisulphide and chlorine. Colourless liquid. B. Pt. 77°. Carbon tetra-bromide, CBr4. Plates. Boils without decomposition. Carbon tetra-iodide, CI4. Dark red octahedra. Decomposes upon heating. Per-chloro- ethane, C^Of^. Rhombic plates of camphor-like odour. Melts and boils at 185". B. — Haloid Derivatives of the Unsaturated Hydrocarbons. These compounds are obtained either by partially withdraw- 70 III. MONATOMIC ALCOHOLS. ing halogen or halogen hydride from the halogen derivatives of the saturated hydrocarbons, or by incompletely saturating the hydrocarbons poorer in hydrogen with halogen or halogen hydride, e,g, C^H^Brg-HBr^CgHgBr. C2H2 +HBr = C2H3Br. The allyl compounds, C3H5X, result from allyl alcohol and halogen hydride or halogen-phosphorus. These unsaturated products are very similar to the corre- sponding saturated ones, but they are of course capable of combining further with halogen or halogen hydride. The following among them may be mentioned : — Bromo-ethylene, vinyl bromide, CgHgBr, = CH2=CHBr. Allyl chloride, -bromide, and -iodide, GR^=GR — CH2X. These are of importance on account of their relation to the allyl compounds found in nature, e.g. oil of mustard and oil of garlic. The iodide is prepared from glycerine, phosphorus, and iodine, and from it, by means of HgCl2, the chloride. Isomeric with them are the a-Propylene compounds, CH2 = CX — CHg, and the /^-Propylene compounds, CHX = CH-CH3. Per-chloro-ethylene, C2CI4. Colourless liquid. B. Pt. 121°. Mono-clilor-acetylene, CgHCl. Gas which catches fire spontaneously. Mono-"brom-acetylene, CgHBr. Also a spontaneously inflammable gas, which burns with a purple coloured and exceedingly sooty flame. Halogen compounds which contain several different halogens are also known. III. MONATOMIC ALCOHOLS. As alcohols are designated those compounds containing oxygen and of neutral reaction, which, like bases, combine with acids with the elimination of water, to form other compounds analogous to salts in constitution, the latter being termed ethers " or " compound ethers," thus : C2H5OH + NO2OH = C2H,.(aN02) + H20. Alcohols are further easily transformable by oxidation into IMEYSTCAL rilOPERTIKS. 71 compounds riclier in oxygen or poorer in hydrogen, (aldeliydes, ketones, and acids) ; they do not undergo sul)stitution hy the action of halogens, but oxidation, etc., etc. According to theory, the alcohols are derived from the hydrocarbons by the replacement of hydrogen by hydroxyl. (See pp. 17 and 74.) Just as we know mono- and poly-acid bases, so are there mono-, di-, tri-, etc., hydric or -atomic alcohols, according to the number of molecules of a monobasic acid which can react with one molecule of the alcohol to form an ether. The poly- atomic alcohols, e.g. glycol, G^JiOll),^^ glycerine, C3H^(0H)^, mannite, CgHg(0H)(5, etc., will be treated of later on. The monatomic alcohols are likewise either saturated or unsaturated, according to the hydrocarbons from which tliey are derived. The unsaturated resemble the saturated closely, excepting in that they are capable of forming addition com- pounds. A. Monatomic Saturated Alcohols, C^H^n+iOH (See Table, p. 72). The lowest members of this series are colourless mobile liquids, the middle ones are more oily, and the highest — from dodecyl alcohol, C12H25OH, onwards — are solid and like paraffin in appearance at the ordinary temperature. Gaseous alcohols are unknown. With analogous constitution the boiling point rises with tolerable regularity ; in the case of the lower members by about 19°, and higher up in the series by a smaller number.' The lowest members are miscible with water, but this solubility rapidly diminishes as the series ascends ; thus butyl alcohol requires 12 parts and amyl alcohol 40 parts of water for solution, while the higher members are no longer soluble in water. The former can be separated or "salted out" from their aqueous solution by the addition of salts, e,g, KgCOg and CaClg. The specific gravity is always < 1 The highest members, (over Cjg), can only be distilled undecomposed in a vacuum ; at the ordinary pressure they break up into olefine and water. III. MONATOMIC ALCOHOLS. !>• lO r-H CO C5 »0 C5 i-H rH ^ '-H «— t (M f-H PI W W M S W 05 (M t-- 00 05 r-( o o o o o o o o o o i ft P o o o A o I wo u?0 W I o A I OO ooo ooooo o p '-^ «^ ^ S o I- _, ^ H Ph c4 pq rH* I— I CO ^' 2 ^ Co O) " — t e« s a =^ O 5-1 _ O . PRIMARY, SECONDARY, ANT) TK.RTFAUY ALCOHOT.S. 73 The lowest members poss<'Ss an alcoholic odour, those over Cg, an odour of fusel, and both liave a burning taste, while the highest members are like paraffin in appearance and without either taste or smell. Constitution and Isomers; Classification of the Alcohols. From CgHgO on, many of the alcohols are known in different isomeric modifications, thus there are two propyl, four butyl, and seven amyl alcohols, etc. Of these, some only are oxidizable to acids, CnHsj^Og, contain- ing an equal number of carbon atoms, an aldehyde, Ci^HonO, being formed as intermediate product. Such alcohols are termed primary alcohols, (primary propyl-, butyl-, and isobutyl alcohols, etc). Another class of alcohols is not oxidizable to acids with an equal number of atoms of carbon, but to ketones, C,iH2hO, with separation of two atoms of hydrogen, e.g. isopropyl alcohol yields acetone, CgHgO. These are termed secondary, (secondary butyl alcohol). Upon further oxidation the ketones do indeed yield acids which, however, contain not an equal but always a lesser number of carbon atoms, the carbon chain having thus been broken up. Lastly, the third class of alcohols, the tertiary, yield upon oxidation neither aldehydes, ketones nor acids with an equal number of carbon atoms, but only ketones or acids containing fewer atoms of carbon. Constitution of the Alcohols. — In the monatomic alcoliols one of the hydrogen atoms plays a part different to that of the others ; thus it is replaceable by metals, (K and Na), and by acid radicles, and, together with the oxygen atom, com- bines with the hydrogen of a halogen hydride to form water, while the other hydrogen atoms of the alcohol remain un- changed. This hydrogen atom, which has already been formulated under the Theory of Types apart from the others, is called the " typical " or " extra- radicle " hydrogen atom. It is not joined directly to the carbon atom but 74 HI. MONATOMIO ALCOHOLS. through the oxygen one, which is apparent from the fact of the alcohols being capable of preparation from the monohaloid substitution products of the saturated hydrocarbons. (See p. 75.) This has been already gone into in some detail for ethyl alcohol (p. 17). The alcohols therefore contain a hydroxyl, OH, and their general constitutional formula is (CnH2„+i).0H. According to theory, this hydroxyl can either replace an atom of hydrogen in a methyl group, in which case an alcohol containing the group CHgOH, (one carbon atom being joined to the other by a single bond), results, e.g. CHg— CHgOH. Or it can replace the hydrogen of aCH2 — group in a hydro- carbon, so that the resulting compound contains the atomic group — CH.OH, the carbon atom being here joined to two other ones. Or, lastly, it is possible that in a hydrocarbon with branching carbon chain, the hydrogen of a methine group CH= (p. 23) may be replaced by hydroxyl, when the result- ing compound consequently contains the group =C.OH, in which one carbon atom is joined to other three. Now, it is easy to see that the group — H further oxidation, be transformed into this other, — The latter, which is termed carboxyl, is contained in the acids C^HsiiOa, = Cn_iH2n_iC00H, which result from the oxidation of the primary alcohols. Consequently it is the primary alcohols which contain the atomic group — CHg.OH. The group =011. OH can likewise be changed into =0=0, (i.e. C<^Qj^ -H20^, which is the characteristic atomic group of the ketones, by oxidation. A further introduction of 0 or OH, whereby acids containing the group — CO. OH would ensue, is not possible in this case without a rupture of the carbon chain, since carbon is tetravalent. Since then it is the secondary alcohols which upon oxidation yield ketones, and not acids with an equal number of carbon atoms, the group = CH.OH is characteristic of these. MK/IHODS OF FORMATION. 75 Finally, the atomic group =C.OH already contains the maximum of oxygen which can be combined with a carbon atom already linked to three other atoms of carhon. A com- pound, therefore, in which this atomic group is present, cannot yield upon oxidation an aldehyde, acid, or ketone with an equal number of carbon atoms in the molecule, but the result of such oxidation must be the breaking of the carbon chain, and the formation of acids or ketones containing a lesser num- ber of carbon atoms in the molecule. This being the be- haviour of tertiary alcohols, the group =C.OH is peculiar to them. The existence of the three classes of alcohols finds in this way a thoroughly satisfactory explanation from theory. The secondary and tertiary alcohols were predicted by Kolhe in 1864 from theoretical considerations, (A. 132, 102). Among the isomeric alcohols the primary possess the highest, and the tertiary the lowest boiling points, and the same holds good for their ethers. The tertiary have the highest melting points. Occurrence. — Different alcohols are found in nature com- bined with organic acids as ethers in ethereal oils and waxes ; e.g. methyl-, ethyl-, butyl-, hexyl-, and octyl-alcohols, and also those with 16, 27, and 30 carbon atoms. /. General Methods of Formation. — 1. By" saponification" of their ethers (see these), by boiling with alkalies or acids or by the action of superheated steam, thus : CH3.O.C7H5O2 + KOH = CH3OH + C7H5O2.OK V ^ ^ ^ Salicylic methyl Potassium ether. salicylate. Some ethers, e.g, ethyl-sulphuric acid, decompose when simply warmed with water : C2H5.O.SO3H + H2O = C2H5.OH + SO4H2. 2, From the halogen compounds C,iH2,i4.iX, and therefore indirectly from the paraffins and olefines (pages 59 and Gl), in which latter case secondary or tertiary alcohols are obtained : a. By warming these, especially the iodides, with excess of 76 III. MONATOMIC ALCOHOLS. water to 100° ; sometimes by simply allowing the mixture to stand, (tertiary iodides) : CgH,! ^- HOH = C^H^.OH + HI. When but little water is used, a state of equilibrium is reached (p. 62). These halogen com])ounds may also be termed the halogen-hydride ethers of th-e alcohols, so that, strictly speaking, the mode of formation 2 is included in 1. b Frequently by digesting with moist silver oxide, (which acts here like the unknown hydroxide, AgOH), or by boiling with lead oxide and water : C^H.I + Ag.OH = C2H5.OH + Agl. c. Upon warming with silver or potassium acetate, the acetic ether of the alcohol in question is formed, and this is then saponified, thus : C^H J + AgO.(C2H30) = C2H,.O.C,H30 + Agl. C2H5O.C2H3O + HOK = C2H5.OH + (C2H30)OK. 3. By the fermentation of the carbohydrates, (e.g. grape sugar), the alcohols with 2, 3, 4, 5, and, under certain condi- tions, even 6 atoms of carbon are produced. (Yeast fermenta- tion.) 3a. From glycerine, by the schizomycetes fermentation, alcohols with 2, 3, and 4 carbon atoms are formed, [Fitz), 4. On treating the primary amines with nitrous acid,^ the nitrous ethers of the alcohols are got : C2H5NH2 + HONO = C2H5.OH + N2 + H2O. 5. From polyatomic alcohols by the partial action of halogen hydride and the backward substitution of the resulting com- po]inds, e.g. : C3H5(OH)3 -1- 2HC1 = C3H,(0H)C1, + 2H2O. Glycerine. Di-chlorhydrin. C3H5(OH)Cl2 + 2H2 = C3H7OH + 2HC1. Isopropyl alcohol. 11. Special Methods of Formation. — 1. Primary alcohols are obtained from aldehydes by reduction with sodium amalgam * For the sake of convenience, the formula of the hypothetical nitrous acid, NO2H, = NO. OH, is used instead of N2O3 + H2O. NOMKNCLATUllK ; BEIIAVIOUll. 77 and very dilute sulphuric acid, {Wurtz) ; or with acetic acid and zinc dust, the acetic ethers of the alcohols resulting here : Similarly from acid anhydrides and nascent hydrogen, or from a mixture of anhydride and acid chloride (see these), when the acid ether of the alcohol is formed. Since the acids can be sjaithetically prepared from alcohols containing one atom of carbon less than themselves, a means is thus given for con- verting one alcohol into another higher in series (Lieben and Rossi). 2. Secondary alcohols are formed by the action of nascent hydrogen (sodium amalgam) on the ketones, CnHgnO : Pinacones are obtained here as bye-products. (See Ketones.) 3. Secondary alcohols are further produced by the action of alde- hydes upon zinc-methyl or zinc-ethyl. 3a. Also by the action of zinc-alkyl upon ethyl formate. 4. Tertiary alcohols are formed by the prolonged action of zinc- methyl or -ethyl (2 mols.) upon acid chlorides in the cold, and decom- position of the resulting product with water, [BiUlerow). When the action is only a short one, ketones and not alcohols are got. 5. Secondary or tertiary alcohols sometimes ensue by the direct combination of an olefine with water, e.g. tertiary butyl alcohol, (0113)30. OH, from isobutylene. The Nomenclature of tlie alcohols, especially of the second- ary and tertiary, is based upon a comparison of them with methyl alcohol, also called carbinol. They are looked upon as carbinol, OH3.OH, in which the three hydrogen atoms are wholly or partially replaced by alcohol radicles, thus : tertiary butyl alcohol, (CH,.)3C.0H, = tri-methyl carbinol; secondary butyl alcohol, CH3— CH2— CH(OH)— CH3, = CH(OH)(CH3)(C2H5), = methyl-ethyl carbinol. Behaviour of the alcohols. 1. The typical hydrogen atom (p. 73) is replaceable by metals, e.g. directly by K or Na, with formation of compounds termed alcoholates ; C2H,0 + H, = C2HoO. C2H5OH + Na = C^HjONa + H. Sodium ethylate. 78 III. MONATOMIC ALCOHOLS. These decompose again into alcohol and alkali on addition of water. (See p. 83.) Primary and secondar}^ but not tertiary, alcohols combine with baryta and lime to alcoholates at 130°. Crystalline com- pounds are formed with calcium chloride, so that this salt cannot be used for drying the alcohols ; these compounds are decomposed by water. 2. They enter into the composition of many compounds, as alcohol of crystallization." (See pp. 79 and 83.) 3. They yield ethers with acids : C^H^OH + (C,H30)0H = C,H,.0.(C,H30 ) + H,0. Acetic acid. Ethyl acetate. 4. Dehydrating agents convert them into olefines. 5. With halogen hydride or halogen phosphorus, mono-sub- stitution products of the hydrocarbons are produced. (See p. 62.) 6. For the behaviour of primary, secondary, and tertiary alcohols upon oxidation, see p. 73. The oxidation of methyl alcohol yields mostly carbonic instead of formic acid, on account of the easy oxidizability of the latter. 6a. The higher primary alcohols go into the corresponding acids u^jon heating with soda-lime. 7. Halogens do not substitute but oxidize. (See above.) 8. The primary, secondary, and tertiary alcohols can also be distin- guished from one another by the behaviour of their nitro-compounds, which are formed by the action of silver nitrate on the iodides, ( F. Meyer). They vary also in the rate of rapidity with which etherification begins, and the point at which it ends, e.g. with acetic acid. Methyl alcohol, TFood Spirit^ CH3OH. Was discovered in wood tar by Boyle in 1661, and its difference from ordinary alcohol recognized in 1812 by Phillips Taylor. Its composition was established in 1834 by Dumas and Peligot. Name derived from [liOv^ wine, and vXt], wood. Occurrence. As salicylic ether in GauUheria procumhens (oil of winter green, Canada); as butyric ether in the unripe seeds of Heracleum giganteum. METHYL AND ETHYL ALCOHOLS. 79 Formation, 1. By chlorinating methane, CH^, and saponi- fying the resulting methyl chloride, (Berthelot), 2. From methyl iodide and water. 3. I3y the destructive distillation of wood. By this distillation there are obtained — (a) Gases (CH4, CgHg, C2H4, C2H2, CgHg, C4H8, CO, CO2, H5, etc.). (6) An aqueous distillate of *' pyroligneous acid," containing methyl alcohol, acetic acid, acetone, methyl acetate, allyl alcohol, etc. (c) Wood-tar, containing paraffins, naphthalene, phenol, guaiacols, etc. {d) Wood charcoal. 4. Also by the dry distillation of vinasse. It is prepared in quantity from the crude pyroligneous acid by repeated distillation after neutralization, and is purified by formation of the CaClg compound, which is stable at 100°, or, better, by transformation into the oxalic or benzoic ether, both of which are easy to purify and saponify. Properties. Colourless liquid. B. Pt. 66°. Sp. Gr. about 0*8. The alcohol of commerce usually contains acetone. Burns with a non-luminous flame. Dissolves fats, oils, etc. Acts as an intoxicant like ethyl alcohol and, like the latter, enters into the composition of compounds as " alcohol of crystallization, " e, g. BaO + 2CH4O ; Mg{\ + GCH^O ; CaClg + 4CH4O (six-sided plates). Is easily oxidized to formic aldehyde and formic acid, being also converted into the latter upon heating with soda-lime. Forms with metallic potassium the crystalline compound CH3OK + CH3OH. Potassium methylate, CH3OK, is a white crystalline powder. The anhydrous alcohol dissolves a small amount of de- hydrated cupric sulphate to a blue-green solution. Distilled over heated zinc dust, it decomposes almost quantitatively into CO + 2H2. Uses. — For tar colours— (also as CH3I and CH3CI) ; as methyl ether in the manufacture of ice ; for polishes and varnishes ; as WiggersheMs preservative liquid ; for methylating spirits of v^^ine, etc. Ethyl alcohol. Spirits of Wine, CgH^OH. Liquids con- taining spirits of wine have been known from very early times, and their concentration either by distillation or by dehydration with car- bonate of potash is also an old art. We read of it as " alcohol " in the 16th century. Lavoisier arrived at the qualitative, and de Saussure in 1808 the quantitative composition of alcohol. 80 III. MONATOMIC ALCOHOLS. Occurrence. In the vegetable kingdom alcohol is only found occasionally, as butyric ether, but in the animal kingdom it occurs in various forms, e.g, in diabetic urine. It is also pre- sent in small quantity in coal tar, bone oil, wood spirit, and bread, fresh English bread containing 0*3 per cent. Formation. 1. From CgHg by conversion into C2H5CI and saponification of the latter according to modes of formation 1 and 2. 2. From and cone. H2SO4. (See I., 1.) This method was discovered by Faraday, and corroborated in 1855 by Berthelot. 3. From aldehyde, C2H/3, by reduction. {Wurtz, A. 123.) 4. Preparation hy the vinous fermentation of sugar. Directly from grape and fruit sugars, CgH^gOe' indirectly from cane sugar, 0^2^22^11' ^^^r previous hydration to 2 mole- cules CgH-L20g ; also from malt sugar (directly), from starch, etc. Fermentations are peculiar slow decomposition-processes of organic substances which go on, as a rule, with liberation of gas and evolution of heat, and which are induced by micro-organisms or by unorganized ferments. (See Diastase.) Th.^ vinous fermentation of sugar, i.e. the fermentation which produces spirit, is caused by the yeast ferment, mycoderma (Torula) cerevisiae, which forms rather long round cells multiplying l)y germination, and which exists in different varieties. Being a plant, it requires for its sustenance inorganic salts, but, as a non-assimilating fungus, no carbonic acid. In the vinous fermentation 94 to 95 per cent, of the sugar breaks up into alcohol and carbonic acid : with 2*5 to 3-6 per cent, glycerine, CgHgOg, and 0*4 to 0-7 per cent, succinic acid, C^H^O^, as invariable bye-products. In addition to these, most of the higher homologues of ethyl alcohol are also formed, the latter being classed together under the name of fusel oil. The chief constituent of fusel oil is fermentation amyl alcohol (iso- butyl-carbinol), C5H11OH, but it has also been proved to contain the two propyl alcohols, (chiefly iso-propyl), normal-, iso-, and tertiary- butyl alcohols, normal and active amyl (methyl-ethyl) alcohols, together ETHYL ALCOHOL ; FERMENTATION. 81 with higher homologues and ethers. They can be separated by means of their hydrobromic ethers. Conditions of fermentation. Fermentation can only go on between the limits of 3° and 35°, the most favourable tempera- ture being between 25° and 30°. It is also dependent on the presence of a certain amount of air, and on the solution not being too concentrated. Yeast loses its activity upon the addition of any reagents which destroy the cells, also when it is thoroughly dried, when heated to 60°, when treated with alcohol, acids and alkalies, and in the presence of salicylic acid, phenol, etc. The following materials are used for the preparation of alcohol or of liquids containing alcohol : (a) Grape sugar, fruit sugar, i.e. grapes and other ripe fruits, for wine, etc. ; (h) cane or beet sugar and molasses for brandy (see Sugar) ; (c) the starch of cereals for beer and corn brandy, and of potatoes for potato brandy. The starch is first con- verted into malt sugar and dextrine under the influence of diastase, or into grape sugar, potato sugar, and dextrine by boiling with dilute acids, and these sugars are then fermented. A wine of medium strength contains to 10 per cent, alcohol, port wine 15 per cent., sherry up to 21 per cent., champagne 8 to 9 per cent., and beer an average of 2 to 6 per cent. The different varieties of brandy or spirits obtained by ** burning," i.e. by distilling fermented liquids, contain 30 to 40 per cent, alcohol, and cognac even over 50 per cent. Purification of alcohol. It is difficult to separate alcohol completely from water by distillation, since their boiling points are only 22° apart from one another. Even after repeated rectification the distillates are found to contain water. On the large scale this separation is excellently effected by the use of dephlegmators and rectifiers or column apparatus, which are based upon the principle of partial volatilization and partial cooling of the vapours, .(Adam and Berard ; improved hj Savalle, Pistorius, Coffey, and others.) In this way an alcohol containing 98 to 99 per cent, can be obtained. Aqueous alcohol can be deprived of the greater part of its water by the addition of strongly heated carbonate of potash or anhydrous copper sulphate, or by distillation over (506) F 82 III. MONATOMIC ALCOHOLS. quick lime, and the last portions can be extracted by baryta, or by several additions of metallic sodium and repeated distil- lation. Alcohol containing water becomes turbid on being mixed with benzene, carbon bisulphide, or liquid paraffin oil, and it gives a white precipitate of Ba(0H)2 on the addition of a solution of BaO in absolute alcohol. Alcohol free from water is termed absolute alcohol. Contraction takes place on mixing alcohol and water together, 53*9 volumes alcohol + 49*8 volumes water giving, not 103*7, but 100 volumes of the mixture. The percentage of alcohol in any spirit is determined either from its specific gravity by reference to a specially calculated table, or by areometers of particular construction, or by its vapour tension as estimated by Geissler's vaporimeter. Properties. Colourless mobile liquid with characteristic spirituous but not fusel smell. B. Pt. 78*3°, or 13° under 21 millimetres pressure. Solidifies at - 130*5°. Sp. Gr. 0*79 at 15°. Burns with an almost non-luminous flame. Is exceedingly hygroscopic, and miscible with water and with ether in all proportions. Forms several cryo-hydrates with water ( + 12Aq., + 3Aq., + ^Aq.). Is an excellent solvent for many organic substances such as resins and oils, and also dis- solves sulphur, phosphorus, etc., to some extent ; consequently it is much used in the laboratory. Gives with cone. H2SO4, according to the conditions, ethyl-sulphuric acid, ether, or ethylene. For its behaviour with HCl, etc., see p. 62. It diffuses through porous membranes into a dry atmosphere more slowly than water, and coagulates albumen, being therefore used for preserving anatomical preparations. It is very easily oxidized by the oxygen of the air, first to aldehyde and then to acetic acid, either in presence of finely- divided platinum or in dilute solutions containing nitrogenous matters ; thus, beer and wine become sour, but not the pure alcohol itself. K^Crfi^ or Mn02 + H2S04 oxidize it in the first instance to aldehyde ; fuming nitric acid attacks it violently with formation of nitrogen tri- and tetr-oxides, aldehyde, ethyl nitrite, and formic, oxalic and hydrocyanic ALCOHOL ; PROPYL ALCOHOL. 83 acids, but, by the action of colourless concentrated HNO3, ethyl nitrate can, without oxidation, be obtained ; in dilute solution glycollic acid is formed. Alkalies also induce a gradual oxidation in the air ; thus, alcoholic potash or soda solutions quickly become brown with formation of aldehyde resin, this latter resulting from the action of the alkali upon the aldehyde first produced. Alcoholic potash therefore frequently acts as a reducing agent, e.g. upon aromatic nitro- compounds. (See these.) Chlorine and bromine first oxidize alcohol to aldehyde and then act as substituents. (See Chloral.) Chlorinated alcohols can therefore only be prepared indirectly (cf. Ethylene chlorhydrin). When the vapour of alcohol is led through a red-hot tube, H, CH^, CgH^, C2H2, C2Hg, C^oHg, CO, C2H4O, C2H4O2, etc., are formed. Of the compounds containing alcohol of crystallization may be mentioned, KOH + 2C2HeO, LiCl + 4C2HeO, CaCl2 + 4C2H6O, and MgCl^ + 6C2HgO. Sodium Ethylate, C2H50Na, is of special importance among the alcoholates. It is formed by the action of sodium upon absolute alcohol. The crystals of C2H5.0Na + 2G^qO, at first obtained, lose their alcohol of crystallization at 200° and change into a white powder of CgH^ONa. Sodium ethylate is of especial value for syntheses, and can frequently be employed in alcoholic solution. When taken in small quantity alcohol acts as a stimulant and an aid to digestion, in larger quantity as an intoxicant. Absolute alcohol is poisonous, and quickly causes death when injected into the veins. Detection of alcohol. 1. By the iodoform reaction (see Iodo- form), when 1 part in 2,000 of water can be recognized. 2. By means of benzoyl chloride, CgHgCOCl, which yields with alcohol the characteristically-smelling benzoic ethyl ether. Propyl alcohols, C3H7OH. 1. Normal propyl alcohol, ethyl carbinolyGR.^ — CH2 — CH2OII, (Chancel, 1853), is obtained from fusel oil by means of its hydro- bromic ether (Fittirj), or directly by fractionation. It has also been got from propionic aldehyde and propionic anhydride by reduction with sodium amalgam (liossi). It is a liquid with a 84 III. MONATOMIC ALCOHOLS. pleasant spirituous odour, and boils 19° higher than ethyl alcohol. Miscible with water in every proportion, and again separated out on addition of chloride of calcium. Gives pro- pionic acid upon oxidation. Its constitution follows from that of propionic acid, and from the preparation of the latter from ethyl alcohol. 2. Secondary propyl alcohol, isopropyl alcohol, or dimethyl carbinol, (CH3)2=CH.OH, (Berthelot, 1855), was at first held to be primary. It is obtained from isopropyl iodide (from glycerine) by methods I. 2a and 2&, also by the action of sodium amalgam on acetone by method II. 2, (Friedel, 1862). It also results unexpectedly, instead of the normal alcohol, from normal propylamine by method I. 4, on account of the intermediate formation of CgHg. Colourless liquid. Boils about 15° lower than its isomer, and like it can be ^'salted out" from aqueous solution. Gives acetone upon oxidation. The constitution of isopropyl alcohol follows from its formation from acetone, whose constitution is CH3 — CO — CH3. Butyl alcohols, C^H^^OH. The four isomers which are theoretically possible are known. 1. Normal butyl alcohol, CH3— CH2— CH2— CH^OH. Present in fusel oil, being formed especially in the wine-yeast fermentation (by elliptical yeast). Is got rather easily from glycerine by the schizomycetes fermentation, (Fitz). Prepared from butyl aldehyde, butyric acid or butyl chloride, according to II. 1, {Lichen and Rossi, 1869). Boils 19° higher than normal propyl alcohol. Has a peculiar odour, and gives rise to coughing when inhaled. Is not miscible with water in all pro- portions, 1 volume requiring 12 volumes water for solution at the ordinary temperature. Can be salted out" from its solu- tion. Gives normal butyric acid, C^HgOg, on oxidation. Its constitution follows from its relation to the acid (see this), and from the preparation of the acid from normal propyl alcohol. 2. Secondary butyl alcohol, methyl-etliyl-carhinol, or hutyhne hydrate, ^|^5\>CH0H, = CH— 3CH,— CH(OH)— CH3. The hydriodic ether is formed from erythiite, C4Hg(OH)4, and HI {de Luynes), or from THE ITJGIIKll ALCOHOLS. 85 normal biitylene and HI, and is tlien sai)oiiified according to L 2. Tlie alcohol is also obtained from aldeliydc and zinc ethyl, according to IL 8, and from formic ether according to II. 4, {Sayl7:eJ/'). Strongly smelling liquid, boiling about 18° lower than the normal alcohol. Gives methyl-ethyl ketone upon oxidation, from which its constitution follows. 3. Isobutyl alcohol, or fermentation butyl alcohol, is the most important of the butyl alcohols. It is contained in fusel oil, (JFurtz, 1852), especially in potato fusel oil — (beer- yeast fermentation) — , and is best isolated from this as the iodide. Colourless liquid, with a spirituous fusel smell resembling that of wild jasmine. Boils about 8° lower than the normal alcohol. Yields isobutyric acid, C^HgOg, on oxidation, hence its constitution. 4. Trimethyl carbinol, or tertiary butyl alcohol, (0113)3 = 0. OH, {Butkrow, 1863). Is contained in small quantity in fusel oil. Prepared, e.g. according to II. 5, but more simply by the action of 75 per cent. H2SO4 on isobutylene, from isobutyl alcohol. (See II. 5.) Rhombic prisms or tables. Smell spirituous and resembling that of camphor. M. Pt. 23*5°; B. Pt. 33° below that of the normal alcohol. Yields ace-tone, acetic acid and carbonic acid on oxidation. Its consti- tution follows, for instance, from method of formation II. 5, and also from the constitution of tertiary butyl iodide. (Pp. 43 and 66.) Amyl alcohols, CgH^^OH. Theoretically eight isomers are possible, four primary, three secondary, and one tertiary, and seven of these are already known. cuUl. M ^-^--o-*^- /sti . 1. Normal primary amyl alcohol, CH3— CH2— CH2-CH2— CH2.OH, is contained in small quantity in fusel oil, and can be prepared from normal valeric aldehyde, (Liehen and Rossi), and from normal pentane, by formation of C^Hj-^Cl. 2. Isobutyl carbinol, (CH3)2=CH— CH2— CH^OH, {Erlen- meyer), forms the chief constituent of " fermentation amyl alcohol, "which was already known to Scheele, and is also found in nature in Eoman camomile oil. It was prepared synthetically ,from isobutyl alcohol in 1876 by the Lieben-Eossi method. M. Pt.-134°; B. Pt. 13r. Has a fusel smell and burning taste, and is poisonous ; causes the disagreeable toxic after- effects of intoxication by brandy, etc. 86 III. MONATOMTC ALCOHOLS. 3. Methyl-ethyl-carbinol, active am/yl alcohol, p t| ">CH — CH2OH, (Pasteur, 1855), is also contained in fermentation amyl alcohol. It turns the plane of polarization of light to the left, its chloride, bromide, iodide, and the valeric acid resulting from its oxidation being also optically active (dextro-rotatory). The action upon polarized light is connected with the presence of an "asymmetric" carbon atom. (See p. 31.) A dextro-rotatory modification of this alcohol, obtained from it by fission-fungus fermentation (p. 31) exists, its iodide being laevo-rotatory. Hexyl alcohols, Gaproyl alcohols, CgHjg.OH. Of these seventeen are possible, and eleven are already known. Normal primary hexyl alcohol, obtained from normal hexane and also from caproic acid, CgHi.202, is found in nature as butyric ether, e.g. in the essential oil of Heracleum sphondylium. Isomeric with it is primary fermentation hexyl alcohol from wine fusel oil. Heptyl alcohols, [Oenanthyl alcohol), C7H15OH Thirty-eight are possible, and, up to now, thirteen or fourteen are known. Octyl alcohols, Q^^jOTL. The normal octyl alcohol is found as acetic ether, together with hexyl alcohol, in varieties of Heracleum, etc. Normal Decyl alcohol, CioHgiOH, Dodecyl alcohol, O^^^b^H, Tetra- decyl alcohol, C14H29OH, Hexadecyl alcohol, CigHggOH, and Octadecyl alcohol, CigHg^OH, were prepared by Krafft in 1881, by reducing the corresponding acids with zinc dust and acetic acid. They are solid and like paraffin in appearance. Normal Hexa-decyl-alcohol, also called Cetyl alcohol, or Ethal, forms as palmitic ether the chief constituent of sper- maceti. The cetyl alcohol of commerce contains, besides, a homologous alcohol, CigHggO. Ceryl alcohol, cerotin, C27Hg50H, forms as cerotic ether Chinese wax. Melissic or Miricyl alcohol, CgoHgiOH or CgiHggOH, is present as pal- mitic ether in bees' wax and in Carnauba wax, and is most conveniently prepared from the latter. The alcohols are obtained from all these ethers (wax varieties) by saponification with boiling alcoholic potash. B. Monatomic Unsaturated Alcohols, CnHgn^iOH. These are very similar to the saturated alcohols both in physical properties and in general chemical behaviour, but are sharply distinguished from the latter by their capability of taking up 2 atoms of halogen or of hydrogen, or 1 molecule of UNSATURATED ALCOHOLS. 87 halogen hydride, and thereby forming saturated alcohols or their mono- or di-haloid substitution products. These latter, as already mentioned at p. 78, cannot be prepared by direct substitution of the alcohols. They thus behave in this respect like the olefines, CnHgn, and so the existence of a double carbon bond must be assumed in their case also. They are to be considered as olefines in which an atom of hydrogen is replaced by hydroxyl. According to theory, the existence of an alcohol with two carbon atoms, CHg^^CH.OH, (vinyl alcohol), might be predi- cated ] this, however, does not exist in the free state but only in its derivatives. By the reactions in which one would expect it to be formed, its isomer, aldehyde, CH3.CHO results ; in fact, the atomic group =:C=CH.OH does not appear to be capable of existence, but always goes into the more stable one =CH — CHO, which is explicable upon the assumption that water, H.OH, is taken up and again split off. Similarly, instead of the group CH2=(C0H) — GHg, we always get the other, CH3— CO— CH3. Allyl alcohol, C3H5.OH, = CH2=CH— CH^OH, {Caliours and Hofmanrij 1856). Present to the extent of 0*1 to 0*2 per cent, in wood spirit. Is formed (1) from allyl iodide ; (2) by re- duction of its aldehyde, acrolein (see this) ; (3) by heating glyce- rine, C3H5(OH)3, with oxalic or formic acid and some ammonium chloride to 260°. This last reaction appears to be a reduction process, thus, C3Hg03 - - 0 = C3HgO ; as intermediate product, however, a formic ether of glycerine (see monoformin) is obtained. Allyl alcohol is a mobile liquid of suffocating smell, having almost the same boiling point (97°) as N. propyl alcohol ; like the latter, it is miscible with water. It does not take up nascent hydrogen directly, but chlorine, bromine, cyanogen, hypochlorous acid, etc. Upon oxidation it yields its aldehyde, acrolein, and acid, acrylic acid, containing the same number of carbon atoms, and is therefore a primary alcohol ; hence the above constitutional formula. With chromic acid it yields, in addition, formic acid. Several higher homologues are known. 88 IV. DERIVATIVES OF MONATOMIC ALCOHOLS. 0. Monatomic Unsaturated Alcohols, CJio,,_.3.0H. These alcohols are derivatives of acetylene and its homo- logues. In addition therefore to the general properties of the alcohols, and those common to the unsaturated alcohols of com- bining directly with 4 atoms of H, CI, Br, or 2 molecules HCl, HBr, etc., most of them possess the further peculiarity of form- ing explosive compounds v^^ith ammoniacal copper and silver solutions, e.g. C3H2AgOH, the former being coloured, e.g. yellow, and the latter white ; acids decompose these com- pounds backwards again. Those of them which do not yield such metallic compounds contain, not a triple bond, but two double ones between the carbon atoms. The most important of the alcohols is Propargyl alcohol, or proj)in?jl alcohol, C3H3OH, = CH=C— CH2OH, a mobile liquid of agreeable odour, lighter than water, and boiling at 114°, i.e. somewhat higher than normal propyl alcohol. It takes up 4 atoms of bromine. IV. DERIVATIVES OP THE ALCOHOLS. These may be classed in the following divisions : — 1. Ethers of the alcohols, e.g. C2H5.O.C2H5, ethyl ether. 2. Thio-alcohols and ethers, e.g. C2H5.SH. 3. Compound ethers and acid derivatives of the alcohols. 4. Nitrogen bases of the alcohol radicles. 5. Other metalloid compounds of the alcohol radicles. 6. Metallic compounds of the alcohol radicles, or organo- metallic compounds. A. Ethers Proper, (Alcoholic Ethers). Under ethers of the monatomic alcohols are understood compounds of neutral character derived from the alcohols by elimination of the elements of water, (1 molecule water from 2 molecules alcohol). They can frequently be prepared by treating the alcohols with sulphuric acid, and are distinguished ETHERS. 89 from the hitter by not combining with acids to form etliors, and by being substituted and not oxidized by the halogens, etc. Only the lowest number of the series is gaseous, most of them are liquid, and the highest are solid. The more volatile ethers are characterized by a peculiar odour which vanishes as the series ascends. Unlike the alcohols, no one hydrogen atom in the ethers plays a role different to that of the others ; consequently metallic sodium has no action upon them. (See p. 17.) Constitution. The ethers may be regarded as the anhy- drides of the monatomic alcohols, analogous to the anhydrides of the mono-acid bases : For their re-transformation into alcohols, see below. They may also be considered as the oxides of the alcohol radicles, e.g, (02115)20, ethyl ether; or, lastly, as alcohols in which the typical hydrogen atom is replaced by an alcoholic radicle : C,H,.OH C^Hs.OCC^H^) C2H,.0(CH3) Alcohol. Ether. Ethyl-methyl ether. The alcoholic radicles contained in them may either be the same, as in ordinary ether and in methyl ether, (CH3)20, in which case they are termed simple ethers"; or they may be different, as in methyl-ethyl ether, when they are known as "mixed" or 'intermediate ethers." The compound ethers of the acids are also frequently termed " ethers," e.g. " acetic ether " = ethyl acetate. Ethers of tertiary alcohols are not known. Modes of formation. 1. By heating the alcohols, CnHo„+i.OH, with sulphuric acid. The reaction goes on in two phases, e.g. for ethyl ether thus : a. C2H5OH + SO4H.H - C,H,.(S04H) -f H2O. h. C2H,S04H + C2H5.OH = C2H5.O.C2H, + H2SO4. In phase a an ether-sulphuric acid is formed, which, when further heated with alcohol, as in &, yields ether and regener- ates sulphuric acid. The latter is therefore free to work anew, 90 IV. DERIVATIVP]S OF MONATOMIC ALCOHOLS. and in this way to convert a very large quantity of alcohol into ether. This process is theoretically a continuous one, but practically it has its limits, through secondary reactions, such as the formation of SOg, etc. The method is only suitable for primary alcohols, secondary and tertiary going too easily into olefines. Hydrochloric, hydrobromic and hydriodic, among other acids, act similarly to sulphuric acid ; thus ether is obtained upon heating alcohol with dilute hydrochloric acid in a sealed tube to 180°, ethyl chloride, C2H5CI, being formed as intermediate product, and then reacting to yield alcohol in a way analogous to that given in the following mode of formation. Upon heating alcohol with hydrochloric acid there ensues, however, a state of equilibrium between the alcohol, ether, ethyl chloride, hydrochloric acid and water, after which the same quantity of each of these products is destroyed as is formed in unit of time. 2. By the action of halogen-alkyl upon sodium-alkylate, or also upon alcoholic potash : C2H5I + C2H5.0Na = G^li,.O.GJI^ + Nal. 3. From halogen-alkyl and dry silver oxide, AggO, (also HgO and NagO) : 2C2H5I + Ag^O = 0. + 2 AgL Modes of formation 1 and 2 yield mixed as well as simple ethers^ e.g. : C2H5.SO4H + CH3.OH = CsH^.O.CHg + H2SO4. + CH3.0Na = C5H11.O.CH3 + Nal. Properties, 1. The ethers are very stable. Ammonia, alkalies, dilute acids, and metallic sodium have no action upon them, nor has phosphorus pentachloride in the cold. 2. When superheated with water in presence of some acid, such as sulphuric, the ethers take up water and are re-trans- formed into alcohols, the secondary more readily than the primary. This change also goes on, but extremely slowly, simply upon standing. 3. Upon warming with concentrated sulphuric acid, alcohol and ethyl-sulphuric acid are formed : C2H5O. C2H5 -f HHSO4 = C2H5. OH -f C2H5. (SO4H). 4. Saturated with hydriodic acid gas at 0°, the ethers split up into alcohol and alkyl iodide : C2H5.O.C2H, -f HI = C2H5.OH -f C2H5I When the ethers are " mixed," the iodine attaches itself to the radicle poorer in carbon. ETHYL ETHER. 91 5. When heated with halogen-phosphorus, the oxygen atom is replaced by two of halogen, two molecules of halogen-alkyl resulting. 6. Like the alcohols, the ethers are oxidizable, e.g. by nitric and chromic acids, but halogens substitute in them and do not oxidize ; in this latter respect they resemble the hydrocarbons. Ethyl ether, Ether;' {G^YL^)jd. Discovered by Valerius Gordus about 1544, and possibly before that time by Raymond Ltdly. It was also called sulphuric ether," and " vitriol ether, " on account of its being supposed to contain sulphur. Its composition was established by Saussiire in 1807, and Gay Lussac in 1815. Preparation. By the continuous process from ethyl alcohol and sulphuric acid at 140°, with gradual addition of the alcohol, according to Boullay. It is freed from alcohol by shaking with water, and dried by distillation over lime or calcium chloride, and finally over metallic sodium. Theories of the formation of Ether. At first the action of the sulphuric acid was considered to consist in an abstraction of water. Later on, it was thought that the acid gave rise to a contact action, {Mitscherlich, Berzelius), but Liebig showed that this view was incorrect, since ethyl- sulphuric acid is formed. Liebig assumed that ethyl-sulphuric acid broke up, upon heating, into ether and SO3, but Graham., on the other hand, proved that the acid gives no ether when heated alone to 140°, but only when heated along with more alcohol. 4. After this, Williamson propounded the theory of etheri- fication at present held, a theory based on the opinion of Laurent and Gerhardt that ether contains two ethyl radicles. Its correctness was proved by mode of formation 2, and also by the preparation of mixed ethers. Properties. Mobile liquid with powerful ethereal odour, very volatile. M. Pt., - 129° ; B. Pt. -f 34°-9 ; Sp. Gr. at 17°-4, 072. Vapour tension equal to 10 atmospheres at 1 20°. Produces great cold on evaporation. Is easily inflammable, and therefore dan- gerous as a cause of fire, from the dissemination of its very heavy vapour ; a mixture of it with oxygen or air is explosive. When burnt very slowly and incompletely, lampenic acid," an acid which is as yet but little known, is produced with phosphores- cence. It is somewhat soluble in water (1 part in 10), and, con- versely, 2 volumes of water dissolve in 100 volumes ether j the 92 IV. DERIVATIVES OF MONATOMIC ALCOHOLS. presence of water can be detected by the milkiness wliich ensues uj)on the addition of carbon bisulphide. Miscible with concen- trated hydrochloric acid. Ether is an excellent solvent or ex- tractive for many organic substances, and also for I, Br, CrOg, Fe2Cl(3, AuClg, PtCl^ and other chlorides. It forms crystalline compounds with various substances, e.g. the chlorides and bromides of Sn, Al, P, Sb, and Ti, being present in them as ether of crystallization." When dropped upon platinum black it takes fire, and when poured into chlorine gas an explosion results, hydrochloric acid being set free. In the dark, however, and in the cold, sub- stitution by chlorine is possible ; the final product of the substitution, perchloro ether, C^CI^^qO, is solid and smells strongly like camphor. Uses. Ether was first employed as an anaesthetic by Simjmn in 1848, but this property had been previously observed by Faraday. It is further used as an extractive in the colour industry, as Hofmann's drops when mixed with 1 to 3 volumes of alcohol, for ice machines, and for the preparation of col- lodion, etc. Methyl ether, ( 0113)20, {Dumas, Peligot)^ closely resembles common ether ; gaseous at the ordinary temperature, but liquid under - 20°. It is prepared on the large scale for the production of artificial cold. As regards the boiling points of the ethers, the following law holds approximately : the boiling point — B. Pt. of the first constituent alcohol 4-B. Pt. of the second alcohol -120°. Thus, the boiling point of (C2H5)20 = 78°4-78°- 120° = 36°. Ethyl-cetyl- and Di-cetyl ethers are solid at the ordinary temperatures. Several ethers with unsaturated alcohol radicles are also known, e.g. Allyl ether, (C3H5)20, and Vinyl-ethyl ether, CgHg— 0— CgHg, B.Pt. 35° '5. These can combine directly with bromine. Isomers. The general formula of the saturated ethers is CnH2n-|-20- To cach ether there is therefore a corresponding saturated alcohol which is isomeric with it, thus C^HqO^ methyl ether or ethyl alcohol, C^H^qO = di-ethyl ether or butyl alcohol, and so on. From C^H^oO on, however, several different isomeric ethers are not only possible, but are also known, e.g. di-ethyl ether, (€2115)20, is isomeric with methyl-propyl ether, CH3.O.O3H7 ; similarly methyl-amyl ether, CH3.O.C5II1P ISOMERISM. 93 ethyl-butyl ether, C2H5.O.C4H9, and di-propyl- ether, C3H7.0.C3H^ are all isomeric. Isomerism of this kind depends upon the fact that the alcoholic radicles — and hydro- gen — are homologous, so that for equal sums total of carbon atoms the sums of the hydrogen atoms must also be equal. Such isomerism, which depends upon the grouping together by a polyvalent element — in this case, oxygen — of alcohol radicles which are individually unequal, but the sums of whose elements taken together are equal, is called metamerism. One of the alcohol radicles may here be replaced by hydrogen. The establishing of the constitution of the ethers is based upon {a) their syntheses according to modes of formation 1 or 2, and {h) their decomposition by HI according to p. 90. Alcohols and ethers containing an equal number of carbon atoms are therefore metameric. Alcohols are accordingly compounds which con- tain hydrogen and one alcohol radicle joined together by means of oxygen. Ethers, on the other hand, are compounds containing two alcohol radicles similarly joined. It stands to reason, of course, that all those varieties of isomerism which are found in the alcohols, and therefore in the alcohol radicles, 'can also occur in the ethers which contain these radicles. Varieties of Isomerism. The cases of isomerism which have been mentioned up to now are of three kinds. The first was the isomerism of the higher paraffins, which, since it is based upon the dissimilarity of the carbon chains, is often termed chain-isomerism. The isomerism between ethylene and ethy- lidene chlorides or between primary and secondary propyl alcohols depends upon the differences in position of the substi- tuting halogen or hydroxyl in the same carbon chain, and is termed isomerism of place or position. In addition to these there is the third kind, metamerism. Further cases will be spoken of under the Benzene derivatives. B. Thio-alcohols and -ethers. Methyl mercaptan, CH^.SH, {Dumas and Feligot). B. Pt. 6°. Ethyl mercaptan, {Zeise, 1833). B. Pt. 36\ Methyl sulphide, (CH.j^S, (EegnauU). B. Pt. 37°. Ethyl sulphide, (CJl,j,S. B. Pt. 92°, etc. From the alcohols and ethers sulphur compounds are derived, 94 IV. DERIVATIVES OF MONATOMIC ALCOHOLS. by the replacement of one atom of oxygen by one of sulphur. These are liquids of a most unpleasant and piercing odour, something like that of leeks ; they are nearly insoluble in water and the lower members are very volatile. The higher homologues are not so soluble in water, but continue soluble in alcohol and ether, and their smell is less strong on account of the rise in the boiling point. They are readily inflammable. The Thio-alcohols, also called mercaptans or alkyl sulph- hydrates, e.g. mercaptan, CgH^.SH, although of neutral reaction, possess the chemical characters of weak acids and are capable of forming salts, the "mercaptides," especially mercury compounds. The name mercaptan" is derived from "corpus mercurio aptum." They are soluble in a strong solution of potash. The Thio-ethers, also termed alkyl sulphides, e.g. ethyl sulphide, (02115)28, are on the other hand neutral volatile lio[uids without acid character. Both classes of compounds are derived from hydrogen sulphide by the replacement of either one or both atoms of hydrogen by alcohol radicles, just as alcohol and ether are derived from water : If only one of the atoms in hydrogen sulphide is substituted by an alcohol radicle, the remaining atom preserves in the new compound its original character and is easily replaceable by metals. The mercaptans are therefore monatomic compounds of faintly acid character. The above thio-compounds are not termed ethers of hydrogen sulphide because they are not saponifiable. The constitution of these compounds follows at once from their modes of formation. Formation. The mercaptans result : 1. By warming halogen alkyl or alkyl sulphate with potassium sulph-hydrate in concentrated alcoholic or aqueous solution : C2H,Br v KSH = C^H^.SH + KBr. THIO-ALCOHOLS AND -ETHERS. 95 2. By heating alcohol with phosphorus sulphide, the oxygen being thus replaced by sulphur, (Kekule). The thio-ethers are similarly obtained — 1. From halogen alkyl or alkyl sulphate and . neutral potassium sulphide : 2C2H5.SO4K + K,S = {G^ll,).^ + 2K2SO4. 2. By treating ether with phosphorus pentasulphide. 3. From halogen alkyl and sodium mercaptide. 4. By the distillation of mercury mercaptide, HgS being formed at the same time. ''Mixed sulphides," comparable with the "mixed ethers," can also be prepared, e.g. methyl-ethyl sulphide, C2H5.S.CH3. Behaviour. A. The Mercaptans. Sodium and potassium act upon the mercaptans to form sodium and potassium salts, white crystalline compounds, which are decomposed by water. The mercury salts are got by warming an alcoholic solution of mercaptan with mercuric oxide, e.g. mercuric mercaptide, Hg(C2H5S)2, (white plates). With mercuric chloride difficultly soluble double comjDounds are formed, e.g. (C2H5.S)Hg.Cl, a white precipitate. The lead salts are mostly yellow-coloured, and are produced upon mixing alcoholic solutions of mercaptan and lead acetate. The copper salt of mercaptan is a bright yellow precipitate. 2. Upon oxidation with nitric acid the mercaptans are transformed into alkyl-sulphonic acids, thus : C2H5.SH-1- 30 = C2H5.SO3H, (ethyl-sulphonic acid). 3. The mercaptans in the form of sodium salts are oxidized by iodine or by sulphuryl chloride, SO2CI2, (B. 18, 3178), and also frequently in ammoniacal solution in the air to di-suV^hides^ e.g. ethyl di-sulphide, (62115)282, thus : 2C2H5S.Na + 12 - (C2H5)2S2 + 2NaL These are disagreeably smelling liquids, which have a much higher boiling point than the mercaptans, are again reduced by nascent hydrogen, and yield with nitric acid di-sulph-oxides, e.g. ethyl di-sulph- oxide, (02115)28202. 4. By the action of concentrated sulphuric acid disulphides result, and not compounds analogous to ethyl-sulphuric acid. B. The Thio-ethers. 96 IV. DERIVATIVES OF MONATOMIC ALCOHOLS. 1. They yield double compounds with metallic salts, e.g. (C^,^^,HgC\^ which can be crystallized from ether. 2. They are capable of combining with halogen or oxygen. Thus ethyl sulphide forms with bromine a dibromide, crystal- lizing in yellow octohedra : (C,H,),S + Br, = (C2H5),SBr,; and with dilute nitric acid, di ethyl sulph-oxide : a thick liquid soluble in water, which combines further with nitric acid to the compound, (02115)280, HNO3. Concentrated nitric acid or permanganate of potash oxidizes the sulphides or sulph-oxides to sulphones, e.g. ethyl sulphide to (di)-ethyl sul- phone, (02115)2802, and methyl-ethyl sulphide to methyl-ethyl sulphone, (OH3)(02H5)S02. The sulphones are solid well- characterized compounds which boil without decomposition. The sulph-oxides are reduced by nascent hydrogen to sulphides, but not the sulphones. 3. The behaviour of the sulphides towards the halogen alkyls is of especial interest. Thus the substances (OH3)2S and OH3I combine even in the cold to the white crystalline tri-methyl- sulphine iodide, (0113)381, which is soluble in water, and which goes back into its components upon heating. This compound behaves exactly like a salt of hydriodic acid, and yields with silver oxide — (but not with alkali) — an oily base, tri-methyl-sulphine hydroxide, (0H3)38.OH, which cannot be volatilized without decomposition. This is as strong a base as caustic potash and resembles the latter so closely that it absorbs carbonic acid, cauterizes the skin, drives out ammonia, and gives salts with acids with the evolution of heat, etc., etc. ; it also yields salts with hydrogen sulphide which are extremely like the alkaline sulphides, e.g. they dissolve 8b283, {Oefele, 1833 ; Cahours). The compoiinds just described are of particular interest with regard to the question of the valency of sulphur. Since in ethyl sulphide both the alcohol radicles are bound to the sulphur, this will also be the case in ethyl sulphone, otherwise the sulphones would manifestly be easily saponifiable. (See P^thyl sulphur- ous acid.) Probably the sulphur in them is hexavalent, corresponding ETHERS OF THE ALCOHOLS. 97 with the formula, ^^2g5^S^Q. Isomers of the sulph ones, which are readily saponifiable, have recently been prepared [Otto, B. 18, 2500). The sulphinic hydroxides also can only be explained very insufficiently as addition compounds, on the assumption of the divalence of sulphur. The formula (0113)28 + CH3OH for tri-methyl-sulphine hydroxide does not indicate in the least the strongly basic character of this substance, since it is not explicable why the mere addition of the neutral methyl alcohol to the equally neutral methyl sulphide should produce such an effect. More probable is one of the two formulae — (CH3)3=S-(OH) ; or, (CH3)3=S-(OH) ; . 'I . even if they do not overcome all the difficulties involved. With respect to isomers, the same general conditions prevail in the sulphur as in the corresponding oxygen compounds. Sulphides of Unsaturated Alcohol Radicles. Vinyl Sulphide, (02113)28. Present in Allium ursinum. Allyl sulphide, (03115)28, {Wertheinfiy 1844), present in the oil of allium sativum — oil of garlic, — in Thlapsi arvense, etc. Prepared from allyl iodide and KgS, {Hofmann, Cahours). Analogous selenium and tellurium compounds of alcohol radicles are also known. They are in part distinguished by their excessively dis- agreeable, nauseous, and persistent odour. 0. Ethers of the Alcohols with Inorganic Acids and their Isomers. The compound ethers may be considered as derived from the acids, (see pp. 78 and 70), by the exchange of the replace- able hydrogen of the latter for alcoholic radicles, just as salts result by exchanging the hydrogen for a metal — HNO3. KNO3. (C2H,)N03. Or, they are derived from the alcohols by exchange of the alcoholic hydrogen atom for an acid radicle, i.e. for the acid residue which is combined with OH — C2H5.O.H. CA.0.(N02). C,H,.0.(S03H). The different ways of writing the formulae of ethers, such as (C2H;^)N03, C2H5.O.NO2, etc. are all equally justifiable. (506) a 98 IV. DERIVATIVES OF THE MONATOMIC ALCOHOLS. Monobasic acids yield only one kind of ether, neutral ethers/^ which are analogous to the neutral salts of those acids. Dibasic acids yield two series of ethers, (1) acid ethers and (2) neutral ethers, corresponding respectively with acid and neutral salts ; thus, C2H5.H.SO4 and (02115)2 . SO4 are the acid and neutral ethyl ethers of sulphuric acid. Tribasic acids yield three series of ethers, etc. The composition of the compound ethers is therefore exactly analog- ous to that of salts, so that in the definition of polybasic acids their behaviour in the formation of ethers may also be included. The neutral ethers are mostly liquids of neutral reaction, and often of very agreeable odour, with relatively low boiling points, and volatile, eventually in a vacuum, without decom- position. Most of them are either almost or quite insoluble in water. The acid ethers, also called ether-acids, on the other hand, are of acid reaction, without smell, usually very easily soluble in water, much less stable than the neutral ethers, and not volatile without decomposition. They act as acids, i.e. form salts and ethers. All compound ethers are characterized by the property of combining with water and going back again into their com- ponents, i.e. of undergoing " saponification," when boiled with alkalies or acids, or when heated with steam to over 100°, e.g. 150-1 80"^ This sometimes takes place simply upon mixing with water at the ordinary temperature. General modes of formaiion. 1. The ethers frequently result directly from their components, with elimination of water. Such a reaction, however, is only possible when the water produced by it is rendered harmless, e.g. by being taken up by the acid employed, for instance, concentrated H2SO4, HCl, or HNO3 ; otherwise the ether obtained would be retransformed into its alcohol. A direct formation of ether does not proceed quantitatively on account of the disturbing effect of the v^ater produced in the reaction. When equivalent proportions of alcohol and acid are used, a definite point of equilibrium is arrived at which cannot be passed even upon prolonged heating ; an excess of acid or alcohol increases the yield. The acid is therefore frequently allowed to act in the nascent state, by distilling a mixture of one of its salts with concentrated H2SO4 and the NITRIC ETHERS, ETC. 99 alcohol in question ; or a mixture of the alcohol and acid is allowed to drop into concentrated sulphuric acid heated to 130°, when the ether distils over ; or the same mixture is saturated with gaseous hydrochloric acid. This last method is very often followed, the reaction going partly according to mode of formation 3. (Cf. also p. 90.) 2. The alcohol is heated with the acid chloride, thus : SO2CI2 + 2C2H5.OH = SO(OC2H5)2 + 2HC1. 3. The silver salt of the acid is heated with alkyl iodide, this being a method generally applicable, although it often leads to isomers of the expected ether : 2C,RJ. + SO.Ag, = SO.iC^H,), + 2AgI. Besides the real acid ethers, there are also treated under this division several other classes of acid derivatives isomeric with them, but dis- tinguished from them by not being saponifiable, i.e. by being more stable, e.g. nitro-compounds, sulphonic and phosphinic acids, etc. The hydrocyanic derivatives of the alcohols will also be described here for the sake of convenience. These latter likewise do not show the normal ether-saponifiability into alcohol and acid, but are broken up by saponifying agents in another direction. Ethers of Nitric Acid. Methyl Nitrate>€H3.(N03), = CH3.0.(N02); colourless liquid, B. Pt. 66°. Ethyl Nitrate, or Nitric Ether, C2H5.O.NO2, (Millon). B. Pt. 86°. Mobile liquid of agreeable odour and sweet taste, but with a bitter after-taste; burns with a white flame. Both these ethers are soluble in water. The latter is prepared directly from its components, with the addition of some urea. Like all nitric ethers, the above compounds contain a large proportion of oxygen in a form in which it is readily given up, and they therefore explode upon being suddenly heated strongly. They saponify easily upon boiling with alkalies. Tin and hydrochloric acid reduce them to hydroxylamine : C2H5(N03) + 3Sn + 6HCl = C2H5OH + NH3O + SSnCl^ + H^O. . Here also the nitrogen separates from the alcohol radiclgj' a reaction similar to saponification. 2. Derivatives of Nitrous Acid. These include Nitrites and Nitro-compounds. 100 IV. DERIVATIVES OF THE MONATOMIC ALCOHOLS. a. Ethers of Nitrous Acid, HNOg. These are obtained by the action of nitrogen trioxide or of potassium nitrite and sulphuric acid, or of copper and nitric acid upon the alcohols. They are liquids of aromatic odour, neutral reaction and very low boiling point, and are easily saponifiable. Nascent hydrogen also reconverts them into alcohol, ammonia being formed at the same time. For constitution, see nitro-compounds. Ethyl Nitrite, C2H5.0.(NO), {Kunhel, 1681). Formerly called sweet spirits of wine or saltpetre ether." Mobile liquid of a piercing ethereal odour, somewhat resembling that of Borsdorf apples, and of a peculiar stinging taste. B. Pt. + 18°. Burns with a bright white flame. Its alcoholic solution is the officinal " Spiritus aetheris nitrosi," and is used as a taste corrective. Ethyl nitrite, as well as amyl nitrite, finds application, e.g, in the preparation of diazo-com- pounds, (see these). Methyl Nitrite, CH3O.NO. Gaseous. Amyl Nitrite, C5H11O.NO. B. Pt. 96^ Pale yellow liquid. Is used in medicine ; it produces expansion of the blood vessels and relaxation of the contractile muscles. Isomeric with these ethers are /?. The Nitro-derivatives of the Hydrocarlons. These are colourless liquids of ethereal odour, almost or quite insoluble in water, and boiling at temperatures up to 100° higher than their isomers. Like the latter they distil with- out decomposition, and occasionally explode upon being quickly heated. They are fundamentally distinguished from the nitrous ethers by not being saponifiable, and by yielding amido-compounds (see these) on reduction, the nitrogen being thus not separated : CH3.NO2 + = CH3.NH2 + 2H2O. Nitro-methane, CH3.NO2, {Kolle, V. Meyer, 1873). B. Pt. 99M01°; Sp. Gr. > 1. Nitro-ethane, C2H5.NO2, (V. Meyer and Stuber, 1872). B. Pt. 113°-114°; the vapour does not explode even at a much higher temperature. Burns with a bright flame. Nri'RO-COJMroUNDS. 101 General modes of formation, 1. By treating alkyl iodide with silver nitrite, (F. Meyer), nitro-methane alone results, nitro-e thane in about an equal proportion with its isomer, and the higher homologues in regularly decreasing amounts as compared with those of their isomers, from which however they are easily separated by distillation : CH3I + AgNOg = CH3.NO2 + Agl. 2. Nitro-methane is further formed from mono-chloracetate and nitrite of potassium, by exchange of CI for NOg and separation of CO2, (Kolbe), Mtro-compounds do not, on the other hand, result from the action of nitric acid upon the fatty hydrocarbons, or at least extremely seldom. (Difference from the aromatic hydrocarbons.) The constitution of the nitro- compounds is arrived at from their not being saponifiable, and from the fact that the nitrogen is not split off on their reduction but remains directly bound to the carbon in the resulting amines, (see these). Conse- quently the nitrogen in them must be directly joined to the alcohol radicle, i.e. to the carbon, and so their constitutional formula is R.NO2; for instance : 0 CH3— N< I , or CH3— N< 0 ' 0 according as N is taken as tri- or pentavalent. Nitrogen which is bound directly to an alcohol radicle is therefore not separated by saponifying agents. Since the nitrogen of the isomeric nitrous ethers, on the other hand, is easily split off from the alcohol radicle either by saponification or by reduction, it is manifestly not directly combined with the carbon but only through the oxygen. The nitrous ethers therefore receive the constitutional formula E.O.(NO), e.g, CH3— 0— N=0, taking nitrogen as trivalent. From this follows for the hypothetical hydrated nitrous acid the formula H.O.N:0, and for anhydride the formula (NOjgO. Simultane- ously we attain from this to the constitution of nitric acid. The aromatic hydrocarbons, e.g. benzene, C(5H(., yield with the latter nitro- compounds, which will be treated of later on, thus : CeH,.H + HNO3 = C,H,.^0, + HA 102 IV. DERIVATIVES OF THE MON ATOMIC ALCOHOLS. Nitric acid therefore contains a nitro-group bound to hydroxyl, cor- responding with the formula : H.O.NO2 = H-O-N^^, or H— 0-N<^>. Behaviour, 1. They yield amines with reducing agents, such as iron and acetic acid, tin and hydrochloric acid, etc. 2. When the alcohol which corresponds to the nitro-com- pound is a primary or secondary one, so that the carbon atom which is joined to the nitro-group is at the same time joined to hydrogen, as in the groups — CH2.NO2 and =CH.N02, this hydrogen is replaceable by metals, and consequently such nitro-compounds possess the characteristics of acids. For instance, by the action of alcoholic soda upon nitro-ethane and nitro-methane, the compounds CH3.CHNa.NO2 and CHgNa.NOg are formed, both crystallizing in fine needles and being explosive. The nitro-compounds of tertiary alcohols behave otherwise. Since they contain no hydrogen joined to the carbon atom which is bound to the nitro-group, they have not an acid character ; the acidifying influence of the nitro-group does not therefore extend to those hydrogen atoms which are joined to other carbon atoms. The hydrogen in the primary and secondary mono- derivatives, which is attached to the same carbon atom as the NOg-group, can also be replaced by bromine. So long as hydrogen, as well as this bromine and the nitro-group, remains joined to the carbon atom in question, the compound is of a strongly acid character, but when it also is substituted by bromine, the compound becomes neutral; e.g. dibromo-nitro-ethane, CH3.CBr2.NO2, is neutral. 3. The primary nitro-compounds yield with concentrated hydrochloric acid at 140°, acids of the acetic series containing an equal number of carbon atoms, and hydroxylamine. 4. The behaviour of the nitro-alkyls to nitrous acid is very varied. The primary yield nitrolic acids and the secondary pseudo-nitrols, while the tertiary do not react with it at all. Thus from nitro-ethane, CH3— C^^2^^, *'ethyl-nitrolic acid," CHg.C^^j^^, an acid crystal- lizing in light yellow crystals and whose alkaline salts are intensely yellow, is formed. Secondary nitro-propane, (CH3)2=CH(N02), gives on the contrary "propyl-pseudo-nitrol," (CHo)2C=N.O.N02, or perhaps (CH3)2C=N.O.N02, a white crystalline, indifferent, non-acid substance, which is blue either when fused or when in solution. These reactions, which, moreover, only go on in the case of the lower molecular alcohols, KTHUllS OF SULPHURIC ACID. 103 (in the primary up to Cg, and in the secondary up to C5), are specially applicable for distinguishing between the primary, secondary, or tertiary nature of an alcohol, (see p. 78). The nitro-hydrocarbons, which are easilj^ prepared from the iodides, are dissolved in a solution of potash to which sodium nitrite is added, the solution acidified with sulphuric acid and again made alkaline, and then observed for the production of a red colouration, (primary alcohol), a blue colouration, (secondary alcohol), or no colouration at all, (tertiary alcohol). Appendix. Chloropicrin, CCI3NO2, a heavy liquid of excessively suf- focating smell, B. Pt. 112°, is formed from many hydrocarbon compounds by the simultaneous action of nitric acid and chlorine, chloride of lime, etc. It is best obtained from picric acid and bleaching powder. Di-nitro derivatives of the saturated hydrocarbons, e.g. Di-nitro-ethane, C2H4(N02)2, whose potassium salt is an explosive yellow crystalline compound obtained from CH3.CHBr(N02) + KNO2, also exist ; further, some tri-nitro derivatives, and even tetra-nitro-methane, C(N02)4 (white crystals), which last boils without decomposition. 3. Derivatives of Hypo-nitrous Acid Hypo-nitrous acid, HNO or H2N2^2> be transformed into an ether of the formula (02115)2X202, Diazo-ethoxane, {Zorn), an oil which explodes even at 40°. The nitroso-compounds R.NO, derived from benzene, . also belong to this category, (see Nitroso-benzene, OgH5.NO). Analogues in the Fatty Series are unknown. 4. Ethers of the Chlorine Acids are known, e.g. ethyl hypochlorite, O2H5.O.OI, and ethyl perchlorate, C2H5.O.OIO3, both violently explosive liquids. 5. Ethers of Sulphuric Acid. The neutral ethers are formed — (o.) From fuming sulphuric acid and alcohol ; (h) From silver sulphate and alkyl iodide ; (c) From sulphuryl chloride and alcohol : SO2CI2 + 2C2H,OH = m.iOG^-R,)^ + 2HCI. 104 IV. DERIVATIVES OF THE MONATOMIC ALCOHOLS. The acid ethers or ether sulphuric acids " of the primary alcohols result directly from their components. Secondary and tertiary alcohols do not yield them. {a) Ethyl sulphate, (02^5)2804, is a colourless oily liquid of an agreeable peppermint odour, insoluble in water, and solidi- fying on exposure to a strong cold ; B. Pt. 208°. It is quickly saponified (to ordinary ether) upon warming with alcohol, also upon boiling with water, but only slowly with cold water; in the latter cases alcohol and sulphuric acid are produced. {h) Ethyl-sulphuric acid, C2H,.S04H, = C2H5.O.SO3H, (Dahit, 1802), is obtained from a mixture of alcohol and sulphuric acid, as given under Ethyl ether, method 1, but not quantitatively, on account of the state of equilibrium that ensues, (see p. 98). It is also formed from ethylene and sulphuric acid at a somewhat higher temperature. It differs from sulphuric acid by its Ba-, Ca-, and Pb-salts being soluble, and it can therefore be easily separated from the former by means of BaCOg, etc. It yields salts which crystallize beauti- fully, but which slowly decompose into sulphate and alcohol on boiling their concentrated aqueous solution, especially in presence of excess of alkali. They are often used instead of ethyl iodide in the preparation of other ethyl compounds by double decomposition. The free acid is prepared by adding the exact quantity of sulphuric acid required to the barium salt. It is a colourless oily liquid which does not adhere to glass, and which slowly decomposes into alcohol and sulphuric acid, i.e. is saponified, on evaporating or preserving its solution, and quickly upon boiling it. The methyl-, amyl-, etc. compounds are analogous; the former is also a syrup which does not adhere to glass. 6. Derivatives of Sulphurous Acid. a. Ethers of Sulphurous Acid, {a) Ethyl sulphite, 803(02115)2, is an ethereal liquid of peppermint odour, which can be prepared from alcohol and SO^Clj or SgClg, and which is rapidly saponified by water. SULPHONIC ACIDS. 105 {h) Ethyl- sulphurous acid, SO3. HiCoHg). The very unstable potassium salt of this acid is obtained by the partial saponification of ethyl sulphite by potash solution — SOslCoHs)^ + KOH = SOgKlCaHg) + C^HgOH. The free acid is incapable of existence, decomposing immediately into its components. Analogous ethers of other alcohols are known. (3, Sulpho- or Sulphonic Acids and their Ethers. (a) Ethyl-Sulphonic Acid, C2H5.SO3H, {Lowig, 1839 ; H, Kojyp, 1840), is a strong monobasic acid, very easily soluble in water and hygroscopic, and sharply distinguished from ethyl-sulphurous acid by its stability, not being saponified upon boiling its aqueous solution either with alkalies or acids. Boiling concentrated nitric acid and free chlorine do not act upon it, and it requires fused potash to effect its decomposition. It has a strongly acid and disagreeable after-taste. It yields crystallizable salts, e.g. CgH^.SOgK + HgO, (hygroscopic), C.Hg.SOsNa, (C2H5.S03)2Ba + H20, etc. Modes of formation. 1. From alkyl iodide and sodium or ammonium sulphite : C2H5.I + Na2S03 = C2H5.S03Na + Nal. 2. By the oxidation of mercaptans by IINO3 : C2H5.SH + 30 = O2H5.SO3H.' The sulphonic acids yield chlorides with PCI5, e.g. ethyl- sulphonic acid gives ethyl-sulphonic chloride, CgH^SOgCl, a liquid which boils without decomposition at 177°, fumes in the air, and is reconverted by water into ethyl-sulphonic and hydrochloric acids. Nascent hydrogen reduces it to mercaptan. With zinc dust it yields the zinc salt of a peculiar, syrupy, easily soluble acid, viz. — Ethyl- sulphinic acid, C2H5.SO2H, which is likewise converted into mercaptan upon further reduction. Its sodium salt yields ethyl sulphone when treated with ethyl bromide, C2HgBr. It also forms an unstable ether, isomeric with this latter compound, (see p. 96). Methyl-sulphonic acid, CH3.SO3H, was prepared by Kolbe in 1845 from trichloro-methyl-sulphonic chloride, 106 IV. DERIVATIVES OF THE MONATOMIO ALCOHOLS. CCI3.SO2CI, (produced from CS2, CI, and H2O). It is a syrupy liquirl. Ethyl-sulphonic ethyl ether, C2H5.S03.C2H^, is isomeric with ethyl sulphite, and, being an ether of the more stable ethyl-sulphonic acid, is only partially saponifiable. It is pre- pared from silver sulphite and ethyl iodide. B. Pt. 213°. The sulphonic ethers have considerably higher boiling points than the isomeric sulphurous ethers. Constitution. From the formation of the sulphonic acids from mercaptans by oxidation, and the (indirect) reversibility of this reaction, it follows that the sulphur in them is directly bound to the alcohol radicle ; if, then, sulphur is regarded as hexavalent, ethyl sulphonic acid has the constitution From this we arrive at the constitution of sodium sulphite as being Na — (SOgNa), of the hypothetical sulphurous acid as H — (SO3H), and of sulphuric acid as H — 0 — (SO3H). The real easily saponifiable sulphurous ethers therefore manifestly contain the sulphur not bound directly to the carbon but through oxygen, so that for them the following formulae hold: ethyl-sulphurous acid, C2H^.O.S02H, and ethyl- sulphurous acid ether, C2H5O.SO.O.C2H5, or Related to methyl-sulphonic acid are ; Methane-di-sulphonic acid, CH2(S03H)2, a crystalline body, Methane-tri-sulphonic acid, CH(S03H)3, also crystalline, Ethylene- and Ethidene-di- sulphonic acids, C2H4(S03H)2, Propane-tri-sulphonic acid, 03115(80311)3, etc. ; these may also be regarded as sulphurous acid derivatives of polyatomic alcohols. 7. Ethers of Tri- and Polybasic Acids. Ethers of phosphoric acid : P0(0E)3, P0(0R)2(0H), and P0(0E,)(0H)2, (E/ = alkyl), exist, as do also similar compounds of phosphorous and hypophosphorous acids. The phosphinic acids, etc., are related to the two last-mentioned classes. (See phosphines.) Ethers of boracic and silicic acids are also known. njtrilb:s and iso-nttiules. 107 8. Alcoholic Derivatives of Hydrocyanic Acid. (Nitriles and Iso-nitriles.) Hydrocyanic acid, HON, yields two classes of derivatives by the exchange of its hydrogen atom for alcohol radicles, neither of which can be grouped among the ethers, since they do not go back into alcohol and hydrocyanic acid on saponification, but decompose in another direction. a. Cyanides of the Alcohol Eadicles (Nitriles). These are either colourless liquids, volatile without decom- position, or solids, of a not unpleasant ethereal odour slightly resembling that of leeks, lighter than water, and relatively stable. The lower members are miscible with water, but the higher ones insoluble in it. They boil at about the same temperatures as the corresponding alcohols. Formation. 1. By heating alkyl iodide with potassium cyanide, or potassium ethyl-sulphate with potassium ferro- cyanide : CH3I + KCN = KI + CH3.CN Methyl cyanide. 2. By distillation of the ammonium salts of monobasic acids which contain one atom of carbon more than the alcohol which would be used in method 1, and treatment of the amides which are at first produced with separation of water, with a dehydrating agent such as P2O5, (Hofmann), PCI5 or P2Sr,, (see imide chlorides and thiamides) ; also by treating the ammonium salts of the acids directly with PgO^ : a. CH3.COOH + NH3 = H2O + CH3.CO.NH2 Acetamide. 6. CH3.CO.NH2 - H2O = CH3.CN. As a consequence of this mode of formation these com- pounds are also termed nitriles of the monobasic acids, e.g, CH3.CN, methyl cyanide or Aceto-Nitrile ; CgHg.CN, propio- nitrile, etc. 3. The higher nitriles, in which C>5, result from the amides of acids of the acetic series containing one atom of 108 IV. DERIVATIVES OF THE MONATOMIC ALCOHOLS. carbon more in the molecule, and also from the primary amines with the same numl)er of carbon atoms, upon treat- ment with bromine and caustic soda solution, (Hofmann). See amides. Behaviour. 1. These compounds are very active chemically. When heated with acids or alkalies or superheated with water, they break up into the acids from which they were originally prepared and ammonia ; amides may be formed here as inter- mediate products : CH3.CN + 2H,0 = CH3.COOH + NH3. This is a reaction of great moment, because it leads from the alcohols C,,Hon+i.OH to the acids of the acetic series, CnHsn+i.COOH, richer than those alcohols by one atom of carbon. (Bumas, Malaguti, Le Blanc, and also Franhland and Kolhe, 1847.) 2. Just as acetamide is formed by the taking up of water, so is thio- acetamide by the taking up of sulphuretted hydrogen. 3. By the addition of halogen hydride, amido-chlorides or imido- chlorides result ; by the addition of ammonia bases, amidines. Halogens also form easily decomposable addition-products, (see acid derivatives). 4. Combination with hydrogen leads to amines, (p. 113): CH3.CN -f 2H2 - CH3.CH2.NH2. Ethylamine. 5. Metallic potassium or sodium frequently induces polymerization ; thus methyl cyanide yields in this way cyanmethine, a mono-acid base crystallizing in prisms. For Constitution, see Iso-nitriles. Aceto-nitrile, CH3.CN, is present in the products of distil- lation from the vinasse of sugar beet and in coal tar. B. Pt. 82° ; combustible, and miscible with water. Propio-nitrile, CgHg.CN, Butyro-nitrile, C3H7.CN, and Valero- nitrile, C4H9.CN, are liquids of agreeable bitter almond oil odour; Palmito-nitrile, C15H31.CN, is like paraffin. Cyanogen compounds of unsaturated alcohol radicles also exist, e.g. AUyl Cyanide, C3H5.CN, (see crotonic acid). Fulminate of Mercury, probably CHg(N02).CN, is to be regarded as a salt of the non-existent Nitro-aceto-nitrile, CH2(N02).CN, whose H-atom has been rendered easily re- ISO-NITRILES. 109 placeable by metals through the acidifying influence of the NO.j- and GN-groups. It is obtained by warming alcohol with nitric acid and mercuric nitrate, and forms silky glancing prisms which explode with the utmost violence upon being heated or struck. The analogous fulminate of silver is even more explosive. Concentrated HCl decomposes them into CO2 and HCl-hydroxylamine. p. Iso-cyanides (Iso-nitriles or Carbamines). Colourless liquids easily soluble in alcohol and ether, but only slightly soluble or insoluble in water, of weak alkaline reaction, unbearable odour, and poisonous properties, and boiling somewhat lower than the nitriles. Formation. 1. By heating the iodides of the alcohol radicles with silver cyanide instead of potassium cyanide, (Gautier), a double compound with cyanide of silver being first formed : CNAg + C2H5l = Agl + C^H^NC. Ethyl iso-cyanide. 2. In small quantity, along with the nitriles, when potassium alkyl- sulphate is distilled with potassium cyanide. 3. By the action of chloroform and alcoholic potash upon primary amines, (Hofmann, 1869) : CH3.NH2 + CHCI3 + 3K0H = CH3.NC + 3KC1 + 3H2O. Behaviour, 1. The iso-nitriles differ fundamentally from the nitriles by their behaviour with water or dilute acids. When strongly heated with water, or with acids in the cold, they split up into formic acid and amine bases containing one atom of carbon less than themselves, from which latter compounds they can be prepared : CH3.NC + 2H2O = CH3.NH2 + HCO2H. Unlike the nitriles, they are very stable towards alkalies. 2. The iso-nitriles are also capable of forming addition products with hydrochloric and hydrosulphuric acids, etc., compounds different from those given by the nitriles ; thus, with HCl they yield crystalline salts which are violently decomposed by water into amine and formic acid. 3. Some of the iso-nitriles change into the isomeric nitriles on being heated. 110 IV. DERIVATIVES OF THE MON ATOMIC ALCOHOLS. Methyl iso-cyanide, CH3.NC. B. Pt. 58°. Ethyl iso-cyanide, CgHg.NC. B, Pt. 82°. Constitution of the Nitrites and Iso-nitriles. The constitu- tion of the nitriles follows from their close relation to the acids. The carbon atom of the cyanogen group — CN remains attached to the alcohol radicle after the action of saponifying agents, and is therefore directly bound to the carbon atom of the latter. The nitrogen on the other hand is split off, and is thus not directly bound to the alcohol radicle. Consequently aceto-nitrile has the constitution : CH3 — C=N. In the case of the iso-nitriles, however, it is the nitrogen which must be directly bound to the alcohol radicle, as their close connection with the amine bases shows, the amines being easily prepared from and reconverted into the iso-nitriles. The carbon atom of the cyanogen group, on the contrary, is split off on decomposition by acid, and is consequently not bound directly to the alcohol radicle but only through the nitrogen. The constitutional formula of the iso-nitriles there- fore is R — NC, probably E — N=C, e,g. methyl carbamine, CH3— N=C, etc. The difference between the two kinds of compounds is sufficiently emphasized as a rule by writing them CHg.CN and CHg.NC. D. Nitrogen Bases of the Alcohol Radicles. By the introduction of alcohol radicles in place of hydrogen into ammonia or its salts, the important class of ammonia bases or amines and ammonium bases of the alcohol radicles is produced. The amines containing the lower alcohol radicles bear the closest resemblance to ammonia, being even more strongly basic than the latter. They have an ammoniacal odour, give rise to white clouds with volatile acids, combine with hydro- chloric acid, etc. to salts with evolution of heat, and yield double salts with platinic and gold chlorides. They further precipitate many metallic salts, the precipitates being fre- quently soluble in excess. The lowest members of this class are combustible gases NITROGEN BASES. Ill readily soluble in water. The next are liquids of low boiling point, also at first easily soluble, but the solubility in water diminishes with increasing carbon (more quickly in the nitrile- than in the amido-bases), and also the volatility, until the highest members of the series, such as tricetyhimine, (Cj(3H33)3N, are at the ordinary temperature solid odourless substances of high boiling point, insoluble in water but soluble in alcohol and ether, readily combining however with acids to salts, like the others. All amine bases are considerably lighter than water. The ammonium bases are solid and very hygroscopic, and exceedingly like potash in properties. Classification, The nitrogen bases of the alcohol radicles are divided into primary, secondary, tertiary, and quaternary bases, according as they contain one, two, three, or four alcohol radicles ; the three first are derived from ammonia, and the last from the hypothetical ammonium hydroxide, NH,.OH. Amines or Ammonia Bases. Ammonium Bases. Primary or Amido-bases. Secondary or Imido-bases. Tertiary or Nitrile-bases. Quaternary Bases. NH,(CH3) Methylamine (Gas.) Ethylamine (B. Pt. 19°). etc. Di-methylamine (B. Pt. 8°). NHlC^Hg), Di-ethylamine (B. Pt. 57°). etc. . N(CH3)3 Tri-methylamine (B. Pt. 9°). N(C2H,)3 Tri-ethylamine (B. Pt. 89°). etc. N(CE3)J Tetra-methyl- ammonium iodide. N(C2H5)40H Tetr-ethyl-am- moniu m -hydroxide. etc. Occurrence, Some individuals of this series occur in nature, e.g. methylamine and tri-methylamine. Modes of formation. 1. Methylamine, ethylamine, etc., are obtained by treating methyl or ethyl etc. cyanate with potash solution, {Wurtz, 1848): CO.NlC^H,) + 2K0H = C2H5.NH2 + K^COg. This method of formation yields only primary bases. 112 IV. DERIVATIVES OF THE MONATOMIC ALCOHOLS. l\ The iso-thiocyanic ethers or mustard oils (see these) also yield those bases upon heating with concentrated acids. 2. By the direct introduction of the alcohol radicle into ammonia by heating a concentrated solution of the latter with methyl iodide, chloride^ or also nitrate, ethyl iodide, etc. In this reaction an atom of hydrogen is first exchanged for an alcoholic radicle, and then the base produced combines with the halogen hydride, formed at the same time, to a salt, thus : (1.) NH^H + CH3I = NH2.CH3, HI. From the methylamine hydriodide thus produced, free methylamine can easily be got by distilling with potash : NH,(CH3), HI + KOH = NH2(CH3) + KI + H^O. The methylamine can now combine further with methyl iodide to hydriodide of di-methylamine : (II.) NH2(CH3) + CH3l = NH(CH3)2HI, which, in its turn, yields the free base with potash. This latter can again combine with methyl iodide : (III.) NH(CH3)2 + CH3l = N(CH3)3HI, the salt so produced yielding tri-methylamine as before. Finally the tri-methylamine can once more take up methyl iodide : (IV.) N(CH3)3 + CH3l = N(CH3y. The compound obtained, tetra-methyl-ammonium iodide, is however no longer a salt of an amine base but of an ammonium one, and is not decomposed on distillation with potash solution. By using various dissimilar alkyl iodides instead of methyl iodide alone, bases are got containing different alcohol radicles together, i.e., "mixed" amines, etc., e.g., methyl-propylamine, NH(CH3)(C3H7)j methyl-ethyl-propylamine, N(CH3)(C2H5)(C3H7). The reactions I. to IV., given above, do not in reality follow each other in perfect order but go on simultaneously, the bases being partly liberated from the hydriodates by the ammonia, and so being free to react with new halogen alkyl. The product obtained by distillation with potash is therefore a mixture of all the three amine bases. These cannot be separated by fractional distillation, and so their different behaviour with oxalic ether, 0202(002115)2, is made use of for the purpose. Methylamine reacts with this ether to form chiefly (1) NITROGEN BASES ; FORMATION OF. 113 di-metliyl-oxamide, C20o(NH. 0113)2, (solid), and (2) some methyl- oxamic ether, C202(OC2H5)(NH.CH3), (liquid); di-methylaiiiine yields (3) the ethyl ether of di-methyl oxamic acid, C202(GC2H5)N(CH3)2, (liquid), while tri-methylamine does not react with oxalic ether. Upon warming the product of the reaction on the waterbath, the latter base distils over, and the remaining compounds can then be separated by special methods, (for which see B. 3, 776 ; 8, 760), and individually decomposed by potash, (1) and (2) yielding methylamine, and (3) di- methylamine. 3. The nitro-compounds yield primary amido-compounds on reduction (see p. 100), thus : CH3.NO2 + 3H2 = CH3.NH2 4- 2Bfi. 4. The nitriles, including hydrocyanic acid, are capable of taking up four atoms of hydrogen (see p. 108), and forming primary amines, (Mendius, 1862): CH3.CN + 2H2 = CH3.CH2.NH2 = C2H,.NH2. Ethylamine. H.CN + 2H2 = CH3.NH2. Methylamine. 4*. The iso-nitriles are decomposed by hydrochloric acid, with forma- tion of the primary amine bases from which they are also obtained (p. 109). 5. Primary amines, in which 0>6, are prepared according to Hofmann's method, by the action of bromine and caustic soda solution upon the amides of acids containing one carbon atom more than themselves (see amides). 6. Primary amines likewise result from the reduction of the oximes or hydrazones, (see pp. 134, 142, and 373). Isomers. Numerous isomers exist among the amine bases, as the following table shows : C2H7N. (J4H„N. Isomers NH(CH3), NH,(C3H,) NH(CH3)(C,H5) N(CH3)3 NH,(C4H,,) NH(CH3)(C,Hj) and NH(C2H5)j This kind of isomerism is the same as that of the ethers (p. 93), i.e., metamerism. From (O3H7) onwards, isomerism can also occur in the alcohol radicles. According to theory, as many amines On as alcohols Cn-i-i are capable of existence. (506) H 114 IV. DERIVATIVES OF THE MONATOMIO ALCOHOLS. Behaviour, 1. For general behaviour, see above. When combined with acids to salts, the amines behave exactly like ammonia, and the ammonium bases like potash : CH3.NH2 + HCl - CH3.NH2, HCl - (CH3)NH3C1. [N(CH3)J0H 4- HCl = [N(CH3)JC1 + H^O. The salts so obtained are white, crystalline, frequently hygroscopic compounds, easily soluble in water. The chlorides form, with platinic chloride, crystalline double compounds whose composition is analogous to that of ammonio-platinic chloride, 2NH4CI, PtCl^ ; e.g., hydrochlorate of methylamine- platinic chloride, 2(NH2[CH3]HC1), PtCl^. The same applies to the gold double salts, e.g., NH2(C2H5)HC1, AUCI3. 2. Saponifying agents such as alkalies and acids do not affect the nitrogen bases of the alcohol radicles, and oxidizing agents only with difficulty. (See B. 8, 1237.) 3. The different classes of amine bases are distinguished from each other by the primary having two hydrogen atoms, the secondary one, but the tertiary none replaceable by alcohol radicles ; the same applies to substitution by acid radicles. The products thus resulting from isomeric amines are dis- tinguished from one another by analysis. Thus propylamine gives with methyl iodide the base C3H^N(CH3)2, = C^H^^N • the isomeric methyl-ethylamJne the base (CH3)(C2H5)N(CH3), = C4H9N; while tri-methylamine, (CH3)3N, = C3H9N, likewise isomeric, remains unaltered. The primary bases further differ from the others in their behaviour with chloroform, carbon bisulphide and nitrous acid. 4. Only the primary bases react with chloroform and alco- holic potash, with formation of iso-nitriles (p. 109). 5. VS^hen warmed with carbon bisulphide in alcoholic solution, the primary and secondary-, but not the tertiary bases, react to form derivatives of thio-carbamic acids. (See carbonic acid derivatives.) Should the amines be primary ones, the characteristically smelling iso- thio-cyanates are produced upon heating the thio-carbamic derivatives with a solution of HgClg, Senfol" reaction). 6. Nitrous acids act upon the primary bases to reproduce the alcohols, e.g,: NITROGEN BASES ; BEHAVIOUR OF. 115 CH3.NH2 + H.O.NO = CH3.OH + N2 + H2O. Secondary bases, on the other hand, yield with nitrous acid nitroso-compounds, e.g. " dimethyl-nitrosamine" : (CH3)2NH + NO.OH = (CH3)2N.NO + H2O. These nitroso-compounds are yellow-coloured liquids of aromatic odour, which boil without decomposition. (Geuther.) They regenerate the secondary bases upon treatment with strong reducing agents, and also upon warming with alcohol and hydrochloric acid. Weak reducing agents however con- vert them into hydrazines (p. 118). The nitrosamines are frequently of great service in the purification of the secondary bases. Nitrous acid has no action upon tertiary amines. 7. While the amine bases are liberated from their salts by alkalies, the free bases of the quaternary salts, e.g. tetra- methyl-ammonium iodide, cannot be prepared from these by treatment with potash, because they are as strongly basic as the latter, if not even more so. The salts however behave like hydriodates, for instance towards AgNOg, and their bases, e.g. N(CH3)40H, can be separated by acting upon them with moist silver oxide. They are extraordinarily like caustic potash. They cannot be distilled without decomposition, but break up on distillation with reproduction of the tertiary base, the tetra-methyl base yielding in addition methyl alcohol, and the homologous bases olefine and water, thus : N(CH3)4.0H = N(CH3)3 +CH3.OH. They are of great interest for the question of the valency of nitrogen, since they are more difficult to explain on the assumption of its being trivalent than pentavalent. (Cf. trimethyl-sulphine hydroxide.) The fact that the salts N(CH3)2(C2H5) + C.HgCl, and N(CH.3)(aH5), + CH3CI are identical, speaks in favour of the nitrogen in them being pentavalent. [Meyer and Lecco. ) 8. The quaternary iodides go back into tertiary base and alkyl iodide ii})on heating. They combine with two or four atoms of bromine or iodine to tri- and penta-bromides or -iodides, e.g. l^{C}i.^\l\ (dark needles), and N(C2H5)4Ll2 116 IV. DERIVATIVES OF THE MONATOMIC ALCOHOLS. (aziire-blue needles). These latter must be looked upon as addition-compounds_, since they readily lose their additional halogen again. Hepta- and Ennea-iodides also exist. Methylamine, CH3NH2. Occurs in Mercurialis perennis and annua mercurialin in the distillate from bones and wood, and in herring brine. It is produced in many decom- positions of organic compounds, e.g. from alkaloids, as when caffeine is boiled with hydrate of baryta; also by heating hydrochlorate of tri-methylamine to 285°. It is most easily prepared from acetamide, caustic soda, and bromine. (B. 18, 2737.) It is more strongly basic and even more soluble in water than ammonia, has a powerful am- moniacal and at the same time fish-like odour, and burns with a yellowish flame. Its aqueous solution, like that of ammonia, precipitates many metallic salts, frequently redissolving the precipitated hydroxides ; it also redissolves silver chloride. Unlike ammonia, it does not dissolve Ni(0H)2 and Co(OH)2. The hydrochlorate, NH2(CH3), HCl, forms large glittermg plates, and is very hygroscopic and easily soluble in alcohol, the platinum salt crystallizes in golden scales or hexagonal tables, the sulphate forms an alum with Al2(S04)3 -f- 24H2O, and a carbonate also exists. Di-methylamine, (CB[3)2NH. Occurs in Peruvian guano and pyroligneous acid, and is formed e.g. by decomposing nitroso-dimethyl-aniline by caustic soda solution. Tri-methylamine, (CH3)3N. Is pretty widely distributed in nature, being found in considerable quantity in Chenopodium vulvaria, also in Arnica montana, in the blossom of Crataegus oxyacantha and of pear, and in herring brine. {JVertheim.) It is obtained as a decomposition product from complicated organic compounds containing nitrogen, e.g. from the betaine of beetroot, and therefore along with ammonia, di-methylamine, etc., methyl alcohol and aceto-nitrile by the distillation of vinasse. It possesses an ammoniacal and pungent fish-like odour. Is used as bicarbonate in the preparation of potash, and combines with carbon bisulphide. HYDRAZINES. 117 Tetra-methyl-ammonium iodide, N(CH3)4l, is obtained in large quantity directly from NH3 + CH3I. It crystallizes in white needles or large prisms, and has a bitter taste. Tetra-methyl-ammonium hydroxide, N(CH3)40H. Fine hygroscopic needles. It forms a number of salts, among others a platinum double salt, sulphide, polysulphide, -cyanide, etc.; many of these are poisonous. Ethylamine, C2II5NH2. For its preparation by Hofmann's method, the crude ethyl chloride which is obtained as a bye- product in the manufacture of chloral may be used. It has a strongly ammoniacal smell and biting taste, mixes with water in every proportion with evolution of heat, and burns with a yellow flame. It dissolves Al2(0II)g but not Fe2(0H)g, also Cu(0H)2 with difficulty, but not Cd(0H)2. Ethyl-nitrogen chloride, C2H5.NCI2, is a yellow oil of a most un- pleasant piercing odour, obtained from the above compound with chloride of lime. Di-ethylamine, (C2H5)2NH, does not dissolve Zn(0II)2. Triethylamine, (C2H5)3N, is an oily strongly alkaline liquid, only slightly soluble in water. The precipitates which it gives with solutions of metallic salts are mostly insoluble in excess of the precipitant. Vinylamine, (CgHgjNHg. Easily decomposable. Appendix: Hydrazines. As hydrazines are designated by E. Fischer (A. 190, 67 ; 199, 281, 294) a series of peculiar bases, mostly liquid and closely resembling the amines, but containing two atoms of nitrogen in the molecule, and diff'ering from the latter especially by their capability of reducing an alkaline solution of cupric oxide, (Fehling^s solution), for the most part even in the cold. They are derived from " Diamide or " Hydrazine," NH2 — NH2, a compound of which but little is yet known. (Ctirtius, B. 20, 1633). We distinguish between primary hydrazines, R — NH — NHg, and secondary, E2=N — NHg, according as one or both of the hydrogen atoms which are 118 IV. DERIVATIVES OF THE MON ATOMIC ALCOHOLS. attached to an atom of nitrogen are replaced by alcohol radicles (R). Ethyl-hydrazine, C2H^— NH— NHg. When di-ethyl urea is treated with nitrous acid, a nitroso-compound is formed, which is changed by reduction with zinc dust and acetic acid into the so-called " di-ethyl-semi-carbazide." This last decom- poses upon being heated with hydrochloric acid into carbonic acid, ethylamine, and ethyl-hydrazine : CO3. B. rt. of the ethyl compound 159". They are permanent in the air but inflammable, and both — especially the methyl compound— 128 V, ALDEHYDES AND KETONES. are very poisonous. HCl reacts to produce Mercury-methyl chloride, Hg(CH3)Cl, a colourless salt, thus : Hg(CH3)2 + HCl = Hg(CH3)Cl + CH4. To this there is a corresponding iodide and also a hydroxide, Hg(CH3)0H, of strongly alkaline reaction. Mercury-ethyl hydroxide, Hg(C2H5)OH, is an oily odourless liquid of extremely caustic taste, slippery to the touch like potash, and gradually blistering the skin. Aluminium methide, A1(CH3)3, is spontaneously inflammable and decomposes violently with water. Lead methide, Pb(CH3)4, and ethide, Fh{C2H.Q) 4 {Cahours). These are formed according to method 3, curiously with separation of lead : 2PbCl2 + 2Zn(CH3)2 = Pb(CH3)4 + Pb + 2ZnCl2. They are stable in the air, and are interesting from the lead in them being tetravalent. The Hydroxide, Pb(CH3)3.0H, forms pointed prisms, smells like mustard, and is a strong alkali ; thus, it saponifies fats, drives out ammonia from its salts, precipitates metallic salts, etc. The compound Pb2(C2H5)g is also known. The tin compounds are similar (Ladenhurg, Frankland), Tin tetra-methide, Sn(CH3)4, Tin tetra- ethide, Sn(C2H5)4, Tin tri- ethide, Sn2(C2Hg)g, Tin di-methide, Sn2(CH3)4, etc., are of interest as proving the tetravalence of tin. V. ALDEHYDES AND KETONES, aH^^O. The aldehydes and ketones are substances which result from the oxidation of the primary and secondary alcohols respec- tively, with separation of two atoms of hydrogen. The Aldehydes are formed from the primary alcohols, and are easily converted by further oxidation into the correspond- ing acids containing an equal number of carbon atoms, oxygen being taken up. They possess in consequence strongly re- ducing properties. The Ketones result from the oxidation of the secondary alcohols, and are more difficult to oxidize further; they do not possess reducing properties. Their oxidation does not lead to acids containing an equal number of carbon atoms in the molecule, but to others containing a smaller number, the carbon chain being broken. ALDEHYDES. 129 The lower members of both classes are neutral liquids of peculiar smell, easily soluble in water and readily volatile, only CH2O being gaseous. With increasing carbon they soon become insoluble in water, and their odour becomes less marked with rise of melting point until the highest members are solid, odourless, like paraffin, and only capable of being distilled without decomposition in a vacuum. The aldehydes are also perfectly analogous to the ketones as regards other modes of formation and in many of their pro- perties. A. Aldehydes. The homologous series of the aldehydes, CnHgi^O, corre- sponds exactly with that of the acids, CiiH2ij02. Their boiling points lie decidedly lower than those of the corresponding alcohols, and rise, in the normal aldehydes, at first by about 27° for each CHg, and later on by a less amount. Modes of formation. 1. By the regulated oxidation of the primary alcohols, CnHsn+iOH, by potassium bichromate or manganese dioxide and dilute sulphuric acid ; often slowly by the oxygen of the air alone, especially in the presence of bone black or platinum : CH3.CH2OH + 0 = CH3.CHO + H2O. Alcohol. Acetic aldehyde. Aldehydes are also produced by the oxidation of many complicated organic substances, such as albumen. 2. From the acids of the acetic series, by distilling a mixture of their calcium or barium salts with calcium or barium formate, {Limpricht). The formic acid acts in this instance as a reducing agent, producing calcium carbonate, thus : CHg.COOca + HCOOca = CH3.CHO + CaC03. (ca - i Ca.) Other reducing agents have for the most part no action. 3. From the di-halogen substitution products of the hydro- carbons containing the atomic group CHX2, by superheating with water or by boiling with water and PbO : CHg—CHCl^ + H2O = CH3— CHO + 2HC1. Ethylidene chloride. ( 51V6 ) I 130 V. ALDEHYDES AND KETONES. Constitution. By the oxidation of the primary alcohols, E — CH2.OH, to their corresponding acids, whose constitution follows as R — CO. OH, the new oxygen atom affixes itself only to that carbon atom which is already combined with oxygen — in the form of hydroxyl — , the hydrocarbon radicle R remaining unaltered. It must consequently also remain unchanged in the intermediate products of the oxidation, the aldehydes, which therefore possess the constitution R — CHO : CH3— CH2.OH CH3— CHO CH3— CO.OH Alcohol. Aldehyde. Acetic acid. The aldehydes thus contain the atomic group — CHO or — ^^H' either to hydrogen as in formic aldehyde, H — CHO, or to an alcohol radicle as in all the other cases. Isomers. Isomerism in the aldehydes is caused solely by isomerism in the alcohol radicles R, which are combined in them with the group — CHO, and therefore contain an atom of carbon less. Otherwise the aldehydes — from C3HgO on — are isomeric with the ketones, with the oxides of the olefines {e.g. aldehyde with ethylene oxide, C2H4O), and with the alcohols of the ally lie series. Behaviour. The aldehydes are distinguished by being exceptionally active chemically. 1. For oxidation, see above. The aldehydes are very readily oxidizable, slowly even by the air alone, and quickly by chromic acid, salts of the noble metals, etc. They conse- quently reduce an ammoniacal solution of silver and often one of copper; this reaction is characteristic and is especially delicate in the presence of caustic soda solution. 2. The aldehydes are easily reducible by nascent hydrogen, e.g. sodium amalgam and dilute acid or zinc dust and glacial acetic acid, to the primary alcohols from which they are derived by oxidation, e.g. : CH3-CHO + H2 = CH3.CH2OH. A glycol is formed as intermediate product, e.g. butylene glycol, C4Hs(OH)2, from G^Rfi, ALDEHYDES; BEHAVIOUR OF. 131 3. Phosphorus pentachloride and -trichloride convert the aldehydes into ethylidene chloride and analogous di-chloro- substitution products of the hydrocarbons. 4. Addition-reactions. One would expect that upon treat- ing ethylidene chloride or analogous chlorides with water and lead oxide, for instance, two hydroxyl groups would replace OH two chlorine atoms, and a compound, CH3 — CH<^qjj, would be produced, which would be a diatomic alcohol, ethylidene glycol." Such compounds are however not formed, being apparently broken up at once into aldehyde and water, thus : CH3— CHroduced are to be regarded as deriva- tives, such as simple and compound ethers, amines, etc., of the hypothetical ethylidene- and homologous glycols. 132 V. ALDEHYDES AND KETONES. The most important addition-reactions are as follows : — {a) Combination with water, which would lead to a diatomic alcohol, does not as a rule take place, for the reasons already given. Should the alcohol radicle of the aldeh^^de, however, contain several negative atoms, e.g. CI, then the hydrates are capable of existence, for instance chloral hydrate : CCI3— CHO + H2O = CCI3— CH(0H)2. But even in these cases the tendency for water to separate is too great to allow of such hydrates behaving as diatomic alcohols ; they react rather, for the most part, exactly like the aldehydes themselves. (Cf. pyroracemic and mesoxalic acids.) (&) Similarly, combination but seldom takes place with alcohol, acetic acid, etc., with the formation of an easily decom- posable alcoholate or acetate. But, upon heating with alcohol or acetic anhydride, stable ethers, simple and compound, of the hypothetical glycols are obtained : CH3— CHO + 2C2H,.OH = CH3— CH(OC2H,)2 + H^O. CH3— CHO + (C^HgO)^ = CH3— CH(OC2H302). The compounds resulting from alcohols, the so-called *'acetals" (see p. 136), are also formed by the partial oxidation of primary alcohols, and are again separated into their com- ponents by sulphuric acid. Thio-alcohols (p. 93), yield with aldehyde, under the influence of gaseous HCl, thio-acetals which are termed Mercaptals. {c) The aldehydes combine with sodium bisulphite, NaHSOg, ammonium bisulphite, etc., to crystalline compounds, easily soluble in water but difficultly in alcohol, e.g, C2H4O + NaHSOg + IH2O. These are to be regarded as sulphonic acids of the ethy- lidene- etc., glycols, for instance, CH3 — CH(0H)(S03Na). Nevertheless they are almost always easily broken up again with re-formation of the aldehyde, warming with soda solution or with acids effecting this. They are therefore of great im- portance for the separation of aldehydes from mixtures. {d) The aldehydes combine with ammonia to aldehyde- ammonias, e.^. Aldehyde-ammonia, CH3 — CH(0H)(NH2). These ALDEHYDES; BEHAVIOUR OF. 133 are crystalline compounds, for the most part easily soluble in water, difficultly in alcohol, and insoluble in ether, whicli go back into the original aldehyde when warmed with dilute acids. Like the bisulphite compounds, they are advantageously used for the preparation of pure aldehydes. (See p. 135.) Imido-compounds of the aldehydes, R — CH=NH, are only known hi a few instances, e.g. chloral-imide, CCI3 — CH=NH ; ethyl-rnethylene- amine, CHg^N — C.2H5, from ethylamine and tri-oxy -methylene (p. 135). Many nitrile compounds are known, e.g. Hydracetamide, (CH3-CH)3N2. {e) The aldehydes combine with hydrocyanic acid to form nitriles of higher acids, thus, acetic aldehyde yields the com- pound CH3 — CJ*<^Q^, ethylidene cyanhydrin, a liquid easily broken up again into its components. (See lactic acid.) 5. The aldehydes show great tendency to polymerize. (See pp. 13 and 48.) In the case of formic aldehyde this poly- merization sets in of its own accord at the ordinary temperature. Acetic aldehyde is polymerized upon the addition of small quantities of hydrochloric, sulphuric, or sulphurous acid, zinc chloride, carbonyl chloride, etc., to para-aldehyde, CgH^gOs? = (021340)3, at the ordinary temperature, and to meta-alde- hyde, at 0°. Why the above-mentioned substances should induce this polymerization is not known. 6. Towards alkalies the aldehydes behave differently. Alde- hyde and several of its homologues are converted by heating with caustic soda solution into a reddish-brown resin termed aldehyde-resin, insoluble in water but soluble in alcohol, a peculiar odour being apparent at the same time. This reaction is characteristic. Other aldehydes are transformed by alkalies into a mixture of equal molecules of alcohol and acid, the one half being oxidized at the cost of the other half, thus : 2HC0H = CH3OH 4- H.CO2H. Formic acid. 7. The aldehydes show great inclination to form condensa- tion products, i.e. two molecules may combine together with a rearrangement of the carbon bonds and formation of a com- pound containing twice as many atoms of carbon, a hydrogen 134 V. ALDEHYDES AND KETONES. atom of the one molecule combining with the oxygen of the other to hydroxyl. In this way, when aldehyde stands for a lengthened period with dilute hydrochloric acid, /?. oxy-butyric aldehyde (see Aldol) is formed : CH3— CHO + CH2H— CHO = CH3— CH(OH)— CH2— CHO. Aldol condensation, Aldol readily separates water and goes into Crotonic aldehyde, CH3— CH=CH— CHO, which also results directly upon warming aldehyde with zinc chloride, (Aldehyde condensation). Sulphuric acid, sodium acetate in aqueous solution, and alkalies, e.g. dilute soda, baryta water, etc. , also induce condensation. The "aldol condensation" is easily explained by assuming the for- mation of an aldehyde hydrate, and subsequent separation of one of the two hydroxyls thus formed with a hydrogen atom of a second aldehyde molecule. For condensation with ketones, see these. 7a. The aldehydes combine in a similar manner with sodium acetate and acetic anhydride to acids poorer in hydrogen, See .e.g'. cinnamic acid. 8. Chlorine and bromine act upon the aldehydes as sub- stituents ; thus, from acetic aldehyde chloral is obtained , CH3— CHO + 3CI2 = CCI3— CHO + 3HC1. 9. Sulphuretted hydrogen converts the aldehydes into thio-aldehydes. These are compounds of unpleasant aromatic odour, which show the same peculiarities of polymerization as the aldehydes, (Klinger,) 10. With hydroxylamine the aldehydes yield the so-called Aldoximes, water being separated, e.g. aldoxime, CH3— CH=N.OH, {V. Meyer, B. 15, 2778). CH3.CHO + NH2OH = CH3.CH=:N.0H + H2O. The aldoximes are liquids which distil for the most part without de- composition, are capable of forming simple and compound ethers in virtue of their hydroxyl hydrogen, and are broken up into their com- ponents upon boiling with acids. Acetic anhydride decomposes them for the most part into nitrile and water : CH3— CH=N.OH = CH3.CN + H2O. By the reduction of the oximes, primary amines result, (p. 113* Qoldschmidt, B. 19, 3232; 20, 728) : CH3— CH : N.OH + 2H2 = CH3-CH2— NH2 + H2O. Y ^ Aldoxime. Ethylamine. ALDEHYDE. 135 11. The analogous reaction follows still more easily in the case of phenyl-hydrazine than in that of hydroxylamine, {E. Fischer). E— CHO + CeHg— NH-NH2 = R— CH=N— NH— CgHg + H,0. The compounds which are formed in this way are termed Hydrazones or Hydrazides. (For further details, see p. 373. ) Tests for aldehydes. (1) Behaviour with ammoniacal silver solution (see p. 130, and also B. 15, 1629). (2) Behaviour with alkaline bisulphites (see p. 132). (3) Behaviour with phenyl-hydrazine and hydroxylamine. (4) Aldehydes colour a fuchsine solution, which has been decolourized by sulphurous acid, an intensive violet-red; some ketones and chloral, but not chloral hydrate, produce the same effect. Schiff, Caw. (B. 13, 2343). Formic Aldehyde, Methyl Aldehyde, H.CHO. This may also be regarded as the oxide of the diatomic radicle methy- lene, CH2=. It is obtained dissolved in excess of methyl alcohol by leading the vapour of the latter, mixed with air, over a glowing platinum or copper spiral or platinum asbestos, {Hofmann, 1869). Other oxidizing agents lead directly to formic acid. It is only known in solution and in the state of vapour, since it polymerizes at the ordinary temperature to Tri-oxy- methylene or para-formic aldehyde, G^Ufi^, a white crystalline mass which again dissociates upon being vaporized, as is shown by the vapour density and the pungent odour evolved. Acetic Aldehyde, Aldehyde, CHg—CHO, was formerly termed "acetyl hydride," CgHgO.H, (Fourcroy and Fauquelin, 1800; composition established by Liehig in 1835; name taken from alcohol dehydrogenatum "). It is prepared by passing ammonia gas into an ethereal solution of the crude aldehyde, obtained by oxidizing alcohol with 1^2^20^^ + H2SO4 and drying over CaClg, washing the precipitated aldehyde- ammonia with ether, and finally distilling it with dilute sulphuric acid. It is obtained in large quantity as a bye- product in the first portions of the distillate in the manu- facture of spirit. For its production in place of vinyl alcohol, C2H3.OH, from acetylene, see p. 54. 136 V. ALDEHYDES AND KETONES. Colourless mobile liquid, B. Pt. 21°; Sp. Gr. about 0-8. Has a peculiar aromatic and suffocating odour, producing a kind of cramp in the chest when inhaled. Burns with a luminous flame and dissolves sulphur, phosphorus, and iodine. Chlorine converts it into acetyl chloride, and carbonyl chloride, COCI2, into a liquid of fairly constant boiling point, formerly termed "chloro-acetene." Para-aldehyde, CqRj^^^.^, is a liquid difficultly soluble in water. M. Pt. + 10° ; B. Pt. 124°, i.e. more than 100° above that of aldehyde. Is used as a soporific. Meta-aldehyde, (CgH^O)^, crystallizes in white prisms insoluble in water, which sublime at a little over 100°, with partial reconversion into aldehyde. (See B. 14, 2271). Meta-aldehyde is changed back again into ordinary alde- hyde by prolonged heating to 115° in sealed tubes, and also, as is the case with para-aldehyde, by distillation with some- what dilute sulphuric acid. Para-aldehyde reacts in the same way as ordinary aldehyde with PCI5, but not with NH3, NaHSOg, AgNOg, and NH2OH. The constitution of para- aldehyde may be taken as : 0— CHv • CH3 CHo . CH< >0 (Kekule and Zincke). \0— CH/CH3 (The connection of 3 molecules of aldehyde by C-bonds cannot be assumed, on account of the readiness with which para-aldehyde breaks up into the former.) With regard to these and other polymeric compounds, the general rule has been proved to hold, that in the case of bodies of similar constitution, the one of simpler composition is the more soluble, possesses the lower melting point, and is the more easily vaporized. Acetal, G^^^iOC^R^),. B. Pt. 104°. Methylal, CH2(OCH3)2. B. Pt. 42°. These, especially methylal, are frequently used instead of aldehyde for the carrying out of condensation reactions, (see p. 134). Methylal is employed in medicine as a soporific. CHLORAL. 137 Iso- valeric aldehyde, (Cll;Oj=C!H — CH^ — CHO, from iso-amyl alcohol. B. Pt. 92". But slightly soluble in water. Normal Heptylic aldehyde, Oevaniliol^ C7H14O, is obtained by the dry distillation of castor oil under diminished pressure. Various Aldehydes C^., Cg, Cy, Cjo, and the normal Aldehydes Cj^, Cj4, C^g, and C18, are also known, the latter being prepared from the correspond- ing normal acids. Mono- and Di-chlor-aldehyde, CHgClCHO, and CHCI2CHO, are liquids boiling respectively at 85° and 89°. Chloral, CCI3.CHO, (Liehig), is a liquid which boils at 98°, and which — when impure — easily changes into a solid poly- meric modification, meta-chloral, but is regenerated from this upon heating. It combines readily with water to chloral hydrate, CCl3.CH(OH)2, (see p. 131), and with alcohol to Chloral alcoholate, CCI3— CH(OH)(OC2H5), and Tri-chloro- acetal, CCI3 — C}1{0. 02^1^)2- The end product of the action of chlorine upon alcohol consists chiefly of the last three sub- stances, which are converted into chloral by distilling with sulphuric acid, and rectifying over lime. Chloral is an oily liquid of a sharp and characteristic odour. It combines with sodium bisulphite, ammonia, hydrocyanic acid and acetic anhydride, and reduces an ammoniacal solution of silver. It is easily oxidized to tri-chloracetic acid, and broken up by alkali into chloroform and alkaline formate : CClgCH.O + HKO = CCl3H-fHC02K. Chloral Hydrate, CCl3.CH(OII)2, forms crystals readily soluble in water, melting at 57°, and boiling with dissociation at 97°. It acts as a soporific and antiseptic. Sulphuric acid converts it into chloral. Of the aldehydes poorer in hydrogen must be mentioned, in addition to Crotonic aldehyde (p. 134), Acrolein, Acrylic aldehyde, Allyl aldehyde, CHg^CH— CHO, which is produced by the oxidation of allyl alcohol, by the distillation of fats, and by heating glycerine with bisulphato of potash. It is a liquid boihng at 52°, of pungent odour (the smell of burning fat being due to it), and of violent action 138 V. ALDEHYDES AND KETONES. upon the mucous membrane of the eyes. It unites in itself the properties of an aldehyde and of a compound poorer in hydrogen. Acrolein-ammonia yields picoline, CgH^N, upon distillation (see pyridine bases), and crotonic aldehyde-ammonia, by an analogous reaction, collidine, C8H;^iN. Acrolein is capable of combining with two atoms of bromine to Di-bromo-acrolein, (di-bromo-propyl aldehyde), CHgBr — CHBr — CHO, a compound which is of importance in the synthesis of the sugars. (See p. 285.) B. Ketones. The lowest member of the series, Acetone, contains three atoms of carbon. The higher members, from solid. They are all lighter than water, e.g.^ the Sp. Gr. of acetone is 0-81 at 0°. Occurrence. Acetone is present in urine, methyl-nonyl ketone in oil of rue, Euta graveolens. For constitution and nomenclature, see below. Modes of formation, 1. By the oxidation of secondary alcohols, which lose thereby two atoms of hydrogen : CH3.CH(OH).CH3 + 0 = CH3.CO.CH3 + H2O. Y ' Y ^ Iso-propyl alcohol. Acetone. Many other compounds also, which contain secondary hydro- carbon radicles, yield ketones upon oxidation, e.g. iso-butyric acid. 2. From acids by the dry distillation of their calcium or barium salts, carbon dioxide being formed : 2CH3— COOca = qh'>^^ + ^^3^^- When two different acids are employed, mixed ketones, i.e. ketones containing different alcohol radicles result, thus r CH3— COOca + CH3.CH2. COOca = >C0 + C03Ca. Calcium acetate and propionate. Methyl-ethyl- ketone. KETONES ; FORMATION OF. 139 From an acid C,, there is thus formed a ketone C2i._i, from two acids and 0,^ a ketone C„+ni-i- When formate of calcium is used, formic aldehyde results. 3. From di-chlorides containing the atomic group ^CClg : (CH3)2CCl2 + H^O = (CH3)2CO Hr 2HC1. Acetone chloride. Acetone. One might expect here that two chlorine atoms would be exchanged for two hydroxyls, and a compound of alcoholic character, a diatomic alcohol, acetonyl-glycol, (CH3)2C=(OH)2, would be formed. But the law, already mentioned under aldehyde, that several hydroxyls cannot as a rule exist beside one another joined to the same carbon atom, is further exemplified in this instance also. Derivatives of such a glycol are, however, capable of existence. 4. By the action of zinc-alkyl upon an acid chloride, e.g, acetyl chloride, CH3.COCI: CH3.COCI + CHgZn = ch'>^^ (^^ = iZn-) An addition compound is first formed^ which must be quickly decomposed by water, otherwise tertiary alcohols are produced. This method of formation, which was devised by Freund in 1861, allows of the preparation of any possible ketone by using the corresponding zinc-alkyl and acid chloride, e.g.: C3H7.CO.CI + C2H5zn = C3H7.CO.C2H5 + Clzn. ^ Y- ' Butyric chloride. Ethyl-propyl ketone. At the same time it elucidates, together with method 2, the constitution of the ketones, from the constitution of the corre- sponding acids. Theoretically, therefore, ketones are com- pounds which contain the carbonyl group, CO, linked on both sides with an alcohol radicle, R— CO — R. If the alcohol radicles are the same, simple'' ketones result, and if diff'erent, mixed " ketones. The ketones may also be regarded as derived from monobasic acids by the exchange of their hydroxyl for alkyl, corresponding with modes of formation 2 and 4, and also from aldehydes by exchange of hydrogen for alkyl. 140 V. ALDEHYDES AND KETONES. The existence of ketones with less than 3 atoms of carbon is theoretically impossible. 5. From the ketonic acids or their ethers, e.g, aceto-acetic ether, CH3 — CO — CH2 — CO.OCgH^, by warming with moder- ately dilute sulphuric acid or with dilute alkalies. This im- portant reaction will be treated of at greater length under aceto-acetic ether. 6. From the hydrocarbons of the acetylene series (see p. 54), by the action of mercuric salts and also of dilute sulphuric acid. Isomers. The ketones show among themselves the same isomerism as the secondary alcohols. This isomerism depends on the one hand upon the isomerism of the alcohol radicles which are linked together by the CO-group, (different carbon atom chains), and on the other by the position of the oxygen atom on similar carbon chains, (isomerism of position) ; thus, C^H^— CO— CH3 is isomeric with C3H7— CO— C2H5. The aldehydes containing an equal number of carbon atoms in the molecule are always isomeric with the ketones, since both classes of compounds are formed from isomeric alcohols by the separation of This kind of isomerism may also be compared with metamerism, e.g. with that of methyl-butyl ether and ethyl-propyl ether. Nomenclature. After the name of the alcohol radicle the syllable "ketone" is appended, e,g. di-ethyl ketone, {G^^\QO, and methyl-ethyl ketone, CH3 — CO — CgH^. Acetone is con- sequently di-methyl ketone. The names of the simple ketones are also derived from the acids which yield them, e.g. " Valerone," (0^119)200, from valeric acid. Baeyer (B. 19, 160) terms the ketones keto-substitutmi products of the hydrocarbons, and betokens the position of the oxygen similarly to that of the hydroxyl in the oxy-acids or of the halogen in the substituted fatty acids, by marking the end carbon atom with w, and the following ones in their order with a, j8, /3', a'. In this way acetone is termed keto-propane, and ethyl-methyl ketone a-keto-butane, etc. Behaviour. 1, The ketones are reducible to secondary alcohols : (GR,),CO + R, = (OH3)2CH.OH. KETONES ; BEHAVIOUR OF. 141 At the same time pinacones are formed in small quantity, (see p. 191), these going into the pinacolines (pp. 77 and 144) correspoiiCCl2. 4. From acid chlorides and zinc alkyl. 5. From ketonic acids, with separ- ation of COg. Properties. 1 . Reducible to secondary alcohols. 2. Oxidizable to acids, Cn-x; uot reducing. 3. Yield with PCI5 dichlorides, >0Cl2. 4. Capable of combining with [{a) water; (6) alcohol, both sel- dom], (c) ammonia, toacetone- amines with separation of water; {d) sodium bisulphite, to crystalline compounds ; (e) hydrocyanic acid, to nitriles of higher acids. Condensible, e.g. C9H14O, C9H12. to CeHioO, to Capable of substitution, e.g, chloro-acetone, CH3— CO-CH2CI. Yield with H2S, thio-acetones. Yield with hydroxy! amine. oximes, >C = N . OH. (606) n means an equal number of carbon atoius. 146 VI. MONOBASIC FATTY ACIDS. We have, for instance, the following relations : Paraffins. Ketones. Acids. CjiHooO Cn^2,£ .»»»;;;;::^CnH2A ' CioHoaO-^^ ""Z.^^ 1 If, for example, the acid C12II24O2 is normal, so is the paraffin C12H26, and also the ketone C13H26O, since the preparation of the last depends upon the exchange of the OH of the acid for CH3, the new C atom being again an end one. Consequently the paraffin C13H28 is also normal and, if this be identical with the paraffin C13H28 from the acid C13H26O2, the latter must likewise be normal. Since, further, the acid G11H22O2 re- sults from the oxidation of the ketone, C13H26O or Ci^Hig — CO — CH3, it must be normal, and therefore also the paraffin C11H24. The paraffins Cii, C12, and Ci3 are thus to be referred to one another through the acid Ci2H2402> hydrocarbons C13, C14, and C^g through the acid C14, and so on; likewise the acids Cg, Cjo, and C^ through the paraffin C^, etc., etc. Now the acids C125 ^u, C^g, and C^g, which occur in nature, yield as a matter of fact ketones, paraffins, and acids which — from their syn- theses — are undoubtedly derived from nonylic acid ; consequently they themselves and all their derivatives are normal. (Cf. the Aldehydes and ketones, table, p. 145.) VI. MONOBASIC PATTY ACIDS. A. Saturated Acids, C^HgA. (See Table, p. 147.) By the oxidation of the primary alcohols or of their corre- sponding aldehydes the monobasic fatty acids are formed, the saturated alcohols yielding the saturated monobasic fatty acids, or " acids of the aliphatic series " as they are termed, corresponding to which, as to the alcohols, there are unsaturated compounds. These acids are monobasic, i.e. contain in the molecule only one replaceable atom of hydrogen, because they give rise to only one series of salts or of ethers. They are known as the fatty acids, on account of many of them being either contained in fats or resulting from these by oxidation. The lower members of the series are liquids of pungent odour and corrosive action which boil without decomposition, VI. MONOBASIC FATTY ACIDS. 147 oooooooooooooo^ (MT)1C000O > ^ O O O o o o o o o ^ (M Tf CO 00 ^ «5 1> 00 C35 rH o o o o o 1=1 ? .2 o O H p ^ ^ rH C W O ^ 148 VI. MONOBASIC FATTY ACIDS. dissolve readily in water, and show a strongly acid reaction. The middle members have an unpleasant smell like that of rancid butter or perspiration, and are oily and but slightly soluble in water. Mobility, odour and solubility diminish with increasing carbon. The higher members, from C^q on, are solid, like paraffin, and insoluble in water, and can only be distilled without decomposition in a vacuum. Their acid character no longer finds expression in their reaction, but in their capability of forming salts with bases. They remain easily soluble in alcohol and especially in ether. For the laws governing the melting and boiling points, see pp. 28 and 26. The Sp. Gr. of the liquid acids is at first > 1, and from C3 onwards < 1, and it decreases continuously down to about 0*8, the paraffin character of the hydrocarbon radicle becoming preponderant. Occurrence. Many of the acids of this series are found in nature in the free state, but more frequently as ethers, viz. : — {a) ethers of monatomic alcohols (see wax varieties), (6) ethers of glycerine or glycerides, in most of the vegetable and animal fats and oils. For further particulars see p. 161. Formation. 1. By the oxidation of the primary alcohols, CuHgn+iOH, or their aldehydes, Ci^HguO, by means of K2Cr207 or MnOg and dilute H2SO4, or by the oxygen of the air in presence of platinum or of nitrogenous substances, e.g. acetic acid from alcohol. 1^. Acids containing less carbon are formed by the oxidation of many other compounds, such as ketones, secondary and tertiary alcohols, etc. , with separation of carbon. The higher molecular acids of this series are likewise converted into their lower homologues upon oxidation. 2. Several acids have been prepared from the halogen com- pounds CnHgn-iXg, which contain the group — CX3, e.g. : HCCI3 + 4K0H - H.CO2K + 3KC1 + 2H2O. From this mode of preparation one might expect an exchange of the three chlorine atoms for three hydroxyls, with formation of the intermediate compounds H . C=(0H)3 or E — C(0H)3. Such compounds are however incapable of existence for the reasons stated under the aldehydes and ketones, going over into acids with elimination of water, thus : E— C(0H)3 - R— CO.OH + H2O. MODES OF INFORMATION. 149 But derivatives of these (whicli may be regarded as triatoniic alcohols and termed "ortho-acids,") are known, e.g. ortho-formic ethyl ether, HC(OC2H5)3, a neutral liquid of aromatic odour, insoluble in water, and boiling at 146°. 3. From the cyanogen compounds of the alcohol radicles, Cj^Hgn+iCN. The cyanides, i.e. nitriles, which are prepared by warming the iodides of the alcohol radicles with cyanide of potassium, are converted into the fatty acids and ammonia by saponification, e.g. by heating with potash, with dilute or concentrated hydrochloric acid, or with sulphuric acid diluted with its own volume of water, thus : CH3.CN + 2H2O = CH3.CO2H + NH3. In this way hydrocyanic acid yields formic acid and ammonia, and it may therefore be regarded as the nitrile of the former. Amides are formed as intermediate products. (See pp. 107 and 180.) The great importance of this reaction, by means of which we can obtain an acid Cn+i from an alcohol C^, has been alread}^ indicated, (p. 108). And since the acids, albeit with some difficulty, can be converted by reduction into the corre- sponding alcohols, it is thus possible to build up synthetically, step by step, the alcohols richer in carbon from those poorer in carbon, a circumstance which is of especial importance in the case of the normal alcohols. {Lieben and Ross% see p. 77.) 4. The acids may be regarded as resulting from the paraffins Cn-iH2(n— 1)+2 and CO2, e.g. acetic acid from CH4 and CO2, and formic acid from Hg and CO2. These two components can in fact be made to combine indirectly, thus carbonic acid unites with potassium or sodium alkyl upon warming, ( WanMyn) : CHgNa + CO2 = CHg.CO^Na. Formic acid is obtained in an analogous manner from nascent hydrogen and carbon dioxide, under the influence of the electric dis- charge : H2 + CO2 = H.CO2H; or from hydrogen, potassium and carbon dioxide, when the potassium is placed in a bell jar filled with moist carbonic acid, (Kolbe and Schmitt^ 1861). 150 VI. MONOBASIC FATTY ACIDS. 5. By passing carbonic oxide over heated caustic alkali or alcoholate, thus : CHg.ONa + CO = CHg.COoNa (at 160°). H.ONa + CO = H.CO^Na. 6. Acid chlorides (p. 176) are produced by the action of phosgene, COCI2, upon zinc alkyl : COCI2 + znCHg = CH3.COCI + znCl; Acetyl chloride. and, on decomposing these with water, the acids themselves are obtained : CH3.CO.CI + Hp = CH3.CO.OH + HCl. 7. From acids poorer in hydrogen by direct or indirect addition of the latter, e.g. propionic acid, CgHgOg, from acrylic acid, C3H4O2. This addition of hydrogen may be effected directly by hydrioclic acid and phosphorus, or indirectly, for instance, by addition of hydrobromic acid and backward substitution. Unsaturated acids also yield saturated ones containing fewer carbon atoms when fused with potash, e.g. 1 mol. crotonic acid, C4Hg02, yields 2 mols. acetic acid, C2H4O2. 8. From the oxy-acids, also termed alcoholic acids, by 'heating them with hydriodic acid : C3Hg03 + 2HI = CgHgOg + I2 + H2O. Lactic acid. Propionic acid. 9. From many polybasic acids, by the partial separation of CO2, thus : C2O4H2 = CO2 + H.CO2H. Oxalic acid. Formic acid. 10. Aceto-acetic ether syntheses. The homologues K_CH2— COOH and ^,>CH— COOH can be prepared from acetic acid by first converting the latter into aceto-acetic ether, CH3 — CO — CH2 — COO.CgHg, intro- ducing the alcohol radicle into this, and then breaking up backwards the compound so obtained by concentrated alcoholic potash. This reaction will be gone into more fully under aceto-acetic ether (p. 226). 10a. An analogous reaction follows on the use of malonic ether (seep. 234). BEHAVIOXTR. 151 Separation. Natural fats are nearly all glycerides of several acids, so that a mixture of acids results on their saponification. This mixture may be separated into its components as follows : {a) By fractional distillation in a good vacuum ; [h) by fractional pre- cipitation of an alcoholic solution of the acids by means of magnesium acetate, calcium chloride, etc., the acids richer in carbon being pre- cipitated first; (c) by fractional solution : the dry barium salts of formic, acetic, propionic and butyric acids are very differently soluble in alcohol, the solubility increasing rapidly w^ith increasing carbon ; [d) by frac- tional saturation, and distillation of the non-combined acid. Behaviour, 1. Salts. The foregoing acids being monobasic, they form neutral salts, e.g. (C2H302)Na. But they also yield acid salts — the so-called super-acid salts — from the existence of which one might feel inclined to doubt their monobasic nature. These salts are, however, only crystallizable from a strongly acid solution, break up on addition of water, and also lose their excess of acid upon heating. It is therefore permissible to regard them as molecular compounds of the neutral salts with the acids, in which the latter play the r61e of water of crystallization. All the other chemical characteristics of the acids go to prove their monobasicity. 2. Besides salts, the monobasic acids, simple or substituted, yield other derivatives in a manner exactly analogous to that of the monatomic alcohols. The typical hydrogen atom is replaceable by an alcohol radicle with formation of a compound ether, or by a second acid radicle with formation of an an- hydride; the hydroxy 1 may further be replaced by halogen, especially chlorine, to an acid chloride or chloro-anhydride, by 8H to a thio-acid, by NHg to an amide, etc. (See Acid derivatives, p. 173.) 3. Halogens act upon the acids as substituents (see p. 168). 4. Upon heating with soda-lime, carbonic acid is separated {uid a paraffin formed, see e.g. methane. Paraffins also result from the electrolysis of the alkaline salts of the acids, (see ethane). 5. Most of the acids are relatively stable towards oxidizing agents, formic acid alone being readily oxidized to carbonic acid, and being therefore a reducing agent. 6. When the lime salts of the acids are heated with calcium formate, they are reduced to aldehydes, and when heated for 152 VI. MONOBASIC FATTY ACIDS. a lengthened period with hydriodic acid and phospliorus, to paraffins. 7. For their transformation into the amine bases, G^_i^ see p. 182. 8. For the building up of the higher acids, see pp. 145 and Constitution, It follows from their modes of formation, especially 3, 4, and 6, and also from their behaviour (see 3 above), that acetic acid and its higher homologues contain alcohol radicles. The conversion of the alcohols into acids containing one atom of carbon more, by means of the cyanides, is especially strong proof of this. The latter contain the alcoholic radicle bound to the cyanogen group — C=N, and when they are saponified the alcohol radicle remains un- changed, and the trivalent nitrogen is replaced by 0" and (OH)', both of these attaching themselves to the carbon atom of the original cyanogen, and so forming the group Consequently all the oxygen in the acid is bound to a singk carbon atom in the form of the group COgH. This group, which is termed carboxyl, is characteristic of the existence of acid properties. The monobasic acids may therefore be re- garded as compounds of the alcohol radicles with carboxyl, thus : Formic acid is, in this way, the hydrogen compound of carboxyl, H.COgH. The acids are distinguished as primary, secondary, or tertiary, accord- ing as the alcohol radicles which they contain are primary, etc. The monobasic acids may be regarded as being derived from the hypothetical carbonic acid, C0(0H)2, by exchange of hydroxyl for alkyl or hydrogen : CO<^Q^^ = Butyric acid ; C)0<^qjj = Formic acid. They are also termed organic carboxylic acids, and may also 182. CONSTITUTION. 153 be considered as derived from the parallius by exchange of an atom of hydrogen for carboxyl. Thus acetic acid is methane- carboxylic acid, etc. There is no room for doubt that it is the hydrogen atom of the carboxyl group, the so-called typical " hydrogen atom, which is replaced by metals in the formation of salts, for the foregoing acids are all monobasic, and consequently the number of hydrogen atoms present in the alcohol radicle is of no moment for the acid character. In the di- and polybasic acids, the presence of two or more carboxyls must therefore be assumed. If one compares the composition of the primary alcohols, R — CHg.OH, with that of the corresponding acids, R — CO. OH, (R = alkyl or hydro- gen), the latter are seen to be derived from the former by the exchange of two atoms of hydrogen of the carbinol for one atom of oxygen. The character of the original substance is thus completely changed by the entrance of the electro-negative (acidifying) oxygen. It must not be forgotten that the constitution of the aldehydes and ketones, of the primary and secondary alcohols, of glycol, ethylene, ethylene bromide, etc., are deduced from the constitution of the acids. The rational formulae of the foregoing acids may be written in various ways, according to the reaction which it is desired to indicate. (Cf. p. 19.) The group G^Rfi — or CH3.CO — , acetyl, which together with hydroxyl is common to most of the acetic acid deriva- tives, and which can be transferred like an element to other compounds by exchange, is termed the radicle of acetic acid (see p. 22). The radicles of the homologues are similarly compounded, e.g. H.CO — , formyl ; C3H5O — , propionyl; C^HyO, butyryl, etc. The aldehydes may be looked upon as hydrogen compounds of the acid radicles, and the ketones as compounds of the latter with alcohol radicles, thus : Isomers. The acids of the acetic series show the same isomerism as the alcohols containing one atom of carbon less, since they are formed from these by means of the cyanides. Thus there exist one propionic acid, two butyric acids, corre- (CH3.CO)CH3 Acetone. 154 VI. MONOBASIC FATTY ACIDS. spending to the two propyl alcohols, four valeric acids, corre- sponding to the four butyl alcohols, and so on. For C^qH2q02, 211 isomeric forms are possible. Among all such isomers there is always only one normal acid. On the other hand, the number of isomeric acids with n carbon atoms is always equal to that of the isomeric primary alcohols contain- ing the same number of atoms of carbon. Formic Acid, aciclum formicum, CH2O2, {Samuel Fischer and John Bay, 1670; Margraf), occurs free in ants, especially Formica rufa, in the processionary caterpillar (Bombyx pro- cessionea), in the bristles of the stinging nettle, the fruit of the soap tree (Sapindus saponaria), and in tamarinds and fir cones ; also in small quantity in various organic liquids, in perspiration, urine, and the juice of flesh. Formation. From HON, CHCI3, CH3OH, COg, etc., (see general methods of formation). It also results from the action of sodium amalgam upon ammonium carbonate or alkaline hydrocarbonates, etc. ; by the dry distillation or oxidation of many organic substances, e.g. starch, (Scheele) ; also by decom- posing them — e.g. sugar — by concentrated sulphuric acid. Preparation. 1. Carbonic oxide is readily absorbed by soda- lime at 210°, with formation of sodium formate (Merz). 2. When oxalic acid is heated, formic acid is obtained in small quantity together with carbonic oxide, carbonic acid and water, and the same effect is produced by the direct action of sunlight upon its aqueous solution containing uranic oxide : C^H^O, = CO, + CH^O^. This decomposition is best effected by heating oxalic acid with glycerine to 100°-110°, (Berthelot, Lorin), the formic acid produced combining with the glycerine to an ether, Monofor- min, (see p. 202) : C3H^)3 + H.CaOH = (^s^K'^Q^l^Q^ +H,0. Glycerine. \ ^ Monoformin. FORMIC ACID. 155 The monoformin is then saponified either by boiling it with excess of water or by the addition of more oxalic acid, through the water of crystallization of the latter. In this case mono- formin and carbon dioxide are again produced, the process repeating itself time after time, a very small amount of glycerine being thus sufficient to convert considerable quantities of oxalic into formic acid. Properties. Colourless liquid which solidifies in the cold and fumes slightly in the air. M. Pt. + 9^; B. Pt. 99°; Sp. Gr. 1*22. Has a pungent acid and ant-like odour, acts as a power- ful corrosive, and produces sores on the soft parts of the skin. Is stronger than acetic acid and a powerful antiseptic. De- composes completely into carbonic oxide and water when heated with cone, sulphuric acid : CH2O2 = CO + H2O. Salts. Potassium-, HCOgK, Sodium-, HCOgNa, and Am- monium formate, HCOgNH^, form deliquescent crystals. The first two go into oxalates when strongly heated, with evolution of hydrogen (see p. 231) ; the ammonium salt into formamide and water at 1 80° : HCO2.NH4 = H.CO.NH2 + H2O. The lead salt, Pb(HC02)2, forms glancing, difficultly soluble needles, the copper salt, Cu(HC02)2 + ^HgO, large blue mono- clinic crystals, and the silver salt colourless crystals. The last-mentioned separates silver upon warming, consequently a solution of nitrate of silver is reduced when heated with formic acid. The easily soluble mercuric salt, IIg(HC02)2, gives up carbonic acid upon being gently warmed, and goes into the sparingly soluble mer- curous salt, Hg2(HC02)2j which separates in white plates; on increasing the temperature further, this decomposes in its turn into carbon dioxide and metallic mercury. Similarly an aqueous solution of mercuric chlor- ide is reduced by formic acid to the mercurous salt, HggClg. Formic acid is thus a strong reducing agent : HCO.OH = CO2 + H2. It decomposes into carbonic acid and hydrogen when heated alone to 160°, or when brought into contact with finely divided rhodium. 156 VI. MONOBASIC FATTY ACIDS. This power of reduction which distinguishes formic acid froni all its higher homologues, may be explained by its close relationship to carbonic acid, and also by the aldehydic character which one can read in its constitutional formula, H — 0 — CHO. Acetic Acid, acidum aceticum, G^Ufi^, was known in the dilute form, as crude wine vinegar, to the ancients. Stahl prepared the concentrated acid about 1700. Glauber mentions wood vinegar (1648). Its constitution was established by Berzelius in 1814. Occurrence. Salts of acetic acid are found in various plant juices, especially those of trees, and in the perspiration, milk, muscles and excrementa of animals. Ethers of acetic acid also occur, e.g. triacetin in croton oil, (see p. 162, and also under glycerine). Formation. (See p. 148 et seq.) Is the final product of the oxidation of a great many compounds, and also of their treat- ment with alkalies. The following synthesis is of historical interest. Perchloro-ethylene, C2CI4, which is prepared from CCI4, i.e. from CI and CSg, yields with chlorine in presence of water in direct sunlight tri-chloracetic acid, carbon trichloride, CgClg, being obviously formed as intermediate product, {Kolbe, 1843) : CCI3— CCI3 + 2H2O = CCI3— CO2H +3HC1. The latter acid is reduced to acetic by nascent hydrogen, (Melsens). Preparation. 1. From Alcohol. A dilute aqueous solution of alcohol, containing up to 15 p.c, is slowly converted into acetic acid on exposure to the air and in presence of nitrogen- ous substances, by the agency of a micro-organism, the " mother of vinegar," acetic ferment, or mycoderma aceti. The acetic fermentation is manifested in the souring of beer or wine, with the production of beer or wine vinegar. Vinegar is an aqueous solution of acetic acid, usually containing only 3 to 5 p. c. , but containing also small quantities of alcohol, of the higher acids, e.g. tartaric and succinic, the ethyl ethers of the acids, albumin- ous matters, etc. It is manufactured on the large scale either, as in France, by the older method in a series of half -full oaken casks, or by the newer quick vinegar process, [Schiitzenhach). 2. From Wood. The dry distillation of wood, which is con- ACETIC ACID. 157 ducted in cast-iron retorts, yields (1) gases, e.g, hydrogen 15 p.c, methane 11 p.c, carbon dioxide 26 p.c, carbonic oxide 41 p.c, and higher hydrocarbons 7 p.c. ; (2) an aqueous solution known as pyroligneous acid which, in addition to acetic acid, contains methyl alcohol, acetone, homologues of acetic acid, and strongly smelling combustible products, (em. pyreuma) ; and (3) wood tar, which contains compounds of the nature of carbolic acid. The pyroligneous acid is worked up for acetic acid by converting it into the sodium or calcium salt, heating these — the former up to its melting point and the latter to 200° — to get rid of empyreumatic substances, and then distilling with sulphuric acid. Properties. Acetic acid is a strongly acid liquid of pungent odour, which feels slippery to the touch and burns the skin, and which solidifies in the cold to large crystalline plates melting at 17°; (Glacial acetic acid). B. Pt. 118°, Sp. Gr. at 15°, 1*055. Its vapour burns with a blue flame. When mixed with water, contraction and consequent increase in density ensue, the maximum point corresponding with the hydrate CH3CO2H + H2O, = CH3C(OH)3, (ortho-acetic acid), which contains 77 p.c. acid and has a Sp.Gr. of 1*075 at 15*5°; after this the specific gravity decreases with further addition of water, so that a 50 p.c. acid has almost the same density as one of 100 p.c. The amount of acid present in a solution is determined either by its Sp. Gr., this contraction being borne in mind, or by titration. The vapour density near the boiling point is much higher than that required by theory, but is normal above 250°. The acid is hygroscopic, and stable towards chromic acid and cold permanganate of potash. It dissolves phosphorus, sulphur and many organic compounds, is corrosive, and gives rise to painful wounds on tender parts of the skin. Salts. All the neutral salts of acetic acid are soluble in water. Potassium acetate, KC2H3O2 ; hygroscopic colourless plates. Acid potassium acetate, C2H3O2K + C2H4O2, crystallizes from the concentrated acid in glancing mother-of-pearl plates. A salt of the composition C2H3O2K + 2C2H4O2 is also known. 158 VI. MONOBASIC FATTY ACIDS. Sodium acetate, NaC2H302, forms transparent easily soluble rhombic prisms, (terra foliata tartari crystallisabilis). Ammonium acetate, NH4C2H3O2, resembles the potassium salt. It is used in medicine as a sudorific, (Liquor ammonii acetici). Its solution loses ammonia on evaporation, and it yields acetamide when distilled. Ferrous acetate, Fe2(C2H302)4, is largely used in the form of ^' iron liquor" as a mordant in dyeing. The normal ferric salt, Fe2(C2H302\,, which is employed for the same purpose, is obtained when a soluble ferric salt is mixed with sodium acetate. Its solution is deep brown-red in colour, and deposits the iron as basic salt when heated with excess of water : Fe,(C,H30)e + 4H,0 = Fe^ { {gJ^^J^^^^ + 4C,HA- It is used in medicine as liquor ferri acetici." The analogous aluminium acetate is only known in solution, and finds a wide application as " red liquor " mordant in calico printing and dyeing. Its use depends upon its easy decom- posability by water, e.g. when exposed to the action of steam, and on the affinity of the residual alumina com]3ound for the colouring matter. It is employed in small doses as an astringent in cases of diarrhoea, etc. Lead salts. (1) Neutral lead acetate or sugar of lead, Pb(C2H302)2 + 3H2O, is manufactured from sheet lead and acetic acid. It forms colourless glancing four-sided prisms, which are poisonous and of a nauseous sweet taste. It com- bines with lead oxide to (2) Basic salts of alkaline reaction, termed sub-acetates. The simplest basic salt has the composition Pb<^|^J^ q ^ but there also exist others, e.g. pv,]^0 etc. •^K(0,H30,) Two molecules of acetic acid can combine with as many as five molecules of lead oxide. These basic acetates are used as Goulard's lotion, and on the large scale for the preparation of lead white, etc. PROPIONIC AND BUTYRIC ACIDS. 159 Cupric acetate, Cu(G2H302)2 + 2H2O, dark green easily soluble crystals, also forms basic salts (Verdigris). It yields double salts with cupric arseniate, e.g. Schweinfurth green. Silver acetate, AgOgHgOg, is a well characterized salt of acetic acid ; glancing needles. Detection of acetic acid. (1) Upon heating an acetate with alcohol and sulphuric acid, the pleasant smelling ethyl acetate is formed ; (2) By means of the silver salt ; (3) By the odour of cacodyl produced upon heating the potassium or sodium salt w ith AsgOg. Propionic acid, = CH3— CH^— CO^H. {GoUlieh, 1844.) Formation, From acrylic and lactic acids (see p. 150); also from lactate or malate of calcium by suitable schizomycetes fermentation, {Fitz), Preparation. By the saponification of ethyl cyanide (pro- pionitrile), (1847). (See pp. 149 and 108.) Calcium chloride separates it from its aqueous solution in the form of an oil, whence its name TrpiaTosy the first, and ttlojv, fat ; the first oily acid. Butyric acids, C4Hg02. (1) Normal Butyric acid, fermentation butyric acid, propyl- carbonic acid, CH3 — CH2 — CH2 — CO2H. Occurrence, Free in perspiration, in the juice of flesh, in the contents of the great gut, and in the solid excrementa ; as hexyl ether in the oil of the fruit of Heracleum giganteum, as octyl ether in Pastinaca sativa, and to the extent of 2 p.c. as glycerine ether in butter, (Chevreul, 1822). Formation. (See also general modes of formation.) Is pro- duced by the decay of moist fibrin and of cheese (being therefore contained in Limburg cheese), by a Schizomycetes fermentation of glycerine, and especially by putrefaction and fermentation in neutral liquids, {Pelouze and Gelis, see below). Further, by the oxidation of albuminates with chromic acid, of fats with nitric acid, of conine, etc., and also by the dry distil- lation of wood. Prejjaration. In the "butyric fermentation" of sugar or starch by fission ferments (Schizomycetes^ especially Bacillus 160 VI. MONOBASIC FATTY ACIDS. subtilis), CaCOg or ZnO being added at the same time, to combine with the acid formed. Lactic and carbonic acids (see lactic fermentation) are first produced here, and then butyric acid, with evolution of hydrogen. Properties. Thick liquid of unpleasant rancid odour, in pre- sence of ammonia like that of perspiration, miscible with water, and separating from the aqueous solution on the addition of salts. B. Pt. 163°. Difficultly oxidizable. The calcium salt, Ca(C4H^02)2 + H2O, forms glancing plates, and is characterized by being more soluble in cold than in hot water ; it therefore separates on warming the concentrated cold aqueous solution. On prolonged heating of the solution, however, it is trans- formed into the Oa salt of iso-butyric acid. The silver salt, Ag(C4H^02), crystallizes in glancing plates, slightly soluble in water. (2) Iso-butyric acid, di-methyl-acetic acid, iso-propyl-formic acid, (CH3)2=CH— CO2H. Is present in the free state in the carob (Bedtenbacher), in the root of Arnica montana, and as ether in Pastinaca sativa and Roman camomile oil. It is obtained from isopropyl cyanide (Erlenraeyer), by the oxidation of isobutyl alcohol, by the aceto-acetic ether syn- thesis (p. 150), etc. It is very like fermentation butyric acid, but is more sparingly soluble in water (1 in 5), and boils 9° lower, i.e. at 154°. Unlike the latter, however, it is easily oxidized to acetone or acetic acid, and carbonic acid. The existence of isobutyric acid was predicted by Kolbe in 1864 upon theoretical grounds. The calcium salt, Ca(C4H702)2, differs from its isomer in being more soluble in hot water than in cold. Valeric acid, C5H^q02, exists in the four different modifica- tions which are theoretically possible : (1) Normal Valeric acid, propyl-acetic acid, CH3— (CH2)3 — CO2H, from normal butyl cyanide, {Lieben and Rossi, 1871), Is best prepared from propyl-malonic acid. (See malonic acid synthesis.) B. Pt. 185°. Only soluble in 27 parts of water. (2) Iso-valeric acid, ordinary valeric acid, isopropyl- acetic acid, isohutyl-forndc acid, (CH3)2=CH — OHg — CO2H, results from isobutyl cyanide. It is found in the free state and in the form VALERIC ACIDS, ETC. ]61 of ethers in the animal kingdom and in many plants, especially (free) in the valerian root (Valeriana officinalis), and in the angelica root (Angelica arch angelica), from which it is obtained by boiling with soda ; further, in the blubber of the dolphin (Chevreul, 1817), in the berries of Viburnum opulus, in the perspiration from the foot, etc. The natural acid is usually mixed with the active valeric acid, and is therefore optically active ; the oxidation of fermentation amyl alcohol by chromic acid yields a similar mixture. When pure it is optically inactive. B. Pt. 175°. It has an unpleasant pungent acid odour, like that of old cheese, and a corrosive action. It is used in medicine. Forms a hydrate with water. (3) Methyl- ethyl-acetic acid, active valeric acid, ^ jj^^CH— COgH, occurs in nature, as already mentioned, and results from the oxidation of the active ( — ) amyl alcohol ; it is in this case ( + ) optically active, while, if prepared synthetically, e.g. by the aceto-acetic ether reaction, it is optically inactive. (See Tartaric acid.) B. Pt. 175°. (4) Tri-methyl-acetic acid, pivalic acid, (CHgjg^C — CO2H, can be prepared from tertiary butyl cyanide, [Butlerow, 1873). M. Pt. 35°, B. Pt. 164°. Has an odour like that of acetic acid. Of the Hexylic acids, eight are theoretically possible, and of these seven are already known. The most important among them is normal caproic acid, CH3— (€112)4 — COgH {Chevreul, 1822), which is found in nature, e.g. in cocoa-nut oil, Limburg cheese, and as glycerine ether in the butter made from goats' milk, and is produced in the butyric fer- mentation of sugar, and by the oxidation of albuminous compounds and of the higher fatty acids, etc. Like valeric acid, it has a very un- pleasant and persistent odour of perspiration and rancid butter. B. Pt. 205°. The higher acids which are found in nature are all of normal constitution (see p. 144), and contain for the most part an even number of carbon atoms. Goats' butter contains the acids Cg, Cg, and C^q, hence the names Caproic, Caprilic, and Capric acids, and cocoa nut oil — in addition to those three — the acid C^g- This last, Laurie acid, is contained more especially in oil of laurels (Laurus nobilis) ; Myristic acid, C^^, is present in oil of iris and nutmeg butter (from Myristica moschata) ; Arachidic acid, C20, in the oil of the earth nut (Arachis hypo- gaea) ; Behenic acid, Cgg) in oil of ben (Moringa oleifera) ; (506) L 162 VI. MONOBASIC FATTY ACIDS. Cerotic acid, G^^, forms in the free state the chief constituent of bees-wax, and as ceryl ether that of Chinese wax ; Theo- bromic acid, Cg^, is present in cocoa butter. Palmitic acid, G-^oR^fi^, and Stearic acid, G-^^H^qO^ (pp. 148 and 202), are very widely distributed, being nearly always accompanied by a third acid poorer in hydrogen, viz. Oleic acid, C^gHg^Og (see p. 166). Most animal and vegetable fats and oils, e.g. tallow, suet, butter, palm, olive and seal oils, consist almost entirely of a mixture of the glycerine ethers of palmitic, stearic and oleic acids, these ethers being termed for the sake of brevity, Palmitin, C3H5(OCi6H3iO)3, Stearin, C3H5(OCi8H350)3, and Olein, 03115(0018^330)3. Palmitin and stearin being solid and olein liquid, the consistence of a fat or oil depends on the preponderance or otherwise of the solid ethers. The constitution of the fats was elucidated by Chevreul in 1811. Most of the varieties of wax are on the contrary ethers of monatomic alcohols; thus bees' wax consists, besides of free cerotic acid, of the melissic ether of palmitic acid, C3QHgi(OOi(jH3iO), Chinese wax (from Oroton Sebiferum, the tallow tree) of the ether 0271155(002711530), and spermaceti, (Oetaceum, in the skull of Physiter macrocephalus), of the ether CieH33(O.CieH3iO). From all these ethers the acids are obtained in the form of potassium salts by saponification with alcoholic potash, thus : C3H,(O.C,3H3,0)3 + 3KOH = 3Ci3H3,0,K + 03H,(OH)3. ^ Y ^ y — Y ' Stearin. Potassic stearate. Glycerine, The separation of the acids is effected by fractional crystallization, fractional precipitation with magnesium acetate, or by fractional distil- lation either of the fats themselves or of their ethers in a vacuum. Oleic acid can be separated from palmitic and stearic by taking advantage of the solubility of its lead salt in ether. The stearine candles of commerce consist of a mixture of palmitic with excess of stearic acid, some paraffin or wax being usually added to prevent them becoming crystalline. The manufacture of candles depends upon the saponification of the SOAPS; PALMITIC AND STEARIC ACIDS, ETC. 163 solid fats, especially of beef and mutton tallow, by means of w ater and lime or of concentrated sulphuric acid. Soaps consist of the alkaline salts of palmitic, stearic and oleic acids, hard soaps containing soda salts, chiefly of the solid acids, while soft soaps contain potash salts, principally oleate. By the addition of common salt to a solution of a potash soap, the latter is converted into a soda soap, which is insoluble in a solution of sodium chloride. The potash soaps dissolve to a clear solution in a little water, but dissociate with excess of water into free alkali and free fatty acid or acid salt, analogous to super-acetate of potassium. Upon this the action of soaps depends. The calcium, barium and magnesium salts are insoluble in water, but partly crystallizable from alcohol. The lead salts are prepared by boiling fats with lead oxide and water, and form the so-called plaisters or lead plaisters. The higher acids with an uneven number of carbon atoms, Cn, C13, Ci5, and C17, are prepared synthetically from the acids containing one atom of carbon more, by transforming them into the ketones, Cn_iH2n-i . CO . CH3, and oxidizing these, {Krafft), see p. 144. Normal nonylic acid, C9H18O2, can be got from normal octyl alcohol l)y the nitrile reaction, and also from many other substances, e.g. by the oxidation of oleic acid and oil of rue (p. 144). It is present in Pelargonium roseum, and is therefore also called pelargonic acid. Undecylic acid, C11H22O.2, is obtained by the reduction of undecylenic acid, C11H20O2, which latter is prepared by the distillation of castor oil in a vacuum. Palmitic acid, G-^oRc^^^^y most conveniently prepared from palm oil, which is a mixture of palmitin and olein, also by fusing oleic acid or cetyl alcohol with potash. Stearic acid, G^^H^fi^^y from the so-called shea-butter or from mutton suet. Hepta-decylic or Margaric acid, C17H34O2, was formerly believed to be present in fats, but this was afterwards found to be a mixture of the acids Cjg and Cjs, (see p. 29). It can be prepared synthetically, e.g. from cetylic cyanide, CjgH33.CN. Cerotic acid, C27Hg402, and the higher molecular acids in general, result upon fusing the corresponding primary alcohols with potash, i.e. from their oxidation. Melissic acid appears from the most recent investigations to have the formula CgiHggOg. 164 VI. MONOBASIC FATTY ACIDS. B. Unsaturated Acids, C„H2^_202. M. Ft. B. Pt M. Pt. Acrylic acid, C3H4O2 r 140° Pyr oterebic acid, CgHiQO. fi 182° Crotonic acids, C4HgO.^-^ 2 172° Hypogaeic acid,Ci6H3oO. 33° 'is 16° 160° Angelic acid, etc. , CgHgOg 45° 185° Oleic acid, ^^18113402 14"=* These acids are known as the acids of the oleic series. In their physical properties they nearly resemble the saturated acids, apart from differences in melting point which are some- times considerable ; and they also behave as acids in an analogous manner, but differ characteristically in that they are capable of combining either with two atoms of hydrogen, when heated with hydriodic acid, or with two atoms of halogen or one molecule halogen hydride, to form the saturated acids or their substitution products. Thus oleic acid, C^gHg^Og, when treated with hydriodic acid and phosphorus, yields stearic acid, CjgHggOg, and with bromine, dibromo-stearic acid, In this way they characterize themselves as derivatives of the unsaturated hydrocarbons of the ethylene series, from which one may imagine them to result by the replacement of an atom of hydrogen by carboxyl. (Olefine-carboxylic acids. ) Upon the addition of halogen hydride, the halogen does not always attach itself to that carbon atom to which the least hydrogen is bound. Modes of formation. 1. By oxidation of the corresponding alcohols or aldehydes, e.g. acrylic acid from allyl alcohol or acrolein. 2. From the unsaturated alcohols or their iodides, by con- verting them into the cyanides and saponifying these, e.g. crotonic acid from allyl iodide. Both these methods of formation are analogous to those of the fatty acids. 3. From the mono-halogen substitution products of the saturated fatty acids, by warming with alcoholic potash, some- THE OLEIC ACID SERIES. 165 times upon simply heating with water. This is analogous to tlie formation of the olefines from halogen-alkyl. 4. From the acids of the lactic series by separation of water, thus : CHoCOH)— CH2— COOH = CH2=CH— CO2H + H^O. Y Y ; Ethylene lactic acid. Acrylic acid. This reaction corresponds with the formation of the olefines from monatomic alcohols. Constitution and Isomers. The constitution of the unsaturated acids, OnH2a_202, is given when they are regarded as olefin e- carboxylic acids. As many isomeric acids as unsaturated alcohols of n — 1 carbon atoms are therefore possible. (See mode of formation 2, and cf. crotonic acid.) The position of the double bond is established by fusing the acids with potash or soda, i.e. by oxidizing them. Oxidation occurs at the point of the double bond, (cf. p. 48), and leads to the formation of 2 mols. of \ monobasic fatty acidf e.g. : CHg-CH^CH-CO^H + 2K0H + 0 = 2CH3-CO2K + H^O. Other oxidizing agents, such as chromic and nitric acids, also break them up for the most part in a similar manner, but they carry the oxidation further. By cautious oxidation, on the other hand, e.g. with KMn04 in the cold, the elements of hydrogen peroxide are simply added, and there are formed di-oxy-acids (p. 219) containing an equal number of carbon atoms, for instance, dioxy-stearic, Ci8H34(OH)20.2, from oleic acid. Acrylic acid, ethylene - carhoxylic acid, CgH^Og, = CHg^OH — COgH, (Redtenbacher), Is prepared by the oxida- tion of acrolein by oxide of silver, or by the distillation of /3-iodo- propionic acid with oxide of lead. (Cf. mode of formation 3.) It is very similar to propionic acid. M. Pt. + 7°, B. Pt. 139°- 140°. Miscible with water and capable of polymerization. It is reduced to propionic acid when warmed with zinc and sulphuric acid, and is broken up, on fusion with alkali, into acetic and formic acids. Crotonic acids, C4Hg02. (1) Ordinary or solid crotonic acid, CHy — CH=CH — CO2H, occurs along with iso-crotonic acid in crude pyroligneous acid, and is prepared from allyl iodidg by means of the 166 VL MONOBASIC FATTY ACIDS. cyanide, notwithstanding that one would expect to get iso-crotonic acid by this reaction. Such abnormal reactions are termed molecular re- arrangements, and they are explained by assuming that addition pro- ducts are first formed, from which atomic groups are then split off, in this case HCl : CH2-CH-CH2-CN + 2H2O = CH2=CH-CH2-COOH -f NH3 ; CH2=CH— CH2— COOH + HCl = CH3— CHCl— CHg—COOH, = CH3— CH=CH— CO2H + HCl. It is also easily prepared by heating malonic acid with para-aldehyde and acetic anhydride. It crystallizes in woolly needles or large prisms, M. Pt. 72°, B. Pt. 189°, has an odour like that of butyric acid, and is fairly soluble in water. (2) Isocrotonic acid, CH2=CH— CH2— COgH, which is present in croton oil, is liquid, and changes into ordinary crotonic acid at 170°-180°. (3) Meth-acrylic acid, G^2=^0 C2H5.CI C2H5.SH Alcohol Sodium ethylate Ethyl ether Ethyl chloride Mercaptan Ethylamine C2H3O.OH CgHaO.OlSra C2H3O C2H3O.CI C2H3O.SH an.o.NH, CH3— CCI2-NHR* CH3— CC1=:NR CH3-CS.NH2 Amido-chlorides Imido-chlorides Thiamides CH3— C(NH)OH CH3-C(NH)SR CH3— C(NH)(NH2 174 VII. ACID DERIVATIVES. A. Ethers of the Fatty Acids. By the replacement of the typical hydrogen of a fatty acid by an alcohol radicle, ethers are produced which are perfectly analogous to the ethers of the mineral acids in their properties, and which are also obtained by analogous methods. Since these correspond to the salts of the acids, they are often designated in a similar way, e,g. acetic ethyl ether = " ethylic acetate." Modes of formation. (1) By direct action of the acid upon the alcohol : C2H5.OH + C2H3O.OH = C2H5.O.C2H3O + H2O. Ethylic acetate. Only a few acids thus react with alcohol by itself to form ethers in quantity, for reasons similar to those already given for mineral acids at p. 98. In the preparation of ethers it is therefore necessary to provide against a re- saponification of the ether after it is formed, which is done as above described (loc. cit.). The method of etherification by leading hydro- chloric acid gas into a mixture of acid and alcohol is especially appli- cable. The ethers are also obtained directly from the acid nitriles by passing hydrochloric acid into their warm alcoholic solution. The limit of etherification agrees with the Guldherg- Waage law of the action of mass, [Berthelot, Menschutkin.) (2) By the action of the acid chlorides upon the alcohols or their sodium compounds (cf. p. 99) : C2H30.C1 + C2H,.0H = C2H3O.O.C2H5 + HCI. (3) By the action of the halogen alkyls upon the salts of the acids (cf. p. 99) : C2H5Cl + C2H30.0Na = C2H5.0.(C2H30) + NaCl. Ethers are likewise obtained by heating the salts of fatty acids with alkyl sulphates. Properties. The ethers of the monobasic fatty acids are for the most part neutral liquids which volatilize without decom- position, only those of them which contain a small number of carbon atoms in the molecule being soluble in water, e.g, acetic ETHERS OF THE FATTY ACIDS. 175 (^t lier (1 : 14). They undergo saponification upon heating or, more generally, superheating with water, or upon boiling with alkalies or acids. It often suffices for saponification simply to mix the ether with alco- holic potash or soda, or to allow it to stand for a lengthened period with water. The compound ethers are very active chemically, since they readily exchange the group — OCgH^, i.e. — OR, for another group, yielding with ammonia, for instance, amides (p. 180). Phosphorus pentachloride decomposes them into the chloride of the alcohol and that of the acid, the oxygen of the hydroxyl being exchanged for two atoms of chlorine. Sodium methylate combines with the ethers to form unstable compounds, /ONa R — C^OCHo, which are derivatives of ^'ortho acids." (See \0R' p. 149; also B. 20, 646.) The odour and taste of many of the ethers is so agreeable that they are manufactured upon a large scale, and employed as fruit ethers or fruit essences. Ethyl formate, formic ethyl ether, H.CO.OC2H5. B. Pt. 55^ Is employed in the manufacture of artificial rum or arrak. Ethyl acetate, acetic ether, C2H3O. OCgHg. B. Pt. 75°. Is used inter- nally as a medicine. Amyl acetate, CgHgO.OCgHn. B. Pt. 148°. The alcoholic solution of this forms the ether of pears. Ethyl butyrate, C4H7O.OC2II5, is the ether of pine apples. Iso-amyl iso-valerate, C5H9O.OC5H11, B. Pt, 196°, finds application as apple oil or apple ether. Cetyl palmitate, CieHgiOalC^eHgg), Ceryl cerotate, C)27^5'a02{C^7B^^), and Mellissic palmitate, C^eHsiOglOgoHgi). (See Wax Varieties, p. 162.) AVhen the ethers of the acids of high molecular weight are distilled under the ordinary pressure and not in a vacuum, they break up into olefine and fatty acid. (See p. 49.) Among the ethers of the haloid-substitution acids may be mentioned ethyl monochlor-acetate, CH2CI — C02(C2H5), B. Pt. 145°, and ethyl trichlor-acetate, CCI3— C02(C2H5), B. Pt. 164% Isomers. All those ethers of the ^ diflferent monatomic 176 VII. ACID DERIVATIVES. saturated alcohols and acids are isomeric, the sums of whose carbon atoms are equal to one another ; thus methyl butyrate is isomeric not only with ethyl propionate but also with propyl acetate and with butyl formate. Further, all ethers are isomeric with the monobasic acids which contain an equal number of carbon atoms with them, e.g. the ethers just men- tioned are isomeric with valeric acid. (See Metamerism, p. 93.) Further cases of isomerism occur when the alcohol on the one hand, or the acid on the other, is unsaturated, e.g. allyl propionate and propyl aery late. B. Chlorides of the Acid Radicles. (Acid Chlorides, or Chloro-anhydrides of the Acids.) Among the halogen compounds of the acid radicles those of chlorine are the most important. Formation. (1) From the acid and hydrochloric acid by means of phosphoric anhydride ; this method is of theoretical value only : C2H3O.OH + HCI = C2H3O.CI + H2O. (2) By the action of chlorine upon the aldehydes ; CH3.OHO + CI2 = CH3.COCI + HCI. (3) By the action of the chlorides of phosphorus, PCI3 and PCI5, upon the acids or their salts : C^H^aOH + PClg = C4H^O.Cl + POCl3 + HCl. The acid chloride is separated from the POCI3 formed at the same time by fractional distillation. In the case of acetic acid PCI3 is conveniently used, being warmed with the free acid upon the water-bath : 3C2H3O.OH + PCI3 = 3C2H3O.CI + PO3H3. Phosphorus oxychloride, POCI3, may also be allowed to act upon the alkaline salts of the acids ; when the latter are present in excess, acid anhydrides are produced (p, 178). ACID CHLORIDES. 177 (4) Several of the acid bromides result from the bromo-derivatives of the olefines by the absorption of oxygen from the air, thus CBr2=CH2 yields CHgBr — COBr, bromo-acetyl bromide. (5) From Phosgene, COCI2, and zinc alkyl (see p. 150). Properties. The acid chlorides are suffocating liquids which fume in the air, distil without decomposition, and are recon- verted by water into the corresponding acids and hydrochloric acid, for the most part at the ordinary temperature : C2H3O.CI + H2O = C2H3O.OH + HCI. They react with alcohol and the alcoholates to form ethers, with the salts of the acids to form anhydrides, and with ammonia to form amides. Sodium amalgam reduces them to aldehydes and alcohols. With zinc alkyl they yield ketones or tertiary alcohols, according to the conditions of the experiment. (Cf pp. 139 and 77.) On treatment with silver cyanide, the cyanides of the acid radicles are formed, e.g. Acetyl cyanide, CH3.CO.CN, from acetyl chloride. These are of great importance for the synthesis of the ketonic acids, being saponified by concentrated hydrochloric acid in the same way as the cyanides of the alcohol radicles, with transformation of — CN into — CO. OH; dilute hydrochloric acid, on the contrary, decomposes them into the original acid and HON. When it is attempted to isolate the acid radicle by removing the halogen, it is found that two radicles unite together with formation of double ketones, R — CO — CO — R, compounds as yet but slightly investigated (see p. 221). Acetyl chloride, CH3.COCI. Mobile colourless liquid of suffocating odour. B. Pt. 55° ; Sp. Gr. at 0°, 1*13. Decom- poses violently with water, with ebullition, and with strong ammonia with explosive rapidity. Is a reagent of exceptional importance, since it serves for the conversion of the alcohols and ammonia compounds (primary and secondary amines) into their acetic derivatives, and thus frequently leads to the explanation of the chemical nature of the substance under investigation. Among the homologues of acetyl chloride which are known are Propionyl chloride, CgHg.COCl, Butyryl chloride, G^H^.COCl, Iso- valeryl chloride, C4Hy.C0Cl, and Palmityl chloride, CjglrLji.COCl ; (606) M 178 VII. ACID DERIVATIVES. likewise Acetyl bromide, CHg.COBr, B. Pt. 81°, and Acetyl iodide, CH3.COI, (from iodine, phosphorus and acetic anhydride). The chloride of formic acid, HCOCl, is however unknown, since it immediately breaks up into CO and HCl when its preparation is attempted. As examples of chlorides of substituted acids we may take Mono-chlor-acetyl chloride, CH2CI.COCI, B. Pt. 106°, and Lactyl chloride, CH3— CHCl— COCl. 0. Acid Anhydrides. Corresponding to the monobasic fatty acids there are anhydrides, which are derived from two molecules of the acid with the separation of a molecule of water, e,g, : CH3.CO.OH _ CH3— CO^p. xrn CH3.CO.OH - CH3— C0>^ ^2^- They may also be considered as oxides of the acid radicles, for instance, (C2H30)20, = Acetyl oxide. Preparation. 1. They do not as a rule result from the acids by direct abstraction of water, but, e.g.^ by the action of acid chlorides upon the alkaline salts of the acids : C2H30Cl + C2H30.0Na = ^2^30^0 + NaCl. P. By the direct action of phosphorus oxychloride upon the alkaline salts of the acids, acid chlorides being formed in the first instance, (see p. 176). 2. By the action of phosgene on the acids, (B. 17, 1286) : 2CH3.CO.OH + COCI2 = (CH3— 00)^0 + CO2 + 2HCL 2'^. The anhydrides of the higher acids are conveniently prepared by treating these with acetyl chloride, (B. 10, 1881) : 2R.C0.0H + CH3.COCI = (R.C0)20 + CH3.COOH + HCl. Properties. The most of the acid anhydrides are liquids, but those of higher molecular weight solids, of neutral re- action and soluble in alcohol and ether. They are insoluble in water, but are gradually decomposed by it into acid hydrates. On warming with alcohol, compound ethers are formed, and by ACID ANHYDRIDES; THIO-ACIDS. 179 tlie action of ammonia, amides. They yield with HCl gas, acid chloride and free acid : (C2HaO)20 + HCl - C,H30.C1 + C2H30.0R Acetic anhydride, (021130)20, is a mobile liquid of suffocat- ing odour, boiling at 137°, and having a Sp. Gr. at 20° of 1*073. Like acetyl chloride it is a reagent of great importance, since it converts primary and secondary ammonia derivatives into acetyl compounds. Intermediate or Mixed anhydrides containing two different acid CHOI radicles are also known, {Gerhardt, Williamson), e.g. q^jj^ 0/^' ^^^y break up into two simple anhydrides upon distillation. We are likewise acquainted with peroxides of the acid radicles, e.g. Acetyl peroxide, (C2H30)202, a thick liquid insoluble in water, which acts as a strong oxidizing agent and explodes upon warming ; it is pre- pared by the action of barium peroxide, BaOg, upon acetic anhydride. D. Thio-acids and Thio-anhydrides. Just as in the alcohols and ethers, so in the acids and their Anhydrides is oxygen replaceable by sulphur. There are thus theoretically possible : (1) Thio-acids, e.g. thiacetic acid, CH3.CO.SH, and their isomers, e.g. CH3.CS.OH, (as yet unknown); (2) Thio-anhydrides, e.g. acetyl sulphide, (021130)28; (3) Di-thio-acids, e.g, CH3CS.SH, (as yet only known in the aromatic series). Thiacetic acid, C2H3O.SH, is a colourless liquid boiling below 100°, which smells of acetic acid and sulphuretted hydrogen, and readily decomposes with water into those two components. It is prepared from acetic acid and phosphorus pentasulphide, P2S5. The other thio-compounds are likewise easily saponifiable, with formation of acetic and hydrosulphuric acids. 180 VII. ACID DERIVATIVES. Ethers of tliiacetic acid are also known, e.g. ethyl thiacetate, CH3CO.S.C2H5, which is obtained from acetyl chloride and sodium mercaptide ; they are liquids which distil without decomposition, and are easily saponified back to acid and mercaptan. E. Amides. By the replacement of the hydrogen in ammonia by acid radicles or, in other words, by the replacement of the acid hydroxyl by amidogen, etc., amides result, these being primary, secondary, or tertiary, according to the number of hydrogen-atoms substituted ; NH,.C,H30 NH(C2H30), N(C2H30)3. ^ ^ ^- Y ^ y Acetamide. Di-acetamide. Tri-acetamide. Of these the primary amides are the most important. They are solid crystalline compounds, at first soluble in water but becoming insoluble with increasing carbon, and soluble in alcohol and ether. They distil without decomposition, when necessary, in a vacuum. They differ characteristically from the amines in being easily saponifiable, breaking up into their components, acid and ammonia, when super-heated with water or when boiled with alkalies or acids. Alkylated amides are compounds derived from ammonia by the replacement of its hydrogen by alcoholic and acid radicles at the same time, e.g. ethyl acetamide, C2H30.NH.(C2Hg) and di-methyl aceta- mide, (CHgjgN.CgHgO. They are to be regarded as acid, e.g., acetyl- derivatives of the nitrogen bases of alcohol radicles ; thus, ethyl aceta- mide is the same as acetyl ethylamine, C2Hg.NH(C2H30). Modes of formation. 1. By the dry distillation of the ammonium salts of the fatty acids or, better, by heating them in a closed vessel to 230° (Hofmann, B. 15, 977), thus : CH3CO.ONH4 = CH3OO.NH2 + H2O. 2. By addition of water to the cyanides of the alcohol radicles containing one atom of carbon less than them- selves : CH3— ON + Hp - CH3— CO.NHg. AMIDES. 181 This assimilation of water is frequently effected by dissolv- ing the nitrile in concentrated sulphuric acid, or in acetic and concentrated sulphuric acids, or by shaking with concentrated hydrochloric acid in the cold; also, and often quantitatively, by hydrogen peroxide, HgOg. 3. By the action of acid chlorides upon aqueous ammonia or solid ammonium carbonate : CH3.COCI + 2NH3 = CH3.CONH2 + NH4CI. 3*. In an analogous manner from acid anliydrides : (C2H30)20 + 2NH3 = C2H3O.NH2 + C2H3O.ONH4. 4. By heating compound ethers with ammonia, sometimes even on shaking in the cold : CH3.CO.OC2H5 + NH3 = CH3,CONH2 + C2H5OH. 5. The secondary and tertiary amines result upon heating the acids or anhydrides with their nitriles : CH3.CN + CH3.COOH - (CH3.C0)NH; CH3.CN + (CH3.CO)20 = (CH3.CO)3N. Behaviour, 1. The amides, although derivatives of ammonia, are hardly basic, the strongly positive character of the hydrogen atoms of the ammonia being cancelled by the entrance of the negative acid radicle. Still the primary amides are capable of forming addition-compounds with some acids, e.g. acetamide yields the compound (C2H30.NH2)2HC1, " acetamide hydrochloride " ; these are however unstable, and are decomposed for the most part by water alone. On the other hand the hydrogen of the amido-group can be replaced by particular metals, especially mercury, the amides therefore playing the role of weak acids in the compounds so obtained^ e.g. mercury acetamide, (CH3.CONH)2Hg. 2. The amides are readily saponifiable. When they also contain alcoholic radicles, only the acid and not the alcohol radicle is separated on saponification, in accordance with the fact that the amine bases are not saponifiable, thus : C2H3O.NHC2H5 + NaOH = CgHgO.ONa + CgH^NHg. 182 VII. ACID DERIVATIVES. 3. Nitrous acid converts the primary amides into the corre- sponding acids, with liberation of nitrogen : C2H3O.NH2 + NO2H - C2H3O.OH + N2 + H2O. This reaction is a general one, and corresponds exactly with the action of nitrous acid upon the primary amines. 4. Upon heating the primary amides with phosphorus pentoxide, P2O5, nitriles are produced (see p. 107). These are also obtained upon heating with PgSg, and PCI5, amido- chlorides or thiamides being in this case formed as inter- mediate products, (see pp. 107 and 184). 5. If bromine in the presence of alkali is allowed to act upon primary amides, there ensue in the first instance amides whose NH2-hydrogen is replaced by halogen, e.g. CH3.CO.NHBr, aceto-bromamide, (colourless rectangular plates), and CH3.CO.NBr2 : CH3— CO.NH2 + Brg = CH3— CO.NHBr -h HBr, etc. These yield peculiar urea derivatives with more amide and alkali, e.g. methyl-acetyl-urea, CO | ^jj Qg^^^j which are split up by further addition of alkali in the normal manner, with formation of amines — in this case CH3.NH2 — containing one atom of carbon less than the original product. (See urea.) This is an excellent method for preparing the amines from C^ to Cg, but less desirable for those from Cg onwards, as in the case of the higher molecular compounds the production of amine diminishes, a nitrile being formed instead by the further action of the bromine, (see below). Such nitriles C?^, in which 71 > 5, can therefore be obtained directly from the amine by the action of bromine and alkali upon it, thus : C.H15— CH2.NH2 + 2Br2 = C.Hi,— CH2.NBr, + 2HBr = C^Hi,.CN + 4HBr. (Eeversal of the Mendius reaction, p. 113; cf. Hofmann, B. 15, 407, 752; 17, 1407, 1920; 18, 2737). Since these nitriles go on saponification into acids containing one atom of carbon less than the amide originally taken, this reaction renders it possible to descend in the series successively AMIDO- AND IMTD0-CI1L0R[])K{H. 183 tVom one acid to another, (p. 145). This has been done in the case of the normal acids from C^^ to C^, and constitutes a further proof of their normal constitution. Form amide, HCO.NH2, is a liquid readily soluble in water and alcohol, which boils with partial decomposition at about 200°, and breaks up into CO and NH3 when quickly heated. It yields hydrocyanic acid when heated with P2O5. Acetamide, CgHgO.NHg. Long needles, readily soluble in water and alcohol. M. Pt. 82°, B. Pt. 222°. The high boiling points of the amides are worthy of notice ; they stand in striking contrast to the low boiling points of the amines con- taining an equal amount of carbon. Among the amides of haloid-substitution acids may be mentioned : Mono-chlor-acetamide, CHgCl— CO.NHg, M. Pt. 116°, B. Pt. 225°. Tri-chlor-acetamide, CCI3— CO.NHg, M. Pt. 136°, B. Pt. 239°. For Isomers of the Amides, see p. 185. F. Amido-chlorides and Imido-chlorides. By the action of PCI5 upon the primary amides, an exchange of CI2 for 0 takes place, giving rise in the first instance to the so-called amido-chlorides, e.g, acet-amido chloride, CH3 — CClg.NHg; these are extremely easily decomposable compounds, being reconverted by water into amide and hydro- chloric acid, and readily giving up HCl, with formation of imido-chlorides, e.g. CH3 — CCl : NH, acet-imido chloride. The imido-chlorides also decompose easily as a rule, likewise yielding with water the amide and hydrochloric acid. When heated, they break up into nitrile and hydrochloric acid. The alkylated amides (p. 180) also yield amido-chlorides, e.g. CH3.CO.NH.C2H5 gives CH3.CCI2.NH.C2H5, ethyl acet-amido chloride, and CH3— CO.NR2 gives CH3—CCI2.NR2; if these still contain amido-hydrogen, they likewise go readily into imido-chlorides, e.g* CH3.CC1=N.C2H5, ethyl acet-imido chloride. The chlorine in these compounds is very active, chemically; it can be exchanged for sulphur or for an ammonia (amine-) 184 VII. ACID DERIVATIVES, residue by the action of sulphuretted hydrogen, ammonia, or amine, with the formation of thiamides and amidines, thus : CH3.CCI2.NHR f H^S - CH3.CS.NHR + 2HC1. CH3.CCI : NR + NH3 = CH3.C(NH2) : NR, etc. Most of the amido- and imido-chlorides known, (0. Wallach, 1S75), contain aromatic radicles, e.g. CgHg, phenyl, and the same remark also applies to the following classes of compounds. G. Thiamides and Imido-thio-ethers. Thiamides are compounds derived from the amides by the exchange of oxygen for sulphur, e.g. CHg.CS.NHg, aceto- thi amide or thiacetamide, CHg.CS.NHCgH^, thiacetanilide. They are mostly crystalline compounds, and result from the addition of to the nitriles, (CaJiours), e.g, : CH3.CN + H^S = CH3.CS.NH2; by treating acid amides with P2S5 ; from the amido- etc. chlorides, as given above ; and by the action of H2S or CS2 upon the amidines. Both simple and alkylated thiamides are known. The thiamides, R — CS.NHg, break up upon heating into nitrile and sulphuretted hydrogen, (see p. 107). They are all easily saponified by alkalies, etc., with formation of the corre- sponding acid, ammonia (amine) and H2S, thus : E— CS.NHR + 2H2O - R— CO.OH + H2S + NH2.R. They are rather more acid in character than the amides, and thus many of them are soluble in alkali and yield metallic derivatives. The alkylated thiamides of formic acid also result from the addition of hydrogen sulphide to the iso-nitriles : CN.R + H2S = H— CS.NHR. SH From the compound CH3— C^-^jj, isomeric with thiacetamide, and which one might term acetimido-thio-hydrate, or iso-thiacetamide, but which is not known in the free state, there are derived a number of compounds, the Imido-thio-etherSf by the replacement of the IMIDO-THIO-ETHKRS ; AMIDINES. 185 sulphydril, and also of the iinido-, hydrogen by an alcohol radicle, e.g. acetimido-thio-ethyl, CH3— C^^j^ ^; methyl iso- thio-acetanilide, CH3 — C^^^^ . They are decomposed by hydrochloric acid into ethers of thiacetic acid, thus : CH3— C(NH).S.CH3 + H2O = CH3— CO.SCH3 + NH3. These imido-thio-ethers are prepared by the action of mercaptans upon nitriles in presence of hydrochloric acid gas {Pinner), and by the action of alkyl iodides upon thiamides ( Wallach, Bernthsen) : ^•C. 186 VII. ACID DERIVATIVES. (2) By treating the imido-chlorides, thiamides and iso-thi- amides with ammonia or with primary or secondary amines ( JFallach, Bernthsen), thus : R_CS.NH2 + NH^R' = R— C(NH)(NHR') + H^S ; R_C(NH)(SR) + NH3 = R— C(NH)(NH2) + RSH. (3) By heating the nitriles with amine hydrochlorate ; this method is a particularly easy one when aromatic amines are used, but not in the case of chloride of ammonium (Bernthsen) : CH3— CN + NH2.R = CH3— C(NH)(NHR). (4) By the action of amine bases or ammonia upon imido-ethers. Behaviour, (1) They decompose into ammonia or amine and acid upon boiling with acids or alkalies (see above), and into ammonia and amide upon boiling with water. (2) In the dry state they easily break up on heating into ammonia or amine and acid nitrile, so long as the imido-hydro- gen atom has not been replaced by alcoholic radicle. (3) Upon heating with hydrogen sulphide, thiamides are formed. In this reaction combination between the two reagents at first occurs, thus : NH /NHg R — C, = C,H,(C,H30,), + 2AgBr; Ethylene bromide. Glycollic di-acetate. C,H,(C,H302)2 + 2K0H = C,H,(OH), + 2G,^f),K. In the actual preparation of glycol from ethylene bromide, potassium acetate and strong alcohol (Demole), this saponifica- tion ensues directly upon prolonged boiling of the mixture. (b) By boiling with water and lead oxide or potassium carbonate, by which means the acid produced is taken up, and so the reaction is facilitated : C2H4Br2 + 2H0H = C2H4(OH)2 + 2HBr. 2. By the reduction of ketones to secondary alcohols, the so-called 190 Vni. POLYATOMIC ALCOHOLS. pinacones, i.e. di-tertiary glycols, result as bye-products, (see pp. 77 and 191), thus : (CH3),C0 + CO(CH3)2 + = (CH3)2=C(OH)-C(OH)=(CH,)2. Pinacone. 3. By the combination of olefines with H2O2, or from their oxidation by means of KMnO^, the glycols are produced directly, and by their combination with ClOH, the chlor- hydrins : C2H4 + ClOH = C^H^CKOH). Behaviour. 1. As in the case of the monatomic alcohols, the hydrogen is directly replaceable by potassium or sodium, with the formation of alcoholates, e.g. C^2H4CO.OH CHO ^ ■CO. OH CO. OH CO. OH Oxalic acid. GlycoUic aldehyde. Glycollic acid. Glyoxalic acid. Possible products : diatomic aldehydes, dibasic acids, alcohol- aldehydes, alcohol-acids, aldehyde-acids. (b) Of the diatomic primary-secondary alcohols. CH3 CH3 rCO >-G0 CH2.OH CHO Acetone-alcohol. (Unknown). CH3 CH.OH CH2.OH a- Propylene glycol, CH3 / CH.OH CO. OH CH3 ^CO CO.OH Pyro-racemic acid. 02 OJ f .2^ ^,0 O rO (Lactic aldehyde, Lactic acid. unknown). ' Possible products : aldehyde-alcohols, ketone-alcohols, ketonc- aldehydes, alcohol-acids, ketone-acids. (c) Of the diatomic di-secondary alcohols: di-ketones. (No dibasic acids or alcohol-acids, Cn). 206 IX. POLYATOMIC MONOBASIC ACIDS. {d) Of the other diatomic alcohols : easy to tabulate. (e) The tri- and polybasic alcohols are capable of yielding the most various products upon oxidation, especially polyatomic ketone-alcohols, alcohol acids, ketone-acids, and polybasic acids. The most important among these compounds are the alcohol- acids, (di-, tri-, etc. atomic monobasic, tri- etc. atomic dibasic acids, and so on), and the polybasic acids ; the ketonic acids also call for especial interest. IX. POLYATOMIC MONOBASIC ACIDS AND COMPOUNDS RELATED TO THEM. A. Diatomic Monobasic Acids. Summary. Glycollic acid, CH2(OH)(C02H) Oxy-propionic acids, C2H4(OH)(C02H) Oxy-butyric acids, Oxy-valeric acids, C4H8(OH)(C02H) Oxy-caproic acids, C5Hio(OH)(C02H) etc. The diatomic alcohol-acids or diatomic monobasic acids are compounds'which unite in themselves the characteristics of an alcohol and of an acid, and are consequently capable of forming derivatives as alcohols, as acids, and as both together. These derivatives are in part easily saponifiable, and corre- spond therefore with the acid derivatives, i.e. the compound ethers, chlorides and amides; in part they are relatively stable as regards saponifying agents, and therefore correspond with the alcoholic derivatives, i.e. the ethers, amine bases, etc., (see table, p. 211). DIATOMIC MONOBASIC ACIDS. 207 The lowest members of the scries of diatomic monobasic acids, which are at the same time the most important, are glycollic acid and lactic acid, both syrupy liquids which solidify to crystalline masses in the exsiccator, and easily give up water to form anhydride. They cannot be volatilized without decomposition. They are readily soluble in water, and for the most part also in alcohol and ether. They are termed diatomic, because they may result from the oxidation of the diatomic alcohols, and contain in accord- ance with theory two hydroxyls. As acids they are mono- basic. They are also frequently called oxy-fatty acids, on account of their being derived from the fatty acids by the exchange of one hydrogen atom for hydroxy 1, in the same way as the alcohols are derived from the hydrocarbons : CH3 — COgH, acetic acid ; CH2(0H) — COgH, oxy-acetic acid. We may also regard them as carboxylic acids of the mona- tomic alcohols, e.g, lactic acid, C2H4(OH).C02H, is ethyl alcohol-carboxylic acid. Formation, 1. By the regulated oxidation of the glycols, (see Summary, p. 205). 2. From the fatty acids, through their mono-haloid substitu- tion products, the halogen of these being easily replaced by hydroxyl, either by means of moist oxide of silver or often by prolonged boiling with water alone. Glycollic acid is thus obtained from mono-chloracetic acid ; CH2CI.CO2H + H2O = CH2(0H).C02H + HC1. For a reaction of these haloid-substitution products in a different direction, see /?- and y-oxyacids, 3. From the aldehydes and ketones containing one atom of carbon less, by the preparation of their hydrocyanic acid com- pounds, (see pp. 133 and 142), and saponification of the latter. Thus, from aldehyde is produced ethylidene cyanhydrin, and from this lactic acid : CH3.CH(OH)(CN)4-2H20 = CH3.CH(OH).C02H + NH, 208 IX. POLYATOMIC MONOBASIC ACIDS. Since the aldehydes and ketones are easily got from the correspond- ing alcohols, this reaction furnishes a means of preparing the acids, CuH2n(0H) (CO2H), from the alcohols, CnH2n+i(0H), of introducing carboxyl into the latter in place of hydrogen ; this is a very important synthesis. 4. From the glycollic cyanhydrins by saponification, e.g. ethylene lactic acid from ethylene cyanhydrin : CH,(OH)— CH2.CN + 2H2O = CH2(0H)— CH2— CO2H + NH3 The cyanhydrins being easily obtained from the glycols, this for- mation of oxy-acids represents an exchange of a hydroxyl of the glycol for carboxyl, and is analogous to the formation of acetic acid from methyl alcohol. 5. By the reduction of aldehyde-acids or ketonic acids, e.g. lactic from pyroracemic acid (p. 223). This reaction corresponds with the formation of the alcohols from the aldehydes or ketones by reduction. 6. By the action of nitrous acid (N2O3) upon amido-acids (see glycocoll) ; a reaction analogous to the formation of alcohols from amines. Constitution and Isomers. As oxy-compounds of the fatty acids, the acids of the foregoing series can exist in as many modifications as there are possible mono-haloid substitution products of the fatty acids. Thus there is only one glycollic acid, corresponding to mono-chloracetic acid, but two lactic acids — corresponding to a- and /3-chloro-propionic acids — are possible, and both actually exist ; they are designated as a- and ^-oxy-propionic acids : CH3— CHCl— CO2H CH3— CH(OH)— CO2H a-Chloro-propionic acid. a-Oxy-propionic acid or common lactic acid. CH2I— CH2— CO2H CH2(0H)— CH2- CO2H /8-Iodo-propionic acid. /3-Oxy-propionic acid or ethylene lactic acid. From the two butyric acids can be theoretically derived : (a) From the normal acid : CH3 — CH2 — CH2 — CO2IIJ 7 P a an a-, jS-, and 7-oxy-butyric acid ; DIATOMIC MONOBASIC ACIDS. 209 (6) From iso-butyric acid : an a- and j8-oxy-isobutyric acid. The constitution of these oxy-acids is often apparent from their formation alone. Thus the preparation of common lactic acid from aldehyde, CH3 — CHO, according to method 3, shows that it contains the group CH3 — CH=, " ethylidene" ; it is therefore termed "ethylidene lactic acid." On the other hand the formation of /?-oxy-propionic acid from glycol, i.e. glycol cyanhydrin, according to 4, is a proof of its containing the group — OH2 — CH2 — , "ethylene"; hence the name "ethylene lactic acid." The behaviour of the oxy-acids usually explains their constitution also ; if they can be oxidized, for instance, to dibasic acids (which con- tain two carboxyis), then they must contain a primary alcohol group, — CH2.OH, since only such a group yields a new carboxyl on oxidation. Ethylene lactic acid is therefore a primary" alcohol-acid. Its isomer, ethylidene lactic acid, is similarly a "secondary" alcohol-acid, while a-oxy-isobutyric acid is a "tertiary" alcohol-acid, i.e. acid and tertiary alcohol at the same time. Behaviour. 1. The double chemical character of the oxy- acids will be gone into more particularly under glycoUic acid. As acids they form salts, compound ethers and amides; as alcohols they yield ethers, amines, etc. Among those deriva- tives the alcoholic amines of the acids, the so-called amido- acids, are of especial interest. (See Glycocoll, p. 212). 2. The oxy-acids form different kinds of anhydrides, viz.: — (a) as alcohols, (see di-glycollic acid) ; (6) one molecule as alcohol forms with a second molecule as acid, a compound ether, with separation of HgO, (see glycollic anhydride) ; (c) such a formation of ether as this proceeds a second time, (see glycolide) ; (d) one molecule loses H2O, with formation of an " intra-molecular " anhydride, a so-called lactone, (see p. 218). 3. For behaviour upon oxidation, see p. 205, and also the individual compounds. 4. Just as the alcohols go into olefines with separation of water, so (50(5) O 210 IX. POLYATOMIC MONOBASIC ACIDS. can many of the oxy -acids, especially the be transformed into unsaturated monobasic acids. (See hydracrylic acid, p. 216), 5. Halogens oxidize and do not substitute. 6. Warming with HI gives rise to the corresponding fatty^ acids, just as the alcohols are converted by this reagent into hydrocarbons. 7. When the a-oxy-acids are warmed with dilute sulphuric acid, formic acid is separated and the aldehyde or ketone which would give rise to the acid, according to method 3, is reproduced. The jS-oxy-acids on the other hand break up in this way, and also when heated alone, into water and acids of the acrylic series. The a-, 7-, etc. oxy-acids also differ from each other in the facility with which they form anhydrides. (See Lactones. ) GlycoUic acid, CH2(0H)— CO.OH, (Strecker, 1848). Occurrence. In unripe grapes and in the leaves of the wild vine, etc. Formation, (See also p. 207.) 1. By the oxidation of glycol with dilute HNO3, (Wurtz), 2. Together with glyoxal and glyoxalic acid, by the oxida- tion of alcohol with dilute HNO3. Further, by the oxidation of glucoses by Ag20, (A. 205, 193). 3. By the reduction of oxalic acid with Zn + H2SO4. 4. Preparation from mono-chloracetic acid, according to p. 207 ; best when boiled with marble. (A. 200, 76). Properties, Colourless needles or plates, stable in the air, and easily soluble in water, alcohol and ether. M. Pt., 80°. Nitric acid oxidizes it to oxalic acid. The alkaline salts are hygroscopic, the calcium salt and the magnificent blue copper salt sparingly soluble in water. Derivatives. (See table, p. 211.) As an acid, gly collie acid forms salts, compound ethers, — e.g. glycollic ethyl ether, — a chloride, glycollyl chloride, and glycollamide, all of which are readily saponified, some of them even on warming with water. All those derivatives still retain their alcoholic character. If, on the other hand, glycollic acid forms derivatives as an alcohol, the properties of the alcoholic derivatives in question are' combined with those of an acid, since the hydroxyl of the GLYCOLLIC ACID. 211 alcoholic group, — CH2.OH, enters into reaction, while the car- boxyl group remains unchanged. These derivatives are either ethers, such as ethyl-glycollic acid (see table), or e.g, amines, such as glycocoll, and, as alcoholic derivatives, they are not saponifiable ; or they are compound ethers of glycollic acid as alcohol, e.g. acetyl-gly collie acid, CH2(O.C2H30) — CO2H, or mono-chloracetic acid, CHg.Cl — COgH (the hydro- chloric ether of glycollic acid), and then they are of course saponifiable. These latter compounds still retain their acid character and therefore form, on their part, compound ethers, chlorides and amides, which are readily broken up backwards by saponification. The following table gives a summary of the more important derivatives of glycollic acid. Acid Derivatives. Alcoholic Derivatives. Mixed Derivatives. CH2(0H)— CCONa Sodium glycollate. CH2(0Na)— CO.ONa Di-sodium glycollate. Hygroscopic ; decomp. by HgO into Na salt and NaOH. CH2(0H)— CO.OC2H5 Ethyl glycollate. Liquid, B. Pt. 160°. CHslOCaHg)— CO.OH Ethyl-glycollic acid. Liquid, B. Pt. 206°. CH2(0C2H;)-C0(0C2H5) Ethylic ethyl-glycollate. Liquid, B. Pt. 158°. CH2(0H)— CO.Cl Glycollyl chloride. Oil ; decomposes on volatilizing. CH2CI— CO.OH Mono-chloracetic acid. CH2CI— COCl Mono-chlor-acetyl chloride. Liquid, B. Pt. 120°, of suffocating odour. CH2(0H)— CO.NH2 GlycoUamide. Crys. M.Pt. 120°; does not form salts with bases. CH2(NH2)— CO.OH Glycocoll. Crys. M. Pt. 170°. Forms salts with acids and bases. CH2(NH2)-CO(NH2) Glycocollamide. Crys. To the compounds of the second vertical row belong also, among others, Thio-glycoUic acid, CH2(SH)— CO.OH, which is at the same time an acid and a mercaptan ; to those of the third row belong mixed compounds such as CH2(NH2)— CO(OC2H5), (see glycocoll). It is easy to see that the corresponding derivatives of the first and second vertical rows are always isomeric. 212 IX. POLYATOMIC MONOBASIC ACIDS. Anhydrides of GlycoUic acid. 1. Di-gly collie acid, C4HgOg, = 0(CH2 — C0.0H)2, is an alcoholic anhydride and a dibasic acid. It is obtained e.g. by boiling mono-chloracetic acid with lime. Large rhombic prisms. Being an alcoholic ether, it is not saponified on boil- ing with alkalies, but on heating with concentrated hydrochloric acid to 120°. 2. GlycoUic anhydride, C4H6O5, = CHaCOH)— C0.0(CH2— CO.OH), is a compound ether-anhydride, which is formed upon heating glycollic acid to 100°. It becomes hydrated again when boiled with water. CH2— 0— CO 3. Glycolide, C4H4O4, = | | is an ether-acid anhydride CO 0— CH2, isomeric with fumaric acid, which results when glycollic acid is heated strongly. It is a powder, almost insoluble in water, and also becomes hydrated again upon boiling with water. Glycocoll, glycocine, amido-acetic acid, CH2(NH2) — CO. OH, (Braconnot, 1820). This is the simplest representative of the important class of " amido-acids," so called because they are derived from the fatty acids by the exchange of a hydrogen atom of the hydrocarbon radicle for amidogen, e.g. CH3.CO2H, acetic acid; GH2(NH2).C02H, amido-acetic acid. Its methods of formation include those of the other amido-acids. Formation. 1. By heating mono-chloracetic acid with ammonia : CH3CI— CO2H + 2NH3 = CH2(NH2)— CO2H + NH/Jl, {Heintz, A. 122, 261). Di- and Tri-glycollamic acids, NH(CH2— C02H)2 and N(CH2— C02H)3, are produced at the same time. a-Chloropropionic acid in like manner yields alanine with ammonia, (see lactic acid), and so on. 2. By boiling glue with alkalies or acids. 3. Together with benzoic acid by decomposing hippuric acid, i.e. benzoyl-glycocoll, by HCl : CH2[1S[H(C0C6H5)]-C02H + H,0 = CHalNHJCO^H + CeHgCO.OH. Hippuric acid. Benzoic acid. 4. Together with cholic acid, by the analogous decomposition of glycocholic acid, C26H43NO6. 5. From cyano-carbonic ether, CN — CO.OC2H5, and nascent hydro- gen, or from cyanogen and liydriodic acid : CN— CN + 2H2 + 2H2O = CHglNHg)— CO.OH -f- NH3. GLYGOCOLL. 213 6. (Of the homologues of glycocoll) : By treating ethylidene-cyan- hydrin (p. 133) etc. with alcoholic ammonia, or aldehyde-ammonias with hydrocyanic acid, amido-cyanides are formed, e.g. CH3 — CH(NH2)(CN), which are saponified to amido-acids upon boiling with HCi. Properties, Glycocoll forms large colourless rhombic prisms, easily soluble in water, but insoluble in absolute alcohol and ether. It has a sweet taste, hence the name "gelatine sugar" or glycocoll (yAi^Kus, sweet, KoXXa, glue). It melts at 170°, and decomposes on being heated more strongly. Behaviour. Glycocoll, like all the amido-acids, unites in itself the properties of a base (being, as an alcoholic amine, non- saponifiable) and those of an acid. It therefore forms salts with acids as well as with bases, e.g. glycocoll hydrochlorate, CgHgNOg.HCl, which crystallizes in prisms, and the char- acteristic copper salt, glycocoll copper, {G<^^O^^G\\ + HgO, which crystallizes in blue needles, the latter being obtained by dissolving copper oxide in a solution of glycocoll. Most of the other amido-acids also form characteristic copper salts of this nature, which serve for their separation. Glycocoll also yields compounds with salts, and, as an acid, forms an ethyl ether, an amide, etc., (see table, p. 211). Heated with BaO, it is decomposed into methylamine and COg, while N2O3 converts it into glycollic acid, (the normal reaction of the primary amines). Ferric chloride produces with it an intensive red, and copper salts a deep blue colouration. Glycocoll ethyl ether yields with NgOg the interesting Diazo-acetic ether, CNgH— CO.OC2H5. (B. 16, 2230; 17, 953; 18, 1283). Constitution^ (see B. 16, 2650). Free glycocoll may be regarded as an intramolecular salt, corresponding to the NH formula, GH2<^qq (see betaine). Alkyl derivatives of Glycocoll ; Methyl-glycocoll Tri-methyl-glycocoll Acetyl-glycocoU or Sarcosine, or Betaine, or Aceturic acid, CH2— NH(CH3) CO.OH CH2-N(CH3). co.o CH2— NHlCaHgO) CO.OH. (a decomposition (contained in beetroot and related to choline). etc. product of creatine and caffeine). 214 IX. POLYATOMIC MONOBASIC ACIDS. The above have all been prepared synthetically. Lactic acids, CgHgOg, = C2H4(OH)(C02H). {Wislkenus, A. 128, 1 ; 166, 3 ; 167, 302, 346). As has been already mentioned at p. 208, two isomeric lactic acids are theoretic- ally possible, viz., a- and /5-oxy-propionic acids, or ethylidene- and ethylene-lactic acids. Both are known, the former being the common lactic acid. There exists, however^ in addition to these, a third modification, sarco-lactic acid, which is chemically identical with the a-acid, but differs from it in physical properties. The minute investigation of the different lactic acids has been of very great importance for the development of chemical theory ; they were formerly held to be dibasic, and the recognition of their diatomic monobasic nature has materially contributed to the acceptation of the theory of the linking of atoms. Modes of Formation. 1. By the regulated 1 oxidation of j 2. By the exchange of halogen for |- hydroxyl from J 3. By saponification) of / 4. By action of N203\ upon / 5. By the reduction \ of I Fermentation lactic acid, a-Propylene glycol, CH3-CH(OH)-CH2(OH). a -Chloro -propionic acid, CH3—CHCI— CO.OH. Aldehyde-cyanhydrin, CH3— CH(OH)— CN. Alanine, CH3-CH(NH2)-CO.OH. Pyro-racemic acid, CHo— CO— CO.OH. 6. By the lactic fermentation of sugar, etc. Ethylene-lactic acid. /3-Propylene glycol, CH2(OH)-CH2-CH2(OH) /3-Iodo-propionic acid, CH2I—CH2— CO.OH. Ethylene-cyanhydrin, CH2(0H)— CHa— CN. 1. Ethylidene-lactic acid, CH3— CH.(OH)— COgH. Dis- covered by Scheele, and recognised as oxy-propionic acid by Kolbe, Occurs in opium, sauerkraut, and in the gastric juice. Preparation. This depends upon the so-called lactic fermen- tation of sugars, e,g, milk, cane and grape sugars, and of LACTIC ACID. 215 substances related to them, such as gum and starch ; it is effected in presence of decaying albuminous compounds, for instance, old cheese, by the action of oval micro-organisms — (lactic bacteria) — if the solution is nearly neutral. This last condition is attained by the addition of zinc white or chalk to the fermenting mixture. The fermentation is completed in eight to ten days at a temperature of 40°-4:5°; should it be prolonged, it changes into the butyric fermentation (p. 159). The free acid is then liberated from the lactate of zinc by sulphuretted hydrogen. Lactic acid is also produced in large quantity by heating grape or cane sugar with caustic potash solution of a certain degree of concentration, (B. 15, 136). The relations of lactic acid to the sugar varieties appear at a superficial glance to be very simple ; thus grape sugar, CgHigOg, and lactic acid, CsHgOg, are polymers. Properties, The acid has not been obtained free from water. When its solution is evaporated in an exsiccator, a thick, non-crystallizing and hygroscopic syrup is got, which is miscible with water, alcohol and ether, and which gradually gives up water, with the formation of (solid) lactic anhydride, CqR-^qO^, before all the water of solution has been got rid of. When heated, it partly goes into the anhydride, lactide, CgHgO^, and partly breaks up into aldehyde, CO, and H2O. Similarly it decomposes into aldehyde and formic acid upon heating with dilute sulphuric acid to 130°, concentrated sulphuric giving rise to carbon monoxide instead of formic acid ; CH3— CH(OH)— CO2H + H2O = CH3— CHO + HCO2H. Upon oxidation it yields acetic and carbonic acids ; hydro- bromic acid converts it into a-bromo-propionic acid, and boiling with hydriodic acid into propionic acid itself. Calcium lactate, (CgHgOajgCa + SHgO : warty masses of microscopic rhombic needles. Zinc lactate, (CsHgOgjgZn + SHgO : glancing needles. Ferrous lactate, (C3HgO;3)2-f-3H20 : bright yellow needles; both the ferrous and zinc salts are used in medicine. When sodium lactate is heated with sodium, Di-sodium lactate, CH3— CH(ONa) — C02Na, which is at the same time a salt and an alcoholate, is formed. 216 IX. POLYATOMIC MONOBASIC ACIDS. The Derivatives of lactic acid are derivatives of it either as acid or as alcohol, and are perfectly analogous to those of glycollic acid, (see table, p. 211). Thus Ethyl-lactic acid, CH3— CH(0C2H,)— CO2H, a thick acid liquid which boils almost without decomposition,"^ corresponds to ethyl-glycollic acid; Ethyl lactate, which can be distilled without decomposi- tion, to ethyl glycollate; Lactamide,CH3— CH(OH)— CO.NH2, to glycollamide, and Alanine, CH3— CH(NH2)— CO.OH, to glycocoU. Alanine results from the action of hydrocyanic acid upon aldehyde ammonia (see p. 213), and forms hard needles of a sweetish taste. By the action of PCI5, lactyl chloride, CH3— CHCl- CO.Cl, (p. 178) is formed; as the chloride of a-chloro-propionic acid it yields the latter acid and HCl with water. The acid just named is therefore to be regarded as the hydrochloric ether of lactic acid. The following anhydrides of lactic acid are known : 1. Lactylic acid or Lactic anhydride, CgHjoOg, which is analogous to glycollic anhydride, and forms a yellow amorphous mass ; 2. Lactide, C6H8O4, analogous to glycolide, (tables, M. Pt. 125°) ; 3. Di-lactic acid, C^jHiqCq, the alcoholic anhydride, analogous to di-glycollic acid. 2. Ethylene-lactic acid, hydracrylic acid, CH2(OH)-CH2-CO.OH, ( TVislicenuSy A. 128, 1 ), forms a syrupy mass. It differs from lactic acid : (a) By its behaviour upon oxidation, yielding carbonic and oxalic acids, and not acetic ; (b) By not yielding an anhydride when heated, but by breaking up into water and acrylic acid, hence the name hydracrylic acid : CH2(OH)~CH2— COOH = CH2--CH— COOH + H^O ; (c) In solubility, and in the amount of water of crystallization of its salts, (e.g. zinc salt : -}- ^HgO, very easily soluble in water ; calcium salt : + 2H2O). 3. Sarco-lactic acid, pam-ladic acid, active lactic acid, CH3— CH(OH)— CO2H, (Liebig), This occurs in the juice of * By the entrance of the ethylic group, the hydroxy 1 is in a certain degree paralysed as regards its action, in consequence of which ethyl- lactic acid resembles propionic acid much more nearly than lactic acid itself does. HOMOLOGUES OF LACTIC ACID. 217 flesh, and results instead of ordinary lactic acid in certain fermentations. Its properties are almost identical with those of the latter, for instance, it possesses an equal facility in forming lactide or aldehyde. It is however optically active (dextro-rotatory), and its salts also differ somewhat from those of the isomeric acid ; thus the zinc salt : + SHgO, is much more easily soluble, and the calcium salt : + 4H2O, much more difficultly soluble than the corresponding common lactates. The isomerism of para-lactic acid and the lactic acid of fermentation can hardly depend upon a difference of consti- tution, since their chemical behaviour is the same, but arises most probably from physical grounds. This kind of isomerism is therefore termed physical isomerism." Either modifica- tion can be converted into the other; thus, common lactic acid becomes optically active ( + ) by the action of fission fungus, (Penicillium). For further details, see p. 32 and under tartaric acid. Oxy-butyric acids, (see p. 208). /3-0xy-"butyric acid, CH3— CH(OH)— CH2— COgH, a syrup, is related to aldol and aceto-acetic acid. An optically active ( — ) modification is contained in diabetic urine and blood. 7- Oxy -"butyric acid, CH2(0H)— CHg — CHg — COgH, is only capable of existence in its salts and not in the free state, as it breaks up into water and its lactone, butyro-lactone. a-Oxy-isobutyric acid, (CH3)2=C(OH)— CO2H, (Wurtz), results from acetone cyanhydrin (p. 142), and is therefore also called acetonic acid. Amido-butyric acids are known, e.g. Piperic acid, C3Hg(NH2)(C02H). Oxy-valeric acids. Several amido-valeric acids have been prepared synthetically, while others have been obtained by the decomposition of albumen and of conine and piperidine derivatives, and have also been found in the pancreas of the ox. Oxy-caproic acids. Leucine or a-Amido-caproic acid, CH3— CH2— CH2— CH2— CH(NH2)— CO2H, is a derivative of a-oxy-caproic or leucic acid (Strecker) ; it forms fatty glancing plates and, like other amido-acids, is nearly related to albumen. It is found in old cheese, also abundantly in the animal organ- ism in the gastric salivary gland, and in the shoots of the vetch and gourd, etc. It forms, along with tyrosine, a con- 218 IX. POLYATOMIC MONOBASIC ACIDS. stant product of the digestion of albumen in the small intestine and of the decay of albuminous substances, and results from the latter by boiling them with alkalies or acids. It also appears to have been prepared syntheticall}^ It closely re- sembles glycocoll, and forms a characteristic sparingly soluble blue copper salt. Leucine is dextro-rotatory, a laevo-rotatory modification being also known (B. 19, Kef. 567). Conic acid, C7H15NO2, and Homo-conic acid, C8H17NO2, are higher homologiies of leucine which have been prepared from conine. Oxy-stearic acid, CigHggOg, is obtained by the action of cold cone. H2SO4 on oleic acid — (addition of H^O) — and forms a white mass. Its sulphuric ether or Oxy-stearo- sulphuric acid, CigHggOglOSOgH), is of importance for the manufacture of Turkey red. Coccerylic acid, C3iHg203, occurs in cochineal wax, combined with cocceryl alcohol. The two following are diatomic monobasic acids : Ricinoleic acid, C18H34O3 from castor oil, and its isomer, Rapinic acid, C18H34O3, from rape seed oil. Appendix. Lactones. The 7-oxy-acids (see 7-oxy-butyric acid) are very unstable in the free state, so that when an acid is added to their salts, not the oxy-acids themselves but anhydrides are obtained, e.g. butyro-lactone, (see p. 209) : CH2(0H)— CH2— CH2— CO.OH = CH2— CHg— CH2— CO + HgO. 6 ^1 These lactones are to be regarded as intramolecular anhydrides {i.e. 1 mol. acid - 1 mol. HgO), or ethers, the acid part of the molecule etherifying in some degree the alcoholic part. The lactones of the 7-oxy-acids, *' 7-lactones," are for the most part neutral liquids of faint aromatic odour, easily soluble in alcohol and ether, and distilling without decomposition. They dissolve in alkalies to the salts of the corresponding oxy-acids, and form brominated fatty acids with HBr, and amido-acids with NH3. 5- and j8-, but only a few a-lactones, from 5-, and a-oxy-acids, are also known. They show marked differences in the ease with which they are formed and in their stability, the 7-lactones being the most stable. The formation of lactones by warming the unsaturated acids, CnH2n-2 02, which are isomeric with them, with HBr or with moder- ately concentrated H2SO4, is worthy of note. For details, see Fittig and his pupils, A. 208, 37, 111 ; 216, 26, etc. TRI- TO HEXATOMIC ACIDS. B. Tri- to hexatomic monobasic Acids. Summary, Name and Formula. Preparation. Remarks. A. Triatomic monobasic acids. (Di-oxy- propionic acid) C^HslOHj^lCO^H). Glyceric acid. 1. inactive ; 2. optically active. From glycer- ine. Alcoholic amine; Serine, C2H3(OH)(NH2)(C02H) from silk-gum and dilute H2SO4; analo- gous to glycocoU. B. Tetratomic monobasic acids. (Tri-oxy-butyric acid) C3H4(OH)3(C02H). Erythritic acid. Fromerythrite; from Isevulose with Ba(OH)2 + HgO C. Pentatomic monobasic acids. (Tetr-oxy-caproic acids) C5H,(OH)4(C02H). 1 1. Saccharic acid ; 2 and 3. Iso- and Meta-saccharic acids. 1. From grape and fruit sugars with , CaO ; 2 and 3. from milk sugar in the same way. Known as salts and as lactones, e.g. Sacch- arine, CgHioOg (iso- meric with starch), which crystallize well. D. Hexatomic monobasic acids. (Pent-oxy-caproic acids) C5He(OH)5(C02H). 1. iVianuiulV/ ctt-iu. y 2. Gluconic acid ; 3. Galactonic acid. 1. From man- nite; 2. from dextrose, cane sugar, etc. , with brom. water and AggO ; 3. from milk sugar in an analogous manner. The constitution of the saccharic acids, etc. , is of importance on account of the deductions which can be drawn from it with regard to the constitution of the sugars. (Cf. B. 17, 1302 ; 18, 2514.) Just as the glycols yield in the first instance diatomic monobasic acids upon oxidation, compounds which possess at 220 IX. POLYATOMIC MONOBASIC ACIDS. the same time the characters of a monatomic alcohol and a monobasic acid, so are the polyatomic alcohols at first con- verted (by cautious oxidation in the air in presence of platinum black, or also by means of nitric acid), into monobasic acids, which likewise retain the characteristics of a mono-, di-, tri-, etc. atomic alcohol, i.e., into tri-, etc. atomic monobasic acids. These correspond entirely with lactic acid in behaviour, but, as alcohols, are polyatomic. Since the oxidation consists in the conversion of a — CH2.OH group into carboxyl, the resulting acids consequently contain as many hydroxyls as the original alcohols, this number being again ex- pressed by the designation **tri-, tetra-, etc. atomic monobasic acids." The number of alcoholic hydroxyls in the molecule is determined — as in the case of the polyatomic alcohols — by the number of acetyl groups which can be introduced upon treatment with acetic anhydride. The law which applies to the polyatomic alcohols, viz., that only one hydroxyl can be bound to one atom of carbon, also holds good for the alcohol-acids. Their carbon-atom chain is the same as that of the mother compound. Most of the compounds belonging to this class either crystallize badly or are gum-like. A number of these acids also result from the cautious oxidation of the sugars or of the unsaturated acids, CnH2n-202, (see p. 164). 0. Aldehyde -alcohols. 1. GlycoUic aldehyde, CH2(0H)— CHO. This is only known in aqueous solution. 2. Aldol, CH3— CH(OH)— CH2— CHO. A condensation product of aldehyde, see p. 134 ( Wurtz), It forms a thick liquid, easily soluble in water. 3. Glyceric aldehyde, 0H2(0H)— CH(OH)— CHO, is the aldehyde of glyceric acid, and is obtained by very careful oxidation of glycerine. It is only known in solution. It acts as a powerful reducing agent, and is changed into a sugar by condensation. (See acrose.) 4. Arabinose, C5H10O5, = CH2.OH— (CH.0H)3— CHO, is produced by boiling gum arable with dilute sulphuric acid, and forms dextro- rotatory prisms. For its constitution see Kiliani, B. 20, 339, 1233. It was formerly reckoned among the glucoses. KETONE-ALCOHOLS, ETC. 221 The Sugars are also to be looked upon as aldehyde-alcohols or ketone-alcohols; they will be treated of separately (p. 28o). D. Ketone-alcohols. Acetone-alcohol, acetol, acetyUarUnol. CH3-C0-CH,0H Only known in aqueous solution. Is prepared from ^l-^^"^]^^^^^^^ "f, AgoO, and by fusing grape sugar, etc., with potash, (B. 16, 837). it reduces Fehling's solution even in the cold. E. Diatomic Aldehydes. Glyoxal, CHO-CHO, {Delus, 1856). Formed by the cautious oxidation of alcohol or, better, of aldehyde. White deliquescent mass. Possesses all the characteristic properties of aldehydes ; being a diatomic aldehyde, its bisulphite results from 1 mol. glyoxal and 2 mols. NaHSOg. Concentrated ammonia converts it into Glyoxaline, C3H4N2, a strong base, of a faintly fish-like odour, having probably the constitution : CH-N >\ ^.^^^^ interesting derivatives, e.g., Oxal-ethyline, CH— NH/ CH-N \^__^^^^ a base of alkaloid nature and of strongly CH-Nie^Hg)/ . -R p^in poisonous properties, (Wallach, A. 184, 1 ; 13. 13, F. Diatomic Ketones. (See also p. 177.) 1. Di-acetyl, di-keto-hutane, CH3-CO-CO-CH3. J^is can be pre- pared by treating iso-nitroso-methyl acetone, CH3-CH(N.OH)-bU-un3 (which results from the action of HNO^ on methyl aceto-acetic ether) with NaHSOg, and subsequently boiling with dilute H2SO4. Yellow- green liquid of quinone odour, its vapour having the colour of chlorme. B. pt. sr-ss\ 2. Acetyl-acetone, CH3-CO-CH,-CO-CH3, is formed by the action of AlaClg upon acetyl chloride {Combes). 3. Acetonyl-acetone, di-keto-hexane, CH3— CO-CH,— CH,-CO ^CE., Prepared from monochlor-acetone and aceto-acetic ether, (p. 226; B. 17. 2756). 222 IX. POLYATOMIC MONOBASIC ACIDS. These three compounds are the simplest representatives of the interesting class of di-ketones. They are distinguished as a, /3, and 7, (1:2, 1 : 3, and 1 : 4) di-ketones according as the carbonyl groups are close together, ( — CO — CO — ), or separated by one carbon atom, (_C0— CH2~C0-), or by two, (— CO— CH^-CHg— CO— ). They show the most varying behaviour as regards condensation with ammonia, phenyl-hydrazine, etc., and are therefore of value for the synthesis of the derivatives of quinoline (from of pyrazol (from of furfurane and pyrrol (from 7-), and of benzene (from a-di-ketones). Their con- stitution frequently follows directly from their modes of formation. G. Ketone-aldehydes. We have also become acquainted recently with ketonic-aldehydes, e.g.— Aceto-acetic aldehyde, CH3 — CO — CH2 — CHO, the aldehyde of aceto- acetic acid, which results from the condensation " of acetone and ethyl formate under the influence of sodium ethylate ; it is, however, incap- able of existence in the free state. (See p. 226 ; also B. 21, 1144.) H. Monobasic Aldehyde-acids. 0^yoxdi\iQd^GiA,glyoxylicadd, CHO-C02H,(orCH(OH)2-C02H), occurs in unripe fruits such as grapes, gooseberries, etc., and may be prepared, e.g,^ by superheating dichlor-acetic acid, CHCI2 — COgH, with water, CI2 being here exchanged for 0 or 2 (OH). It crystallizes in rhombic prisms, easily soluble in water, and is volatile with steam. The acid and most of its salts contain 1 mol. HgO, which points to the formula CH(0H2) — COgH, analogous to that of chloral hydrate, from which it is derivable by the exchange of 3C1 for 0 and OH. Formyl-acet/ic acid, CHO — CHg — COgH, which is at the same time the semi-aldehyde of malonic acid, is formed as ether by the action of sodium upon a mixture of ethyl formate and acetate (see p. 226). It is readily condensible to trimesic acid (p. 430). I. Monobasic Ketonic acids. Ketonic acids are compounds which possess at one and the MONOBASIC KKTONIC ACIDS. 223 same time the properties of acids and ketones; thus, besides being capable of forming salts, ethers, etc., they also combine with sodium bisulphite, yield oximes with hydroxylamme hydrochlorate (see p. 142), are reduced by nascent hydrogen to secondary , alcohol-acids, and so on. The most important members of this class are pyroracemic acid, CH3— CO— CO2H, aceto-acetic acid, CH3-C0-0H,-C0,H, and levulinic acid, CH3-CO-OH2-~CH2-C02H. Constitution and Nomenclature. The ketonic acids are charac- terized theoretically by the presence of carboxyl and of car- bonyl, the latter being linked to carbon on both sides. They may be derived from the monobasic fatty acids in such manner that one hydrogen atom of the radicle of the latter is replaced by an acid radicle R— CO— , (in the cases above mentioned by CH —CO, acetyl)—, as the name aceto-acetic acid indicates. Levulinic 'acid is therefore /5-aceto-propionic acid, and pyro- racemic acid is acetyl-formic acid; or, the ketonic acids are derived from the fatty acids by the replacement of the two hydrogen atoms of a CHg— group by an atom of oxygen. The position of the oxygen atom may therefore be indicated by the prefixes a, /3, and 7, etc., as in the case of the oxy-acids (p. 208), and the haloid substitution acids. Pyroracemic acid is thus a-keto-propionic acid, aceto-acetic acid is jS-keto-butyric acid, and levulinic acid is 7-keto-normal-valeric acid. (Cf. Baeyer, B. 19, 160.) The constitution of the ketonic acids is as a rule easy to determine, either from the mode of their synthesis, or from their transformation into the corresponding alcohol-acids- (oxy-acids)— of known constitution, by means of nascent hydrogen, and so on. For the constitution of aceto-acetic acid see also p. 227. While the a- and 7-ketonic acids are stable liquids, some of which may even be distilled, the jS-ketonic acids are very unstable in the free state and break up very readily into COg and the corresponding ketone. Pyroracemic acid, C3H4O3, = CH3— CO -CO^H, is a liquid which is readily soluble in water, alcohol and ether, boils with slight decomposition at 165°-170°, and smells of acetic acid and extract of beef. Formation. 1. By the dry distillation either of tartaric or of racemic acid, hence its name. 224 IX. POLYATOMIC MONOBASIC ACIDS. 2. By the oxidation of lactic acid by means of KMn04. 3. By saponifying acetyl cyanide with HOI, {Claisen, Shadwell) ; CH3— CO— CN + 2H2O = OH3— CO— CO2H + NH3. Pyroracemic acid has a tendency to polymerize. Its salts crystallize only with difficulty. Nascent hydrogen reduces it to ethylidene-lactic acid : CH3 — CO^ — COgH + H2, = CH3 — CH(OH) — COgH, from which reaction and from mode of. formation 3, its constitution follows. It possesses in a marked degree the ketonic property of forming condensation products, going either into derivatives of benzene, (B. 5, 956), or — in presence of ammonia — into those of pyridine. Sulphuric acid causes it to condense with the aromatic hydrocarbons, just as in the case of the ketones, (B. 14, 1595). Cystine, 0^11^2^2^204' disulphide of amido-thio-lactic acid or cysteine, C2H3(NH2)(SH)C02H, is to be regarded as a derivative of pyroracemic acid, (see ethyl di-sulphide). It is found in urinary sediments and gravel, (B. 18, 258). a-Keto-but3rric aciCi, propionyl-carboxylic acid, CH3 — CHg — CO — COgH, resembles pyroracemic acid. Aceto-acetic acid, /S-keto-butyricacid, CII3 — CO — OH2 — OOgH. A strongly acid liquid, miscible with water, and breaking up into acetone and carbonic acid upon warming. It is prepared by the cautious saponification of its ethyl ether, (B. 15, 1376 ; 1871). Its aqueous solution is coloured violet-red by ferric chloride. The Na- or Oa-salt is sometimes contained in urine, (B. 16, 2314). Aceto-acetic acid may also be looked upon as acetone-carboxylic acid, 03H50(002H). Aceto-acetic ether, OH3 — 00 — OH2 — OO2O2H5, is obtained in the form of its sodium compound, sodio-aceto-acetic ether, by the action of sodium upon ethyl acetate, {Geuther, 1863; Frankland and Duppa) : 2OH3— OO.OC2H5 -1- Na = OH3— 00— OHNa— OO.OO2H5 + 02H,0H + H. According to Claisen (B. 20, 651), there is first formed in this reaction some sodium ethylate, C^HgONa, by the decomposition of a small portion of the acetic ether, and this then combines with more ACETO-ACETIC ETHER. 225 /OC,H, ether to the compound CHo— Cv— OCgHg, which is a derivative of ortho- \ONa acetic acid (p. 175). This last compound now reacts with a further molecule of acetic ether to yield sodio-aceto-acetic ether, with separa- tion of 2 mols. alcohol, the alcohol thus separated yielding sodium ethylate with further sodium, and so on. By this synthesis 2 mols. of acetic ether combine together under the influence of sodium ethylate. The compound ethers homologous with acetic ether, and also mixtures of two different ethers, behave in the same way, thus : X— CO.OR + HX'— CO.OR = X— CO-X'— CO.OR + R.OH. In like manner mixtures of ketones or aldehydes with compound ethers can be condensed" by means of sodium ethylate to ketone-aldehydes, di-ketones, etc. (Cf. aceto-acetic aldehyde, p. 222. ) The ether is obtained from the sodium compound upon the addition of acid. It is a liquid of neutral reaction, boiling at 181°, only slightly soluble in water but easily in alcohol and ether, and of a pleasant fruity odour. Ferric chloride colours its aqueous solution violet-red. It is split up upon being boiled with alkali, dilute aqueous alkali or baryta water (or also dilute sulphuric acid) producing mainly carbon dioxide, acetone and alcohol; (^^ketonic decomposition"): CH3— CO— CH2— C02(C2H5) + H2O = CH3— CO— CH3 -t- CO2 + HO.C2H5; very concentrated alcoholic potash, however, produces chiefly (2 mols.) acetic acid ; ("acid decomposition," Wislicenus) : CH3— CO— CH2— C02(C2H5) + 2H2O = 2CH3— CO.OH + HO.C2H5. One atom of hydrogen in aceto-acetic ether is easily replace- able by metals {Geuther ; Conrad, A. 188, 269). The sodium salt results with evolution of hydrogen upon the addition of sodium, and also upon mixing the alcoholic solution of the ether with the calculated amount of sodium dissolved in absolute alcohol : ^^"^fP^i^^^,) + C^H^.ONa = + C^H.^.OH. In agreement with this the ether dissolves in dilute alkali, being again separated from the solution by the addition of acid. (506 p 226 IX. POLYATOMIC MONOBASIC ACIDS. Sodio-acelo acetic ether, CH3— CO— CHNa— COaCgH^ ; long needles or a faintly glancing loose white mass. Copper salt : bright green needles. The constitution of aceto-acetic ether follows from its formation and behaviour. The latter shows that it is a hydrogen atom of the methylene group, CH2, which is replaceable by metals, this capability of replacement being explained by the acidifying influence of the two carbonyl groups which are directly bound to the methylene, viz., the CO of the group CH3— CO, and the CO of the group CO. OH. (Compare the relation of hydrated carbonic acid, C0(0H)2, to two molecules of water, H(OH).) The metal in sodio-aceto-acetic ether is readily replaced by an alcohol radicle by the action of iodo- or bromo-alkyl, sodium iodide or bromide being formed at the same time. We thus obtain alkylated aceto-acetic ethers, e,g, : Methyl-aceto-acetic ether or Ethylic methyl-aceto-acetate, CH3— CO— CH(CH3)— C02(C2H5), and the corresponding Ethyl- and Propyl-aceto-acetic ethers, etc. In these com- pounds the H may be again replaced by Na, and this again substituted by alkyl, with the production of di-alkylated aceto- acetic ethers, e.g. : Dimethyl-aceto-acetic ether or Ethylic di- me thy 1-aceto -acetate, CH3-CO-C(CH3)2-C02(C2H5) ; Methyl- ethyl-aceto-acetic ether, CH3-CO-C(CH3)(C2H5)-C02(C2H5), and so on. These alkylated aceto-acetic ethers exactly resemble their mother substance, especially in that they undergo either the " ketonic decomposition " or the " acid decomposition," accord- ing to their degree of concentration, upon treatment with alkalies; the latter decomposition also upon treatment with dilute acids, (see above, also A. 190, 275). The first-named decomposition leaves the substituting alcohol radicles in the acetone residue of the molecule, and the last-named in one of the two resulting acid molecules, i.e., there are formed either alkyl-acetones (homologues of acetone), or alkyl-acetic acids (homologues of acetic acid). We have thus at command here a most excellent method for the synthesis of any simple or double alkyl ketone or acid ; DIBASIC ACIDS. 227 1. CH3— CO— CRR'— CO2C2H5 + H2O = CH3— CO— CHRR' + HO-C^H^ + CO2; 2. CH3— CO— CRR— CO2C2H5 + 2H2O = CH3— CO.OH + CHRR'— CO2H + HO.C2H5. (RR' = alcohol radicles. Cf. Wislicenus and his pupils, A. 186, 161.) In a perfectly analogous manner we can introduce acid instead of alkyl radicles into aceto-acetic ether, and thereby give rise to the most various compounds, e.g., from acetylchloride, di-aceto-acetic ether, (CH3— C0)2CH— C02(C2Hg) ; from chloro-carbonic ether, CI— CO2C2H5 (p. 269), acetol-malonic ether, (CH3— CO)— CHlCO.CsHgja ; from monochlor-acetic ether, CH2Ci — COgtCgHg), acetol- succinic ether, CH3— CO— CH(CH2— C02C2H5)(C02C2H5), (see malonic and succinic acids, and also the synthesis of dibasic acids), etc. Iodine acts upon sodio-aceto-acetic ether to produce di-acetol succinic ether, which is interesting from its transformations, thus : CH3-CO -CHNa-C02C2H5 CH3-CO-CH-CO2C2H5 + I2 = I + 2NaI. CH3-CO-CHNa-C02C2H5 CH3-CO-CH-CO2C2H5 Chlor- and Dichlor-aceto-acetic ethers, which are very active chemi- cally, are produced by the replacement of the H of the methylene group by CI. The two methylene hydrogen atoms are also replaceable by the iso-nitroso group, =N — OH (by the action of N2O3), and by the imido group, =NH, (cf. A. 226, 294). In many reactions aceto-acetic ether behaves as if it were in the first instance changed into the isomeric form — the pseudo-form — CH3C(0H)=CH— C02(C2H5), /3-oxy-crotonic ether. (See the furfurane group, and the appendix to the cyanogen compounds.) Levulinic acid, CgHgOg, = CH3— CO— CHj— CH2— CO2H. Plate crystals, M. Pt. 33°, B. Pt. 239°. Results from the action of acids upon cane sugar, Isevulose, cellulose, gum, starch and other carbo-hydrates, (A. 175, 181 ; 206, 207), and has also been prepared synthetically. It is employed in cotton printing. X. DIBASIC AOIDS. Dibasic acids are those which are capable of forming two series of salts, acid and neutral, with monatomic bases, and likewise two series of ethers, chlorides, amides,, etc. The dibasic acids proper are characterized theoretically by the presence of two carboxyls in the molecule. 228 X. DIBASIC ACIDS. These acids may either possess the acid character pure and simple, or also at the same time the character of an alcohol, e.g. lactic acid ; in the latter case they still contain alcoholic hydroxyl. A distinction is drawn between diatomic dibasic and tri-, tetra-, etc. atomic dibasic acids. They may be either saturated or unsaturated compounds. The dibasic carbonic acid will be treated of later on (pp. 266 seg^.). A. Saturated diatomic dibasic Acids, CnH2n_204. Oxalic acid, CgHg 0^ Suberic acid, Cg H^^O^ Malonic „ C3H4 O4 Lepargylic, „ Cg H^gO^ Succinic „ C^Hg 0^ Sebacic „ CiQH^g04 Pyrotartaric „ CgHg O4 Brassylic „ C-^^^fi^ Adipic „ C^H^oO^ Eocellic „ G^>jR^NH. ' ' ' ^ r> — \ ' Succinic acid. Succinimide. Like the amides they are easily saponifiable, (cf. succini- mide). Oxalic acid, acidwn oxalicum, C2H2O4 + 2H2O. This acid has been known for a very long time ; it was investigated by Scheele. Occurrence. In many plants, especially in oxalis acetosella (wood sorrel), as KHC2O4 in varieties of Eumex, free in varieties of Boletus, as Na2C204 in varieties of Salicornia, and as calcium salt in rhubarb root, etc. Formation. (See also p. 228) : 1. By the direct combination of carbon dioxide with sodium at 360° : 2CO2 + Na2 = C204Na2. 2. By raising sodium formate quickly to a high temperature: 2HC02Na = + Cfi^^^. 3. By the oxidation of sugar, starch, etc., with HNO3, or by fusing cellulose with the hydrates of potash and soda. This last method is followed for its preparation on a large scale. The frequency of its formation in processes of oxidation is explained by its close relation to carbonic acid, which is the final product of all oxidations. 232 X. DIBASIC ACIDS. Properties. Fine transparent monoclinic prisms which effloresce in the air. Easily sohible in water and moderately in alcohol. The anhydrous acid, which is obtained at 100°, can be sublimed, but it decomposes upon rapid heating into carbon dioxide and formic acid, or into carbon dioxide, carbon monoxide and water. The latter decomposition also takes place upon heating with concentrated sulphuric acid : = CO2 + CO + H2O. Oxalic acid is stable as regards nitric acid and chlorine, but permanganate of potash or manganese dioxide in acid solution oxidizes it to carbonic acid : C^H^O^ + O = 2CO2 + H2O. Salts and Derivatives, The alkaline salts, acid and neutral, are readily soluble in water, the normal sodium salt being the least so. The "salt of sorrel" of commerce is a mixture of C2O4HK and a per-salt, CsOJiK + CgO^Hg + 2H2O, (cf. p. 157). The calcium salt, CgO^Ca + H2O (or SH^O), is insoluble in water and acetic acid, and serves for the recognition of oxalic acid. Ferro-potassic oxalate, (C20^)2FeK2 + H20, finds apphcation in photo- graphy as a powerful reducing agent. Antimonic oxalate is, like tartar emetic, employed as a mordant in dyeing. Ethyl oxalate, oxalic ether, 0204(02115)2, which can be directly pre- pared from its components, is liquid, while Methyl oxalate, 0204(0113)2, is solid, crystallizing in plates which melt at 51° ; both of them possess an aromatic odour, distil without decomposition, and are easily saponi- fiable. Partial saponification (with one mol. KOH in alcoholic solution) produces e.g. Potassium ethyl-oxalate, 0204(02H5)K, from which the free Ethyl-oxalic acid, 0304(02115)11, which is readily saponifiable, and its chloride, Ethyl-oxalyl chloride, 002(02115) — 0001, can easily be pre- pared. The normal chloride of oxalic acid, O2O2OI2, does not exist. Oxalic ether yields, with two mols. NH3, oxamide, and with one mol. , the mixed derivative oxamic acid, analogously to mode of formation 4 of the amides (p. 180). Oxamide, C202(NH2)2, the normal amide of oxalic acid, is obtained, among other methods, by the distillation of ammonium oxalate (cf. p. 180), by the partial saponification of cyanogen, and by the action of MALONIC ACID. 233 bydrogen dioxide, HgOg, upon hydrocyanic acid, (B. 18, 355). It is a white crystalline powder. As an amide it is easily saponifiable, and convertible into cyanogen by the abstraction of HgO, etc. Oxamic acid, C202(NH2)(OH), the acid amide or aminic acid of oxalic acid, results from the heating of acid oxalate of ammonia. It is a crystalline powder, difficultly soluble in cold water. Ethyl oxamate, oxamethane, COlNHs) — CO.OCgHg, (see above). Corresponding to oxamide we have Di-methyl-oxamide, COlNHCHg)— C0(NHCH3), and corresponding to oxamethane, Ethyl-dimethyl-oxamate, CO(N[CH3]2)— CO.OC2H5, both already mentioned at p. 113. PCI5 converts oxamethane into Cyano- carbonic ether, CN — CO.OC.^Hg, a liquid of pungent odour, which is to be regarded as a semi-nitrile of oxalic acid. Amide- and Imido- chlorides of oxalic acid are also known. CO Oximide, | ^NH, is got by the action of PCL upon oxamic acid, CO"^ and forms colourless prisms easily soluble in water and of neutral reaction. It is quickly saponified by hot water, and transformed into oxamide by ammonia, (B. 19, 3228). Malonic acid, C3H4O4, = CH2(C02H)2. Occurrence. In beetroot. Formation. (1) By the oxidation of malic acid by means of chromic acid, hence its name ; (2) by the saponification of malonyl-urea (p. 282), (JBaeyer); (3) by the saponification of cyan-acetic acid, (Kolbe, MuUer ; A. 131, 348; 204, 121): CH2(CN)— CO2H + 2H2O = GB^iCO^R)^ + NH3. Large plates or tables, readily soluble in water, alcohol and ether. M. Pt. 132°. Decomposes upon heating, as given at p. 230. Ethyl malonate, malonic ether, CB.^{CO.OG^ll^)^. This ether, which is directly obtainable from cyan-acetic acid by leading HCl gas into its solution in absolute alcohol, is a liquid of faint aromatic odour boiling at 195°, and having a remark- able similarity to aceto- acetic ether. Thus the hydrogen of the methylene group is here, as in the case of the latter, replaceable by sodium, through the influence of the carbonyl groups, CO, which are also bound to the methylene ; and the resulting sodio-malonic ether readily exchanges the metal for 234 X. DIBASIC ACIDS. alkyl upon treatment with alkyl iodide. By this means the higher homologues of malonic ether, e.g. methyl-, ethyl-, propyl- etc., malonic ethers, are obtained. Further, the second hydrogen atom in these can be exchanged in exactly the same manner for sodium and then for alkyl, whereby di-alkyl malonic acids result. This is an important method for the preparation of the higher dibasic acids, being applicable even in complicated cases ; it is termed the malonic-ether synthesis." (Of Conrad and Bisclioff, A. 204, 121.) By the splitting off of COg from these, the higher monobasic acids . are obtained, (indirect synthesis, see p. 150, 10''). Upon heating malonic ether with its sodium compound, a derivative of phloroglucin results. (See this, also B. 18, 3454.) Chloro-malonic ether, CHC1(C02C2H5)2, a liquid boiling at 222°, is employed in analogous syntheses, and otherwise reacts in a similar way to chloracetic ether. Succinic acids. (1) Common Succinic acid, ethylene-succinic acid^ symmetrical ethane-dicarboxylic acid, acidum succinicum (from succinum, amber), COgH — — CHg — COgH. This acid has been known for a long time ; its composition was determined by Berzelius. Occurrence. In amber, in various resins and lignites, in many compositse, in Papavaraceae, in unripe wine grapes, urine, blood, etc. Formation, (a) From ethylene cyanide, according to 2, p. 228 ; (b) From /^-iodo- (and cyano-) propionic acid, according to 2* ; (c) By the reduction of fumaric and maleic acids, C^H^O^ ; (d) By heating its oxy-acids, malic or tartaric, with hydriodic acid, and also by certain fermentations of these, e.g. from the former according to the equation : CJI,{OR)0, + 2HI = + I2; (e) As a bye-product in the alcoholic fermentation of sugar ; (/) By the oxidation of fats, fatty acids and paraffins by means of nitric acid. Preparation. From calcium malate according to d, by fer- mentation, or by the distillation of amber. SUCCINIC ACIDS, ETC. 235 Properties, Monoclinic prisms or tables of an unpleasant faintly acid taste. Rather easily soluble in water. M. Pt. 185°, B. Pt. 285°. Yields succinic anhydride — (long needles) — upon distillation. For its electrolysis, see p. 49. Is very stable towards oxidizing agents. Of the Salts of succinic acid, the basic ferric salt, obtained by the addition of a ferric salt to ammonium succinate, is used in analysis for the separation of iron from alumina. The calcium salt is soluble in water. The Derivatives of succinic acid correspond exactly with those of oxalic, e.g. Succinamic acid, C2H4(C02H)(CO.NH2), is analogous to oxamic acid ; in this case, however, the normal chloride, Succinyl chloride, C2H4(C0C1)2, the analogue of acetyl chloride in all its important properties, is known. In addition to the Amides, there exists — as in the case of other dibasic acids — an imide, Succinimide, CO C2H4<^QQ^NH. The latter crystallizes in rhombic plates, and is formed by heating acid succinate of ammonium. The basic properties of the NHg are so modified by the two carbonyl groups of the acid radicle that the imido-hydrogen is replaceable by metals, such as K, Ag, etc. Mono- and Di-bromo-succinic acids, C2H3Br(C02H)2 and C2H2Br2(C02H)2, are easily prepared and are valuable for the syntheses of the oxy-suc- cinic acids. By the action of sodium upon succinic ethyl ether there is formed succino- succinic ether, C6H602(C02G2H5)2, a derivative of benzene. For Acetol- and Di-acetol-succinic ethers, see p. 227. (2) Iso-succinicacid,e%?i6?67i6-5i^camca(5i6?, CH3 — CH(C02H)2, is formed e.g. by the malonic ether synthesis, or from a-chloro- (or iodo-) propionic acid, (pp. 234 and 229). Needles or prisms. Decomposes upon heating into COg and propionic acid, and yields no anhydride, (p. 230). Pyrotartaric acids, C3Hg(C02H)2. Of these four are known, this being the number theoretically possible. The two follow- ing may be mentioned here : 1. Glutaric acid, normal pyrotartaric acid, COgH — CH2 — CHg — CH2 — COgH, is of interest on account of its relation to piperidene. 2. Pyrotartaric acid, methyl-succinic acid, COgH— CH2 — CH(CH3) — COjH, results, among other methods, along with 236 X. DIBASIC ACIDS. pyroracemic acid hy the dry distillation of tartaric acid, by the ace to-acetic ether synthesis, etc. Small triclinic prisms. M. Pt. 1 1 2°. Forms an anhydride. The higher homologues (see Summary, p. 228) are formed along with succinic and oxalic acids by the oxidation of fats, oils, cork, etc., by means of nitric acid. B. Unsaturated dibasic Acids, C^Hg^.A. Fumaric acid,\p tt -rrx Itaconic acid,] Maleic „ /^2^2l^^2^;2- Citraconic „ C3H4(C02H)2. Mesaconic J Hydro-muconic acid ) Q jj Q Teraconic C^H-^^^O^, Pyro-cinchonic „ | 6 8 4- q^q^ The unsaturated acids stand in the same relation to the saturated dibasic acids as acrylic acid does to propionic. As acids they yield derivatives analogous to those of the acids CnH2n-204, whilc as unsaturated compounds they possess, in addition, the faculty of combining with two atoms of hydrogen or halogen, or with one molecule halogen hydride. Formation. 1 . By the elimination of water from the dibasic oxy-acids. Thus malic acid yields upon distillation water and maleic anhydride, which volatilizes, and also fumaric acid, which remains behind : Citric acid yields in a similar way CO2, H2O, itaconic acid and citraconic anhydride. 2. By the separation of halogen hydride from the mono-haloid substitution products of succinic acid and its homologues, monobromo- succinic acid yielding fumaric, thus : C4H5Br04-HBr = C4H4O4. 2\ From the analogous di-substitution products by the separation of the halogen. The cases of isomerism among the acids C^H2n_404 are of great interest (see next page). FUMARIC AND MALEIC ACIDS. 237 Constitution, The acids of this series may be regarded as di-carboxylic acids of the olefines, e.g. fumaric and maleic acids, C2H2(C02H)2, as those of ethylene. Their mode of formation 1. corresponds exactly with the production of ethylene from alcohol, or with that of acrylic from ethylene-lactic acid, while 2. agrees with that of ethylene from ethyl iodide. Maleic acid, CgHglCOgHjg. Large prisms of a grating nauseous acid taste, very readily soluble in cold water. Distils unchanged, excepting for partial transformation into maleic anhydride, €2112(002)20. Is conveniently prepared by heating the acetyl derivative of malic acid, (see p. 239, also B. 14, 2791). Fumaric acid, C2H2(C02H)2. Small prisms of a strong, purely acid taste, almost insoluble in cold water. Sublimes at about 200° with formation of maleic anhydride. Occurs in Fumaria officinalis, various fungi, truffles, Iceland moss, etc., and is obtained from maleic acid either by prolonged heating of the latter at 130°, or by the action upon it of hydrobromic or other acids. Both acids are converted into their ethers on treating their silver salts with alkyl iodide, these ethers also standing in very close relation to one another ; thus ethylic maleate is changed into ethylic fumarate when warmed with iodine, and the latter results directly from the etherification of maleic acid in alcoholic solution by means of HCl. Both acids yield common succinic acid with nascent hydrogen, and probably contain in consequence the same carbon chain, which would lead to the same constitutional formula for both, viz., C02H-^CH-CH-C02H (I.). The explanation of the isomerism of these acids has thus to contend with difficulties which it has been attempted to remove as follows : (a) by the assumption that maleic acid has the formula (I.), but fumaric — on the other hand — the constitution CH2=C(C02H)2 (II.), the latter atomic grouping being held to be easily convertible into the isomeric form (I.) ; (6) by the aid of conceptions with regard to the arrangement of atoms in space, according to van H Hoff (cf. pp. 19 and 31), concep- tions which Wislicenus has extended in the most interesting manner at p. 180 of the memoir already cited (p. 19) ; (c) by the assumption of relations between fumaric and maleic acids similar to those between racemic and inactive tartaric acids, {KehuU and Anschutz, B. 14, 717 ; 18, 1400) ; (d) by the assumption of free affinities in maleic acid, {Fittig), Similar isomeric relations exist between the homologous acids, itaconic and citraconic. (Cf. KdcuJAy A. Suppl., I. 129 ; II., Ill ; Fittig, A. 188, 95; 195, 56; 216, 77, etc.) 238 X. DIBASIC ACIDS. Appendix. Acetylene-dicarboxylic acid, CO^H— C=C— CO2H, Di - acetylene dicarboxy lie acid, COgH— C = C— C=C— COgH, and Tetr- acetylene-dicarboxylic acid, COgH— C=C— C=C— C=C— C=C— COgH, have been prepared by Ba^yer (B. 15, 2695 ; 18, 678 and 22C9). With increasing length of chain they show an increasing tendency to explode, (cf. copper-acetylene.) For Baeyer's theory of explosions see B. 18, 2277. 0. Triatomic dibasic Acids, C^Hsn-aOg. 1. Tartronic acid, oxy-malonic acid^ C3H4O5, = CH(OH)(C02H)2. This acid forms large prisms (+ ^HgO), easily soluble in water, alcohol and ether. It cannot be distilled unchanged, since it breaks up on heating into carbon dioxide and glycolide. Formation. 1. As oxy-malonic acid, from chloro-malonic acid by the exchange of CI for OH. 2. As a derivative of the triatomic glycerine, by oxidizing the latter with permanganate of potash. 3. By reduction of the corresponding ketonic acid, mesoxalic acid, CO{C02H)2, just as lactic acid is obtained from pyroracemic acid. Preparation. By the spontaneous decomposition of the so-called nitro-tartaric acid (p. 241, Dessaignes), dioxy-tartaric acid being formed as intermediate product (KehuU) ; also from chloral hydro- cyanate, (B. 18, 2852). 2. Malic acid, oxy-succinic acid, acidum malicum^ C^HgOg, = C2H3(OH)(C02H)2, = CO2H— CH2— CH(OH)— CO2H, {ScheeU, 1785). Occurrence, Is very widely distributed in the vegetable kingdom, being found in unripe apples, sorb-apples, grapes, barberries, quinces, Crassulacese, etc. Formation. 1. As oxy-succinic acid, by treating bromo- succinic acid with moist oxide of silver : C2H3Br(C02H)2 + HgO = C2H3(OH)(C02H)2 + HBr. 2. By the reduction of tartaric or racemic acid with HI. 3. From aspartic acid or asparagine by means of N2O3. 4. By heating fumaric or maleic acid with water, (A. 192, 80). MALIC ACID. 239 Properties. Hygroscopic glancing needles, usually in round groups, readily soluble in water and alcohol, but only slightly in ether. M. Pt. 100°. When it is distilled, maleic anhydride passes over and fumaric acid remains in the retort. Yields, when heated with concentrated H2SO4, Cumalic acid, CgHgOslCOgH). (B. 17, 936.) Malic acid exists in several optically dilfferent modifications which correspond exactly with those of tartaric acid. The dilute solution of the natural acid is Isevo- rotatory ; the acid obtained from dextro- tartaric acid is dextro-rotatory ; while the, acid prepared from racemic, succinic, or fumaric acid is inactive, and can be separated into the active modifi- cations. The alkaline salts and the acid calcium salt of malic acid are readily soluble in water, while the neutral calcium salt is only sparingly soluble. As an alcohol, the acid yields ethers, e.^., an Acetyl-malic acid, C2H3(O.C2H30)(C02H)2. Amides and Amines of malic acid. Like glycoUic acid, malic acid forms — as an acid — amides (saponifiable), and — as an alcohol — an amine (not saponifiable). The amides are : Malamide, C2H3(OH)(CO.NH2)2, crystallizing in prisms, and Malamic acid, C2H3(OH)(CO.NH2)(C02H), the latter being known as ethyl ether. The alcoholic amine, aspartic acid, C2H3(NB[2)(C02H)2, unites in itself like glycocoll the properties of a base and of an acid, but the acid character predominates. Its acid amide is asparagine. The neutral amide has also been prepared synthetically from bromo-succinic ethyl ether and ammonia ; it is readily transformed into asparagine, (B. 20, E. 511). \^ Asparagine, C2H3(NH2)(CO.NH2)(C02H), which is isomeric with malamide, is very widely distributed in the vegetable kingdom, being present in the young leaves of trees, in beet- root, potatoes, the shoots of peas, beans and vetches, and in asparagus ; it was first found in the last-named vegetable in the year 1805. It forms glancing rhombic prisms (-1-H2O), easily soluble in hot water, but insoluble in alcohol and ether. Goes into aspartic acid on saponification. Is optically active. Aspartic acid, C2H3(NH2)(C02H)2, is present in beet molasses and forms an important product of the decomposition 240 X. DIBASIC ACIDS. of albuminoid substances by means of acids or alkalies. Small rhombic tables, rather easily soluble in hot water. It exists in several optically dilferent modifications, which differ in taste and are convertible, the one into the other, (B. 20, E. 510). Nitrous acid transforms it, as well as asparagine, into malic acid, (normal amine and amide reaction). Just as glycocoU is to be regarded as amido-acetic acid, so is aspartic acid to be looked upon as amido-succinic. Isomers of malic acid are both possible and known. Higher Homologues, a-Oxy-glutaric "v Diaterebic acid, C5H9(OH)(C02H)2. Itamalic acid, psHstOHllCOaHja. Di^^-^^pg^yii^, CgHnlOHXCOaHja. Citramalic acid, ^ etc. Glutamlne, C3H5(NH2)(CO.NH2)(C02H), and Glutamic acid, C3Hg(NH2)(C02H)2, are the ammonia derivatives of a-oxy-glutaric acid, being homologous with asparagine and aspartic acid. The former is likewise found in beetroot and in the shoots of the vetch and gourd, while the latter is produced, together with aspartic acid and leucine, by boiling albuminous compounds with dilute sulphuric acid. D. Tetratomic dibasic Acids. Tetratomic dibasic acids are such as unite in themselves the properties of a diatomic alcohol with those of a dibasic acid. Theoretically they are characterized by the presence of two alcoholic hydroxyls and two carboxyls in the molecule. The simplest possible member of the series, the compound C(OH)2(C02H)2, is unstable and has not the characters of an alcoholic acid, but those of the hydrate of a ketonic acid, since it contains two hydroxyls bound to the same carbon atom. (See Mesoxalic acid, p. 244.) Tartaric acid, dioxy-succinic acid, oxy-malic acid, G^^Oq, = C2H,(OH)2(C02H),, = C02H-CH(OH)-CH(OH)-(C02H). This acid exists in four " physically isomeric " modifications. 1. Dextro-tartaric acid, acidum tartaricuin, is the tartaric TARTARIC ACIDS. 241 acid found in nature. It was discovered by Scheele in 1769. It occurs in the free state or as salt, chiefly acid potassium salt, in various fruits, especially in the juice of grapes, from which bitartrate of potash or tartar — (tartarus) — separates in crystals during fermentation. When this is boiled with chalk and chloride of calcium it is transformed into the neutral lime salt, from which the acid is liberated on addition of HgSO^. Large transparent monoclinic prisms, of a strong and purely acid taste, very easily soluble in water, readily also in alcohol, but almost insoluble in ether. M. Pt. 135°. Reduces an ammoniacal silver solution upon warming. When melted, it is changed into an amorphous modification and then into an anhydride, and when heated more strongly it carbonizes, with the dissemination of a characteristic odour and formation of pyroracemic and pyrotartaric acids. Oxidation converts it either into dioxy-tartaric or tartronic acid, and then into formic and carbonic acids, etc. Neutral potassium tartrate, C4H4O6K2 + JHgO, forms monoclinic prisms easily soluble in water. Acid potassium tartrate, Tartar, or Cremor tartari, C4H5O6K. Small rhombic crystals of acid taste, sparingly soluble in water ; is much used in dyeing, medicine, etc. Potassium-sodium tartrate, Rochelle or Seignette salt, C4H406KIsra 4- 4H2O (1672), forms magnificent rhombic prisms. Calcium tartrate, C4H406Ca + 4H2O, is a powder insoluble in water but soluble in cold caustic soda solution ; on warming the solution it separates as a jelly, which redissolves upon cooling. Potassio-antimonious tartrate, Tartar emetic, C4H4(SbO)'KOg + JH2O, (see B. 15, 1540), is obtained by heating cream of tartar with antimony oxide and water. Rhombic efflorescent octahedra, easily soluble in water. It is poisonous and acts as an emetic, and is used as a mordant in dyeing. Feldimfs solution is a solution of cupric sulphate mixed with alkali and seignette salt. The Di ethyl ether is a thick oil, while the Mono-ethyl ether crystallizes in prisms. Acetyl -tartaric acid and Amides of tartaric acid are known, and also various anhydrides. As an alcohol, it forms with nitric acid a di-nitric ether, the so-called Nitre -tartaric acid, C2H2(O.N02)2(CO.^H).j, which as an ether is readily saponifiable and, generally speaking, easily decomposable with formation of Dioxy- tartaric or of tartronic acid. ( 50(5 ) Q 242 X. DIBASIC ACIDS. Aqueous solutions of ordinary tartaric acid or of its salts turn the plane of polarization of light to the right ; the nature of the solvent affects this action, (B. 18, Ref. 591). The acid is employed in medicine, dyeing, etc. 2. Laevo-tartaric acid is identical in its chemical and also in almost all its physical properties with ordinary tartaric acid, but differs from it in that it turns the plane of polarization of light to the left, in a degree equal to that in which the other turns it to the right. The crystallized salts show hemihedral faces like the salts of dextro-tartaric acid, but oppositely situated (see below). When equal quantities of both acids are mixed together in aqueous solution, the solution becomes warm, and we obtain 3. Racemic acid, GJIqOq + HgO, the composition of which was first established by Berzelius, who recognized it as being different from tartaric acid, and who developed the idea of isomerism from this first example in 1829. Racemic acid is obtained from tartar mother liquor. It differs from dextro- tartaric acid in that its crystals are rhombic and efflorescent and also less soluble in water than the former; further, the free acid is capable of precipitating a solution of calcium chloride and is optically inactive (see below). The salts, which are termed racemates, and also the ethers (B. 21, 518), show small differences from the tartrates in the proportions of their water of crystallization and in solubility. When a solution of sodium-ammonium racemate, C4H4Na(NH4)Og + 4H2O, is evaporated, beautiful rhombic crystals which show hemihedral faces are obtained. Pasteur observed that these faces were not always similarly situated, but that certain crystals were dextro-hemihedral while others were Isevo-hemihedral, so that one crystal formed the reflected image of the other. The Isevo -hemihedral crystals are opti- cally dextro-rotatory and vice versa. If now the two kinds of crystals be separated from one another mechanically and the free acid liberated from each, this will be found to consist, not of racemic acid, but in the one case of dextro- and in the other of Isevo-tartaric acid. An analogous decomposition of racemic acid is also possible by other means, (cf. p. 31). 4. Me£0-tartaric acid, a fourth tartaric acid, is inactive like FORMATION OF THE TARTARIC ACIDS, ETC. 243 the foregoing but not decomposable into the active acids, although it can be transformed into the latter (see below). It crystallizes in efflorescent rectangular plates. The acid potas- sium salt is easily soluble in water. 1. The oxidation of mannite by means of HNO3 yields racemic acid, and that of sorbin, meso- tartaric acid. 2. The treatment of dibromo-succinic acid, C2H2Br2(C02H)2, with moist oxide of silver yields racemic and meso-tartaric acids (KekuU), 3. Racemic acid results from the saponification of the cyanhydrin of glyoxal, (cf. p. 133). 4. The oxidation of fumaric acid by means of KMn04 yields racemic acid, and that of maleic, meso-tartaric acid (KeJcuU), 5. When dextro- or Isevo-tartaric acid is heated with some water to 170°, racemic and meso-tartaric acids are formed ; meso-tartaric acid changes partially into racemic acid under analogous conditions, a state of equilibrium being reached here. For the splitting up of racemic acid, see above. The isomeric relations of the tartaric acids are easily explic- able by the aid of conceptions as to the modes in which the atoms and atomic groups are linked in space to asymmetric carbon atoms, which are present not only in them but also in malic acid, asparagine, lactic acid, active amyl alcohol, etc., (see pp. 19, 31, and 32). E. Penta- and Hexatomic dibasic Acids. Pentatomic : Aposorbic acid, C3H3(OH)3(C02H)2. Hexatomic : Dioxy-tartaric acid, C2(OH)4(C02H)2, (see Ketonic acids). Saccharic acid,^ Formation of the Tartaric Acids, Mucic Iso-saccharic Glycuronic 244 X. DIBASIC ACIDS. Saccharic acid is produced by the oxidation of cane sugar, glucose, mannite or starch by HNO3, and Mucic acid by that of gums, mucilages and milk sugar. The former is hygroscopic and easily soluble in water, the latter a difficultly soluble white crystalline powder. Isosaccharic acid is obtained by the oxidation of glucosamine, C6H]_i05(NH2). These acids form, as tetratomic alcohols, tetra-acetyl derivatives, etc., and, as acids, two series of salts, ethers, etc. Their constitution still requires further investigation. Mucic acid readily changes into f urfurane deriva- tives (see p. 298). Glycuronic acid is a decomposition product of a series of complicated compounds which are found in the urine after the con- sumption of camphor, phenol, etc., (** phenyl-glycuronic acid"). It forms a syrupy mass. F. Dibasic Ketonic Acids. Dibasic ketonic acids unite in themselves the properties of a ketone and of a dibasic acid. The following are known : 1. Mesoxalic acid, CO(C02H)2 or C(OH)2(C02H)2 (see p. 240), is prepared from dibromo-malonic acid, CBr2(C02H)2, and baryta water or oxide of silver, thus : CBr2(C02H)2 + H2O = CO(C02H)2 + 2HBr; also by boiling alloxan (p. 282) with baryta water. It crystallizes in deliquescent prisms ( + H2O). As a ketone it combines with NaHSOg, reacts with hydroxyl- amine (p. 142), and is reduced by nascent hydrogen to the corresponding secondary alcohol-acid, tartronic acid : CO(C02H)2 + H2 = CH(OH)(C02H)2. Since the acid and its salts still retain a molecule of water at tempera- tures above 100°, this may be chemically bound as in chloral hydrate, corresponding to the formula, C(OH)2(C02H)2, di-oxy-malonic acid." In agreement with this, a di-acetyl compound, C(0. 031130)2(00202115)2, can be prepared. 2. Acetone-dicarboxyHc acid, OgHgOg, = C0=(CH2 — 002H)2, results upon treating citric acid with concentrated H2SO4. It breaks up readily into acetone and 2CO2, (see B. 17, 2542). Dioxy-tartaric acid, OOgH— 00 — 00 — COgH, or probably CO2H— C(0H)2— C(0H)2— OO2H, is formed from pyro-catechin and nitrous acid, and by the gradual decomposition of nitro- tartaric acid. It does not exist in the free state. The characteristic difficultly soluble TRI- TO HEXATOMIG ACIDS. 245 sodium salt decomposes easily into CO2 and tartronate of sodium. It reacts with two mols. hydroxylamine. With phenyl-hydrazine-sulph- onic acid, a dye "tartrazine" is produced, (cf. KeJcuUy A. 221, 230.) XL TRI- TO HEXABASIO ACIDS. The tribasic organic acids are those which, like phosphoric acid, are capable of forming three series of salts, viz., neutral, mono-acid and di-acid salts. They contain according to theory three carboxyl groups. There are not only triatomic tribasic acids, such as methane- and propane-tri-carboxylic acids, etc., which are of purely acid character, but also tetratomic, pentatomic and hexatomic tribasic acids, alcoholic acids which possess at the same time the characters of alcohols. Further, these may be derived either from saturated or from unsaturated hydrocarbons. A. Triatomic tribasic Acids. 1. Methane-tricarboxylic acid, CH(C02H)3, 2. Ethane-tricarboxylic „ 03113(00211)3, 3. Propane-tricarboxylic „ 03H5(002H)3, 4. Tricarballylic „ 03H5(002H)3. The above acids 1 to 3 have been prepared by the malonic ether synthesis ; they are for the most part known as ethers, some of them being incapable of existence in the free state, while others readily break up upon heating into CO2 and dibasic acids. Propane-tricarboxylic acid is unsymmetrically constituted. Tricarballylic acid, symmetrical propane-tricarhoxylic acid, 03X15(00211)3. Occurs in unripe beet, and is prepared synthetically from glycerine by transforming it into tri-brom- hydrin, 03H5Br3, treating this with KON, and saponifying the cyanide formed, 03H5(ON)3. Since the three hydroxyls in glycerine are distributed among three carbon atoms, the same holds good for the carboxyls in the acid, which has therefore the symmetrical constitution : 246 XI. TRI- TO HEXATOMIC ACIDS. CH2— CO2H CH— CO2H CH2— CO2H. This acid is of importance in determining the constitution of citric acid, from which it can be obtained by heating with HI. It also results from the addition of Hg to aconitic acid, CgHgOg. It crystallizes in rhombic prisms, easily soluble in water, etc. M. Pt. 166^ B. An Unsaturated tribasic Acid is Aconitic acid, CgHgOg, = 03113(00211)3, which contains two atoms of hydrogen less than tricarballylic acid. It is found in nature, in Aconitum Napellus, shavegrass, sugar cane, beetroot, etc., etc., and is prepared by heating citric acid, CgHgO^, water separating. It is a strong acid, crystallizable, and easily soluble in water. M. Pt. 186°. Nascent hydrogen transforms it into tricarballylic acid, hence it is an unsaturated acid and its constitution is : CH— OO2H C^002H CH2— CO2H. 0. Tetratomic tribasic Acids. Citric acid, acidum citricum^ G^^O^, = 03H4(0II)(002H)3. (Scheele, 1784; recognized as tribasic by Liehig'm 1838.) Occurs in the free state in lemons, oranges and red bilberries, and mixed with malic acid in gooseberries, etc., also as calcium salt in wood, potatoes, beetroot, etc. Preparation. From the juice of lemons by means of the lime salt. Properties, Large rhombic prisms (+ H2O), very easily soluble in water and rather easily in alcohol, but only slightly in ether. It loses its water of crystallization at 135°, melts CITRIC ACID. 247 at l!)^, and breaks up at a higher temperature first into aconitic acid and water, and then into carbon dioxide and itaconic acid (and also acetone, etc.). Oxidizing agents effect a very thorough decomposition. Citrate of calcium is precipitated as a white sandy powder upon boiling a mixture of calcium chloride and alkaline citrate. The three series of salts are well characterized ; the alkaline salts are soluble in water, the others mostly insoluble. Among the derivatives may be mentioned mono-, di-, and tri-ethyl citrates and tri-ethyl aceto-citrate, €3114(0. C2H30)(C02C2H5)3, which, last forms a proof of the alcoholic character of citric acid ; it boils without decomposition. The Amides of citric acid are converted by concentrated H2SO4 into Citrazinic acid, C6H5NO4, a pyridine derivative, (B. 17, 2681.) The constitution of citric acid is arrived at both from its relation to aconitic acid, which results from it as ethylene does from alcohol, and from various syntheses ; it is : CH2— CO2H C(OH)— CO2H CH2— CO2H. Thus it is obtained from /3-dichloro-acetone as follows : CH,.CO,H C(0H)-C02H' H2CI 0 H2CI CH2CI C(OH)-CN CH2CI CH2CI CH2CI CH2.CN C(0H)-C02H CH2.CN C(0H).C02H CH2.CO2H. An Iso-citric acid, isomeric with citric, has also been pre- pared synthetically, {Fittig, B. 20, 3179). Appendix. D. Pentatomic tribasic acids. Desoxanc acid, CgHeOg, = C2H(OH)2(C02H)3, and Oxy-citric acid, CgHgOg, the latter of which is present in the juice of turnips. E. Tetra-, penta-, and hexabasic acids do not occur in nature but have been prepared in considerable numbers by means of the aceto-acetic or malonic ether synthesis, e.gr., ethane-tetra-carboxylic acid, propane-penta-carboxylic acid and butane-hexa-carboxylic acid. They are obtained in the form of ethers, most of them being either very unstable or incapal)!:; of existence in the free state. For their preparation, see B. 15, 1109; 17, 2781 ; A. 214, 31. 248 XII. CYANOGEN COMPOUNDS. XII. CYANOGEN COMPOUNDS. Under the name of the cyanogen compounds is included a group of bodies which are derivable from cyanogen, CgNg. Cyanogen itself is a gas of excessively poisonous properties which behaves in many respects like a halogen, and its hydrogen compound, hydrocyanic acid, HON, is an acid which is very similar in many ways to hydrochloric. In many cyanogen compounds the monovalent group (CN) plays the part of an element ; cyanogen is to be regarded as the isolated radicle (CN), often written Cy, which however possesses the double formula C2N2, just as a molecule of chlorine (Clg) is made up of two atoms. The cyanogen group is further capable of combining with the halogens, hydroxyl, sulphydril (SH), amidogen, etc., etc. From the compounds so obtained numerous others are derived by the entrance of alcohol radicles in place of hydrogen. Such derivatives nearly always exist in two isomeric forms, sharply distinguished from one another by their properties, and whose isomerism is of very great interest. (See table, pp. 250 and 251.) There exist further polymeric modifications of most of those compounds (see table). The number of cyanogen compounds known is thus a very large one. Formation. 1. Carbon and nitrogen cannot combine directly with one another but only when they are heated in presence of an alkali ; thus, when nitrogen is led over a red-hot mixture of coal and carbonate of potash, potassium cyanide, KCN, is formed. 2. By passing ammonia over red-hot coal, ammonium cyanide, NH4CN, is produced. 3. Carbon and nitrogen combine most readily with metals when in the nascent state, e.g,^ when nitrogenous organic compounds such as leather, horn, claws, wool, blood, etc., are heated with potashes. 4. Hydrocyanic acid is formed when electric sparks are passed through a mixture of acetylene and nitrogen, and also by the action CYANOGEN ; FORMATION AND PROPERTIES. 249 of the silent electric discharge on a mixture of cyanogen and hydrogen. For further modes of formation, see below. The original material for the preparation of most of the cyanogen compounds is potassic ferrocyanide, which is manu- factured on the large scale and possesses the great advantages over potassium cyanide of being stable in the air and non- poisonous. A. Cyanogen and Hydrocyanic Acid. Cyanogen, CgNg. Discovered by Gay-Lussac in 1815. Occurs in the gases of blast-furnaces. Formation. 1. As the nitrile of oxalic acid, by the abstraction of the elements of water from oxalate of ammonia by means of PgOg ; also in the same way from the intermediate product of this reaction, oxamide : CA(NH4)2 - 4H2O = C2N2; C20,(NH,), - 2H,0 = C,N,. 2. By heating silver cyanide, AgCN, or mercuric cyanide, Hg(CN)2, strongly ; this is the method followed for its pre- paration : Hg(CN)2 = Hg + C,N,. Further, in the wet way, by heating a solution of cupric sulphate with potassium cyanide, (B. 18, Eef. 321). Cyanogen is a colourless gas of a peculiar unpleasant odour resembling that of bitter almonds, and is terribly poisonous. Sp. Gr. 1-8. Easily condensible. M. Pt. -34°. B. Pt. of liquid cyanogen - 21°. Soluble in \ vol. of water and in even less alcohol. The solutions become dark upon standing, with separation of a brown powder (" Azulmic acid while oxalic acid, ammonia, formic acid, hydrocyanic acid and urea are to be found in the liquid. The formation of the oxalic acid and ammonia dejjends upon normal saponification, and that of formic acid upon the saponification of the [Gontinwid on p. 252. 250 XII. CYANOGEN COMPOUNDS. SUMMARY OF THE CYANOGEN COMPOUNDS AND OF Relation to carbonic Original Compounds. acid, etc. (See p. 269.) Normal Isomeric Form. Nitrile of oxalic acid, Cyanogen, C2N2 Nitrile of formic acid, Hydrocyanic acid, Alcoholic derivatives : (a) Nitriles, {b) Iso-nitriles, N=C.H CH3— C=N CH3— NC Cyanogen chloride, bro- mide, iodide, N=C.C1 CO3H2 + NH3-2H2O, (Partial Nitrile, event- ually Carbimide, see p. 269), Cyanic acid, Alcoholic derivatives : (a) Methyl cyanate, (6) ,, iso-cyanate. N=C— OH N=C-O.CHo 0=C=N.CH3 Alcoholic derivatives : (a) Ethyl thiocyanate. All,,! J-Ui^ \o) Ailyl iso-tnio- cyanate, N=C— SH N^C-S.CgHs — S=C=NC3H5 DO H + 2NH„ - .^H^O (Nitrile and amide, eventually Carbo-di- imide, see p. 269), Cyanamide, Alkylated : {a) Alkyl cyanamide, (b) Carbo-di-imide, N=C— NH2 N=C— NH.CH3 RN=C=NR* CO3H2 + NH3-H2O, (Aminic acid). Carbamic acid, C0(NH2)0H /^r\ TT 1 OATTT OUT r\ (JU3XI2 + rig - Zti20f (Carbamide), Urea, CO(NH2)2 Thio-urea, Alkylated : (a) Alkyl-thio-ureas, (b) Imido-thio-carba- mine compounds. CS(NH2)2 CSN2H3R C(NH)^^^ CO3H2 + 3NH3-3H2O, (Amidines), Guanidine, C(NH)(NH2)2 * R = Alcohol radicle. SUMMARY. SEVERAL RELATED CARBONIC ACID DERIVATIVES. 251 Polymeric Compounds. Normal Isomeric Form. Paracyanogen, (CN)x *' Tri-hydrocyaiiic acid,^^ Alcoholic derivatives : Cyanethine, (CNH)k (CN)3(C2H5)3 — Cyanuric chloride^ etc.^ (CN)3Cl3 Cyanuric acid, Alcoholic derivatives : (CN)3.(OH)3 — (a) Cyanurates, (b) Iso-cyanurates, (CN)3.(OC2H5)3 (CO)3.(NC2H5)3 Dithio-dicyanic acid," Thio-cyanuric acid, Alcoholic derivatives : (a) Thio- cyanurates, (CNSH)x (CN)3.(SH)3 (CN)3.(SC2H5)3 Dicyan-diamide, Melamine, Alkylated : (a) Alkyl-melamine, (b) Alkyl-iso-melamine, C2N4H4 (CN)3.(NH2)3 (CN)3.(NHC2H5)3 (C:NH)3(NC2H5)3 No Polymers. 252 XII. CYANOGEN COMPOUNDS. hydrocyanic acid formed as an intermediate product. In presence of a minute quantity of aldehyde, oxamide results from the taking up of water. Cyanogen combines with heated potassium to KCN, and dis- solves in aqueous potash to form KCN and KCNO. It yields with HgS the thiamides Flavean hydride, NC — CS.NH2, and Rubean hydride, CS(NH2)-CS(NH2). Paracyanogen (CN)x is a polymer of cyanogen. It is an amorphous brown powder which results as a bye-product when mercuric cyanide is heated ; upon further heating, it is transformed into cyanogen. Hydrocyanic acid, prussic acid, CNH. Discovered about the year 1782 by Scheele, and investigated closely by Gay- Lussac. Formation. 1. By decomposing metallic cyanides by means of stronger acids ; also by the distillation of potassic ferro- cyanide with dilute sulphuric acid : K4Fe(CN)g + 5H2SO4 = 6HCN -f FeSO^ + 4KHSO4. The ferrous sulphate produced reacts with more ferrocyanide to form ferro-potassic ferrocyanide, FeKglFeCyg) (see p. 256), which is not affected by dilute acids ; consequently only half of the cyanogen present is converted into hydrocyanic acid. When concentrated instead of dilute sulphuric acid is employed, carbonic oxide and not hydrocyanic acid is obtained. 2. From ammonium formate or formamide by the separation of water : H.0O.O(NH4) = H.CO.NH2 + H2O = HON + 2H2O. Hydrocyanic is therefore the nitrile of formic acid. 3. Together with oil of bitter almonds, C^HgO, and grape sugar, CgHjgOg, through the decomposition of amygdalin under the influence of " emulsin," (see p. 294) : C20H27NO11 -f 2H2O = CNH + C^HgO + 2C6H12O6. The oil of bitter almonds and its aqueous solution — (aqua am arum amygdalarum) — prepared from the almonds themselves, consequently contain HON. 4. By the action of ammonia upon chloroform under pressure : CHCI3 + NH3 rr HCN + 3HC1. For other syntheses, see p. 248. HYDROCYANIC ACID. 253 Preparation. From yellow prussiate of potash. In order to obtain the anhydrous acid, the vapours are dried over calcium chloride. Properties, Colourless liquid, solidifying at - 15°. Sp. Gr. 0-70. B. Pt. 26*5°. It has a peculiar odour and produces an unpleasant irritation in the throat, is miscible with water, etc., and burns with a violet flame. Like potassium cyanide, it is one of the most terrible of poisons. When absolutely pure it can be preserved unchanged, but it decomposes in presence of traces of water or ammonia, with separation of a brown mass and formation of ammonia, formic acid, oxalic acid, etc. The addition of minute quantities of mineral acids renders the aqueous solution more stable. Hydrocyanic acid combines with nascent hydrogen to methylamine : HON + 2H2 = HCH2.NH2. With hydrochloric acid it forms a white crystalline product (HON + HCl), which appears to be the imido-chloride of formic acid, CH — CC1=NH. It also combines with many metallic chlorides to crystalline compounds which are easily decomposable. Hydrocyanic acid is a weak monobasic acid, in accordance with the mildly acidifying nature of the cyanogen radicle; its salts are decomposed even by carbonic acid. Its constitutional formula, H — C=N, follows from its relations to formic acid and chloroform. In some reactions, however, it yields com- pounds which are derived from its hypothetical isomer =C=N — H or C=N — H. Its alcoholic derivatives each exist in two isomeric modifications, nitriles and iso-nitriles, which are derived from the two atomic groups H — ON and ON — H. (See table, p. 250, and the appendix to the cyanogen group, p. 265.) Hydrocyanic acid can be detected by converting it either into Prussian blue or into ferric sulphocyanide. In the former case the solution to be tested is treated with excess of caustic soda and some ferrous and ferric salt, boiled, and acidified, when Prussian blue results ; in the latter the solution is evaporated to dryness along with a little yellow sulphide of ammonium, the residue taken up with water and ferric chloride added, when the blood-red colour of ferric sul[;lio- cyauide is obtained. 254 XII. CYANOGEN COMPOUNDS. Tri-hydrocyanic acid, (CNH)x, results from the polymerization of hydrocyanic acid under certain specified conditions. It forms white acute-angled crystals which go back into hydrocyanic acid with violence when heated above 180^. Its molecular weight is still unknown. Potassium cyanide, KCN. For formation^ see p. 248. Preparation, 1. Anhydrous ferrocyanide of potassium is heated to fusion : K4Fe(CN)6 = 4KCN + Fe + 20 + N^. In order to prevent the decomposition of a portion of the cyanide, potash may be added to the melted mass, but the product will in this case contain potassic cyanate, (Liebig's cyanide of potash.) 2. By heating potassium in cyanogen gas. 3. By the combination of HON with KOH, and precipita- tion from the aqueous solution by means of alcohol. Properties, Colourless deliquescent cubes, readily soluble in water but only slightly in alcohol. It is sold in sticks. It absorbs water from the air and is decomposed by the carbonic acid of the latter. The aqueous solution precipitates nearly all the metallic salts, the precipitates redissolving in excess, with formation of double cyanides. Simple Cyanides. Ammonium cyanide, NH4.CN". White deliquescent mass. It is also produced by the passage of the silent electric discharge through a mixture of marsh gas and nitrogen. Mercuric cyanide, Hg(CN)2. Colourless prisms, stable in the air and readily soluble in water. Excessively poisonous. Silver cyanide, AgCN. White flocculent precipitate, closely resembling chloride of silver both in appearance and solubility. Double Cyanides. The double cyanides, which are produced by dissolving the insoluble metallic cyanides in a solution of cyanide of potas- sium, are divided into two classes. The members of the one class are broken up again on the addition of dilute mineral POTASSIUM FERRO- AND lERRIGYANIDES. acids with separation of the insoluble cyanide and formation of hydrocyanic acid, e.^. KCN + AgCN ; 2KCN + m{GN),. The members of the other class do not separate hydrocyanic acid, but comport themselves as salts of particular acids; to the latter belong, in especial, potassic ferrocyanide, K^FeCy^, ( = 4KCy + FeCyg), and potassic ferricyanide, KgFeCyg, ( = 3KCy + FeCyg),* which yield with acids hydro-ferro- and hydro-ferricyanic acids. Many salts of the latter acid are not decomposed at all by dilute acids, for instance Prussian blue, but they are by caustic potash (which converts Prussian blue into Fe(0H)3 and K^FeCyg). Potassium ferrocyanide, yellow ^russiate of potash, K^FeCye + SHgO. Formation. 1. By adding excess of potassium cyanide to a solution of ferrous sulphate. 2. By dissolving iron in a solution of cyanide of potassium, when hydrogen is evolved, thus : 2KCN + Fe + 2H,0 = Fe(CN)2 + 2K0H + ; Fe(CN)2 + 4KCN = K4Fe(CN)e. Iron is therefore previously added to the ''melt" in practical I working (see p. 248, 3). ' It forms large lemon-coloured tetragonal plates, which are I stable in the air and easily soluble in water, but insoluble in ' alcohol. Concentrated HCl separates Hydro-ferrocyanic acid, H^FeCyg, in white decomposable needles. With a solution of CUSO4, a red-brown precipitate of Cupric ferrocyanide, or Hatchetfs brown, CugFeCyg, is thrown down, and with solutions of ferrous and ferric salts the well known characteristic precipi- tates. Chlorine oxidizes it to Potassium ferricyanide, red ^russiate of potash, EgFeCy^, thus : 2K4FeCye + Cl^ = 2K3FeCye + 2KC1. This crystallizes in long dark-red monoclinic prisms which are readily soluble in water. The solution decomposes upon standing, and acts as a strong oxidizing agent in the presence of alkali, K^FeCyg being reproduced. * For the sake of brevity, iron is here and in the following pages regarded as di- and trivalent. 256 XII. CYANOGEN COMPOUNDS. Hydro-ferricyanic acid, HgFeCyg, forms brown needles, and is easily decomposed. FERRO- AND FERRI- CYANIDES OF IRON. Ferrocyanides. Ferricyanides. Ferrous salts, Ferric salts, Potassium-ferro-ferrocyanide, K2Fe"(FeCy6)^\ fromFeS04 + K4FeCyg ; white, becom- ing rapidly blue in the air from conversion into Potassium-ferri-ferrocyanide, KFe^^HFeCye). Insoluble Prussian blue or Williamson^ s blue, Fe/HFeCy6)3, from FeClg + K4FeCy6 ; blue powder with a copper glance. KFe»'(FeCy6)i^ = Soluble Prussian blue, from : excess of ferro- or ferri-cyan TurnhuWs blue, Fe/(FeCy6)2"S from FeS04 + KsFeCye. (FeClg + K3FeCy6 give no precipitate, but only a brown colouration. ) KFe"(FeCy6)"' = erric or ferrous salts and ide of potassium. The formation of Prussian blue was first observed by Diesbach soon after the year 1700. As regards the constitution of hydro-ferro- and hydro-ferricyanic acids, one may make the assumption that they contain the trivalent radicle (C3N3)"', *' tricyanogen," of cyanuric acid (see p. 140) : Potassium ferrocyanide. Potassium ferricyanide. TurnbulFs blue. When ferrocyanide of potassium is oxidized by nitric acid, there is formed Nitro-prussic acid, whose sodium salt, FeCy5(NO)Na2 + 2H2O, crystallizes in red prisms soluble in water and forms a valuable reagent for the detection of sulphuretted hydrogen, an alkaline solution yielding with the latter a splendid but tiansietit purple-blue colouration. CYANOGEN CHLORIDE; CYANIC ACID. 257 B. Halogen Compounds of Cyanogen. Cyanogen chloride, CN.Cl, {Berthollet). Colourless con- densible gas of a most obnoxious pungent odour, somewhat soluble in water. B. Pt. of its liquid - 12°. It is prepared by the action of chlorine upon mercuric cyanide or upon dilute aqueous hydrocyanic acid, thus : CNH + CI2 = CNCl + HCl. It polymerizes readily to cyanuric chloride, and yields potassic chloride and cyanate with aqueous potash, appearing thus as the chloride of cyanic acid : CN.Cl + 2K0H = CN.OK + CIK + H^O. " Cyanogen bromide, CNBr. Analogous to the chloride. Transparent prisms. Cyanogen iodide, CNTI. Beautiful white prisms, smeUing intensely both of cyanogen and iodine, and subliming with the utmost ease. Very poisonous. Prepared from mercuric cyanide and iodine. Cyanuric chloride, tri-chloro-cyanogen, (CN)3Cl3. This polymer is obtained from cyanogen chloride, or from hydro- cyanic acid and chlorine in ethereal solution. It forms beauti- ful white crystals, of an unpleasant pungent odour. M. Pt. 140°, B. Pt. 190°. Boiling water decomposes it with formation of hydrochloric acid and cyanuric acid, (CN)3.(OH)3, of which latter it appears as the chloride. It contains the trivalent radicle (CN)3'" = tri-cyanogen, (see Cyanuric acid). 0. Cyanic and Cyanuric acids. Cyanuric acid is formed when urea is heated, either alone or in a stream of chlorine gas ; by subjecting it to dry distillation and condensing the vapours evolved in a freezing mixture, one obtains Cyanic acid, CNOH, as a mobile liquid of a pungent odour : C3N3O3H3 = 3CN0H. It is exceedingly unstable ; when taken out of the freezing mixture it changes, with explosive ebullition, into the poly- (506) R 258 XII. CYANOGEN COMPOUNDS. meric Cyamelide, (CONH)^, a white porcelain-like mass which goes into cyanic acid again upon heating. Cyanic acid com- bines with ammonia to cyanate of ammonium. Potassium cyanate, CNOK, frequently also termed potas- sium isocyanate, is prepared by fusing potassic cyanide or yellow prussiate of potash with PbOg or MnOg : (CNK + 0 = CNOK). White plates, readily soluble in water and alcohol. Ammonium cyanate, CN0(NH4), forms a white crystalline mass, and is of especial interest on account of the readiness with which it changes into the isomeric urea, CONgH^. When hydrochloric acid is added to these salts, there result — instead of free cyanic acid— its products of saponification, CO2 and NH3 : CONH + H2O = CO2 + NH3. This decomposition is avoided by the addition of dilute acetic acid (instead of hydrochloric), but in the latter case the cyanic acid changes into its polymer cyanuric acid, the hydrogen^otassium salt of the latter slowly crystallizing out. From cyanic acid are derived two isomeric classes of alco- holic derivatives, by the replacement of the hydrogen by alcohol radicles. The derivatives which are constituted on the type N=C.OR are termed the normal, and those on the type 0=C=NR the iso-compounds. I. When potassium cyanate is distilled with ethyl iodide or, better, with potassium ethyl-sulphate, there is obtained Ethyl iso-cyanate or cyanic ether, CO.NC2H5, a colourless liquid of suffocating odour, which boils unchanged at 60° and is decomposed by water. It does not possess the properties of a compound ether, but is broken up by alkalies or acids into ethylamine and carbon dioxide, thus ; CONC2H5 + H2O = CO2 + NH2.C2H5. Water, which acts in a similar manner, gives rise to the more complicated urea derivatives ; ammonia and amine bases CYANIC AND CYANURIC ACIDS. 259 also produce derivatives of urea (p. 272), and alcohol yields derivatives of carbamic acid (p. 270). Constitution, — The formation of ethylamine proves that the N of the cyanic ether is linked directly to the alcohol radicle, so that the consti- tution is : 0=C=N.C2H5. It is questionable, however, whether free cyanic acid and cyanate of potassium possess analogous constitutions, since frequent observations have shown that the normal cyanic com- pounds readily change into the iso-(see below); theoretical considerations indeed make it more probable that cyanic acid has the constitution N=C — OH, according to which it appears as the normal acid, with cyanogen chloride as its chloride. Potassium cyanate would then be ]sr=c— 0— K. II. The so-called cyan-etholines, which are said to result from the action of cyanogen chloride upon sodium alcoholates, are regarded as isomeric with these cyanic ethers, e.g. Cyan-etholine, CN.OCgBIs. From this mode of formation, the cyan- etholines appear to be derivatives of normal cyanic acid, CN.OH ; their chemical nature is, however, not yet sufficiently investigated. Cyanuric acid, C3N3O3H3, = (CN)3(OH)3 (Scheele). The formation of cyanuric acid by heating urea, already mentioned on p. 257, is easily understood when one remembers that it is made up of the constituents of cyanic acid and ammonia, so that, when the latter is split off, the former becomes free and then polymerizes. Cyanuric acid forms transparent prisms which contain 2 mols. HgO of crystallization and weather in the air, and which are readily soluble in hot water. It is a tribasic acid. The sodium salt is sparingly soluble in cone. NaOH ; the copper salt possesses a characteristic beautiful violet colour. Upon prolonged boiling with hydrochloric acid it is saponified to COg and NH3, while phosphorus penta- chloride converts it into cyanuric chloride, the acid being regenerated from this by water. Cyanuric acid also gives rise to two isomeric classes of alcoholic derivatives, viz. : 1. The Normal cyanuric ethers, e.g. C3N3(OC2H5)3 (a colourless liquid), which result from the polymerization of the cyan-etholines and also by the action of methyl iodide etc. upon cyanurate of silver at the ordinary temperature. They easily change into the isomeric 2. Iso-cyanuric ethers or tri-carbimido ethers, e.g. C303(NC2Hg)3, colourless liquids which frequently result instead of the cyanic ethers, 260 XII. CYANOGEN COMPOUNDS. for example, on the distillation of cyanurate with ethyl-sulphate of potassium. They are further formed by the polymerization of the iso- cyanic ethers, being thus obtained as bye-products in the preparation of the latter. The normal compounds are broken up by saponification with the formation of alcohol, and the isomers with formation of ethylamine. The constitution of cyanuric acid follows from its relation to cyanuric chloride as (CN)3(OH)3, and that of the alkyl derivatives from their behaviour upon saponification. The normal compounds therefore contain, like cyanuric chloride, the trivalent radicle tri-cyanogen, (CN)3, whose N- and C-atoms one assumes to be linked to each other alternatively by single and double bonds in a closed ring," while the iso-cyanic ethers are to be regarded as derived from a hypo- thetical original substance consisting of three CO- and NH-groups joined together in the form of a ring. (Cf, A. W, Hofmann, B. 18, 2755, 3261 ; also Benzene derivatives) : OH I (OC2H5) If N C1_C^ ,C— CI HO— C Cyanuric chloride. Cyanuric acid. C-OH (CsHgO-C C-IOC^H,) Cyanuric ether. O oc. ,co (C2H5) Isocyanuric ether. In addition to cyanuric acid and cyamelide, various other polymers of cyanic acid have been described, but only some of them have been closely studied. (Cf. among others, J. pr. Ch. 32, 461.) Further, in the aromatic series, derivatives of a Di-isocyanic acid, (CO)2.(lSrH)2, are known, (B. 18, 764). THIOCYANIC ACID. 261 D. Thiocyanic Acid and its Derivatives. Potassium thiocyanate, -sulphocyanate, -sulphocyanide, -rhodanide, CNSK. Potassium cyanide not only combines readily with oxygen to cyanate but also with sulphur to thio- cyanate, either when fused with sulphur or when its solution is evaporated with yellow sulphide of ammonium : KCN + S = CNSK. It is prepared hy fusing yellow prussiate of potash with sulphur and potashes. It forms long colourless deliquescent prisms, extremely soluble in water with absorption of much heat, and also easily soluble in hot alcohol. Ammonium thiocyanate, ammonium rhodanide, CNS(NH4), results upon warming a mixture of carbon bisulphide, concen- trated ammonia and alcohol (Millon), di-thiocarbamate and tri-thiocarbonate of ammonia being formed as intermediate products (see p. 275) : CS2 + NH3 = CNSH + H^S. Colourless deliquescent plates, readily soluble in alcohol. Upon being heated to 130°-140°, it is partially transformed into the isomeric thio-urea, just as ammonium cyanate is into ordinary urea. It precipitates silver thiocyanate, CNSAg, (white) from solutions of silver salts, and is therefore employed in the titration of silver, with ferric sulphate as indicator ; and it gives with ferric salts a dark blood-red colour- ation of ferric thiocyanate, Fe2(CNS)(> l^HgO This last reaction is exceedingly delicate. Mercurous thiocyanate, Hg2(CNS)2, is a white powder insoluble in water, which increases enormously in volume upon being burnt, (Pharaoh's serpents). The Barium salt is used in printing with alizarin red. The free Thiocyanic acid, CNSH, is a pale yellow liquid with a pungent odour resembling that of glacial acetic acid, miscible with water, and boiling at 102°. It is prepared either by leading HgS over the warmed mercury salt or into its aqueous solution, and also by dis- tilling the potassium salt with dilute sulphuric acid. It is only stable in a freezing mixture or in aqueous solution, readily decomposing other- wise with formation of Persulphocyanic acid, CgNgSgHg (yellow crystals). 262 XII. CYANOGEN COMPOUNDS. Concentrated sulphuric acid decomposes the thiocyanates with formation of carbon oxy-sulphide : CNSH + HgO = COS + NH3 ; sulphuretted hydrogen decomposes them into carbon bisulphide and ammonia : CNSH + HgS = CSg + NH3. Cyanogen sulphide, (CN)2S, is to be regarded as the thio-anhydride of thiocyanic acid ; it is prepared from cyanogen iodide and silver thio- cyanate, and forms readily soluble plates of sharp odour. Just as in the case of cyanic acid, so are there derived from thiocyanic acid two isomeric classes of alcoholic derivatives, by the replacement of hydrogen by alcohol radicles. I. Compound ethers of thiocyanic acid result from the entrance of alcoholic radicles in the place of the hydrogen of the acid. Ethyl thiocyanate, CN.SCgH^, is obtained either (1) by the distillation of potassium ethyl-sulphate with potassium thio- cyanate, or (2) by the action of cyanogen chloride upon a mercaptide. It is a colourless liquid with a peculiar pungent odour of leeks, and almost insoluble in water. B. Pt. 142°. Alcoholic potash saponifies it in the normal manner with reproduction of potassium thiocyanate ; in other reactions, however, the alcoholic radicle remains united to the sulphur. Thus nascent hydrogen reduces it to mercaptan, and fuming nitric acid oxidizes it to ethyl-sulphonic acid. It follows from mode of formation (2) and also from the reactions of the thiocyanic ethers that the sulphur in them is linked to the alcohol radicle. Consequently in the salts it is linked to the metal in question, and in the free acid to hydrogen. We have therefore the following constitutional formulae ; AUyl thiocyanate, CN.SC3H5. Colourless liquid smelling of leeks. B. Pt. 161°. Changes upon distillation into the isomeric mustard oil. II. Isomeric with the thiocyanic ethers are the mustard oils Senfole.") AUyl iso-thiocyanate, common mustard oil, CS : N.C3H5, is N=C— SH N=C— SK N^C— SC2H5 Potassium thiocyanate. Ethyl thiocyanate. Thiocyanic acid. THE ISO-THIOCYANATES. 263 prepared by distilling the seeds of black mustard (Siiiapis niger) with water. It is a liquid sparingly soluble in water and of exceedingly pungent odour, which produces blisters on the skin. B. Pt. 151°. It results on distilling allyl thiocyanate, by a molecular rearrangement, and it is also obtained by the action of carbon bisulphide upon the corresponding primary amine, allylamine, thus : CS2 + NH2.C3H5 = CS : N.C3H5 + H^S. This reaction does not, however, proceed exactly as indicated in the above equation, there being first formed the allylamine salt of allyl- di-thiocarbaniic acid, which is changed into allyl iso-thiocyanate upon distillation with mercuric chloride. (See di-thiocarbamic acid, p. 276. ) Ethyl iso-thiocyanate, C2H5N.CS, (B. Pt. 134°), and Methyl iso-thio- cyanate, CH3N.CS, (solid, M. Pt. 34°, B. Pt. 119°), etc., closely resemble the allyl compound, and are obtained in an analogous manner by the action of carbon bisulphide upon ethylamine, methylamine, etc. The mustard oils also result from the distillation of alkylated thio- ureas (p. 277) with syrupy phosphoric acid {Hofmann, B. 15, 985), or with concentrated hydrochloric acid. They break up on being saponi- fied, with reproduction of the primary amines from which they can be prepared : CS.NC3H5 + 2H2O = NH2.C3H5 + H2S + CO2. They are connected with the thio-ureas by various reactions, and also with the cyanic ethers, since in the latter 0 can be replaced by S, but in the mustard oils, on the contrary, S by 0. The constitution of the mustard oils follows from their relation to the primary amines, the alkyl being linked to nitrogen in both classes of compounds ; the constitutional formula of methyl iso-thiocyana.te is therefore S=C=N — CH3. Iso-thiocyanic acid, SC=NH, is itself unknown. Polymers. Dithio-dicyanic acid, CgNgSgHg. The potassium salt of this polymer has been described, but little is known about it. Thio-cyanuric acid, (C3N3)(SH)3, is a tribasic acid. Yellow powder. The primary sodium salt, C3No(SH)2SNa, crystallizes well. It is formed e.g. by the action of cyanuric chloride upon sodium sulphide, whence its constitution follows. Its Tri-methyl ether results along with methyl iso-thiocyanate upon heating methyl thiocyanate to 180°, by the polymerization and subsequent molecular transformation of the latter. 264 XII. CYANOGEN COMPOUNDS. E. Oyanamide and its Derivatives. Cyanamide, CN.NHg, {Bineau), is formed : 1. By leading cyanogen chloride into an ethereal solution of ammonia : CNCl + 2NH3 = CN.NH2 + NH4CI. 2. By the action of HgO upon thio-urea in aqueous solution, (" desulphurization ") : NH2— CS— NH2 = NC.NH2 + H2S. Colourless crystalline hygroscopic mass, readily soluble in water, alcohol and ether. M. Pt. 40°. When heated to 150°, it changes into the polymeric melamine with explosive ebullition. In the same way it easily goes into the polymeric dicyan-diamide on evaporating its solution or allowing it to stand. Dilute acids cause it to take up the elements of water, with formation of urea: CN.NHg + HgO ^ CONgH^; and it combines in an analogous manner with sulphuretted hydrogen to thio-urea. When heated with ammonia salts it yields salts of guanidine. Cyanamide behaves as a w^eak base, forming crystalline easily decomposable salts with acids and, at the same time, as a weak acid, yielding a sodium salt, CN.NHNa, a lead and a silver salt, etc. The last is a yellow powder and has the composition CNgAgg. Cyanamide also gives rise to two isomeric series of alcoholic deriva- tives, by the replacement of the hydrogen by alkyl. I. Methyl- and Ethyl- cyanamides are prepared e.g. from methyl- and ethyl-thio-urea. Di-ethyl-cyanamide, CN2(C2H5)2, is obtained by treat- ing silver- cyanamide with ethyl iodide. Acids saponify it to CO2, NH3 and NH(C2H5)2, hence it possesses the constitution N^C — N(C2H5)2 : N=C-N(C2H5)2 + 2H2O = NH3 -f CO2 + NH(C2H5)2. From this it follows that cyanamide has most probably the constitu- tion which corresponds with its name, viz., N=C — NHg. II. Other cyanamide derivatives, which are chiefly known in the aromatic series, spring from a hypothetical isomer of cyanamide, viz., Carbo-di-imide, NH=C=NH ; for instance, Diphenyl-carbo-di-imide, CN2(C6H5)2. Boiling with acids likewise decomposes them into OOg and an amine, but the latter can only be a primary one. ISOMERISM IN THE CYANOGEN GROUP. 265 Polymers. Dicyan-diamide, parame^ C2N4H4 (p. 264). Crystallizes in beautiful broad needles or prisms, and has probably the constitution N=C— NH— C^^^ , (B. 19, 440). Like cyanamide, it yields mela- mine when strongly heated. Melamine, cyanuramide, CgNgHg, (Liebig^ 1838), forms glancing rhombic octahedra, insoluble in alcohol and ether, and possesses basic properties. When it is boiled with acids, the NHg- groups are succes- sively replaced by OH with the formation of Ammeline, (CN)3(N"H2)20H, Ammelide, (CN)3N"H2(OH)2, and finally cyanuric acid, (CN)3(OH)3. Melamine has therefore the constitution (CN)3(NH2)3, = tricyan- triamide. Further, alkylated melamines are derived from the latter by the replacement of hydrogen by alkyl, and in addition to these there exists an isomeric class of compounds of which the hypothetical *'Iso -melamine," [C(NH)]3(NH)3, is the basis. To this class belong the polymerization products of the alkyl cyanamides. The following con- stitutional formulae are ascribed to these two series, (R= Alcohol radicle) : /^\ and RN"^ RN I II II Melamines. Iso-melamines. For particulars see A. W. Hofmann, B. 18, 2755, 3217, P. Appendix. Theoretical Considerations as to isomerism in the Cyanogen Group. As has already been explained, there are derived from hydrocyanic acid, cyanic acid, thiocyanic acid and cyanamide, and also from their polymers, two classes of isomeric alcoholic derivatives which differ sharply from one another in their products of decomposition. They correspond, properly speaking, to two isomeric mother substances — the "normal " and *'pseudo " forms {Ad. Baeyer) — only one of which, however, is known in the free state, viz., the normal compound, (cf. Hofmann, loc. cit.). The fact that the isomeric form has never been obtained may be explained by assuming that it represents an unstable state of equilibrium of the atoms, and that, when attempts are made to 266 XIII, DERIVATIVES OF CARBONIC ACID. prepare it, it immediately undergoes molecular transformation into the other, stable, form. When the hydrogen is replaced by alkyl, both varieties of atomic groups are in most cases capable of existence, although even here also a difference in stability is observed, the normal compounds changing very readily into the iso- (or pseudo-) com- pounds. In consequence of this one obtains the iso-cyanic ether directly from potassium cyanate instead of the normal one, allyl thiocyanate readily changes into the iso- thiocyanate, and iso-cyanuric ether is usually got instead of cyanuric, etc., etc. It is also conceivable that the mother substances may possess both the above constitutional formulae, i.e. that, by the wandering of an atom of hydrogen, their atoms may sometimes arrange themselves in the one and sometimes in the other form, and that they may accordingly show the reactions of either, (" Tautomerism "). The discussion upon this point is still going on. (Cf. Laar, B. 18, 648; 19, 730.) Among other compounds regarding which considerations of this nature have been advanced, may be specially mentioned thio-urea, CS(NH2)2 or C(NH)||^^2 (p^ 277), thiamides of monobasic acids, R — CS.NHg or R — ^^S^ ^P* ^^^)» aceto-acetic ether, CH3-CO-CH2-CO2R or CH3-C(OH)=CH-C02R, succino-succinic ether, phloroglucin, isatin, carbostyril, etc. One of the formulae in question of these substances is convertible into the other simply by the wandering of a hydrogen atom. It has been proved that many of these compounds react in a manner which corresponds as well with the one formula as with the other. When a " change in the bonds" of such tautomeric" substances occurs, it is termed *'desmo- tropism," {Hantzsch and Herrmann, B. 20, 2081). In the case of the derivatives of succino-succinic ether, these desmo tropic states" are coincident with changes in physical properties ; the compounds are sometimes coloured, sometimes colourless, and at the same time one of the states is unstable, the other being stable. XIII. OARBONIO AOID DERIVATIVES. Carbonic acid is a dibasic acid, forming two series of salts, e.g, Na2C03 and NaHCOg. The hydrated acid itself, OH CO3H2, = C)=C)<^Qjj, is unknown, but may be supposed to exist in the aqueous solution. Its empirical formula shows carbonic to be the lowest oxy-acid CnH2n03, i. 6. it is homologous with glycollic acid and may be looked upon ETHERS OF CARBONIC ACID. 267 as oxy-formic acid. Its dibasic nature is explained by the carbonyl group apparently extending its acidifying character over both hydroxyls equally. Since the latter are both linked to one carbon atom, the non- existence of the free hydrate is readily understood (see p. 131, etc.). The salts of carbonic acid and those of several of its deriva- tives, such as carbon bisulphide, CSg, and carbon oxy-sulphide, COS, have been already treated of under inorganic chemistry. But there still remain for description the compound ethers, chlorides and amides of carbonic acid, two series of which exist, acid and neutral, as in the case of all the dibasic acids, CnH2„_204. The neutral compounds are well characterized and are very similar to those of oxalic or succinic acid ; the acid compounds on the other hand are unstable in the highest degree when in the free state, and are known almost only as salts. Many mixed derivatives have also been prepared, e,g, carbamic ether, CO(NH2)(OC2H5), analogous to oxamethane (p. 233). Summary, Neutral derivatives. Ethyl carbonate. COClg Carbonyl chloride. CO(NH2)2 Urea. Acid derivatives. CO(OC2H5).OH Ethyl carbonic acid. C0(C1)(0H) Chloro-carbonic acid. C0(NH2)(0H) Carbamic acid. Mixed derivatives. CO(Cl)(OC2H5) Chloro-carbonic ether. CO(NH2)(OC2H5) Urethane. The modes of formation of these compounds are for the most part exactly analogous to those of the corresponding derivatives of the monobasic acids and of oxalic acid. A. Ethers of Carbonic Acid. Ethyl carbonate, GO{OG^^^, is formed : 1. By the action of ethyl iodide upon silver carbonate ; 268 XIII. DERIVATIVES OF CARBONIC ACID. 2. By the action of alcohol upon chloro-carbonic ether, and therefore indirectly from carbon oxychloride and alcohol : CO(OC2H5)Cl + C2H5OH = COiOG^R,)^ + HCl. It is a neutral liquid of agreeable odour, lighter than water and insoluble in the latter. B. Pt. 126°. Analogous Methyl-, Propyl-, etc. carbonates are known, and also ethers containing two different alcohol radicles. It is a matter of no consequence which of these radicles is introduced first into the molecule, a proof of the equal valency of the two hydroxyls. Ethyl-carbonic acid, CO(002H5)(OH), corresponds exactly with ethyl-sulphuric, but is much less stable and only known in its salts. Potassium ethyl-carbonate, CO(OC2H5)(OK), results upon passing CO2 into an alcoholic solution of potassium ethylate : COg + KOC2H5 = 003(02115) K. It crystallizes in glancing mother-of-pearl plates, but is decomposed by water into potassium carbonate and alcohol. B. Chlorides of Carbonic Acid. Carbon oxy-chloride, carbonyl chloride, johosgene, COClg, (/. Davy). This compound is analogous to succinyl chloride, 03114(0001)2, and to sulphuryl chloride, SOgOlg. It is ob- tained by the direct combination of carbonic oxide and chlorine in sunlight, etc., and also by the oxidation of chloro- form by means of chromic acid. Oolourless gas, condensing to a liquid below 4-8°, of exceptionally suffocating odour. Soluble in benzene. As an acid chloride it decomposes violently with water into OO2 and HOI. It therefore trans- forms hydrated acids into their anhydrides, with separation of water, and converts aldehyde into ethylidene chloride. It yields urea with secondary amines of the fatty series, and carbamic chlorides with secondary amines of the aromatic. Is employed in the preparation of salicylic acid. Chloro-carbonic acid, OOOl(OH), the acid chloride of car- bonic acid analogous to chlor-oxalic acid (p. 232), has too great a tendency to break up into OO2 and HOI to allow of its AMIDP]S OF CARBONIC ACID. 269 existence either in the free state or in that of salts. As a monobasic acid, however, it forms ethers, e.g. Chloro-carbonic ether, CO(Cl)(OC2H5) ( - chloro-formic ether, CI— CO.OCgH^), Avliich results from the action of carbon oxy-chloride upon alcohol, (Dumas, 1833) : COCI2 + C2H5OH = COCl(OC2H5) + HCl. This is a volatile liquid of very pungent odour, which boils at 94°. It reacts as an acid, chloride, being decomposed by water, and is therefore specially fitted to effect the synthetical entrance of the carboxyl group into many compounds. The corresponding Methyl- etc. ethers are very similar. 0. Amides of Carbonic Acid. The neutral amide of carbonic acid is urea or carbamide, the acid amide or aminic acid is carbamic acid. Imido-carbonic OH acid, C(NH)qjj, would be an imide of carbonic acid, but it is only known in its derivatives, (Sandmeyer, B. 19, 862). The hypothetical form of cyanic acid, CO=NH (see table, p. 250), would also be an imide of carbonic acid, and that of cyanamide, C(NH)2, a di-imide, while cyanic acid itself is to be regarded as a half nitrile, with cyanamide as its amide. The recently prepared Imido-carbonic ether, C.NH(O.C2Hg)2, (B. 19, 864), is an imido-compound of carbonic acid. The amidine of carbonic acid is guanidine. The " ortho-amide " of carbonic acid, which would possess the formula C(NH2)4, is un- known ; when it might be expected to be formed, guanidine and ammonia result instead. The modes of formation of urea and of carbamic acid are exactly analogous to those of the amides in general : 1. By the action of ammonia upon ethyl carbonate : CO(OC2H,)2 + 2NH3 = CO(NH2)2 + 2C2H,.OH. CO(OC2H,)2 + NH3 = CO(OCA)NH, + C,H,OH. 2. By the abstraction of the elements of water from car- bonate or carbamate of ammonia. Dry carbon dioxide and ammonia combine together directly to ammonium carbamate, the 270 XIII. DERIVATIVES OF CARBONIC ACID. so-called anhydrous carbonate of ammonia, C0(NH2).0H, NH3, which goes into urea when heated to 135°, or when exposed to the action of an alternating current of electricity, thus : CO(NH2).OH,NH3 = CO(NH2)2 + H2O. 3. By the action of ammonia upon carbon oxy-chloride : COCI2 + 4NH3 = CO(NH2)2 + 2NH4CI. CO(OC2H5)Cl + 2NH3 = CO(OC2H5)NH2 + NH^Cl. Carbamic acid, C0(NH2)0H. Carbamate of ammonia, which forms a white mass, dissociates at 60° into 2NH3 + CO2. Its aqueous solution does not precipitate a solution of chloride of calcium at the ordinary temperature, since calcium car- bamate is soluble in water, but, if it is heated, saponification into CO2 and NH3 ensues and calcium carbonate is thrown down. Urethane, CO{NH2)(OC2H5), is the ethyl ether of carbamic acid. It is formed according to method 3, and also by the direct union of cyanic acid with alcohol. Large plates, easily soluble in water, etc. M. Pt. 4:7°-50°, Boils unchanged and acts as a soporific. Analogous Methyl- etc. ethers of carbamic acid are also known. They are all readily saponified by alkalies into the alcohol, CO2 and NH3, and go into urea when heated with ammonia. Carhamic chloride, CO^^ ^ is obtained by the action of COClg upon NH4CI at 400°. It forms long, compact, colourless needles of pungent odour. M. Pt. 50°, B. Pt. 61-62°. It reacts violently with water, ammes, etc., and serves for the synthesis of organic acids (see these). Among its derivatives is e.g. Di-methyl- carbamic chloride, C0[N(CH3),]C1. In the same way alkylated carbamic acids, CO(NHR)OH, which are only stable as ethers, have been prepared, e.g, Ethyl-carhamic ether, ethyl-urethane, COlNH.CgHsjtOCaHs), a liquid, B. Pt. 175°, which is formed e.g. by the direct combination of cyanic ether with alcohol at 100°. Urea, carbamide, CO(NH2)2. Was first found in urine in 1773. Is contained in the urine of mammals, birds and some reptiles, and also in other animal fluids. A grown man pro- duces about 30 grm. daily. Urea is the final decomposition UREA. 271 product from the oxidation of the nitrogenous compounds in the organism. Formation. From ethyl carbonate, carbamic acid and phosgene, as given above, and synthetically by the molecular transformation of ammonium cyanate, by warming its aqueous solution or allowing it to stand, {JFohler, 1828; see pp. 1 and 258) ; CN.OH, NH3 = CO(NH2)2. It is further formed from cyanamide and water : CN— NH2 + H2O = CO(NH2)2 ; by the partial saponification of guanidine (p. 278) : C(NH)(NH2)2 + H2O = CO(NH2)2 + NH3 ; by heating oxamide with mercuric oxide, by the breaking up of creatine, by means of alkali, and by the oxidation of uric acid, etc. etc. Preparation. 1. By evaporating urine, adding nitric acid, and decomposing the separated and purified nitrate of urea by barium carbonate. 2. By mixing a solution of potassium cyanate (from the ferrocyanide), with ammonium sulphate and evaporating : 2CN0K + (NH4)2S04 = CO(NH2)2 + K^SO^. It crystallizes in long rhombic prisms or needles of a cooling taste, which are very readily soluble in water, readily also in alcohol, but not in ether. M. Pt. 132^ When strongly heated it yields ammonia, cyanuric acid, biuret and ammelide. As an amide it is readily saponified by boiling with alkalies or acids, or by superheating with water : CO(NH2)2 + H2O = CO2 + 2NH3. Nitrous acid reacts with it to produce carbon dioxide, nitrogen and water : CO(NH2)2 + 2NO2H = CO2 + 2N2 + 3H2O. Sodium hypochlorite and hypobromite act in a similar manner, (Bavj/, Kriop). Hufner^s method of estimating urea quantitatively depends upon the measurement of the nitrogen thus obtained, (J. pr. Ch. [2] 3, 1). When warmed with 272 XIII. DERIVATIVES OF CARBONIC ACID. alcoholic potash to 100°, urea is converted into cyanate of potassium and ammonia. The basic character of ammonia is greatly weakened in urea by the influence of the negative carbonyl. Among the salts of urea with acids may be mentioned Urea nitrate, CON.2H4, HNO3, which crystallizes in glancing white plates, easily soluble in water but only slightly in nitric acid ; also the chloride, oxalate and phosphate. But like acetamide urea also forms salts with bases, especially with mercuric oxide, e.g. CON2H4 + 2HgO ; finally it yields crystalline compounds with salts, e.g. Urea sodium chloride, CON2H4 + NaCl + HgO (glancing prisms), and Urea silver nitrate, CON2H4 + AgNOg (rhombic prisms). The precipitate which is ob- tained on adding mercuric nitrate to a neutral aqueous solution of urea has the formula 2CON2H4 + Hg(N03)2 + 3HgO ; upon its formation depends Liebig^s method for titrating urea. (See the memoirs of Pfluger and Bohland on the subject, e.g. Pfli'iger^ Arch. f. Phys. 38, 575). Isomeric with urea is the amid-oxime Isuret, CH(NH)(NH.OH), which results from HON and NHgOH ; it crystallizes in prisms. Alkylated ureas are obtained by the exchange of the amido-hydrogen atoms for 1, 2, 3, or 4 alcohol radicles. They are produced by WdJiler^s method of synthetizing urea, viz. by the combination of cyanic acid with amines, or of cyanic ethers with ammonia or amines, thus : CO.NC2H5 + NH2.C2n5 = CO(NH.C2H5)2. Also from amines and carbon oxy-chloride. As examples may be men- tioned : Methyl urea, 00<^g2^jj^ ; a-Di-ethyl urea, CO<^g-^2H5. Ethyl urea, C0<^^2^^^^ . /3-Di-ethyl urea, C0<^J^2 jj^^^. They are in part very similar to urea, in part however liquid and volatile without decomposition. Their constitution follows very simply from the nature of the products which result on their saponification ; thus, a-di-ethyl urea breaks up into CO2 and 2 mols. NHg.CgHg, and the /3-compound into CO2, NH3 and NH(C2H5)2, in accordance with the law enunciated on p. 101, that alcoholic radicles which are directly bound to nitrogen are not separated from it by saponifying agents. For Hydrazine derivatives of urea, see p. 118. Acid derivatives. By the entrance of acid radicles into urea, its acid derivatives or "Ureides" result. These are DERIVATIVES OF UREA. 273 formed by the action of acid chlorides or anhydrides upon urea, or by the action of phosphorus oxy-chloride, POCI3, upon a mixture of the latter with the acid. They correspond in their properties to di-acetamide (p. 180). To this class belong Acetyl urea, CON2H3(C2H30), and Allophanic acid, CO(NH2)(NH.C02H). Divalent monobasic acids also form ureides, not only in virtue of their alcoholic nature, but as alcohol and acid at the same time, thus : Hydantoic acid, C0<^H.^3jj^_^.q^jj^ CH-CH3 TT J 4. nr, /NH.CO Lactyl urea, C0< | Hydantoin, ^'^ which gives up water with formation of Glycocyamidine, C(NH) • . If, instead of JN xi — glycocoll, its methyl derivative sar cosine is used, one obtains in an analogous manner creatine and creatinine, ( Volhard) : Creatine. Creatinine. Creatine, C4H9N3O2, (Chevreul), is present in the juice of muscle and is prepared from extract of meat, (Liehig). It crystallizes in neutral glancing prisms ( + HgO) of a bitter taste, moderately soluble in hot w^ater but only slightly in alcohol. When heated with acids it loses water and goes into Creatinine, C4H7N3O, which is an invariable constituent of urine and which forms a characteristic double salt with zinc chloride, 2C4H^N30 + ZnClg. It is a strong base and much URIC ACID GROUP. 279 more readily soluble in water and alcohol than creatine, into which it can be reconverted by taking up water. When mildly saponified, creatinine yields ammonia and methyl-hydantoi'n, while creatine gives urea and sarcosine. F. Uric Acid Group. Just as the dibasic acids oxalic, malonic, tartronic and mesoxalic yield amides with ammonia, so can they react with the ammonia derivative, urea, to form compounds of an amidic nature. In such reactions either two molecules of water separate, so that no more carboxyl remains in the compound, or only one molecule is eliminated and a carboxyl group remains. In the former case the so-called ^*ureides" result, and in the latter the so-called " ureide-acids," e,g., from oxalic acid, parabanic and oxaluric acids : CO.OH ^NH.CO ^jj^ CO.OH ^°\nH.CO ^^^NHfcO.CO^H Oxalic acid. Ureide (parabanic acid). Ureide-acid (oxaluric acid). In an analogous manner the ureide barbituric acid, O4H4N2O3, is derived from malonic acid, the ureide dialuric acid, C4H4N2O4, from tartronic acid, and the ureide alloxan, C4H2N2O4, and ureide-acid alloxanic acid, C^H^NgOg, from mes- oxalic acid. These are solid and, for the most part, beautifully crystalliz- ing compounds of a normal amidic character, and therefore easily broken up backwards by saponification into urea (or CO2 and NH3) and the respective acid. The ureide-acids may be regarded as half-saponified ureides, resulting in fact from the latter in this manner. Analogous compounds are also derived from the aldehydic- or alcoholic-acids, glyoxalic acid, CH(0H)2 — COgH, and gly- coUic acid, CH2(0H) — CO2H ; from the former allanturic acid, C3H4N2O3, and from the latter the ureide hydantoin and the ureide-acid hydantoic acid, (see p. 273). They show, however, a somewhat different behaviour on saponification. In addition 280 XIII. DERIVATIVES OF CARBONIC ACID. to these so-called " mono-ureides " there exist also " di-ureides/' ^. 6., compounds into whose composition two molecules of urea have entered. These are uric acid, C^H^N^Og, and its near relations xanthine, theobromine, C5H2(CH3)2N402, caffeine, C5H(CH3)3N402, hypoxanthine, C^H^N^O, and guanine, ; further, purpuric acid, CgHgN^Og, alloxantin, CgH^N^O^, allantoin, 0^11^^403, and other compounds. Several of these di-ureides occur in nature. Uric acid is contained in the urine, blood and muscle juice of the carnivora, in gravel and chalk stones, in guano, and in the excrementa of serpents ; xanthine in small quantity in the urine, blood and liver, and sometimes in gravel, almost always together with hypoxanthine; guanine in guano; and carnine in extract of meat. Theobromine is present in the cocoa bean (Theobroma Cacao), and caffeine in the coffee bean, in tea, in Paraguay tea (Ilex paraguayensis), and in the guarana (the fruit of Paullinia sorbilis), etc. Many of these compounds are nearly related to one another ; thus ' xanthme and hypoxanthine are formed by the action of sodium amalgam upon uric acid, (taking away of 0), xanthine by the action of nitrous acid upon guanine, (exchange of N and H for 0), theobromine and caffeine by the methylation of xanthine, and hypoxanthine by the action of nitric acid upon carnine. Formation. The ureides mentioned above or other diureides result, frequently together with urea, by the oxidizing de- composition (or oxidation) of the diureides which have been enumerated. Thus uric acid yields allantoin with water and PbOg and either purpuric acid, alloxan, alloxantin or parabanic acid with nitric acid, according to the conditions, while caffeine yields dimethyl-alloxan and methyl-urea with chlorine. These decomposition products also stand in an intimate relation to one another, e.g., alloxan gives alloxan- tin, dialuric acid and barbituric acid on reduction ; hydantoin results e.g. from the oxidation of alloxanic acid and is itself oxidized to allanturic acid ; while dialuric acid and alloxan combine to alloxantin with elimination of water, etc., etc. Some of these ureides have also been prepared synthetically from urea and the requisite acid, phosphorus oxy-chloride having proved itself to be particularly useful as a dehydrating agent in such cases ; in this way parabanic acid has been obtained from oxalic, and barbituric PARABANIO ACID. 281 acid from malonic. Uric acid may be syntlietized by heating glycocoll Avith urea, {Horhaczeivski, B. 15, 2678), and also by heating trichloro- lactic or monochlor-acetic acid with urea, (B. 20, R. 472, R. 723), and therefore also xanthine, theobromine and caffeine indirectly. The constitution of the simpler ureides and ureide-acids follows directly from their decomposition products, syntheses and relations to one another, while considerations of a more com- plex nature have led to the constitution of uric acid, (Medicus), and of xanthine and its more nearly allied compounds, {E. Fischer, A. 215, 253) : / >C0; / (1) . >C0 C0( C— NH^ COC(0H)-0-CH0. When heated with ammonia it is converted into Murexide, the acid ammonium salt of Purpuric acid, CgH5N50g( -i- H^O), perhaps CO<5JgZco>^(OH)-NH-CHCO, which is formed when uric acid is evaporated with dihite nitric acid, and ammonia added to the residue ; this is the " murexide test for uric acid. Murexide crystallizes in four-sided tables or prisms (-fHgO) of a golden-green colour, which dissolve to a purple-red solution in water and to a blue one in potash. The free acid is incapable of existence. Allantoin is a di-ureide of glyoxylic acid, of the constitution NH-CH— NH ^ C0<^ I ^CO, which is found in the allantoic NH — CO NHg liquid of the cow, the urine of sucking calves, etc. It forms glancing prisms of neutral reaction, yields salts with alkalies, and can be prepared synthetically from its components. Uric acid, C^H^N^Og, {Scheele, 1776). For occurrence and synthesis, see above. Is prepared from guano and the excre- ment of serpents and crystallizes in small tables. Almost insoluble in water and insoluble in alcohol and ether, but con- centrated sulphuric acid dissolves it without decomposition, and from this solution it is thrown down unchanged by water. For the murexide reaction, see above. Uric acid is a weak dibasic acid ; its common salts are the primary (i.e., hydrogen) ones, e.g. C5H3KN4O3, a powder sparingly soluble in water. When the two lead salts are treated with methyl iodide, Methyl- and Dimethyl-uric acid are obtained, both of which also are w^eak dibasic acids, since they still contain replaceable imido-hydrogen atoms. Uric acid yields alloxan and urea when cautiously oxidized, and dimethyl-uric acid methyl-alloxan and methyl-urea, a de- 284 XIII. DERIVATIVES OF CARBONIC ACID. composition which is readily understood from the above consti- tutional formula, thus : G0( C-Nir H-O + H^O^CO^ co'^'nh^ Xanthine, C5H4N4O2, is produced from guanine and nitrous acid, and from uric acid and sodium amalgam. It is a white amorphous mass, and is at the same time base and acid ; thus it yields e.g. the lead compound CgH2PbN402, which is converted into theobromine by methyl iodide. Hypoxanthine, sarcine, C5H4N4O. Sparingly soluble in water and very like xanthine. Theobromine, C^HgN^Og. Crystalline powder of bitter taste, sparingly soluble in water and alcohol. Forms salts both as base and as acid. The silver salt, C^H.jrAgN402, yields caffeine when treated with CH3I, (Strecker, Fischer). Caffeine or Theine, CgH^oN^Og. Crystallizes ( -i- HgO) in beautiful long glancing silky needles of faintly bitter taste, which are sparingly soluble in cold water and alcohol, and can be sublimed. The salts are readily decomposed by water. Chlorine breaks it up into dimethyl-alloxan and mono- methyl-urea, a reaction easily understood from the constitu- tional formula given on p. 281. Guanine, C5H5N5O. White amorphous powder insoluble in water but soluble in ammonia. It is a divalent base, but also forms salts with bases. Yields guanidine, parabanic acid and carbon dioxide with KCIO3 + HCl. Is an imide of xanthine, containing NH instead of O, and hence nitrous acid converts it into the latter compound. Adenine, C5H5N5, which is a polymer of hydrocyanic acid, is a base which results from the decomposition of nuclein (see this) ; it has been obtained from the pancreatic glands of oxen and from tea leaves. It crystallizes in long needles and is converted by nitrous acid into hypoxanthine, whose imide it therefore is. Carnine. A powder rather easily soluble in hot water. ,NH-C-Na ,NH-CO NHg, THE CARBOHYDRATES. 285 XIV. CARBOHYDRATES. As carbohydrates are designated three groups of compounds nearly allied to one another and which are very widely distri- buted in nature, viz., those of grape sugar, CgH^gOg, of cane sugar, and of cellulose, (CgHioOg)!,. All of them contain 6 atoms of carbon or some multiple of 6, and hydrogen and oxygen in the same proportion in which these elements are present in water. They are nearly related to the hexa- tomic alcohols, CgH^^Og, from which they are respectively derived by the abstraction of or of Hg + HgO. Most of the carbohydrates have been known for a long time. Cane sugar was found in the sugar beet by Margrafin 1747, and dextrose in honey by Glauber. The transformation of starch into sugar (p. 293) was first observed by Kirchoff in 1811. A characteristic and extremely delicate reaction of the carbohydrates consists in their giving a beautiful deep violet colouration with a-naphthol and concentrated sulphuric acid, [Molisch, B. 19, R. 746). A. The Grape Sugar Group, G^iP^. {Glucoses^ Gly coses.) The glucoses are sweet and for the most part crj^stalline compounds easily soluble in water, sparingly soluble in abso- lute alcohol and insoluble in ether. They possess the character of polyvalent — (pentavalent) — alcohols and closely resemble mannite, etc., but differ from it in being fermentable, in having strongly reducing properties, and in their behaviour towards phenyl-hydrazine (see below). Most of them are optically active. The glucoses result, apart from their formation in plants, from the carbohydrates of the cane sugar and starch groups by the taking up of water, and also from the decomposition of the glucosides by dilute acids. Those which occur in nature can- not yet be said to have been prepared synthetically with certainty, but glucoses which very closely resemble them have. 286 XIV. CARBOHYDRATES. Butlerow (A. 120, 295) obtained the so-called " methylenitan " by the action of lime water upon paraformic aldehyde (tri-oxy- methylene, p. 135), and 0. Loew (J. pr. Ch. [2] 33, 321) prepared "formose" from formic aldehyde itself in a similar manner. Both of these, especially the former, are sweet amorphous mixtures of various compounds, possessing reducing powers and containing at least one real glucose. Fischer and Tafel (B. 20, 2566) then succeeded in synthetizing sugar varieties which they termed a- and ^-acrose (see below), by the action of baryta water upon acrolein bromide or glycerine aldehyde, but it is as yet impossible to state absolutely whether or not these are identical with natural glucoses. Lsevulose and mannose result from the cautious oxidation of mannite. Their constitution has not yet been determined with certainty. On account of the close connection of dextrose, laevulose and galactose with the hexatomic alcohols, one must regard them as the first oxidation products of the latter, and therefore assume that their carbon chain is normal and that each of their hydroxyls is linked to a different carbon atom. They may thus be either aldehyde-alcohols {Baeyer, Fittig)^ or ketone- alcohols (F". Meyer), in either of which cases their reducing properties are easy to understand, (see acetol, p. 221). Dex- trose, Isevulose and galactose unite with HON to cyanhydrins, which are converted into carboxylic acids of the formula CgH^30g(C02H) upon saponification. The constitution of the latter speaks in favour of the following formulae, (Kiliani, B. 18, 3066 ; 19, 767) : Dextrose = CH2(0H)— [CH(0H)]4— CHO ; Lsevulose = CH2(0H)— [CH(0H)]3-C0— CH2(0H). Behaviour. 1. Fermentation. Most of the glucoses are directly fermentable. With the exception of sorbin, they ferment with yeast (galactose only with difficulty), undergo the lactic or butyric fermentation with bacteria, and are trans- formed under certain conditions into mucous dextrine-like substances by the " mucous " fermentation. 2. Grape sugar is a pentatomic alcohol, yielding e,g, a di- GLUCOSES; GRAPE SUGAR. 287 and a tri- acetyl compound, a tetra- acetyl chlorhydrin, C^H^OCKO.C^H^O)^, and a tetra-acetyl nitrin, C6H^O(O.N02) (O.CgHgO)^. The other glucoses show a similar behaviour. 3. The glucoses form alcoholates (saccharates) with bases, especially with lime, compounds which are decomposed by CO2, and which become brown in the air from oxidation. By the further action of lime, saccharic acids are produced. Alkalies decompose glucoses with production of a brown colour and formation, e.g. of lactic acid. 4. Lsevulose is converted into mannite by sodium amalgam, and dextrose also, though less completely: lactose is similarly transformed into dulcite. 5. The glucoses are readily oxidizable, and therefore they reduce an ammoniacal silver solution and also Fehling's solution if warmed with it. The oxidation of grape sugar yields, according to the conditions, gluconic, saccharic, tartaric or oxalic acid; that of fruit sugar, glycollic, erythritic or racemic acid, etc.; and that of lactose, galactonic or mucic acid. 6. When boiled with dilute sulphuric acid, the glucoses — especially Isevulose — are, like the other carbohydrates, converted into laevulinic acid. (Cf. A. 243.) 7. With phenyl-hydrazine, CeHs — NH — NHo, there are first produced, with elimination of water, compounds of the formula C6Hi205(N2HC6H5), compounds which are "hydrazones," and the for- mation of which demonstrates the aldehydic or ketonic character of the glucoses. When the action is allowed to go further, a second molecule of phenyl-hydrazine enters the compound, or rather [ is replaced — OH ) by rrNoHCeHs, and "osazones," C6Hio04(N2HC6H5)2, result, e.g. phenyl- dextrosazone, phenyl-acrosazone, and phenyl-lactosazone. These are yellow crystalline compounds which are of great value for the recogni- tion of the carbohydrates. By the action of nascent hydrogen upon them, the phenyl-hydrazine radicles are eliminated down to one amido- - group, the glucosamines result, e.g. iso-glucosamine, CGHHO5NH2, from phenyl-glucosazone ; the latter may then in their turn be converted into glucoses by nitrous acid [Fischer and Tafel, B. 20, 2566). The con- ception of the osazones has also been extended to the analogously con- stituted derivatives of other aldehyde- and ketone-alcohols, e.g. glyceric aldehyde. 288 CARBOHYDRATES. 8. When heated, the glucoses at first change into compounds of the nature of anhydrides and then into others of the nature of caramel (p. 291), and finally they become charred. 9. They do not show the aldehydic reaction with fuchsine and sulphur dioxide. Grape sugar or Dextrose, OgH^gOg + HgO, occurs along with Isevulose in most sweet fruits, also in diabetic urine, etc., etc. It is prepared from other carbohydrates, as given at pp. 289 and 292. The sugar which is obtained from starch and termed starch sugar contains, in addition to dextrose, dextrine and unfermentable substances. It crystallizes from water in granulous masses made up of six-sided plates, and from methyl alcohol in small anhydrous prisms. M. Pt. 146°. It is dextro-rotatory, hence the name ^'dextrose." A freshly prepared solution turns the plane of polarization almost twice as much as one which has been kept or heated to boiling, a phenomenon which is known as bi-rotation." For the estimation of grape sugar by means of Fehling''s solution, see e.g, J. pr. Ch. [2] 21, 254. Truit sugar or LsBVulose, G^-^^O^, is almost invariably found along with dextrose in the juice of sweet fruits and also, together with the latter, in honey. It is formed along with dextrose by the inversion of cane sugar, and together with mannose by the cautious oxidation of mannite by nitric acid, and is easily prepared by heating inulin with water and a little acid. It crystallizes with, difficulty in needles of M. Pt. 95°, being usually obtained as an amorphous gum, and turns the plane of polarization more stronglj?- to the left than dextrose does to the right. Phenyl-glucosazone, C6Hio04(N2HC6H5)2, M. Pt. 204°, forms difficultly soluble needles, (B. 17, 579). It results from the action of phenyl- hydrazine upon either dextrose or Isevulose. When reduced it goes into iso-glucosamine, which is converted by nitrous acid into Isevulose. By this reaction it is thus possible to convert dextrose into Isevulose. Galactose or Lactose, CgH^gOg, is produced along with THE CANE SUGAR GROUP. 289 dextrose from milk sugar and dilute acid. Fine needles, M. Pt. 143°. Dextro-rotatory. a- and |8.Acrose, CqR^^Oq, {Fischer and Tafel, B. 20, 2566). For synthesis, see p. 286. a-Acrose resembles dextrose so closely that it is possibly only a physical (optically inactive) modification of the latter. Mannose, CgHigOg. See above, also B. 21, 1805. Sorbin, CgHigOe. Present in the juice of the sorb apple. Large crystals. Inosite, phaseo-mannite, damhose, CgHigOg + 2H2O, is probably also a glucose. It is found in the animal organism in the muscles of the heart, and also in many plants, e.g. unripe beans, peas and lentils. It forms large crystals which weather on exposure, and does not reduce Fehling's solution. Glucosamine, CgHiiOg(NH2), is a derivative of glucose resulting from the action of dilute acids upon chitin (p. 518), (B. 17, 241). An isomer, iso-glucosamine, has already been mentioned (p. 287). B. The Oane Sugar Group, G^2^22^^v To the cane sugar group belong all the compounds of sweet taste, which are converted into true glucoses, CgHjgOe* action of dilute acids, and which are conse- quently to be regarded as the anhydrides of the latter ; also raffinose, GigHggOjg, which shows a similar chemical behaviour. The compounds of the cane sugar group possess a sweet taste, crystallize more readily and are more stable than the glucoses, but resemble the latter in solubility. They are optically active. With the exception of maltose they are not directly fermentable, but only after being broken up (see below), and, with the exception of milk and malt sugar, they either do not reduce Fehling^s solution or do so only with difficulty. They are split up into glucoses, with assimilation of water, when boiled with dilute mineral acids or when subjected to the action of ferments such as diastase and soluble yeast ferment, (see p. 293) : C12H22O11 + HgO = 2GqH.^Pq. Cane sugar is broken up in this way into equal quantities of dextrose and laevulose. This assimilation of water is termed (506) T 290 XIV. CARBOHYDRATES. an "inversion" and the laevo-rotatory mixture, so obtained, invert-sugar, because the original dextro-rotatory action upon polarized light has been reversed. Milk sugar breaks up in an analogous way into grape sugar and galactose, and maltose into 2 mols. dextrose. On account of this decomposition into 2 molecules of glucoses, the sugars of the above group are also termed **-dioses," e.g. milk sugar is lacto-diose. Raffinose may be called a ** -triose." Constitution. The compounds of the cane sugar group are thus ethereal anhydrides of the glucoses, e.g. cane sugar is dextrose-laevulose anhydride, and malt sugar dextrose anhy- dride, etc. In this formation of anhydride there remain four hydroxyls over for every six carbon atoms of the glucose in question, CgH^0(0H)5, thus : 20eH,0(0H), = [Q,U,0{OB.),\0 + H^O; hence cane sugar etc. are octatomic alcohols. In accordance with this stands the production of oct-acetyl ethers, O^g-^uOs (0. 621130)3, by the action of acetic anhydride. Oct-aceto-saccharose is also formed directly by acetylating a mixture of dextrose and Isevulose, and the oct-acetate of milk sugar in an analogous manner from dextrose and galactose. These ethers may be saponified by cautious treatment with baryta water, and cane and milk sugar thus indirectly synthetized. Since lactose and maltose, in contradistinction to saccharose (cane sugar), possess reducing properties and yield hydrazones, they probably contain the atomic group — CH(OH) — CO — , which is altered in the case of cane sugar by the formation of anhydride. (Fischer, B. 20, 834.) Behaviour, 1. For decomposition by mineral acids and for- mation of compound ethers, see above. 2. They form saccharates Avith bases, (see cane sugar). 3. Fermentation. Maltose is directly fermentable by yeast, milk sugar only with difficulty, and cane sugar not at all until it has been "inverted,'^ which process is effected by the soluble yeast ferment itself. Milk sugar readily undergoes the lactic fermentation. 4. Oxidation gives rise to the same products as are obtained from the glucoses which form their basis. CANE AND MILK SUGARS. 291 5. Cane sugar only reduces Fehling's solution after inversion, maltose and milk sugar however upon boiling; the last named also reduces an ammoniacal silver solution. 6. The reducing sugars form compounds with phenyl- hydrazine, e.g. phenyl-lactosazone and phenyl-maltosazone, (B. 17, 580); cane sugar, on the other hand, is indifferent towards this reagent. Cane sugar or Saccharose, saccharobiose, CigHggOii. Occurs in red beet (Beta), in the sugar cane (Saccharum), in the sugar millet (Sorghum), and in many other plants, chiefly in the stem. It crystallizes in large monoclinic prisms, as is well seen in sugar-candy, and is soluble in one-third of its weight of water. It is not turned brown when heated with potash, and yields saccharates with lime and strontia, e.g. C12H22O11 + CaO + 2H2O; C12H22O11 + 2CaO; 0^2^^^^^ + 3CaO. These compounds are of great value for the working up of the uncrystallizable beet sugar mother liquors known as molasses. The further action of lime converts it into saccharic acid, which is isomeric with the glucoses, (cf. B. 16, 1727). Concentrated sulphuric acid produces charring, (difference from dextrose). Cane sugar melts at 160° and remains in the amorphous condition for some time after cooling (barley-sugar) ; when heated more strongly, it becomes brown from the form- ation of caramel or sugar dye, and finally chars. As already mentioned, it readily undergoes inversion. The percentage of sugar in a, solution of unknown strength (p) can be determined from the specific rotatory power ([a]^^ = + 64-1°), by measuring the angle through which the solution turns the plane of polarization of a ray of polarized light passed through it. This is known as Saccharimetry. Milk sugar or Lactose, ladohiose, C12H22O11 + H2O, occurs in milk, and only occasionally in the vegetable kingdom. It is obtained by evaporating sweet whey. It crystallizes in hard rhombic prisms, and is much less sweet than cane sugar, and also much less soluble in water. It is converted into lacto- caramel" at 186°. For its reducing power, see previous page. Maltose or Malt sugar, maltohiose, C^2^22Pi^ + HgO, results 292 XIV. CARBOHYDRATES. from the action of diastase upon starch during the germination of cereals (preparation of malt), and also as an intermediate product on boiling starch with dilute sulphuric acid. It forms a hard white crystalline mass, very similar to grape sugar, and strongly dextro-rotatory. Its power of reducing Fdiling's solution is only about two-thirds of that of dextrose. Related to the sugar varieties of this class is Raffinose or melitose, Ci2H220ii + 3H2O, which is found in the sugar beet and therefore in molasses, in the manna of the eucalyptus, and in cotton seed cake, etc. It is very like cane sugar but tasteless, polarizes very strongly, does not reduce FeUing^s solution, and goes into galactose and Isevulose on inversion. 0. The Cellulose group, G^^i^O^, The molecular formula of the members of this series must always be a multiple of the simple analysis-formula CgHj^Og. They are for the most part amorphous and tasteless, insoluble in alcohol and ether, partly soluble in cold water and partly insoluble ; thus cellulose is insoluble and also mucilage, the latter merely swelling up with water, while starch forms a jelly with hot water. When boiled with dilute acids or subjected to the action of ferments, they break up into glucoses or maltose, water being taken up, thus : Like the foregoing compounds therefore, they are to be regarded for the most part as the anhydrides of glucoses. Consequently they still possess an alcoholic character and yield acetic and nitric ethers, etc. Most of them are optically active. Dilute nitric acid forms the same oxidation products with them as result from the corresponding glucoses, and iodine frequently gives characteristic colourations. Cellulose, (CgH^oOg),,, is widely distributed in nature as the membrane of plant cells; cotton, elder pith, wood, etc., consist of cellulose in a more or less pure state. It can be prepared by extracting wadding or Swedish filter paper with caustic potash, hydrochloric acid, water, alcohol and ether successively. STARCH. 293 It forms a white amorphous powder, insoluble in the ordinary reagents but soluble in an ammoniacal solution of cupric oxide, from which it is again thrown down by acids. When boiled with dilute sulphuric acid, it yields dextrine and dextrose, while the concentrated acid converts it first into Amyloid, an amorphous mass which is turned blue by iodine, and finally into dextrine. Parchment paper is simply unglazed paper which has been transformed superficially into amyloid by sulphuric acid. A mixture of nitric and sulphuric acids gives rise to nitric ethers, viz. (according to the intensity of the reaction) either Gun cotton or Pyroxyline^ Ci2H^4(N02)60io, an important explosive, insoluble in alcohol-ether, or Collodion, which contains less of the nitric radicle, is not so explosive, and is soluble in alcohol-ether. Celluloid is produced by treating nitrated cellulose with camphor. Starch or Amylum, (C(.Hio05)x, [Cg^HggOgi ?], is present in all assimilating plants, being built up in the chlorophyll granules from the carbonic acid absorbed, and is found especially in the nutriment reservoirs of the plants, e.g, in the grains of cereals, in perennial roots, potatoes, etc. It is con- verted into sugar during the transference of the sap. It forms a white velvety hygroscopic powder which consists of round or elongated granules in concentric layers, insoluble in cold water. The interior of these granules consists of " granu- lose " and their husk probably of cellulose. When they are warmed with water, the latter is broken open and a jelly formed. Both the granules of starch and its jelly are coloured an intense blue by iodine and bright yellow by bromine, from the formation of loose addition compounds. The colour of the iodine starch paste vanishes on heating but reappears on cooling. When heated with glycerine, the so-called " soluble starch is formed, also when boiled with water containing sulphuric acid or by the action of diastase. Further treatment with acid converts it into dextrine and dextrose, and with diastase into dextrine and maltose. Warming with very little dilute nitric acid to 110° yields dextrine. Ferments. As has already been repeatedly mentioned, starch is transformed by the action of diastase into maltose and dextrine. This 294 XIV. CARBOHYDRATES. diastase is an albuminous substance of unknown composition which is termed an unorganized ferment," in contradistinction to the *' organ- ized ferments," the micro-organisms (p. 80). It is produced during the germination of barley and other varieties of cereals, is precipitated as a white powder in the aqueous malt extract, and causes the conversion of starch into sugar when added to starch paste. Among other unorganized ferments may be mentioned emulsin, which is contained in bitter almonds, the soluble ferment of yeast," the ptyalin of the saliva, the pepsin of the gastric juice, and the trypsin of the pancreas. The following substances, among others, closely resemble starch : Lichenin or moss starchy present in many lichens, e.g. in Iceland moss (Cetraria islandica), which is coloured a dirty blue by iodine ; and Inulin, present in the roots of the dahlia and many composites (Inula Helenium), which is coloured yellow by iodine and converted into laevulose when boiled with water. Glycogen or Animal starcli, liver starch, is present e.g. in the livers of the mammalia. It is a colourless amorphous powder which is turned wine-red by iodine ; after the death of the animal it rapidly changes into dextrose, the same conversion being effected by boiling with dilute acids, while ferments transform it into maltose. Gum varieties, GgH^oOg. The gums are amorphous trans- parent substances widely distributed in the vegetable world, which yield sticky liquids with cold water and are precipitated by alcohol. The gums proper dissolve in cold water to clear solutions while the mucilages only swell up with water to a liquid which cannot be filtered. Dextrine or starch gurriy CgH^oOg, is formed by heating starch either alone or with a little nitric acid, together with dextrose by boiling it with dilute sulphuric acid, and together with maltose by diastase. It exists in various modifications (amylo-dextrine, erythro-dextrine, achroo-dextrine, malto- dextrine), which differ from one another in their behaviour with iodine. It does not reduce Fehling^s solution even when warmed, and is not directly fermentable by yeast but only after the prolonged action of diastase, maltose being formed. Its applications are numerous. Arabic acid, 2C6H10O5 -f HgO. Gum arabic or arabin, a clear glassy secretion of many plants, which dissolves to a clear solution in water and is much used as a gum, consists of the potassium and calcium salts of arabic acid. The latter is a white amorphous Isevo- rotatory mass, TRANSITION TO THE AROMATIC COMPOUNDS. 295 which is broken up by dilute acids into arabinose and dextrose ; it is not yet certain that it belongs to the class of carbohydrates. Bassorin (a mucilage), is the chief constituent of gum tragacanth and gum bassora. XV. TRANSITION TO THE AROMATIC COMPOUNDS. In the compounds which have been treated of up to now, a so-called open carbon chain" has been assumed, i.e. one in which the end and middle carbon atoms have to be distin- guished from one another. For benzene and its extraordinarily numerous derivatives, on the other hand, it is very probable that six carbon atoms are linked together in a " closed chain," or, in other words, that the two end carbon atoms of the original open chain 0 — C — C — C — 0 — C are now joined together. Such a linking is also termed a " ring," (c£ p. 52). The question, what kinds of closed carbon chains are capable of existence, has therefore of late been the subject of much investigation, and it would seem — so far as our present know- ledge goes — that such compounds with three, four, five and possibly seven carbon atoms can be prepared. The simplest compounds of this nature which are theoretically possible consist of three, four, or five methylene groups, viz., tri- methylene, CgHg, tetra-methylene, C^Hg and pentamethylene, C^H^o, the two last being only known in the form of deriva- tives. A. Tri-, Tetra-, and Penta-methylenes. Derivatives of tri- and tetra-methylene, in especial carboxylic acids, e.g. Tri-methylene-mono-carboxylic acid, C3H5CO2H, Tri-methylene- di-carboxylic acid, C3H4(C02H)2, and Tetra-methylene-di- carboxylic acid, C4H(5(C02H)2, etc., have been prepared (at first as ethers) by W. H. Perkin, jun., by the action of ethylene bromide and tri-methylene bromide upon sodio-malonic ether (see B. 17, 1652, etc., also various papers in Ch. Soc. J.), thus : 296 XV. TRANSITION TO THE AROMATIC COMPOUNDS. • ^ + NaoC< = • ^>C< + 2NaBr. Such a mode of formation points to the atomic grouping which has just been indicated, (Cf. also Fittig and Marburg ^ B. 18, 3413), as does also the fact that these compounds show much less tendency to combine with bromine, hydrogen or hydrobromic acid than the okfines or the unsaturated acids do. Bromine either does not act at all or adds itself on with difficulty, nascent hydrogen is without action and, although combination with hydrobromic acid is more readily effected, that also is relatively difficult. Such an addition can, according to theory, only be brought about by a breaking up of the ring," i.e., by the formation of an open chain and the taking up of two monovalent atoms. A Penta-methylene-dicarboxylic acid, C5H8(C02H)2, has also been obtained by means of the malonic ether synthesis, (B. 18, 3246). Leuconic acid, or penta-Tceto-'pentamethylene, C5O5 + 4H2O, = CO^ ^ and its near relation Croconic acid, CgOgHg, are derlva- tives of penta-methylene. Both of these have been prepared from potassium carboxide, a bye-product in the manufacture of potassium, and are highly interesting from a theoretical point of view, (Nietzki ajid BenckiseVf B. 19, 293; 20, 1617.) See hex-oxy-benzene. For Penta-methylene derivatives, cf. also Fittig , B. 18, 3410 ; Hantzsch, B. 20, 2780. Closed chains which contain other polyvalent elements (0, S, N) in addition to carbon are known in considerable number; they must manifestly be assumed, for example, in succinic anhydride, nr^^^ succinimide, ^^^^ j>JN, CHg — CH2 — in y-butyro-lactone, | | , in parabanic acid, 0 00 alloxan, etc., and also in pyridine, quinoline, etc. At this point must be described three compounds in which closed atomic rings are likewise to be assumed, viz. : FURFURANK ; THIOPHENE ; TYRROL. 297 B. Furfurane, C^H^O, Thiophene, C^H^S, and Pyrrol, C,H4(NH). From these compounds a whole series of derivatives are ob- tained by the substitution of hydrogen by halogen, and also by the entrance of the groups — CH3, — CHgOH, ~CHO, — COgH, etc. In their properties furfurane, thiophene and pyrrol remind one of benzene. Thiophene in particular is delusively like the latter, e.g, in odour and boiling point, and its various derivatives often show a marvellous similarity in their chemical and physical relations to the corresponding derivatives of benzene. (See table, below.) Summary, Furfurane, C4H4O. Pyrrol^ Thiophene, C4H4S. Benzene, Dibromo- furfurane C4H2Br20. Tetra-iodo-pyrrol C4l4(NH). Dibromo- thiophene C4H2Br2S. Dichloro-benzene C6H4CI2. Methyl -furfurane C4H80(CH3). a-, j8-Methyl- pyrrol C,H3NH(CH3). a-, jS-Methyl- thiophene C4H3S(CH3). Toluene Furfurane alcohol C4H30(CH2.0H). Thiophene alcohol C4H3S(CH2.0H). Benzyl alcohol CeH,(CH2.0H). Furfurol C4H30(CHO). Thiophene aldehyde C4H3S(CHO). Benzoic aldehyde C(,H5(CH0). Pyromucic acid C4H30(C02H). a-, ^-Pyrrol- carboxylic acid C4H3NH(C02H). a-, /3-Thiophene- carboxylic acid C4H3S(C02H). Benzoic acid CaH^iCO^H). Dimethyl- furfurane C4H20(CH3),. a-, /3-Dimethyl- pyrrol C4H2NH(CH3)2. Dimethyl- thiophene 641128(0113)2. Xylenes C6H4(CH3)2. Methyl-pyrrol C4H4(N.CH3). Etc. Amido-thiophene C4H3S(NH2). Thiophene- sulphonic acid C4H3S(S03H). Aniline Benzene- sulphonic acid 298 XV. TRANSITION TO THE AROMATIC COMPOUNDS. Furfurane, pyrrol and thiophene also resemble one another in many respects. All three boil at relatively low temperatures, ( + 32°, 126°, 84°), are either insoluble or only slightly soluble in water, but easily in alcohol and ether, and show many analogous colour reactions. Thus pyrrol and thiophene and their derivatives give, for the most part, an intensive violet to blue colouration when mixed with isatin and concentrated sulphuric acid, and a cherry-red or violet colouration with phenanthrene-quinone and glacial acetic or sulphuric acid. The vapour of pyrrol colours a pine shaving which has been moistened with hydrochloric acid carmine red (iryppos^ fiery- red), while furfurol vapour colours it an emerald green; the latter likewise colours a piece of paper moistened with xylidine- or aniline acetate red. Furfurane is converted by hydrochloric acid, i.e. by mineral acids, into an insoluble amorphous powder, and pyrrol into an insoluble amorphous brown-red powder ^'pyrrol-red" (with evolution of ammonia), while thiophene remains unaltered ; the derivatives show a similar behaviour. Pyrrol is distinguished from the two other compounds by having weakly basic properties. Formation. 1. From mucic acid, C4H4(OH)4(C02H)2. This is converted into pyromucic acid ( = furfurane-carboxylic acid), C4H30(C02H), upon dry distillation, the latter in its turn yielding furfurane when heated with caustic soda. By the action of ammonia, i.e. by the dry distillation of the ammonium salt, mucic and pyromucic acids are transformed into pyrrol. Lastly, thiophene -carboxylic acid, and from it thiophene, result upon heating mucic acid with barium sulphide : (a) C4H4(OH)4(C02H)2 = C^H^O -f 2CO2 + 3H2O ; (&)04H4(OH)4(C02H)2 + NH3 = C4H4(NH) -h 2CO2 + 4H2O ; (c) G,B,{OB.)^(CO,-B.)^-\-R,S -C^H^S 2CO2 4- 4H2O. 2. From succinic acid, C2H4(C02H)2. Succinimide, C4H402(NH), yields pyrrol when strongly heated with zinc dust, and sodium succinate yields thiophene when heated with PgSg, {Folhard-Erdmann, B. 18, 454.) 3. Pyrrol also results from acetylene and ammonia at a red heat, and thiophene when ethylene is led over glowing pyrites. FURFURANE. 299 4. By the action of NH3 or PgSg respectively upon aceto-acetic ether and diaceto- succinic ether, complicated pyrrol and thiophene derivatives are obtained, {Knorr, B. 17, 1635; 18, 307, 1558.) 5. From acetonyl-acetone, CH3— CO— CH^— CH2— CO— CH3, dimethyl-furfurane results with separation of water, dimethyl- pyrrol by heating it with alcoholic ammonia, and finally dimetliyl-thiophene with pentasulphide of phosphorus, {Paal, B. 18, 58, 367 ; 20, 1074.) This behaviour would indicate that the acetonyl-acetone changes first into the isomeric compound, CH3— C(OH)-CH— CH=C(OH)— CH3, or CH=C(CH3)(0H) ... ^. ^, . ^. „ . . rN-rr n,r>TT\fr\TT\ > ^pou this assumption the formation of dimethyl- Cxi=0(CH3)(0H) furfurane appears simply as that of an anhydride, that of dimethyl- pyrrol as an exchange of 2(0H) for NH (imide formation), and that of dimethyl -thiophene as the formation of a sulphide, i.e. exchange of 2(0H) for S, according to the following equations : CH=C(CH,).OH _ CH=C(CH3k CH=C(CH3).0H CH=C(CH3r ^ CH=C(CH3).0H _ CH=C(CH3k + CH=C(CH3).0H ~ CH=C(CH3r^" + CH=C(CH3).0H CH=C(CH,) + CH=C(CH8).0H CH=C(CH3)^^ Prom the above we have the constitutional formulae ; Furfurane. Pyrrol. Thiophene. CH=CH^ CH=CH. CH=CH. CH=CH^ CH=CH'^ CH=CH'^ ((3) (a) These formulae receive corroboration from the frequently observed fact that those substances are capable of yielding addition compounds with bromine or hydrogen, (see pyrroline). According to the above formulae, two isomeric mono-derivatives of each of the three substances are possible, e.g. of thiophene : 1. one in which the hydrogen atom which stands nearest to the S (0, or NH), and 2. one in which a quasi middle hydrogen atom is substituted. As a matter of fact two such isomers have been observed in many cases, e.g. two thiophenic acids, (see table). These crystallize mixed together, the crystals having a homogeneous appearance although they contain both acids, ( V. Meyer ^ A. 236, 200). Furfurane, C4H4O, is a colourless mobile liquid of chloroform odour which boils at 32°. It appears to be present in pine 300 XV. TRANSITION TO THE AROMATIC COMPOUNDS. wood tar, as does also Methyl-furfurane or sylvane, B. Pt. 63°. Dimethyl-furfurane, 0^112(0113)20, is a colourless mobile liquid of a characteristic odour, B. Pt. 94°. Ooncentrated acids convert it into a resin ; it can be retransformed into acetonyl-acetone. Furfurol, furfurane aldehyde, O^H^Og, {Ddbereiner)^ results from the action of moderately concentrated sulphuric acid upon carbohydrates, for instance, sugar, and is found e.g. in fusel oil. It is a colourless oil of agreeable odour which is turned brown by the air; B. Pt. 162°. It has the nature of an aldehyde and shows characteristic reactions, (B. 20, 540). Pyromucic acid, O5H4O3, = 04H3O(0O2H). Needles or plates of a character similar to that of the crystals of benzoic acid, subliming easily and being readily soluble in hot water and alcohol. M. Pt. 134°. The furfurane derivatives are frequently termed **furane" deriva- tives for shortness' sake. Pyrrol, O^H^NH, is a constituent of coal tar (Bunge) and of bone oil (Anderson), and possesses, like many of its homo- logues, a chloroform odour. It is a secondary base. Its imido-hydrogen is replaceable by alkyl, acetyl or metals. Potassium -pyrrol, C4H4NK, which is obtained from pyrrol and potassium or potash, is a colourless compound which is decomposed backwards by water, and which is converted into pyridine by CH2I2 and NaO(CH3). By the action of iodine and alkali, substitution takes place with the formation of Tetra-iodo-pyrrol or lodol, C4l4(NH), which crystallizes in yellowish-brown plates and is an antiseptic. Zinc and glacial acetic acid convert pyrrol into Pyrroline, C4Hg(NH), a colourless liquid and strong secondary base, B. Pt. 90° ; and when this latter is heated with hydriodic acid, it is further reduced to Pyrrolidine, C4H8(NH), a colourless, strongly alkaline base resembling piperidine, and boiling at 85-88°. Pyrrolidine yields pyrrolylene, C4H6, with methyl iodide and caustic alkali, (see Conine; also p. 57.) Pyrrolidine is formed synthetically by treating ethylene cyanide with sodium and alcohol, thus : CH,-CN ^ _ CH,-CH2.NH, _ CH,-CH,. _ CH^-CN ^ " ~ ~ CH^-CHa-^^ ^ " it is consequently designated Tetra-methylene-imine, {Ladenburg, B. 19, 782 ; 20, 442). THIOPHENE. 301 PyrocoU, CgHgNO, (yellow plates), the anhydride of a-Pyrrol- carboxylic acid, C4H 3^11(00211), results from the distillation of gelatine. The acid itself crystallizes in metallic green prisms, M. Pt. 191°. (Cf. table of pyrrol derivatives, also B. 20, 2594.) Thiophene, C4H4S, (K Meyer, B. 16, 1465 etc.), is likewise present in coal tar, being invariably found in benzene (up to 0*5 p.c.) ; the same applies to its homologues thiotolene (methyl-thiophene), and thioxene (dimethyl-thiophene), which accompany toluene and xylene, etc. Its boiling point (84°) is almost the same as that of benzene (80-4°), from which it is extracted by repeated shaking up with small quantities of concentrated sulphuric acid, which chiefly dissolves the thio- phene (to sulphonic acid). (Cf. B. 17, 2641, 2852.) It is also attacked more readily than benzene by other reagents such as iodine and bromine. Thiophene is also obtained synthetically by leading the vapour of ethyl sulphide through a red-hot tube (KekuU), and in small quantity by heating crotonic acid, normal butyric acid, para-aldehyde, erythrite, ether etc. with P2S5. The preparation and properties of the thiophene derivatives are in part almost literally the same as those of benzene. Thus nitric acid acts on thiophene to produce a Nitro- thiophene, analogous to nitro-benzene, which can in its turn be reduced to amido-thiophene ; the latter is, however, much less stable than the corresponding amido-benzene (aniline). Thiophene-sulphonic acid, 641138(80311), decomposes into thiophene and sulphuric acid when superheated with water. Thiotenol, C4H2S(CH3)(OH), the phenol of thiotolene, is formed by heating levulinic acid with P2S5, (B. 19, 553). The blue colouration which results upon shaking up benzene contain- ing thiophene with isatin and concentrated H2SO4, depends on the for- mation of the blue colouring matter " Indophenin, " C12H7NOS. CH CH Penthiophene, ^■^2 and has received the name * ' Phenyl-methyl-pyrazolone " on account of its possessing a ketonic character. When methylated, it goes into the valuable febrifuge : Antipyrine, phenyl-dimethyl-pyrazolone, CnHigNgO, the hydro- chloride of which crystallizes in thick colourless prisms. For the constitution of these compounds see i. Knorr, A. 238, 137. All the compounds which are constituted similarly to aceto-acetic ether (/3-ketonic acids, j8-ketonic aldehydes, j8-diketones), likewise yield derivatives of pyrazol with phenyl-hydrazine. CH— N As derivatives of the as yet unknown TMazol, •• ^CH, (which CM — o is derivable from thiophene by the exchange of CH for N), are regarded a series of peculiar compounds which nearly resemble the bases of the pyridine series in properties, and which in fact are derived from these latter in the same way as thiophene — which so closely resembles benzene — is from the latter, i.e. by the exchange of CgHg for S. To this class belongs e.g. Dimethyl-thiazol, ^ 'A a — ^-^3> which is formed from monochlor-acetone and aceto-thiamide (p. ), with elimination of HgO and HCl, and which is exceedingly like a-lutidine (dimethyl- pyridine, p. 487), especially in odour and basic character. Amido-thiazol, thiazoline, •• — NHg, which is produced by 0x1 — o the action of mono-chloraldehyde upon thio-urea, is a base of perfect *' aromatic" character, like that of aniline. (Cf. Hantzsch and Weber j B. 20, 3118 ; 21, 938, 942). THE BENZENE DERIVATIVES. ao3 Class II.— CHEMISTRY OF THE BENZENE DERIVATIVES. XVI. SUMMARY. All the compounds which have been treated of up to now are derivable from the homologous hydrocarbons GJi2n+2y CnHgn, Ci,H2n-2j ^tc. by the exchange of hydrogen for halogen, hydroxyl or oxygen, amide, carboxyl, etc. ; and since all the hydrocarbons already mentioned may also be regarded as deri- vatives of methane (e.g. C^^e - ^^^3(0113) = methyl-methane, C3H8 = CH2(CH3)2 = dimethyl-methane, G^U^ = CH2 : CHg = methylene-methane, C2H2 = CH • CH = methine-methane, etc.), we may term the compounds which have been described in the foregoing portion of this book Methane derivatives. But in addition to this first class of organic compounds there is a second great class, viz. that of the Aromatic com- pounds or Benzene derivatives. The first of these two names is historical but no longer justified by facts, since compounds of agreeable as well as unpleasant odour are to be found in both classes. As benzene derivatives are designated the members of this class which are derivable from the hydrocarbon benzene, CgH^ (and also from more complicated hydrocarbons such as anthracene, naphthalene, etc., which are themselves derivatives of benzene), just as the methane derivatives are from methane. Benzene is, as its formula CgHg shows, a compound much poorer in hydrogen than the paraffins, containing eight H-atoms less than hexane, C^H^^ ; in the same way all benzene deriva- 304 BENZENE DERIVATIVES. XVI. SUINIMARY. tives are much poorer in hydrogen, i.e. richer in carbon than the analogous methane derivatives, as is seen by comparing e.g. benzoic acid, C^HgOg, with heptoic acid, C^H^^Og, or aniline, C^^H^N, with ethylamine C2H^N, etc. etc. The hydrogen atoms of benzene are, like those of methane, replaceable by the most various elements and atomic groups. By the entrance of halogens, substitution products result, by the entrance of NHg, aromatic bases, of OH, phenols, of NOg, nitro-compounds, and of CH3 etc., the homologues of benzene ; there are, in addition to these, aromatic alcohols, aldehydes, acids etc. (See table on following page.) These benzene derivatives are partly analogous in their properties to the methane derivatives of corresponding com- position ; in part, however, they show new and peculiar properties of their own, (see pp. 306, 333, 359). One dis- tinguishes between mono-, di-, tri-, etc. benzene derivatives according as one or two or more hydrogen atoms are replaced by the elements or groups in question ; thus, for instance, toluene and chloro-benzene are mono -derivatives, dimethyl- benzene and dichloro-benzene di-derivatives, and so on. Further, just as it was found when speaking of the polyatomic alcohols and acids, that the replacing groups need not be identical, so in this class also innumerable compounds are known containing various substituents. Such compounds have usually some of the characteristics of all those mono- derivatives which result from benzene by the exchange of one H-atom for one of these substituents. All the derivatives of benzene can be converted either into benzene itself or into very nearly allied compounds by rela- tively simple reactions. Thus all the carboxylic acids of benzene (benzoic, phthalic, mellitic, etc.), yield benzene on distillation with lime, while other acids, such as salicylic, give up CO2 and yield phenol, and so on ; the last-named com- pound goes into benzene when distilled with zinc dust. The homologues of benzene are converted by oxidation into benzene-carboxylic acids, which give benzene when heated with lime. BENZENE DERIVATIVES; SUMMARY. 305 The relation of a benzene derivative to its mother substance is \ therefore a very simple one, ! This circumstance is one particularly worthy of note, since the atomic group CqH^ is already a tolerably complicated molecule in itself, and also because benzene cannot by any means be transformed into a simpler hydrocarbon containing 5, 4, or 3 C-atoms ; when oxidized, which is a matter of difficulty, it goes into carbon dioxide or similar simple organic acids. Summary of a few Benzene derivatives. Methyl-benzene or C(5H4(CH3)2 QH3( 0113)3 Trimethyl-benzenes. Dimethyl-benzenes toluene. or xylenes. C,H,.C1 C6H4CI2 Chlorobenzene. Dichloro-benzenes . CeH^tOH)^ C6H3(OH)3 Phenol. Resorcin, etc. Pyrogallol, etc. C,H5.CH2.0H Benzyl alcohol. C6H3(N02)20H Nitrobenzene. Dinitro -benzenes. Dinitro-phenols. CeH4(NH2),_ . CeH3(NH2)3 Aniline. Phenylene diamines. Tri-amido-benzenes. CgTl5. SO3H Benzene-sulphonic acid. C6H4(NH2)(S03H) Benzene-tri-sulphonic acid. Sulphanilic acid, etc. CeHs— CHO Benzaldehyde. C„H5.00,H 96^3(00211)3 Benzoic acid. Phthalic acids. Hemi-mellitic acid, etc. C6H4(OH)(C02H) Salicylic acid, etc. Benzo-nitrile. The benzene derivatives are connected with one another by the most various reactions. The NOg-group is readily con- vertible into NH2, and the latter is replaceable by halogen, hydrogen and hydroxyl ; the halogen is also replaceable by methyl, carboxyl, etc. (606) u 306 BENZENE DERIVATIVES. XVI. SUMMARY. Differences between the aromatic and fatty hydrocarbons. Benzene differs from the fatty hydrocarbons by the follow- ing reactions in particular : 1. It forms nitro-benzene with nitric acid : CeHg + HO.NO2 = CfiH^.NOg + H^. 2. It yields benzene-sul phonic acid with sulphuric acid : C.Hg + HO.SO3H = C6H,(S03H) + H2O. Similarly, almost all the benzene derivatives are capable of forming nitro-compounds and sulphonic acids in nearly theor- etical quantity. As has been already seen, the paraffins are either unaffected by con- centrated HNO3 or H2SO4, or only attacked with difficulty, while the olefines form addition products with the latter acid, without separation of water. 3. The homologues of benzene differ from the paraffins especially in their capability of oxidation ; while the latter are only attacked with difficulty by oxidizing agents, the former are readily converted into benzene-carboxylic acids. There are not wanting other distinguishing characteristics between the aromatic hydrocarbons and the paraffins. Thus the halogen compounds C^H^X are less active chemically, and the hydroxyl compounds, e.g. C^^{OYi.), are of a more acid nature than the corresponding fatty bodies ; further, diazo-compounds are known almost only in the aromatic series, etc. V. Meyer defines as " aromatic " hydrocarbons such as are nitrated by nitric acid, converted into sulphonic acids by sulphuric acid, sub- stituted by bromine with the formation of stable products, and trans- formed into ketones (p. 399) by organic acid chlorides together with chloride of aluminium. The compounds derived from these are aromatic" compounds. Thiophene, which behaves in a manner exactly analogous to benzene, is thus also an aromatic compound. Characteristic of the benzene derivatives are their ISOMERISM IN THE BENZENE SERIES. 307 Isomeric relations. 1. While several isomeric mono-derivatives are both theor- etically possible and have been practically obtained from each hexane, CgH^^, benzene is only capable of forming a single mono-derivative in each case ; isomeric mono-derivatives of benzene are unknown. The six hydrogen atoms of benzene thus possess an equal value. This is not merely an empirical law, but one which has been proved experimentally. Proof of the equal value of the six hydrogen atoms. Let the six H-atoms be designated as a, &, c, d, e and / respectively. 1. Phenol, C6H5(OH), whose hydroxyl may have replaced the H-atom a, may be converted into bromo-benzene, CgHgBr, and this latter into benzoic acid, CeHglCOgH). The carboxyl in the latter has therefore also the position a, i.e. it has replaced the H-atom a. 2. The three existing oxy-benzoic acids, C6H4(OH)(C02H), can either be prepared from benzoic acid or converted into it ; their carboxyl therefore has the position a, and consequently their hydroxyl must replace some one of the other H-atoms, be it b, c, or d. 3. The oxy-benzoic acids can all give up carbon dioxide, yielding thereby the same phenol, CgHgOH, in every one of the three cases : C6H4(OH)(C02H) = CgHglOH) + COg. And since the latter compound contains the hydroxyl in position a, according to 1, while the hydroxyl in the oxy-benzoic acids replaces the H-atoms 6, c and d, it follows that the hydrogen atoms a, 6, c and d are of equal value. 4. Now, as will be explained on p. 308, there are present for each H-atom two other pairs of similarly-linked or symmetrical hydrogen atoms, i. e. pairs of which either the one or the other may be replaced by any given atomic group, without different substances resulting. But the atoms of such a pair cannot be present in the positions a, 6, c and dj as in this case three oxy-benzoic acids could not exist. It must therefore be the remaining H-atoms e and / which are respectively united symmetrically to one of the former, and which are therefore of equal value with them, e.g. e = f = b. Since, however, a = b = c = d, it follows that all the six hydrogen atoms are of equal value, (Laden- burg, B. 7, 1684.) 2. If two hydrogen atoms in benzene are replaced by other elements or groups, so that di-derivatives result, these latter 308 BENZENE DERIVATIVES. XVI. SUMMARY. must exist in three different isomeric forms. We have thus three di-chloro-benzenes, CgH^Clg, three di-amido-benzenes, CgH4(N"H2)2, three di-methyl-benzenes, GqH.^{GB.^)2, three oxy- benzoic acids, CgH4(OH)(C02H), and so on. And this is no mere empirical law, for it has been proved that only three isomeric di-derivatives of benzene are capable of existence. It can be shown that for each H-atom of benzene, e.g. for a, two other pairs of H-atoms, e.g. b and /, c and e, are symmetri- cally linked, so that it makes no difference whether, after a is replaced, the second substituent replaces the one or the other of the symmetrically linked hydrogen atoms. According to the above notation, therefore, ab = af, and ac = ae. On the other hand the combinations ab and ac are not equivalent but represent isomers ; the combination ad, the only remaining case, represents the third isomer. Proofs, that for every H-atom {a) two other pairs of symmetrically hnked H-atoms exist, have been advanced by various scientists, especially by Ladenburg. One of these may be shortly sketched here. 1. According to Huhner and Petermann (A. 149, 129 ; cf. also Hiibner, A. 222, 68, 166), the (so-called meta-) bromo-benzoic acid, which is obtained by brominating benzoic acid, and whose Br-atom may be in position c and COgH in position CH II II or iVl HO .CH HC / ^CH ^C^ ^C^ H2 Hg Certain terpenes probably possess a ** para-bond," i.e. have the C-atoms 1 and 4 linked diagonally ; such formulae would correspond with the benzene formula of Deioar or with that of Koriitr and Glaus. The benzene nucleus in GqHq is designated by Baeyer as a " tertiary/' and that in C^H^g? hexamethylene, as a "secondary" or " reduced " benzene ring. (See Baeyer on the constitution of benzene, A. 245, 103.) Laws governing substitution, and influence of the substituents upon one another. 1. A polyvalent element never replaces several hydrogen atoms together in a single benzene nucleus ; compounds such as GqHl^^O and CgH3=N are unknown. 2. In the formation of di-derivatives, several isomers usually result simultaneously, one of them generally in preponderating amount. The position of the new substituents depends upon that of those already present ; thus nitro-benzene yields chiefly 318 BENZENE DERIVATIVES. XVI. SUMMARY. m-nitro-chloro-benzene when chlorinated, and chloro-benzene chiefly j>nitro-chloro-benzene when nitrated. As a general rule, when CI, Br, I, NO2 and SO3H enter chloro-, bromo- or iodo-benzene, phenol, C^jH^.OH, aniline, CgH^.NHg, or toluene, CgHg.CHg, it is always the para-compound which is produced in largest quantity, often together with the ortho-, but only in rare cases with the meta-compound. On the other hand when 01, Br, I, NOg and SO3H enter into a compound which already contains NOg-, SO3H-, or OOgH-, they almost always take up the meta-position to these latter groups. Through the entrance of (negative) nitro-groups or of halogen atoms, the acid character of phenol is heightened, while the basic character of amido-compounds is either diminished or entirely done away with. The firm linking of halogen or amidogen in the benzene nucleus is there- by loosened, so that these substituents become more easily exchangeable, e.g. for hydroxyl. (Cf. trinitro-chloro-benzene, trinitro-phenol and tri-nitraniline.) The intensity of the influence in question is dependent upon the position of the newly-entering substituent ; thus ortho- and para-chloro- (or bromo-) nitro -benzenes, CgH4Cl(N02), are transformed into the corresponding nitro-phenols, C6H4(OH)(N02), when heated with a solution of potash to 120°, and into the corresponding nitranilines, C6H4(NH2)(N02), with ammonia at 100°, while meta-chloro- (or bromo-) nitro-benzene does not react at all. In an analogous manner, o-dinitro- benzene exchanges a nitro-group for hydroxyl when boiled with caustic soda solution, while the jp- and m-compounds do not. Further Isomers of the Benzene derivatives. 1. The isomerism of the di-, tri-, etc. derivatives, "isomerism of position " or " nucleus isomerism," has already been treated of on pp. 307 et seq. 2. When a substituent enters the benzene nucleus in the first instance and a side chain (p. 325) in the second, the so-called " mixed isomerism " is the result, e.g. : C6H4CI— CH3 and CeHg— CH2CI ; C6H4(CH3)2 and C6H5(CH2.CH3). Mono-chloro- Benzyl chloride. Xylene. Ethyl-benzene, toluene. 3. When the side chains are isomeric, one speaks of **side chain isomerism," e.g. : CgHg— CH2— CH2— CH3 and CgHg— CH(CH3)2. Normal- and Iso-propyl-benzene. OCCURRENCE OF THE BENZENE DERIVATIVES. 319 4. Should the atoms in the side chains (including those chains which are built up from 0, S, or N) be unequally divided, '* metamerism " in the narrower sense of the word results, e.g. : Salicylic ethyl ether. Ethyl-salicylic acid. Occurrence of the Benzene derivatives. Many benzene derivatives occur in nature, e.g. oil of bitter almonds, benzoic acid and salicylic acid, while others result from the destructive distillation of organic substances, especially of coal. The destructive distillation of coal yields (a) gases (illumi- nating gas) ; (b) an aqueous distillate containing ammonium salts etc. ; (c) tar ; and (d) coke. Coal tar contains : (a) Fatty hydrocarbons in small amount. (6) Aromatic hydrocarbons, the most important of which are the following : Benzene, . . . CgHg Toluene, . . . CyHg 0-, m-, and p- Xylenes, . . CgHjo Mesitylene, . . C9H12 Pseudo-cumene, CgH^g Durene, . , Styrene, . . Naphthalene, CsHg Di-phenyl, . G12H10 Acenaphthene, C12H10 Fluorene, . . C13H10 Anthracene, . C14H10 Phenanthrene, C14H10 Pyrene, . Chrysene, (c) Other neutral bodies, e,g, alcohol (in very small quantity) and carbazole, C12H9N. (d) Phenols, e.g. : Phenol or carbolic acid, CgHgO ; 0-, m-, and p-cresol, CyHgO. Pyrrol, . . . C4H5N Pyridine, . . C5H5N and its homologues. Aniline, . . C6H7N Quinoline, . C9H7N and its homologues. Acridine, (See SchultZy Chemie des Steinkohlentheers, ' Braunschweig, 1886. The presence of the hydrocarbons CgHg, C^Hg, CgHj^ (m- and p-), and C^H^g Ie3i8t of their hydro- 320 BENZENE DERIVATIVES. XVI. SUMMARY. compounds, has recently been proved in most natural petroleums, American petroleum containing, for instance, 0.2 p.c. Cc)Hi2' (cf- P- 5^ ; also A. 234, 89 etc). Modes of formation of Benzene derivatives. The benzene derivatives can only be produced from the fatty compounds by a relatively small number of reactions. 1. Many methane derivatives, e.g. alcohol, yield a mixture containing a large number of the derivatives of benzene when their vapours are led through red-hot tubes. Acetylene, C2H2, polymerizes at a low red heat to benzene, CgHg, (Berthelot) : HC CH HC^ ^CH III = I II HC CH HC^v /CH In an analogous manner allylene, C3H4, = CH3 — C=CH, yields mesitylene, CgH^g? = 1:3:5 tri-methyl-benzene, CgH3(CH3)3, when distilled with dilute sulphuric acid, while its homologue crotonylene, C^Hg, yields hexa-methyl-benzene, CjgHig, = Cg(CH3)g ; brom-acetylene and iod-acetylene poly- merize to tri-bromo- and tri-iodo-benzene when exposed to light; propargylic acid, C3H2O2, polymerizes to trimesic acid, CgHgOg, and so on. 2. Ketones condense to benzene hydrocarbons (p. 142) when distilled with dilute sulphuric acid, e.g, acetone yields mesity- lene {Kanej 1838), and methyl-ethyl-ketone tri-ethyl-benzene, etc. : CH3 CH3 (H2)CH CH(H)2 yield CH3— C(0) C(0)— CH3 CH3— C C-CH3 (H2)CH H 3 mols. Acetone. Mesitylene. MODES OF FORMATION. 321 *R0 JOaR)— HC i H 3. Hexyl iodide, CgHjgl, is converted into hexa-chloro-benzene, CgClg, by heating it with ICI3. and into hexa-bromo-benzene, CgBrg, by bromine at 260° ; the latter compound can also be obtained by heating CBr4 to 300°. 4. By acting with sodium upon succino-di-ethyl ether {Herrmann^ A. 211, 306 ; B. 16, 1411), or upon brom-aceto-acetic ether (Buisberg), we obtain the so-called succino- succinic ether" (p. 430), which is a ** diketo-hexamethylene-dicarboxylic ether," and is easily convertible into dioxy-terephthalic ether and hydroquinone : CH, «= (CO.Il)— HC CHo , r 1 I I HjCH— (CO2R) >. H2C CH-(COjR) OR ^CO^ 2 mols. Succino-di-ethyl ether. Succino-succinic ether. *R = C2H5. 5. When sodio-malonic-ether, CHNa(C02R)2> is heated, there is formed Phloroglucin-tricarboxylic ether, = triketo-hexamethylene-tri- carboxylic ether, [Baeyer, B. 18, 3454), which goes into phloroglucin on saponification, the carboxyl groups being broken up, thus : (CO2R) CHiNa / s •ROi.OC CO;OR (CO2R)— HNaiC CiNaiH— (CO2R) ' \, i ■ :6r yields (CO2R) DC CO I I + 3R0Na. (CO2R)— HC CH-lCOaR) 6. Trimesic ether (B. 20, 2930) results from the condensation of 3 mols. formyl-acetic ether, CHO — -CH^ — CO2R, and tri-acetyl-benzene, CgH3(CO.CH3)3, in an analogous manner from aceto-acetic aldehyde, CH3— CO— CH2— CHO, (B. 21, 1114). (500) X 322 BENZENE DERIVATIVES. XVI. SUMMARY. The reactions just detailed under 2, 5 and 6 depend upon the formation of a benzene nucleus out of three atomic groups — CO — CHg — , with elimination of 3 mols. HgO. 7. MeUitic acid, C6(C02H)g, is produced by the oxidation of graphite or lignite by means of KMn04. 8. Potassium carboxide, which is formed by the action of carbonic oxide upon potassium, is the potassium compound of hex-oxy-benzene, C6(OH)6, (see p. 392). 9. Di-acetyl, CH3— CO— CO— CHg, goes into Xylo-quinone (p. 394) under the influence of alkalies, (B. 21, 1411.) The converse transformation of Benzene derivatives into Patty compounds. 1. When the vapour of benzene is passed through a red-hot tube, it is partially decomposed into acetylene. 2. Benzene is oxidized by chloric acid to " Trichloro-pheno- malic acid, i.e, ^-trichlor-aceto-acrylic acid, CCI3.CO.CH : CH.CO2H, {KeJcuU and Strecker, A. 223, 170). When chlorine is allowed to act upon phenol in alkaline solution, the benzene ring is broken, and the acids, CgH5Cl304, C6H5CIO4, etc., are produced, {Hantzsch, B. 20, 2780); bromine, acting upon bromanilic acid, yields perbromo-acetone, CBrg — CO — CBrg. 3. Nitrous acid (NgO^) converts pyro-catechin etc. into dioxy-tartaric acid. 4. Oxidizing agents which are capable of destroying the benzene ring yield carbonic, formic and acetic acids. 5. Hexa-hydro-benzene is transformed into hydrocarbons of the methane series when treated with hydriodic acid at 280° (Berthelot). This decomposition appears, however, to be very difficult of accomplishment. BENZENE HYDROCARBONS. 323 XVII. BENZENE HYDROCARBONS. A. Saturated Hydrocarbons. Summary.- [ ] = M. Pt. ; ( ) = B. Pt. ^6^6 CgHg, Benzene (80-5°). CyHg CgHglCHs), Toluene (111°). CeH,(CRs),, Xylenes (3) o- = (142°); m-=(137°);2)-=(137°) C6H5(OH2.CH3), Ethyl-benzene (134°). CeHgC 0113)3 Trimethyl-benzenes (3). s = Mesitylene (163°). a = Pseudo-cumene (169°) v=Hemellithene (175°). 06H4(OH3)(02H5) Methyl-ethyl- benzenes (3) (e.g. 162°). ^6^5(03117) Propyl-benzenes 1. Normal-propyl- (157°) 2. Iso-propyl- ( = Oumene)(153°). C10H14 ^6112(0113)4 Tetra-methyl- benzenes (3): s=Durene [79°] (190°). a=Iso-durene (195°). v=Prehnitene [-4°] (204). ^6113(0133)2(02115) Dimethyl- ethyl- benzenes (6 isomers possible). ^6^14(02115)2 Diethyl-benzenes (3). CeH,(CH3)(C3H,) Oymene (176°) (6 isomers possible). ^^6115(04119) Butyl- benzenes (4 possible) (167 -180°). 06H(OH3)5, Penta-methyl-benzene, [51-5°] (231°); CoH^iCQHii), Amyl-benzene, etc. C12H18 06(CH3)6, Hexa-methyl-benzene, [164°] (263°); 06H3(02Hg)3, Tri-ethyl-benzene, etc. ^14^22 CqTL^{CqH.i>^), Octyl-benzene, etc. C6(C2H5)6, Hex-ethyl-benzene [126°] (305°). 324 XVII. BENZENE HYDROCARBONS. The benzene hydrocarbons are for the most part colourless liquids insoluble in water but readily soluble in alcohol and ether, which distil without decomposition; (durene, and penta- and hexa-methyl-benzenes are crystalline). They possess a peculiar and sometimes pleasant ethereal odour, and burn with a very smoky flame. In addition to benzene itself, the presence has been proved in petroleum of its methyl derivative toluene, the three xylenes, the three tri-methyl- benzenes and durene. Modes of formation. 1. By treating a mixture of brominated hydrocarbon and iodo- (or bromo-) alkyl with sodium in ethereal solution, (the Fittig reaction, A. 131, 303, analogous to the Wurtz reaction, p. 38) : CeH^Br -t- CH3I + 2Na = CgHs.CHg + Nal + NaBr ; C6H4Br(C,H5) + C2H5I + 2Na = C6H4(C2H5)2 + Nal + NaBr ; C6H4Br(CH3) +C3H^I + 2Na = C6H4(C3H^)(CH3) + Nal + NaBr 2. By the action of methyl chloride upon benzene or its homologues in presence of aluminium chloride, {Gustavson, the so-called Friedel and Crafts'^ reaction) : CgHg + CH3CI = CgH^CHg + HCl CgHe + 2CH3CI = C6H4(CH3)2 + 2HC1, etc. This reaction is, like the preceding one, capable of very wide application ; by means of it all the hydrogen atoms in benzene can be gradually replaced by methyl. Zinc and ferric chlorides act in the same way as chloride of alum- inium, while ethyl chloride and other haloid compounds, such as chloroform and acid chlorides, may replace methyl chloride. (See respectively triphenyl-methane and the ketones ; cf also B. 14, 2624 ; B. 16, 1745 ; Ann. de chim. et phys. [6] 1, 419.) In addition to this synthetical action, aluminium chloride also exerts a breaking up" or differentiating action on the homologues of benzene, e.g. it partly transforms toluene into benzene and xylene, and so on, (B. 17, 2816 ; 18, 338 and 657). Related to the Friedel- Crafts reaction is the Zincke reaction with zinc dust, (see diphenyl-methane). Alcohols also, like their haloid ethers, are capable of reacting in an analogous manner in presence of ZnClg : CfiHe + C4H9OH = C6H5.O4HC, + HgO. FORMATION ; CONSTITUTION. 325 3. The benzene hydrocarbons result from their respective carboxylic acids by the splitting off of the carboxyl, e.g., by distillation with soda-lime : CgH^C02H = C^jHg + ; CeH,(CH3)C02H = CeH5.CH3 + CO^. 4. From sulphonic acids (p. 37 4) by the separation of the SOgH-group : CeH3(CH3),S03H + H^O = + H,SO,. This reaction can be effected by dry distillation, by heating with concentrated hydrochloric acid to 180°, by distillation of the ammonium salt {Caro), or by treatment with superheated steam, e.g., in presence of some concentrated sulphuric acid, (Armstrong, Kelhe.) 5. From the amido-compounds by transforming these into diazo-compounds (p. 360), and boiling the latter with absolute alcohol or with stannous chloride. 6. By distillation of the phenols (or ketones) with zinc dust. 7. For synthesis, see above. The method of synthesis for paraffins, which was mentioned on p. 39, is also occasionally applicable (see propyl-benzene). Isomers and Constitution. The table given on p. 323 shows that the benzene hydrocarbons, from CgH^Q on, exist in many isomeric modifications ; thus, isomeric with the three xylenes we have ethyl-benzene, with the three tri-m ethyl-benzenes the three methyl-ethyl-benzenes and the two propyl-benzenes, with durene, cymene, and so on. The constitution of these hydrocarbons follows very simply from their modes of formation. A hydrocarbon C^qH^^ for instance, which is obtained by means of CH3CI by the Friedel- Crafts reaction, can only be a tetra-methyl-benzene ; another of the same empirical formula C^qH^^, which has been prepared from bromo-benzene, butyl bromide and sodium, must be a butyl-benzene ; while a third, from ^-bromo-toluene, normal propyl iodide and sodium, must be a ^-propyl-toluene (^-methyl-N-propyl-benzene), etc. The synthesis therefore determines the constitution. The (carbon containing) groups CH3, CgHg, etc., which replace hydrogen in benzene, are termed " side chains." 326 XVII. BENZENE HYDROCARBONS. According to the number of side chains it contains, a benzene hydrocarbon is converted by oxidation into a benzene- mono-, di- or tri-, etc., carboxylic acid, e.g. benzoic acid, CgH^.COgH, m-, p-phthalic acid, G^^{GO^)^^ etc. In this way a further means is afforded of determining the constitu- tion of the compounds in question. If, for example, a hydrocarbon C9H12 yields a benzene-tri-carboxylic acid, CgH3(C02H)3, upon oxidation, it must contain three side chains, i.e., must be a tri -methyl-benzene ; should a phthalic acid on the other hand result, then it can only be an ethyl-toluene. Since cymene yields p- (or tere-) phthalic acid, C6H4(C02H)2, in oxidation, its two side chains must be in the ^-position towards one another. The respective isomers resemble each other closely in physical properties, their boiling points — for example — lying very near together. The ortho-derivatives often boil at about 5° and the meta- at about 1° higher than the para-compounds; the boiling point rises with an increasing number of methyl groups, (cf. p. 26). Behaviour. 1. The benzene hydrocarbons are as a rule easily nitrated and sulphurated, mono-, di- and even tri-derivatives being all usually capable of preparation, according to the conditions. It is only the H-atoms of the benzene nucleus which enter into reaction here, in accordance with the theory which regards the side chains as paraffinic residues, as which they behave. Hexa-methyl-benzene can thus neither be nitrated nor sulphurated. 2. Oxidation. Benzene can only be oxidized with difficulty; permanganate of potash converts it slowly into formic and oxalic acids, some benzoic acid and phthalic acid being produced at the same time. These doubtless result from some previously formed diphenyl. The homologues of benzene, on the other hand, are readily oxidized to carboxylic acids, the benzene nucleus remaining unaltered, and each side chain — no matter how many carbon atoms it may contain — being converted as a rule into carboxyl. Nitric acid allows of a successive and often a partial oxidation of individual side chains ; chromic acid mixture (KgCrgOy -f H2SO4) acts more energetically, converting all the side chains in the p- and m- Behaviour. 327 compounds into carboxyl, and completely destroying the o-compounds. The latter may be oxidized to benzene-carboxylic acids by KMn04 in the cold. As is manifest from these two points, the homologues of benzene differ somewhat materially from benzene itself ; the H-atoms of the side chains show a different function to those of the benzene nucleus, the former behaving like the hydrogen atoms in a paraffin. It thus follows that toluene and the higher homologues may be derived from methane etc. by replacement of H by CgHg, "phenyl," etc. 3. Eeduction. As mentioned on p. 312, benzene and most of its derivatives are capable of taking up six atoms of hydrogen. Benzene itself is only converted into hexa- hydro-benzene, CgH^g, with difficulty, but toluene, xylene and mesitylene combine with hydrogen more easily, when they are heated with phosphonium iodide, PH4I, to a rather high temperature, the compounds C^Hg.H2, CgHj^.H^ and CgH^g-He being formed. The two former can then be made to take up more hydrogen by energetic reaction. Benzene hydride and its analogues are colourless liquids insoluble in water and of somewhat lower boiling point than their mother com- pounds, into which they can be readily retransformed by oxidation, either by heating with sulphur or by means of fuming nitric acid, nitration also taking place in the latter case. They are identical with the naphthenes " found in certain varieties of petroleum. 4. Behaviour with halogens. Chlorine and bromine react differently, according to the conditions. In direct sunlight they yield with benzene the addition-products CgHgClg and CgH^jBrg, while in diffused daylight, especially in presence of a little iodine, SbClg or M0CI5, they give rise to the substitu- tion products CgH^Cl, CgH^Br, etc. (For further details see pp. 61 and 334.) Those hydrocarbons which do not contain their full complement of hydrogen behave exactly like un- saturated hydrocarbons, in so far that they are capable of taking up bromine until the point of saturation, C^X^^, is reached, (B. 21, 836). 5. Chromium oxychloride, CrOgCla, converts the benzene hydrocar- bons into aromatic aldehydes, (p. 398). Cumene or phenyl-propane. 328 XVIL BENZENE HYDROCARBONS. The numerous * condensations ' which benzene can undergo with oxygenated compounds in presence of ZnClg, ^2^5 H2SO4, and with chlorinated compounds in presence of AlgClg, are of great interest; thus benzene yields diphenyl-ethane with aldehyde and sulphuric acid, and benzophenone with benzoic acid and phosphorus pentoxide. The Hydrocarhon OgHg. Benzene, CgH^. Discovered by Faraday in 1825, and detected in coal tar by Hofmann in 1845. Benzene is obtained from the portion of coal tar which boils at 80-85°, by fraction- ating or freezing. It may be prepared chemically pure by distilling a mixture of benzoic acid and lime. The ordinary benzene of commerce usually contains thiophene and thus gives the indophenin reaction, but it may be freed from it by repeated shaking up with small quantities of sulphuric acid. M. Pt. 4° ; B. Pt. 80.5° ; Sp. Gr. at 0°, 0.9. It burns with a luminous smoky flame and is a good solvent for resins, fats, iodine, sulphur, phosphorus, etc. When its vapour is led through a red-hot tube, diphenyl is obtained. Benzene hexa-hydride, CeHe-Hg. B. Pt. 69°. Sp. Gr. at 0°, 0.76. Benzene hexa-chloride, OgHgClg, is produced by the action of excess of chlorine on benzene in sunlight. It is a solid mass, which is broken up into tri-chloro- benzene and hydrochloric acid on distillation, or when treated with alkalies. Benzene hexa-bromide, CgHgBre. M. Pt. 212". The Hydrocarbon C^-Hg. Toluene, C^Hg, = CeH^.CHg. Discovered in 1837. For- mation : by the dry distillation of balsam of Tolu and of many resins. Synthesis according to Fittig (see above). Prepara- tion : from coal tar, in which it is found accompanied by thio- tolene. Toluene is very similar to benzene. It boils at 110°, and is still liquid at — 28°. Cr02Cl2 converts it into benzoic aldehyde, and HNO3 or CrOg into benzoic acid. XYLENES, ETC. 329 Toluene di-hydride, C^jHsiHaj.CHa, and -hexa-hydride, CgHglHej.CHg, are liquids boiling respectively at 105- 108° and 97°. Hydrocarbons, CgHjo. {a) m-, andj^-Di-methyl-benzenes or Xylenes, CgH4(CH3)2. The xylene of coal tar consists of a mixture of the three isomers, 77i-xylene being present to the extent of 70 to 85 p.c. These cannot be separated from one another by fractional dis- tillation. ??i-xylene is more slowly oxidized by dilute nitric acid than its isomers and can thus be obtained with relative ease. For the separation of those isomers by means of H2SO4, see B. lO, 1010, 14, 2625; 17, 444; and for their recognition see B. 19, 2513. Benzene and toluene yield chiefly ortho-, together with a little para- xylene, when subjected to the Friedel- Grafts synthesis, (B. 14, 2627). 1. o-Xylene, which can be prepared synthetically from o-bronio- toluene, methyl iodide and sodium, is oxidized to carbonic acid by the chromic acid mixture, and to o-toluic acid, C6H4(CH3)C02H, by dilute nitric acid ; it is difficult to nitrate. 2. m-Xylene or Iso-xylene also results from mesitylene, CgH3(CHg)3, 1 : 3 : 5, when this is first oxidized to mesitylenic acid, CgH3(CH3)2C02H, and the latter then distilled with lime. Dilute nitric acid only oxidizes it at a temperature of 120°, while chromic acid mixture converts it into iso-phthalic acid, C6H4(C02H)2. It yields a Tetra- and Hexa-hydride, CgH^^.H^ and CgHiQ.Hg. 3. 2^-Xylene. Is prepared e.g. from ^-bromo-toluene or, better, p-dibromo-benzene, methyl iodide and sodium, (B. lO, 1356 ; B. 17, 444.) M. Pt. 15°. Dilute nitric acid oxidizes it to ^-toluic acid, C6H4(CH3)C02H, and terephthalic acid, C6H4(C02H)2. {h) Ethylbenzene, C6H5-C2H5. Results from QHgBr and C2HgBr by the Fitlig reaction, from styrene, — C2H3, and HI, and from CgHg and C2H5CI by the Friedel-G rafts reaction. Is oxidized to benzoic acid. EydrocarhonSy C^Hig, (see table). The most important of these are : 330 XVII. BENZENE HYDROCARBONS. (a) Tri-methyl-benzenes. 1. Mesitylene, 1:3: 5-tri-methyl-benzene, 0^113(0113)3. This is contained in coal tar along with its two other isomeric tri- methyl-benzenes (" tar-cumene " ), and can be prepared from acetone or allylene (p. 320). It is a liquid of agreeable odour. Nitric acid oxidizes the side chains one by one, while chromic acid mixture decomposes it completely. It does not form any isomeric substitution products and has therefore a symmetrical constitution, (Ladenburg, A. 179, 160.) Mesitylene hexa-hydride, CgHig.He, boils at 138°. 2. Vsevido-cumenef 1 :2'A-tr{-methyl-benzene. Present in coal tar. It is separated from mesitylene, not by fractional distillation, but by taking advantage of the sparing solubility of pseudo-cumene-sulphonic acid, (B. 9, 258). Its constitution follows from its formation from bromo-p-xylene, 1:4:2, and also from bromo-m-xylene, 1:3:4, by the Fittig reaction. Nitric acid oxidizes the side chains successively. 3. Hemellithene, l:2:3-tri-methyl-benzene, (see B. 15, 1853). Present in coal tar, (B. 20, 903). (b) Ethyl-toluenes, C6H4(CH3)(C2H5). The m- and ^-compounds are known. (c) Propyl-benzenes, CgH^ — CgH^. These are oxidized to benzoic acid. 1. N-Propyl-benzene, CgHg — CHg — CHg — CH3, results from bromo- benzene and normal propyl iodide by the Fittig reaction, and also from benzyl chloride, CgHg. CH2CI, and zinc ethyl. 2. Iso-propyl-benzene or Cumene, CgH^ — CH=(CIl3)2, is produced by the distillation of cumic acid, CgH4(C3lI^)(C02H), with lime ; from benzene and iso- or normal propyl iodide by means of AlgCl^, in the latter case with molecular rearrange- ment (p. 65) ; and from benzylidine chloride, CgHg — CHClg, and zinc methyl, this last method furnishing proof of its con- stitution. For the transformation of the normal- into the iso-propyl group in cumene and cymene derivatives, see B. 18, Ref. 152. Hydrocarbons^ CiqHj^. (See table.) Among these may be mentioned UNSATURATED BENZENE HYDROCARBONS. 331 Durene, 1:2:4:5- or s-tetra-methyl-benzene, C(3H2(CH3)4, which has recently been found in coal tar and can be prepared from toluene and methyl chloride by the Friedel-Crafts reaction, or from dibromo-m-xylene (from coal tar xylene), methyl iodide and sodium, (A. 216, 200). It is a solid, M. Pt. 79°, and possesses a camphor-like odour. For its constitution, see B. 11, 31. Both of its isomers are known (see table). Methyl-propyl-benzenes, CgH4(CH3)C3H^. The most impor- tant of these is cymene or p-methyl-N-propyl-benzene. It is found in Eoman cummin oil (Cuminum cyminum), and results upon heating camphor with PgS^ or, better, PgO^, also by heating oil of turpentine with iodine, etc. It has been synthetically built up from ^-bromo-toluene, N-propyl iodide and sodium. It is a liquid of agreeable odour, and yields either j9-toluic, terephthalic or cumic acid upon oxidation, according to the conditions. Isomeric with the above are the Butyl-benzenes, C6H5(C4H9), of which three are known. Hydrocarhon, O^gH^g. Hexa-methyl-benzene, melUteney C6(CH3)g, crystallizes in prisms or plates which melt at 169°. It can neither be sulphurated nor nitrated, (see p. 326). KMn04 oxidizes it to mellitic acid, C6(C02H)6. For the higher homologues see table, p. 323. B. Unsaturated Benzene hydrocarbons. The benzene hydrocarbons containing less hydrogen comport themselves on the one hand like benzene itself, and on the other like the unsaturated hydrocarbons of the fatty series, combining readily with hydrogen, halogen, halogen hydride, etc. They are derived from the olefines or acetylenes by the exchange of H for CgH^, thus : (CgIl5)CH=CH2, styrene or phenyl-ethylene ; {CqH.^)G=GR, phenyl-acetylene. styrene, CeHg.CH^CHg, occurs along with other compounds in storax (styrax officinalis), and in the juice of the bark of Liquidambar orientale. It results upon heating cinnamic acid (p. 417) with water to 200°: 332 XVIII. HALOID SUBSTITUTION PRODUCTS. CfiHg— CH-CH— COoH = CgHg— CH=CH2 + CO2. For its preparation see A. 195, 131. Styrene is a liquid like benzene and of agreeable odour. B. Pt. 146°. It changes on keeping into the polymeric meta-styrene, an amorphous transparent mass, and goes into ethyl-benzene when heated with hydriodic acid. Addition of HBr converts it into a-bromo-ethyl-benzene, CgHg — CHg — CHgBr. Phenyl-acetylene, CeHg.C^CH, is produced e.g. by the separation of CO2 from phenyl-propiolic acid (p. 419) : CeHg-CEEC— CO2H = CeHg— C=CH + COg. It is a pleasant smelling liquid boiling at 139°, and gives proof of its being an acetylene derivative by yielding white and pale yellow explosive metallic compounds with solutions of silver and cuprous oxides. It combines with water to aceto-phenone, CgHg.CO.CHg, when it is dissolved in sulphuric acid and the solution is diluted with water. XVIII. HALOID SUBSTITUTION PRODUCTS. Summary, The numbers in the square brackets [...] indicate melting, and those in the round ones (...) boiling points. CeH^Cl Chloro-benzene (133°). C6H4CI2 Di-chloro-benzenes 0- : (179°) ; m- : (172°) ; p- : [56°], (173°). CeH^Br Bromo-benzene (154°). Di-bromo-benzenes 0- : (224°) ; m- : (219°) ; p- : [89°], (219°). lodo-benzene (185°). Di-iodo-benzenes (e.g., 285°). CeHgCls, (3), Tri-chloro-benzenes (208° to 218°). C6H2GI4, (3), Tetra-chloro-benzenes. CetlClg, (1), Penta-chloro-benzene. CgCle, (1), Hexa-chloro-benzene [226°], (332°). CeH4Cl(CH3) ^^6^6 CH2CI (3) Chloro-toluenes (156°-160°). Benzyl chloride (179°). 115^12(^113) ^6^5 — CHCI2 (6) Di-chloro-toluenes (e.g., 196°). Benzal chloride (206°). etc. ^6^5 — CCI3 Benzo-tri-chloride (213°). C6H3C1(CH3)2, (6) Chloro-xylenes. C6H4(CH3)(CH2C1), Xylyl chlorides. C6H4(CH2Br)2, (3) Xylylene bromides, etc., HALOID SUBSTITUTION PRODUCTS. 333 Haloid substitution products in immense number are derived from the benzene hydrocarbons by the exchange of hydrogen for halogen. They are either colourless mobile liquids or crystalline solids, insoluble in water but readily soluble in alcohol and ether, which distil unchanged, and are distinguished by their peculiar odour and also, in part, by their irritant action upon the mucous membrane. They are heavier than water. The substitution products of benzene itself and those of its homologues have to be distinguished from one another. In the former the halogen is bound very firmly, far more so than in methyl chloride, ethyl iodide, etc. ; it cannot be exchanged for OH (through AgOH), or for NHg (through NH3), etc., sodium almost alone being capable of bringing it into reaction, (see the Fittig reaction^ p. 324). The substitution products of toluene, etc., on the other hand, do not all show a similar behaviour. Some of them, e,g., chloro-toluene, contain the halogen bound very fast, while in others of them, e.g., benzyl chloride, the halogen atoms enter into reaction as readily as do those of the haloid sub- stitution products of the methane series. After oxidation, which transforms all the side chains into carboxyl (p. 326), the halogen remains in the former compounds, with formation of chlorinated, etc., benzoic acids, e.g., CgH^Cl — COgH, but it is eliminated in the latter, benzyl chloride e.g. giving benzoic acid, CgHg — COgH. From this it follows that the halogen is present in the one case in the benzene nucleus, and in the other in the side chain. This is in accordance with the conclusion arrived at on p. 327, of toluene being phenylated methane; chloro-toluene, C6H4C1.(CH3), is quasi-methylated chloro-benzene and is therefore stable, while benzyl chloride, CgHg— CHgCl, is quasi-phenylated chloro-methyl, and is therefore very active chemically. The same relations repeat themselves in xylene and the other homologues of toluene, so that it is always easy to arrive ?t the con- stitution of a compound from the behaviour of its halogen atoms .and from its products of oxidation. Thus a compound CyH/^l^, which yields mono-chloro-benzoic acid upon oxidation, has manifestly the formula CgH^Cl— CHgCl (chloro-benzyl chloride). 334 XVIII. HALOID SUBSTITUTION PRODUCTS. For the capability of reaction of the chlorinated benzenes, cf. also p. 318. The boiling points of the (position-) isomeric substitution products (o-, m-f and p-compounds), always lie near to one another, and those of the other isomers also are not very far apart from these. Modes of formation, 1. By the action of chlorine or bromine upon aromatic hydrocarbons there result, according to the conditions, either addition or substitution products, the latter class particularly easily in presence of iodine. (Cf. p. 327, also B. 18, 607.) Iodine only substitutes directly under the conditions already detailed at p. 61. From benzene all the chlorinated derivatives up to CgClg can be obtained in succession, the last named compound resulting with the aid of MoCl^, ICI3, etc., at a somewhat high temperature. A hexa-bromo-benzene also exists, but not a hexa-iodo-compound. In the case of toluene and its homologues the halogen enters the benzene nucleus alone, if the operation is performed in the cold, with the exclusion of direct sunlight or with the addition of iodine ; while, if its vapour is led into the boiling hydrocarbon, or if the experiment is conducted in sunlight and without addition of iodine, it goes almost exclusively into the side chain, (Beilstein; Schramm; see also B. 13, 1216). 2. From compounds containing oxygen (the phenols, aromatic alcohols, aldehydes, ketones, and acids), by the action of phos- phorus pentachloride or bromide : CgH^.OH + PCI5 = CgH^Cl + POCI3 + HCl. 3. From the (nitro- or) primary amido-compounds, these being first converted into diazo-compounds (p. 360). Upon boiling the latter with cuprous chloride or bromide, they are transformed into the corresponding chlorine or bromine com- pounds {Sandmeyer, B. 17, 1633, 2<">50) and upon boiling with iodide of potassium, i^tvj iodo-substitution products : OoH,.N=N.Cl = CgH^Cl + N2; CgH,.N=N.Cl + KI = CgH.I + N2 + KCI. The bromine compounds also result upon boiling the diazo-per- bromides (p. 304) witli absolute alcohol, and the fluorine compounds by a similar reaction, ( Wallachy A. 236, 255). CHLORO- AND BROMO-BENZENES, ETC. 336 4. By heating the haloid-substitution acids with lime ; CgH^Cl-COaH ^ C,B,Cl + H,0. Mono-chloro-, bromo-, and iodo-benzene are colourless liquids of peculiar odour. Their boiling points have been given in the summary. Di-chloro- and Di-bromo -benzenes exist as o-, m-, and ^j-compounds. The p-, and also the o-compounds in smaller amount, are obtained directly (see p. 318), while the m-compounds are obtained indirectly from m-dinitro-benzene according to method 3, The para-compounds are solid and the others liquid. The significance of the di- and tri-bromo-benzenes for the benzene theory has been already indicated at p. 314. The tri-chloro-benzene which results by direct substitution has the (asymmetric) constitution 1:2:4. It may also be formed by the separation of 3HC1 from CgHg.Clg. Hexa-chloro- and -bromo-benzenes are produced by the thorough chlorination or bromination of benzene, toluene, naphthalene, etc., and also from carbon tetrachloride and bromide, as given at p. 321. They are solid and can be distilled. Fluo-benzene, CqH^Y, is a liquid boiling at 85°; the entrance of fluorine into the benzene molecule thus alters its boiling point only in slight degree. Mono-chloro- and -bromo-toluenes, CgH^C^CHg) and CgH4Br(CH3). These mono-substitution products of toluene likewise exist as di-derivatives of benzene in the o-, m-, and ^-modifications. When toluene is chlorinated or brominated, as given on p. 334, the para- and ortho-compounds are formed in approximately equal quantities. m-Chloro -toluene is obtained from chloro-^-toluidine, C6H3.C1(NH2)CH3 (from ^^-toluidine and CI), according to method 3. The ^-compounds are solid in the cold and the others liquid. Oxidation by HNO3, Cr03 or KMn04 converts them into the haloid-benzoic acids, but chromic acid mixture must only be used in the case of the p- and m-f and not in that of the o-compounds, as it completely disintegrates the latter. Benzyl chloride, CgH^— CHgCl (Cannizaro), results upon chlorinating boiling toluene, and benzyl bromide in an analogous manner; the latter can be converted into benzyl iodide by iodide of potassium. The behaviour of these com- pounds shows them to be the haloid ethers of benzyl alcohol, 336 XIX. NITRO-SUBSTITUTION PRODUCTS. C^^Hg — CHg.OH, from which they result by the action of halogen hydride, and into which they are transformed by prolonged boiling with water or, better, with a solution of carbonate of potash. Boiling with potassium acetate yields the acetic ether of this alcohol, with potassium sulph-hydrate the mercaptan, and with ammonia the amine base. They are colourless liquids, heavier than water, which boil without decomposition and, like o-bromo-toluene, etc., irritate the mucous membrane of the nose and eyes exceedingly. Oxidation converts them into benzoic acid. Benzyl chloride is used on the large scale for the preparation of oil of bitter almonds and for modifying the tints of dyes. Benzal chloride, benzylidene chloride, CgH^ — CHClg, and Benzene tri-chloride, C^H^ — CCI3, are produced by the further chlorination of boiling toluene and also by the action of PCI5 upon the corresponding oxygen compounds, benzoic aldehyde, CgHg — CHO, benzoic acid, CgH^ — CO2H, and benzoyl chloride, CgHg — COOL They are liquids resembling benzyl chloride, and are reconverted into the original oxygen compounds by superheating with water, and into benzoic acid by oxidizing agents. For their relations to cinnamic acid and malachite green, see these. CMoro-bromo-benzenes, C6H4ClBr, Cblor-iodo-benzenes and other mixed derivatives also exist in large number. Substitution compounds of unsaturated hydrocarbons are likewise known, e.g. jS-Bromo-styrene, CgHg — CBr=CH2, a-Bromo-styrene, CgHg— CH=CHBr, etc., etc. XIX. NITRO-SUBSTITUTION PRODUCTS OF THE AROMATIC HYDROCARBONS. When benzene derivatives (not merely hydrocarbons) are treated with concentrated nitric acid, most of them are easily dissolved, with evolution of heat, and transformed into nitro- compounds which are precipitated on the addition of water. According to the conditions of the experiment and the nature of the compound to be nitrated, one or more nitro-groups enter NITRO COMPOUNDS ; PROPERTIES. 337 the molecule (see e.g, phenol). The iiitro-groups substitute in the nucleus and only very seldom in the side chain. Summary, C,^,m,) CeH^iNO^)^ CeH3(N03)3 Nitro-benzene. o-, m-, and ^^-Dinitro- s-Trinitro-benzene. Liq. B. Pt. 206°. benzenes. Solid. M. Pt. 121°. Solid. M. Pts. 118°, 90°, and 171°. 0; m-,p-Nitro-toluenes. B.Pts.223°,230°and238° 7?-compound solid. CeH3(CH8)(N02)2 Dinitro-tolaeues. C6H3(CH3),N02 Nitro-xylenes. e.g. 1:3:4, (CH3 in 1) Liq. B. Pt. 238°. CeH^CllN-O^) Nitro-chloro-benzenes. etc. C6Pl2(CH3)3N02, etc. Nitro-mesitylene. Solid. M. Pt. 42^ B.Pt. 255°.. CeBr^lNO^)^ Tetrabromo-dinitr 0- benzene. Nitro-compounds are also produced by the action of nitrous acid upon diazo-compounds, in the presence of cuprous oxide, {Sandmeyer, B. 20, 1414) : CgHg— N r =:]Sr— C I + NHO2 = CgHg-NOs + HCl + N2. Diazo-benzene chloride. Nitro-benzene. The nitro-compounds are for the most part pale yellow liquids which distil unchanged and volatilize with water vapour, or colourless or pale yellow needles or prisms ; some- times they are also of an intensive yellow or red colour. Many of them explode upon being heated. They are heavier than water and insoluble in it, but most of them are readily soluble in alcohol, ether and glacial acetic acid. The nitro-group in most aromatic nitro-compounds is bound very firmly, as in the case of the nitro-methanes, and is not exchangeable for other groups. Like the latter compounds also, they are easily reduced in acid solution to the correspond- ing amido-derivatives ; in alkaline solution they are converted into azoxy-, azo- and hydrazo-compounds, (see pp. 366 and 367). (606) ' Y 338 XIX. NITRO-SUBSTITUTION PRODUCTS. On the other hand, they cannot be prepared according to mode of formation 1 for nitro-methane (p. 101), i.e. by the action of AgNOg on CgHgCl etc. Nitro-benzene, C6H5(N02), {Mitscherlich, 1834). Eesults, with evolution of heat, on the gradual addition of benzene to fuming nitric acid, or on treating it with a mixture of sulphuric and the calculated quantity of nitric acid. It is a yellowish liquid with an intensive odour of oil of bitter almonds, which solidifies in the cold ; M. Pt. + 3°- Dinitro-benzenes, CgH4(N02)2. These are produced when benzene is boiled with fuming nitric acid; in this, as in all analogous cases, the two nitro-groups take up the meta-position to one another, very little of the o- and j9-compounds being formed, and, by recrystallizing from alcohol, pure m-dinitro- benzene is obtained in long colourless prisms or needles. The o-compound crystallizes in tables and the ^-compound in needles, both being colourless ; they are prepared indirectly by elimination of NH2 from the corresponding di-nitranilines. Upon reduction there result first the three nitranilines and then the phenylene-diamines (pp. 352 and 359). o-Nitro -benzene exchanges a nitro-group for hydroxyl when boiled with caustic soda, and for amidogen when acted on by ammonia, with the formation of o-nitro-phenol, C6H4(N02)(OH) and o-nitraniline, C(jH4(N02)(NH2)- The m-compound is oxidizable by KgFeCyg to a- and /3-dinitro-phenol. Nitro-toluenes, CgH4(CH3)(N02). When toluene is nitrated, the ;p- and o-compounds, with hardly any of the m-compound, result. The first is solid, crystallizing in large prisms, and the second liquid, the latter being used as a perfume under the name of "oil of mirbane.'' m-Nitro-toluene can be prepared indirectly from m nitro-^-toluidine, CgH3(CH3) (N02)(NH2), by the Griess reaction (p. 363). Further nitration gives rise to : Dinitro-toluenes, C6H3(CH3)(N02)2, of the constitution CHgiNOgiNOg = 1:2:4 and 1:2:6, the two nitro-groups being again in the m-position to one another in both cases. (Cf. p. 316.) NITRO- AND NITROSO-COMPOUNDS. 339 Most of these nitro-compounds are of great technical importance, on account of their convertibility into amine bases. Chloro- and Bromo-nitro- benzenes. When chloro- or bromo-benzene is nitrated, p-chloro- (or bromo-) nitro-benzenes, and in smaller quantity the o-compounds, result. The m-compounds must be prepared indirectly by replacing an amido-group in m-nitraniline by halogen. The ^-derivatives have a higher melting point than their isomers, and the m-compounds for the most part a higher one than the o -derivatives, this IsiW frequently repeating itself in other cases also. The ^^-derivatives are usually also less soluble in alcohol. The o- and p -compounds, but not the m-, exchange halogen for hydroxyl when boiled with potash, and for amidogen when heated with ammonia. In Trinitro-chloro-lbenzene, C6H2(N02)3C1, the chlorine atom has been rendered so easily exchangeable by the acidifying influence of the nitro-groups that the compound behaves as an acid chloride ; hence the name " picryl chloride," the chloride of picric acid (p. 318). Nitro-xylenes, -mesitylene and -pseudo- cumene are also known in many isomeric modifications, (see table). We are further acquainted with nitro -derivatives of styrene, viz., o-, m-, and p -Nitro- sty renes, C6H4(N02)(C2H3), which can be prepared by indirect methods, and also a -Nitro -styrene, C6H5CH=CH(N02), which results directly from the nitration of styrene and contains the nitro- group in the side chain, a necessary consequence of its preparation from benzoic aldehyde and nitro-methane by means of zinc chloride, thus : C^Hg.CHO + CH3NO2 = C(jH5.CH=CH(N02) + H2O. This is one of those relatively rare cases in which the nitro-group enters the side chain upon direct nitration. (Cf. B. 18, 935, 2438 ; 19, 836.) Nitroso-derivatives of the Hydrocarbons. There exist but few aromatic nitroso-compounds, i.e. substances which contain the nitroso-group, NO, in place of a benzene hydrogen atom. Nitroso -"benzene, C5H5(NO), is produced by the action of NO. CI upon mercury di-phenyl dissolved in benzene.* It is only known mixed with benzene ; the mixture is a green liquid of sharp smell, which yields aniline when treated with tin and hydrochloric acid, and azo-benzene with aniline acetate. * Mercury di-phenyl, Hg(C(.H5)2, is an analogue of mercury di-ethyl ; it results from the action of mercury upon mono-bromo-benzene, and crystallizes in needles or prisms melting at 120°. 340 XX. AMIDO-COMPOUNDS. Nitroso-derivatives of tertiary amines result directly by the action of nitrous acid upon the latter. (See Nitroso-dimethyl-aniline, C6H4(NO)N(CH3)2, p. 354.) XX. AMIDO-DERIVATIVES OP THE BENZENE HYDROCARBONS. (See table, p. 341). Aniline, the simplest of the aromatic bases, may be regarded (1) as benzene in which a hydrogen atom is replaced by amidogen, amido-benzene "), or (2) as ammonia in which a hydrogen atom is replaced by phenyl, OgH^ — , (^'phenyl- amine"). According to the former view, amido-compounds are derived from all the benzene hydrocarbons, and not only monamines (containing NHg), but also di-amines (2NH2), tri-amines, etc. ; according to the latter, the phenyl group may enter anew with the formation of secondary or tertiary amines. Secondary and tertiary amines, and even quaternary ammonium compounds may also result from the entrance of alcohol radicles into the above monamines, diamines, etc. NHg, etc., may likewise substitute in the side chain. An extraordinarily large number of aromatic bases are thus theoretically possible and also actually known (see table). They closely resemble in some ways the nitrogen bases of the alcohol radicles, form salts with acids — frequently with evolu- tion of heat — and double salts with chloride of platinum, possess a basic odour, give rise to white clouds with volatile acids, and distil for the most part unchanged, etc. Speaking generally, however, they are weaker bases than the alcoholic amines, since the phenyl group, CgH^, possesses a negative character, and not — like the alcohol radicles — a positive; thus the salts of diphenylamine are decomposed even by water, and triphenylamine no longer possesses basic pro- perties, while dimethyl-aniline has a strongly marked basic character. [Continued on p, 342. AMIDO-COMPOUNDS. 341 Summary, Primary. Secondary. Tertiary. 1 ■ MONAMINES. 1 Aniline [-8°] (183°). (CeH,),,NH Diphenylamine [54°] (302^^). Trlphenylamine [127']. C«H4(CH3)NH2 Toluidines. 0- : m- : p- : (199°), (197°), [45°] (198°). C6H3(CH3)2NH2 (6) Xylidines,(e.r7. 217°). C6H2(CH3)3NH2 Pseudo-cumidine [62°]. C6H4(N0,)NH2 NitrodiilinGS, 0- : m- : p- : [71°] [114°] [147°] (285°). CeH5(CH2.NH2) Benzylamine (183°). C6H5(CH2.CH2.NH2) Phenyl-ethylamine \ (193°), etc. Alhylat CeH5.NH.CH3 Methyl-aniline (192°). C6H5.NH.C2H5 Ethyl-aniline (204°). Nitroso-{ (CA)2N.N0 Nitroso-diphenylamine [66°] Acid D C6H5.]SrH(C2H30) Acetanilide [114°]. CO.(NHC6H5)2 Carbanilide [235°]. CS(NHC6H5)(NH,) Phenyl-thio-urea [154°] etc. ed Bases. C6H5.N'(CH3)2 Dimethyl-aniline (192°). C6H5.N(CoH5)2 Diethyl-aniline (213°). ierivatives. CeH,(N0).F(CH3), Nitroso-dimethyl-aniline [85°] erivatives, Methyl-acetanilide [99°]. COCN.QHg) Phenyl cyanate (163°). CS(N.CeH,) Phenyl-isothiocyanate (222°) etc. 1 Diamines, etc. / C6H4(NH2)2, Phenylene-diamines, (o-i [102°] (252°) \ m- : [63°] (287°) [p-: [1471(267°). C,H3(CH3)(NH2)2 Toluylene-diamines e.g. 1:2:4 [99°] (286°). C6H4(NH2)[N(CH3)2] Amido-dimethyl-aniline, p- ; [4r] (257°). C6H4(NH2)(NH. CgHg) Amido-dipheny lamine, p- : [66°]. ■^^'\C6H4'nH2 P-^iamido-dipheny lamine [158°]. NH[C6H4. N(CH3)2]2 75-TetramethyI-diamido- diphenylamine. Triamido-benzenes. \ Tetramido-benzene. 342 XX. AMIDO-COMPOUNDS. The diamines have a more strongly basic character than the monamines and are more readily soluble in water. A. Primary Monamines. Isomers. The isomerism of the aromatic is in part analogous to that of the fatty amines (p. 113), e.g., dimethyl-aniline is isomeric with the methyl-toluidines and the xylidines. Cases of isomerism are also caused by the amido-group being present in the benzene nucleus in the one case and in the side chain in the other. Finally all the isomeric relations of the aromatic hydrocarbons (bi-derivatives, etc.) may also come into play here. Constitution. As already seen at pp. 114 et seq., amines are very easy to characterize as primary, secondary, etc. Not only their modes of formation but also their behaviour shows whether the amido- group is present in the benzene nucleus or in the side chain. Modes of formation. 1. The most important mode of pre- paration of the primary aromatic bases, and also of the di-amines, etc., consists in the reduction of the nitro-compounds : CeHj.NO^ + STL, = 2Rp + CeH^.NH^ Nitro-benzene. Aniline. CeH,(N0,)2 + = AR,0 + CJi.m,), V > ^ Y T Di-nitro-benzenes. Phenylene -diamines. The reduction of nitro- to amido-compounds goes on espe- cially well in an acid solution, e.g., by the gradual addition of the latter to a warm mixture of tin or stannous chloride and hydrochloric acid. On a manufacturing scale iron and a limited amount of hydrochloric acid are used (Bechamp), also frequently zinc dust and hydrochloric or acetic acid. Am- monium sulphide (Zinin), ferrous sulphate and baryta water, etc., also effect the reduction. Sulphide of ammonium acts more mildly than tin and hydrochloric acid and is therefore of special value for the partial reduction of dinitro- compounds (see nitraniline). An alcoholic solution of stannous chloride containing hydrochloric acid may also be used for this purpose, (B. 19, 2161). Amines also result from the reduction of nitroso-compounds, (see nitroso-dimethyl-aniline. ) PRIMARY AMINES ; FORMATION. 343 2. By heating phenols with the compound of zinc chloride and ammonia, or of calcium chloride and ammonia, to 300° (Tl/erz), secondary amines being formed at the same time : CeHg.OH + HNH2 = CgHg.NHa + H^O. This reaction goes on more easily in the presence of negative groups, e.g. with the nitro-phenols, (B. 19, 1749). 3. By distilling amido-acids with lime, sometimes by merely heating them alone : C6H4(NH2)C02H = C6H5.NH2 + CO2. 4. By heating secondary and tertiary bases (such as mono- and dimethyl-aniline), which have been formed by the intro- duction of the alcohol radicle into primary aromatic bases, with strong hydrochloric acid to 180°, the alcoholic radicle can be eliminated again in the form of alkyl chloride with repro- duction of the primary bases : C6H5.N(CH3)2 + 2HC1 = CeH5,NH2 + 2CH3CI. If the temperature is raised higher, the separated CH3CI (i.e. chloro-alkyl) acts further upon the primary amine, causing the replace- ment of hydrogen of the benzene nucleus by alcoholic radicle and the consequent formation of primary bases which are homologous with the original amine ; in this way toluidine hydrochloride results upon heating hydrochloride of methyl-aniline to 335° : C^Hg.NHCCHg), HCl = CgHg.NHs + CH3CI = C6H4(CH3)NH2, HCl. The methyl groups which thus enter the nucleus take up the 0- or p-, and not the w,-position, to the regenerated NHg. In an analogous manner one finally obtains from trimethyl-phenyl-am- monium iodide, 0(^115. N(CH3)3l, mesidine hydriodide, €2112(0113)3. NHg, HI. Hydrochloride of diphenylamine does not show this reaction. 4^. The formation of {e.g. ) amido-isobutyl-benzene, by heating aniline hydrochloride with isobutyl alcohol to 250°, depends upon the same principle, thus : C6H5.NH2, HCl + C4H9OH = C6H4(C4H9).NH2, HCl + H2O. 5. For the formation of amido-compounds from nitro-haloid-benzenes or o-dinitro-benzenes, see p. 339. 6. By heating the potassium salts of sulphonic acids with sodio- amide, NaNH2, (B. 19, 902). 7. The aromatic amines cannot be obtained by heating chloro-benzene, etc. with ammonia (see p. 333). Benzylamine, however, and all analogously constituted bases, which contain 3U XX. A]\rrDO-COMPOUNDS. the NH2-group in the side chain, result by the methods which apply in the preparation of amines of the fatty series. Thus benzylamine is formed by the action of ammonia or, better, of acetamide upon benzyl chloride (the latter method giving, rise, of course, to the readily saponifiable acetyl-benzylamine), by reduction of benzaldehyde-hydrazone (p. 373 ; B. 19, 1924), etc. The above also holds good for secondary and tertiary bases of this kind. Properties. The primary monamines are partly liquid, partly solid and beautifully crystallizing bases. They are colourless when pure, but readily become brown when exposed to the air, and possess a weakly basic and not disagreeable odour. Aniline is somewhat soluble in water (1 : 31), its homologues less so. Behaviour, 1. Most of them yield with acids salts which crystallize well and which are usually readily soluble in water. They do not however unite with very weak acids, such as carbonic, and they are therefore separated from their salts in the free state by sodium carbonate. Sodium acetate often acts in the same way (when no acetates exist). They yield double compounds with many metallic salts, especially with platinic chloride [e.g. 2(C6H^N,HC1) + PtClJ, and with gold chloride; also with stannous and zinc chlorides, etc. The platinum double salts are often sparingly soluble and therefore suited for the isolation of the bases. Besides these there exist the so-called addition salts of those bases, e.g. aniline' zinc chloride, 2C6H7N + ZnClg, aniline mercuric chloride, 2C(iH7N + HgClg, and so on. 2. When aniline is heated with potassium or sodium, the hydrogen is replaced by metal with formation of the compounds CgHgNHK and CgHgNKg. These yield di- and triphenylamine with bromo-benzene, and decompose immediately with water. 3. For behaviour with sulphuric and nitric acids and with halogens, see pp. 352 and 375. 4. The primary aromatic bases are analogous in every respect to the primary fatty ones, methyl iodide, benzyl chloride etc. transforming them into secondary, tertiary and quaternary compounds : PRIMARY AMINES ; BEHAVIOUR. 345 C.Hg.NH., + CH3I = C„H,.NH(CH3), HI ; CeH5.NH(CH3) + CH3I = C„H,.N(CH3)2, HI ; CeH5.N(CH3)2 + CH3I = C«H,.N(CH3)3l. The secondary and tertiary bases can be liberated from their hydriodides by soda, but moist oxide of silver must be used in the case of the ammonium bases, (see p. 115). 5. Aldehydes react with the primary bases, with elimination of water, thus : CH3.CHO + 2C(5H5.NH2 = CH3.CH(NH.C6H5)2 + HgO. Ethylidene-diphenyl-diamine. Benzoic aldehyde, however, reacts as follows : C6H5.CHO + NH2.C6H5 = CgHs.CH-N— CgHg + HgO. ^ — , Benzylidine-aniline. 6. Just as acids yield , amides with ammonia, so are they capable of forming '^anilides" with aniline, etc., e.g, acetic acid and aniline give acetanilide : C6H5.NH2 + C2H3O.OH = C6H5.NH(C2H30) + H2O. These anilides may either be looked upon as acetylated etc. amines or as phenylated etc. amides, the formula C2H30.NH(C(3H5) corresponding with the latter view. They are in every respect analogous in their chemical behaviour to the ordinary amides, especially to the alkylated amides (p. 180), being broken up again into their components by alkalies, and resulting by analogous methods, e.g. by heating the acid or, better, its anhydride or chloride with the amine in question, thus : C,H4(CH3)NH2 + CH3.C0C1 = C6H4(CH3).NH.C2H30 + HCl. Toluidine. Acet-toiuide. 7. When warmed with chloroform and alcoholic potash, the primary bases, like those of the fatty series, yield iso-nitriles of stupefying odour. When they are warmed with carbon bisulphide thio-ureas result, and from the latter iso-thiocyan- ates, e.g, on treatment with phosphoric acid, (cf. pp. Ill and 276). 346 XX. AMIDO-COMPOUNDS. 8. Nitrous acid converts the primary aromatic amines in acid solution into diazo-compounds (p. 360), and in the absence of acids into diazo-amido-compounds (p. 364). The diazo-com- pounds go into phenols when boiled with water, so that NHg is here indirectly exchangeable for OH, as is the case directly with the amines of the fatty series. When the amines are warmed with ethyl nitrite in alcoholic solution, the amido group is eliminated, i.e. replaced by hydrogen (p. 362). 9. The oxidation products of the primary bases are very various, phenols, quinones, azo-compounds, aniline black, etc., resulting according to the conditions; a mixture of aniline and toluidine yields fuchsine. 10. The bases which contain the amide in the side chain possess, in contradistinction to the purely aromatic amines, the character of the amines of the fatty series. They are thus e.g. not convertible into diazo-compounds. B. Secondary Monamines. We have to distinguish here between purely aromatic secondary amines, such as diphenylamine, and mixed secondary bases which contain an aromatic residue and a radicle of the fatty series. Modes of formation. 1. Mixed secondary bases result from the primary by treatment with methyl iodide, etc. (Hofmann), (see p. 112). This reaction does not usually stop short with the introduction of one alcoholic radicle, but extends further with the formation of tertiary bases. In order to avoid this, the alkyl iodide etc. may be allowed to act upon the acetylated primary bases, e.g. acetanilide [or upon their sodium compounds {Hepp),] and the resulting acetyl compound be saponified : C6H5.]SrH(C.,H30) + CH3I = C6Hg.N(CH3)(C2H30) + HI. The secondary bases are separated from the tertiary by treatment with nitrous acid (see below, under Nitrosamines). 2. The purely aromatic secondary amines result upon heat- ing the primary bases with their hydrochloric acid salts : SECONDARY MONAMINES. 347 CgH^.NHH + CeH^.NH^HCl = ^^c^s^nh, HCl + NH3. Unsymmetrical" bases (i.e. those containing two different radicles) have also been prepared in this way. 3. Diphenylamine can further be got by heating phenol with aniline zinc chloride, (B. 17, 2632), and : 4. By the action of bromo-benzeile upon potassium-aniline. Behaviour. 1. The mixed secondary bases have strongly marked basic properties, while the purel}^ aromatic have not, (cf. p. 340). 2. For the breaking up of the mixed bases by hydrochloric acid, see p. 343. 3. The hydrogen of the imido-groiip is replaceable by an alcoholic or acid radicle, and also by potassium or sodium : (CeH5),NH + CH3I = HI + (CeH5)2N(CH3) Methyl-diphenylamine. (CeH,)2NH + (C2H30),0 = C,H,0, + (0^11^(0^130) Acetyl-diphenylamine. 4. The secondary bases give neither the iso-nitrile nor the "mustard oil" reaction (p. 114). 5. With nitrous acid, nitrosamines are formed, (cf. p. 115): CeH5NH(CH3) + NO.OH = H^O + C6H5.N(NO).(CH3) ^ , ^ Nitroso -methyl-aniline. These Nitrosamines are neutral oily liquids insoluble in water, which regenerate the secondary bases when heated with stannous chloride or with alcohol and hydrochloric acid, and which yield hydrazines with mild reducing agents. They serve for preparing the secondary bases pure, since they alone are precipitated by sodium nitrite as non-basic oils from the acid solution of a mixture of primary, secondary and tertiary bases. When such nitrosamines are digested with alcoholic hydrochloric acid, a molecular rearrangement takes place and compounds of the nature of nitroso-dimethyl-aniline (p. 318) are formed, the nitroso-group going into the nucJeus, (0. Fischer and Hepp, B, 19, 2991) : CeHg— N(N0)-CH3 = C6H4(NO)-NH.CH3. 348 XX. AMIDO-COMPOUNDS. 0. Tertiary Monamines. These also are either purely aromatic or mixed (fatty- aromatic) bases. Modes of formation. 1. The latter result upon alkylating the primary or secondary bases (cf. p. 345), which, however, may be heated with methyl alcohol and hydrochloric acid instead of methyl chloride or iodide. 2. Tri-phenylamine, a purely aromatic base, is formed by the action of bromo-benzene upon di-potassium-aniline : CeHgNKg + 2C6H5Br = [Q.TL,)^^ + 2KBr. Behaviour, 1. Unlike the mixed (fatty-aromatic) amines, the purely aromatic tertiary amines are incapable of forming salts. 2. They do not yield iso-nitriles with CHCI3, iso-thiocyanates with CSg, or acid derivatives with acid chlorides, but they do yield quaternary compounds with methyl iodide. 3. Nitrous acid acts upon the tertiary aromatic bases (which thereby differ from the tertiary bases of the fatty series) with the formation of nitroso-compounds which contain the NO- group linked to the benzene nucleus : CeH,.N.(CH3)2 + NO.OH = G,11^(^0).^{GR^\ + H^O. V ^ ^ ^ Nitroso- dimethyl- aniline. Such nitroso-derivatives are, in contradistinction to the nitrosamines already mentioned, changed into amido-com- pounds (di-amines) by reduction, (see below). D. The Quaternary Bases C3]'respond entirely with the quaternary bases of the fatty series. Trimethyl-phenyl-ammonium hydroxide, CgH5.N( 0113)3. OH, for in- stance, is a colourless, strongly alkaline, bitter substance which breaks up into dimethyl-aniline and methyl alcohol when heated. Some of the tertiary amines hLwever are not capable of yielding ammonium compounds. DIAMINES AND TRIAMINES. 349 E. Di-amines, Tri-amines, etc. Formation. 1. By the reduction of the dinitro-hydrocarbons or of the nitro-amido-compounds. In this way the phenylene- diamines, CgH4(NH2)2, result from the dinitro-benzenes (see table, p. 341.) The o- and ^-diamines are best obtained from the 0- and j?-nitro-amido-compdunds (p. 352). 2. Further, a new amido-group can be introduced in the p-position into a monamine, especially a secondary or tertiary such as C gHg — N(CH3)2, by first transforming the latter into an azo-dye (e.g. benzene-azo- dimethyl-aniline, p. 371) hy uniting it with diazo-benzene chloride, and decomposing this by reduction (p. 370). Tri-amido compounds can be prepared in a manner exactly analogous. 3. For the preparation of di-amines from nitroso-compounds of tertiary amines, see amido-dimethyl-aniline, C6H4(NH2)[N(CH3)2]. 4. Tetr-amido-benzene, C6H2(NH2)4, is formed by nitrating (pre- viously acetylated) di-amido-benzene, and reducing the resulting dinitro-compound, the two acetyl groups being finally split off, (B. 20, 328). Behaviour. The diamines and triamines are solid compounds which crystallize in tables or plates and distil unchanged. They are soluble in water, especially upon warming. Though originally without colour, most of them quickly become brown in the air, their instability increasing with the number of amido-groups present. In accordance with the readiness with which they are oxidized, they frequently yield characteristic colourations with ferric chloride, e.g, o-phenylene-diamine a dark red, and 1:2: 3-tri-amido-benzene a violet and then a brown colour. The three isomeric varieties of diamines differ materially in their behaviour : (a) Ortho- diamines. 1. Ferric chloride yields a crystalline precipi- tate of yellow-red needles with a solution of o-phenylene-diamine. 2. The acid derivatives of the o-compounds change into compounds of the nature of amidines, the so-called " anhydro-bases," through the formation of intramolecular anhydride ; thus, by the reduction of o-nitr- acetanilide by tin and hydrochloric acid, there results *'phenylene- ethenyl-amidine," a derivative of ethenyl-amidine, CHg— C^^^ (A. 209, 339) : 350 XX. AMIDO-COMPOtJNDS. C6H4C-CH3 + H,0. Compounds of this nature are also obtained by heating o-diamines with acids. 3. A similar reaction takes place between aldehydes and diamine hydrochlorides, with the formation of the so-called aldehydine bases," HOI being set free, {Ladenburg, B. 11, 590; 19, 2025). In the same way glyoxal, CHO — CHO, yields quinoxaline, and many of the double ketones react analogously. With CSNH, isothiocyanates are formed, (A. 221, 1). 4. Nitrous acid converts the o-diamines into the so-called *'azimido- compounds," compounds which contain three atoms of nitrogen, e.g. o-phenylene-diamine into azimido- benzene, = amido-azo-phenylene, ^6H4<^>N (B. 9, 214, 1524; 15, 1878, 2195; 19, 1757). (6) Meta-diamido-bases. 1. These form yellow-brown dyes with nitrous acid, even when only traces of the latter are present (see azo- colouring matters). 2. They yield azo-dyes with diazo-benzene chloride (see chrysoidin). 3. With nitroso-dimethyl-aniline, or on oxidation together with para-diamines, blue colouring matters are obtained, and, upon boiling, red (see toluylene red). 4. With CNSH, phenylene-di-ureas are formed (A. 221, 1). (c) Para-diamido-compounds. 1. When warmed with FcgClg or, better, with MnOg + H2SO4, quinone, C6H4O2 (or a homologue), results and may be recognized by its odour. 2, All p-diamines which contain a primary NHg-group yield violet or blue colouring matters containing sulphur and belonging to the thio- diphenylamine group (p. 356), when 'Fe^Clg is added to their dilute acid solution containing sulphuretted hydrogen. Aniline, Aniline, amido-benzene, phenylamine, CqR^.^JI^' Was first obtained in 1826 by Unverdorben, from the dry distillation of indigo, and termed by him crystalline " ; then Eunge found it in coal tar in 1834 and called it ''cyanol." In 1841 Fritsche i^repared it by distilling indigo with potash and gave it the name of aniline, while in 1842 Zinin obtained it by the reduction of nitro-benzene and called it "benzidam." It was accurately investigated by A, W. Hofmann in 1843. ANILINE. 351 Occurrence. In coal tar and also in bone oil. Preparation. Since 1864 aniline has been prepared on a manufacturing scale by reducing nitro -benzene with iron filings and a regulated quantity of hydrochloric acid, and distilling with steam. It is a colourless, oily, strongly refract- ing liquid of weak but peculiar odour, which quickly turns yellow or brown in the air and is finally converted into a resin. M. Pt. -8°, B. Pt. 184°, Sp. Gr. 1-036. It dissolves in 31 parts of water, has no action upon litmus, and is a weaker base than ammonia in the cold, but displaces the latter at higher temperatures. It is poisonous, burns with a smoky flame, and is a good solvent for many compounds which are otherwise difficult of solution, e.g, indigo and sulphur. The salts have an acid reaction. The behaviour of aniline has been investigated with the utmost care. Oxidation in alkaline solution leads to azo- benzene, while arsenic acid produces chiefly violaniline, C^gHj^Ng, a violet colouring matter which also results under the oxidizing influence of nitro-benzene. A solution of free aniline is temporarily coloured violet by one of bleaching powder, this reaction being an extremely delicate one. A solu- tion in concentrated HgSO^ is first coloured red and then blue b}^ a small grain of bichromate of potash. A solution of KgCrgO^ produces in an acid solution of aniline sulphate a dark green and then a black precipitate of aniline black, which finally goes into quinone, CgH^Og. A mixture of aniline and toluidine is oxidizable to fuchsine, mauveine, etc., and a mixture of aniline and ^-diamines to safranines (p. 503). Chlorine yields trichlor-aniline and iodine mon-iodo-aniline, while chlorate of potash and hydrochloric acid produce chloranil. For the action of NgOg, see diazo-compounds ; of HNO3, nitraniline ; and of H2SO4, sulphanilic acid. When aniline is heated with glycerine and concentrated sulphuric acid in the presence of nitro-benzene, quinoline is obtained ; when it is boiled with sulphur, thio-aniline, (CgH4.NH2)2S ; and when it is heated with urea, diphenyl-urea, CO(NHC6H5)2, with elimination of NH3. Many reactions analogous to the last-named are known. Salts. Aniline hydrochloride, CgH5.NH2, HCl: large colour- 352 XX. AMIDO-COMPOUNDS. less tables which become greenish-grey in the air and distil unchanged. Aniline sulphate, (CgH^N)2H2S04 : beautiful white pjates, difficultly soluble in water. The double salt with platinic chloride, (CgH^N, HC1)2, PtCl^, crystallizes in moderately soluble yellow plates. Substitution Products of Aniline. Aniline is much more readily substituted by halogens than benzene, an aqueous solution of chlorine or bromine causing substitution of as many as three atoms of hydrogen, while iodine produces mono- iodaniline. In the preparation of mono-chlor- (or brom-) aniline, the aniline must be protected" by using it in the form of its acetyl compound, acetanilide. When this is suspended in water, it is mostly transformed by chlorine into jo-chlor-acetanilide, which readily yields p-chlor- aniline on saponification ; the latter forms colourless crystals, M. Pt. 75°, B. Pt. 235°. The o- and m-compounds, which are both liquid, are prepared indirectly, e.g. by the reduction of o- or m-chloro- (or bromo-) benzene. The basic character is weakened in the mono-chlor- (and brom-) anilines by the entrance of the halogen, this being the case particularly in the o-compounds. It is still more striking in a-triehlor-aniline, QH2Cl3(NH2) (crystals, volatile without decomposition), which no longer combines with acids, o- and p-chlor-anilines are only capable of taking up two more atoms of chlorine with the formation of trichlor- aniline : NHgi CI: CI: CI = 1.2.4.6 ; 7?i-chlor-aniline, on the other hand, can be further chlorinated to tetra- and penta-chlor-anUine. The Brom-anilines resemble these in every respect. Nitmnilines, Aniline is likewise attacked far more violently than benzene by concentrated nitric acid, and therefore, when it is wished to prepare the mono-nitro-compounds, the aniline must again be ^* protected," either by using its acetyl compound or by nitrating in presence of excess of concentrated sulphuric acid. In the latter case all three nitranilines result, the m-compound preponderating. When acetanilide is nitrated, 2?-Nitracetanilide, CgH4(N02)(NH.C2H30), together with some of the o-compound, result, both of them being easily saponified by potash or hydrochloric acid. NITRANILINES, ETC. 353 The 0- and j9-nitranilines are also formed upon heating o- and p-chloro- or bromo-nitro-benzenes, or the ethers of the correspondhig 0- and 29-nitro-phenols, C6H4(N02)(O.C2H5), or these nitro-phenols them- selves with ammonia to 180°, (cf. B. 19, 1749). o-Nitraniline may also be prepared by nitrating acetyl-sulphanilic acid, (B. 18, 294). The nitranilines are further obtained by the partial reduction of the corresponding dinitro-benzenes, e.g, by means of sul- phide of ammonium. The three nitranilines crystallize in yellow needles or prisms, readily soluble in alcohol but only very slightly in water, (cf. table, p. 341). The o- and m-compounds are volatile with steam, but not j?-nitraniline. They go into phenylene-diamines on reduction. The 0- and ^-nitranilines are converted into nitro-phenols when boiled with alkalies, the former more easily than the latter, thus : C6H4(N02)(NH2) + H.OH C6H4(N02)OH + NH3. Di- and tri-nitranUines, C6H3(N02)2(NH2) and C6H2(N02)3(NH2), are likewise known ; the latter, which is termed Picramide, and which crystallizes in yellow needles, M. Pt. 186°, comports itself as the amide of picric acid, since it is readily transformed into the latter compound by saponifying agents, (cf. p. 318). ^9 -Nitroso -aniline, CgH4(NO)NH2, is formed by the action of am- monium acetate upon ^-nitroso-phenol, OH being exchanged for NHg. It crystallizes in blue needles, and is very similar to nitroso-dimethyl- aniline in behaviour, (cf. p. 322, also B. 20, 2471). For Aniline-sulphonic acids, see p. 375. Alkylated Anilines. Methyl-aniline, CgH5NH(CH3), (Hofmann), is obtained from the methyl-aniline of commerce (from aniline hydrochloride and methyl alcohol) either by means of its nitroso-compound or as given at p. 345, (cf B. 10, 327, 588). It is lighter than water, and has an odour like that of aniline but stronger and more aromatic. Its sulphate is soluble in ether and non-cry stallizable. A solution of bleaching powder colours it violet and then brown. For its ti ans- formation into p-toluidiue, see p. 343. (50G) i5 354 XX. AMIDO-COMPOUNDS. Methyl-aniline-nitrosamine, C6H5.N(NO)(CH3), is a yellow oil of aromatic odour without basic properties, which can be distilled with steam but not alone. It shows the Liehermann (nitroso) reaction, giving an intensive ** king's-blue " colouration when it is warmed with phenol and sulphuric acid, and the mixture then diluted with water and saturated with caustic potash. This reaction is characteristic of all the nitrosamines and of many other nitroso-compounds. Under the influence of alcoholic hydrochloric acid it undergoes molecular trans- formation into ;9-nitroso-monomethyl-aniline, C6H4(NO) — NH.CH3, a compound precisely similar to nitroso-dimethyl-anlline and crystalliz- ing in green plates or steel blue prisms. Di-methyl-aniline, CgH5.N(CH3)2, (Hofmann\ is an oil of sharp basic odour, solidifying in the cold. Its salts are not crystallizable. It combines with methyl iodide, even in the cold, to the compound N(CgH5) (0113)31, which breaks up into its components upon distillation. The corresponding ammonium base is mentioned on p. 348. Bleaching powder only colours dimethyl-aniline a pale yellow. The H-atom in it, which is in the j?-position as regards the N(CH3)2, is easily exchange- able, e.g. for a nitroso-group, when acted on by NgOg. Dimethyl-aniline consequently yields compounds of somewhat complex composition with acid chlorides, aldehyde, etc. ; for example, tetramethyl-diamido-benzophenone or, finally, methyl violet with carbonyl chloride, COClg, leuco-malachite green with benzoic aldehyde, etc. Mild oxidizing agents, such as chloranil, convert it into methyl-violet. p-Nitroso-dimethyl-aniline, C6H4(NO).N(CH3)2, crystallizes in beauti- ful green plates or tables of M. Pt. 85° ; its HCl-salt forms yellow needles. It is used for the preparation of dyes (methylene blue, indophenol, toluylene red). It is oxidized by KMn04 or KgFeCyg to 2>Nitro-dimethyl-anmne, C6H4(N02).N(CH3)2, M. Pt. 162° (a compound which is also obtained directly together with the m-compound by the nitration of dimethyl-aniline), and is reduced by nascent hydrogen to amido-dimethyl-aniline, C6H4(NH2).N(CH3)2, which belongs to the p-diamines (p. 360). Boiling with soda converts it into nitroso-phenol and dimethylamine. Since nitroso-phenol probably has, according to p. 384, the formula C6H4<^^^^^^ (quinone-oxime), the nearly related nitroso-dimethyl-aniline and its hydrochloride may possibly have the following formula?, (cf. B. 20, 532) : DI- AND TRIPHENYLAMINES. 355 The free base. >0. The hydrochloride. Di- and Tri-phenylamines, Diphenylamine, (CgH5)2NH, {Hofmann), crystallizes in white plates of flowery odour and burning taste which are almost insoluble in water, but readily soluble in alcohol, ether and ligroin. The hydrochloride, C^g^ii^j HCl, is a white crystalline meal which turns blue in the air. A solution of diphenylamine in concentrated HgSO^ is coloured an in- tensive blue by traces of nitric acid, this reaction being a very delicate test for the latter. When diphenylamine is heated with formic acid and zinc chloride, it yields acridine. It is used for the preparation of diphenylamine blue. Diphenyl-nitrosamine, {C6Hg)2N.NO, is obtained by the use of ethyl nitrite and crystallizes in bright glancing yellowish tables. o-Dinitro- diphenylamine, (C6H4.N02)2NH, forms red needles, and the analogous p-compound yellow prisms. Hexa -nitre -diphenylamine crystallizes in yellow prisms and has the properties of a weak acid, this being due to the acidfying influence of the nitro-groups upon the imido-hydrogen ; its ammonium salt is the yellow dye Aurantia. For the Amide- and Oxy-cempeunds of diphenylamine, which are tabulated on p. 341, and the colouring matters derivable from them, see also safranine and indophenol (p. 356). Methyl-diphenylamine, (CeHgjaN.CHo, is a liquid which results on methylating diphenylamine ; it also is employed on a manufacturing scale. TMe-diphenylamine, C12H9NS, = NHS , is the leuco-compound of CgHs— NH2 Thionine, N'<^ , whose HCl salt is Lauth's Violet ; and the I ^C«H,— NH hydrochloride of Methylene Blue {Caro, 1876), a very valuable blue dye, C6H3— N(CH3)2 especially for cotton, has the constitution N<^ , I ^CeHa— N(0H3)2C1 J {Bernthsen, A. 230, 1 ; cf. also pp. 350 and 360.) (b) Indamines and Indophenols. As Indamines are designated, according to Nietzhi, those green or blue colouring matters which are produced by the action of nitroso-dimethyl- aniline upon amines, e.g. dimethyl-aniline, or by the conjoint oxidation of p-diamines and monamines in the cold. The simplest representative of this class is the indamine '*Plienylene Blue," C12H11N3, = N<^6H4-NH2^ which results from the oxidation of a mixture of aniline and /?-phenylene-diamine, and is converted by reduction into ^j-diamido-diphenylamine, NH(CgH4.NH2)2 (p. 341). Dimethyl-phenylene Green," CigHi9N3, is obtained in an analogous manner from ^^-amido-dimetliyl-aniline and dimethyl-aniline, and yields tetramethyl-diamido-diphenylamine, NH[C6H4.N(CH3)2]2 (p. 341), on reduction. The indamines are unstable compounds but are of import- ance as being intermediate products in the manufacture of safranine. Oxygenated compounds, WiW^s ''Indophenols," are likewise derived here by the exchange of NH2 or N(CH3)2 for OH, which is achieved by warming with alkali ; e.g. Phenol Blue (indo-aniline), N<;^6H4.N(CH3)2^ is produced by the oxidation of amido-dimethyl-aniline with phenol. Its analogue, a-Napthol Blue, N<^&^''^^^3^2^ prepared by means of napthol (p. 466), is a colouring matter which finds technical application. Such compounds exchange N(CH3)2 for OH when boiled with a solution of NaOH ; thus, from phenol blue there results Indophenol (" quinone- ANILIDES. 357 phenol-imide "), N<^^y4-^^^ a dye of phenolic nature (p. 376), which dissolves in alcohol to a red, and in alkali or ammonia to a blue solution. It may also be obtained by the action of phenol upon quinone chlor- imide (see quinones) : yO /O /C6H4.OH C,h/ I + CeHgOH = CeH / | = N<( + H( \n.C1 \N-C6H4.OH, I NC6H4.O Quinone I I chlor-imide. Indophenol. and also by the oxidation of p-amido-phenol with phenol. Its leuco- compound is /^-Dioxy-diphenylamine, NH(C6H4.0H)2, a substance which unites in itself the properties of diphenylamine and a diatomic phenol. (Seep. 376; of. B. 16, 2843; 18, 2912.) Acid Derivatives of Aniline, Anilides. Acetanilide, CgHj^.NH.(C2H30), is most conveniently pre- pared by boiling aniline with glacial acetic acid for several days. It crystallizes in beautiful white prisms which are readily soluble in hot water, alcohol, ether and benzene ; M. Pt. 115% B. Pt. 295°. It is easily saponifiable (cf. p. 345). Its imido-hydrogen is replaceable by sodium with the formation of the crystalline Sodium-acetanilide, CgH5.N.Na(C2H30), which is again decomposed by water (see p. 181). Acetanilide is used, under the name of **antifebrine," as a medicine in cases of fever. TMo-acetanilide, CH3 — CS.NHCgHg, results upon heating acetanilide with P2S5 (analogously to aceto-thiamide, p. 184), and from it Imido- thio-compounds, Amidines, etc. can be prepared (cf. p. 185). Acetanilide yields the dye Flavaniline when heated with zinc chloride. In nearly all those compounds of the fatty series which are ammonia derivatives of alcohols, acids or alcohol-acids, and which still contain unreplaced ammoniacal hydrogen, the latter can be substituted either wholly or partially by phenyl, for the most part indirectly. The number of these phenylated 358 XX. AMIDO-COMPOUNDS. (tolylated, xylylated, etc.) compounds is thus extremely large. Among them may be mentioned : NH C H Phenyl-glycocoU, * ^ ^, from chloracetic acid and aniline ; CO 'OH Phenyl-imido-butyric acid, CH3— ClNCeHg) — CH^— CO2H, from aniline and aceto-acetic ether ; Carbanilide or diphenyl-urea, CO(NHCgH5)2, from aniline and carbon oxy chloride, (cf. p. 272) ; Phenyl cyanate, COiN.CgHg, a sharp-smelling liquid exactly analogous to the cyanic ethers, and whose vapour gives rise to tears, from COCI2 and fused aniline hydrochloride ; Phenyl isothio cyanate, CeHgNiCS, (B. Pt. 220"), a liquid possessing all the characteristics of the mustard oils ; Diphenyl- thio-urea, CS(NHC6H5).2, from aniline and carbon bisulphide, (glancing plates, M. Pt. 154°, decomposed into phenyl isothiocyanate and tri- phenyl-guanidine by boiling with concentrated HCl) ; Mono-, Tri-, and Tetra-phenyl-thio-ureas ; Phenylated guanidines, etc., (cf. table, p. 341). Eomologues of Aniline. 1. The three Toluidines, C6H4(CH3)(NH2), result from the reduction of the three nitro-toluenes, ^-toluidine (Musjpratt and Hofmann, 1845) being solid, and o-toluidine liquid; they are also present in coal tar. The crude nitro-toluene of commerce yields a mixture of 0- and p- with a little m-toluidine upon reduction ; the two first may be separated from one another, e.g. by taking advantage of the relatively sparing solubility of p-toluidine oxalate, (cf. B. 16, 908). m-Toluldine, which is liquid, may be prepared from m-nitro- toluene or m-nitro-benzaldehyde, (cf B. 15, 2009). The boiling points of the three isomeric toluidines are almost identical (see table, p. 341), but the melting points of their acetyl compounds differ widely, the o-compound melting at 107°, the p- at 147°, and the m- at 65° ; these are therefore of value for the character- ization of the toluidines. o-Toluidine is coloured violet by a solution of chloride of lime, and blue by sulphuric and nitrous acids and also by ferric chloride, but not ^-toluidine. For their conversion into fuchsine by oxidation, see p. 451. If, during oxidation, the amido-group be protected by the introduction of acetyl, the methyl can be oxidized to carboxyl and in this way an (acetyl derivative of) amido-benzoic acid obtained, while the amido-compounds are transformed into azo-com- pounds by KMn04. BENZYLAMINE, ETC. ; DI- AND TRIAMINES. 35d Compounds such as Methyl- and dimethyl-p-toluidines, acet-toluide, C(.H4(CH3).NH(C2H30), di-tolylamine, (C(.H4.CH3),NH, phenyl-tolyl- amine, NH[C6H5](C6H4.CH3), nitre -toluidines, C6H3(CH3)(NO,)(NH2), etc., have been prepared in large numbers, and are in every respect similar to the corresponding phenyl compounds. 2. Isomeric with the toluidines is : Benzy lamina, CgH^ — CH2.NH2, the alcoholic amine of benzyl alcohol, a colourless basic liquid which distils un- changed. It is best prepared, at first as the acetyl com- pound, CgHg — CH2.NII(C2H30), by heating benzyl chloride, C^jHg — CH2CI, with acetamide, NH2(C2H30). Its behaviour is entirely analogous to that of methylamine, as the phenyl derivative of which it is to be regarded, (cf. p. 346). 3. Xylidlnes, £[3(0113)2. NH2. According to theory, these may exist in six modifications, all of which are known. Amido-o -xylene (CHgiCHgiNHa = 1:2:4) is solid, melting at 49°, while the other five are liquid. The boiling points lie between 212° and 226°. The xylidine of commerce contains five of these compounds, but principally m-xylidine (CH3:CH3:NH2 = 1:3:4), B. Pt. 212°, and p-xylidine (1:4:2) ; it is used for the manufacture of azo-dyes. 4. Amido-trimethyl-benzenes, C6H2(CH3)3NH2. The hydrochloride of amido-trimethyl-benzene is formed when HCl-xylidine is heated with methyl alcohol to about 300°. In this way there have been prepared \|/- (Pseudo-)cumidine or amido-pseudo-cu7nene{ CHg :CH3 :CH3:NH2 = 1 :2 :4 :5), M. Pt. 63°, B. Pt. 235°, and Mesidine or ajnido -mesitylene {l:S:5:2), a> liquid, B. Pt. 230°. i/'-Cumidine is also used for manufacturing azo- dyes. Isomeric with the above bases are amide - ethyl - benzene C6H4.(NH2)(C2H5), and amido-propyl benzene, C6H4(NH2)(C3H7), of which the /^-modifications, for instance, are obtained by heating aniline with the alcohol in question and chloride of zinc. 5. Amido-isobutyl-benzene, C6H4(NH2)(C4Hc)), has likewise been prepared. Tetramethyl-amido -benzenes {amido-durene, prehnidine), C6H(NH2)(CH3)4, m-isocymidine, C6H3(NH2)(CH3)(C3H7), and penta- methyl-amido-benzene, C6(NH2)(CH3)5, are also known. Diamines, Triamines, etc. Of the Phenylene- diamines, C6H4(NH2)2, the meta-compound (Zininy 1844) is the most easily prepared, by reducing m-dinitro-benzene. It 360 XXI. DIAZO- AND AZO-COMPOUNDS ; HYDRAZINES. crystallizes in tables. Nitrous acid converts it into Bismarck brown, the presence of the merest trace of this acid being shown by the yellow colouration it gives with the diamine, (cf. B. 14, 1015). Para- phenylene- diamine {Hofmann, 1863), crystallizes in plates and its HCl-salt in white tables ; an acid solution of it yields the violet dye thionine (p. 356) with H^S and FegClg. Its unsymmetrical dimethyl- derivative, p-amido- dimethyl-aniline, C6H4(NH2)[N(CH3)2], which may be prepared as given at p. 349, but most easily by the reduction of the azo-dye helianthin (p. 371 ; B. 16, 2235), gives methylene blue with Fe^Cle and H2S, this being the most delicate test for sulphuretted hydrogen known, and it is coloured a magnificent purple by FegCIg in dilute neutral solution. Ortho-phenylene- diamine (Griess, 1861), is transformed into hydro-phenazine (p. 502) when heated with pyro- catechin. o-p-Toluylene- diamine, C6H3(CH3)(NH2)2 (1:2:4), is, as a m-diamine, easily obtained by reduction of the common dinitro-toluene (p. 338). It is used for the preparation of toluylene red, etc. m-^-Toluylene- diamine, C6H3(CH3)(NH2)2 (1:3:4), is the o-diamine which is most easily prepared, viz., by nitrating acet-^-toluide, saponifying and reducing. The Xylylene-diamines, CeH2(CIl3)2(NH2)2, are homologous with the above. XXI. DIAZO- AND AZO-OOMPOUNDS ; HYDRAZINES. A. Diazo-Oompounds. The primary amido-compounds of the benzene series differ characteristically from those of the fatty series in their behaviour towards nitrous acid. The latter are converted into alcohols by NgOg without the formation of intermediate products, (cf. p. 114): C2H5.NH2 + NO.OH = C2H5.OH + N2 + H2O. The aromatic amines can indeed undergo an analogous transformation, but there result in their case well-characterized intermediate products, the so-called diazo-compounds, which are of especial interest both scientifically and technically (cf. p. 379). They were discovered by P. Griess in 1860 DIAZO-COMPOUNDS ; FORMATION. 361 and were carefully investigated by him, (A. 121, 257; 137, 39) ; their constitution was elucidated by KekulL Formation, When nitrogen trioxide is led into a cream of aniline nitrate and dilute nitric acid, the aniline salt dissolves and a liquid is obtained from which alcohol and ether precipitate beautiful long white needles of diazo-benzene nitrate, (CgH5N2).N03. These are tolerably stable in dry air but quickly decompose in moist, and they are distinguished by the violence with which they explode when heated or struck. The base itself, diazo-benzene (p. 364), appears to have the formula (CgH^ — N2)0H, just as the base KOH corresponds to the salt KNO3. In a similar manner other salts of diazo-benzene, e,g. the chloride, CgH^Ng.Cl, and the sulphate, (CgH5N2).S04H, are obtained from aniline hydrochloride and sulphate in the presence of free acid. Double salts with PtCl^, AuClg, etc., are also known. The homologues of aniline and the diamines show a similar behaviour, e.g. ^-toluidine yields salts of diazo-toluene, Most of the diazo-compounds are prepared only in aqueous solution, and not in the solid form, on account of their instabihty and tendency to explode. One mol. aniline, for instance, is dissolved in two or more mols. hydrochloric acid, and the calculated quantity of a solution of sodium nitrite is allowed to flow into it, the whole being cooled by ice. The liquid must remain clear and no nitrogen to speak of must be evolved. Any excess of nitrous acid can be got rid of by blowing air through the solution. Occasionally the amido-compound dissolved in concentrated sulphuric acid is treated with NgOg. The formation of the diazo-compounds is shown by the following equation : Diazo-benzene nitrate. The conversion of amido- into diazo-compounds is termed diazotizing." The constitution of the diazo-compounds, e.g. CgH^-N^N-Cl or CgH^N=N — SO4H, follows especially from these two re- e.g. CeH4(CH3)N2.CL N;02H I 3 = CeH,.N= N.N03 + 2H2O. 362 XXI. DIAZO- AND AZO-COMPOUNDS ; HYDRAZINES. actions : 1. from their transformation into hydrazines upon reduction; 2. from the formati n of azo-dyes by the action of diazo-compounds upon many amines and phenols. Many of the properties shown by the diazo-compounds admit of an easier explanation if one makes the assumption that they are also capable of reacting as if they were constituted according to the other hypothetical formula, CgHg — NH — NO ( = free diazo-benzene), or CgHg— NH— N<^p (diazo-benzene chloride) (Caro, Ost.; cf.pp. 265-6). Behaviour. 1. Towards water. An aqueous solution of a diazo-salt, especially one containing sulphuric acid, gives off all its nitrogen in the form of gas upon warming, and there results a phenol, thus : ^^iN=N|gl ^ (.^jj^ Qjj ^^^^ This reaction, which is of very universal application, there- fore allows of the exchange of amidogen for hydroxyl. 2. Towards alcohol. When diazo-compounds, either in the solid state or dissolved in concentrated sulphuric acid, are heated to boiling with absolute alcohol, the diazo-group is generally replaced by hydrogen. In this reaction the alcohol gives up two atoms of hydrogen and goes into aldehyde : + H = C^He + + HCl. By this means we are enabled completely to eliminate a diazo-group and therefore an amido- one from a benzene derivative. Instead of this reaction there occurs in many cases an exchange of the diazo-group for the alcohol radicle, O.CgHg, with the formation of ethyl ethers of phenol ; thus chlorinated cresoi ethyl ether results, in place of chloro-toluene, from chlorinated toluidines, (B. 17, 2703; 21, 978). 2a. Under certain conditions stannous chloride acts in an analogous manner, while under others it gives rise to hydrazines (p. 372). 26. In like manner NHg may be replaced by H, by first converting an amido-compound into a hydrazine and then decomposing the latter with CUSO4, (Baeyer). 3. When a diazo-compound is warmed with a concen- DIAZO-COMPOUNDS ; BEHAVIOUR. 363 trated solution of cuprous chloride in hydrochloric acid, the diazo-group is replaced by chlorine {Sandmeyer, B. 17, 1673); the same reaction takes place on distilling the platinum double salt of the diazo-compound with soda, and sometimes on simply treating the diazo- compound itself with fuming hydrochloric acid : CeH^.N^N.Cl = CgH.Cl + Ng. 4. Warming with cuprous bromide yields in the same way a bromine compound (Sandmeyer, B. 18, 1482), and treatment with hydriodic acid or potassium iodide an iodine one, while cuprous cyanide effects an exchange of the amido-group for cyanogen, (B. 17, 2650) : 2C,H5.N2.CI + Cu2Br2 = 2C6H5Br + Cu^Cl^ + 'N^; GqR,.^^.G\ + KI = CgH^I + KCI + ; etc. The NHg-group may further be exchanged for Br by boiling the diazo-perbromides (see diazo-benzene perbromide) with absolute alcohol. Phenyl sulphide results from diazo-benzene chloride and sulphuretted hydrogen, (cf. B. 15, 1683). The reactions 1 to 4, which are classed together under the name of the Griess reaction, are invaluable for effecting the exchange of nitro- or amido-groups for OH, H, CI, Br, I and CN, and are constantly made use of in the laboratory. The diazo-group is also exchangeable for the nitro- one, (Sandmeyer ; cf. also p. 337). 5. When a diazo-compound acts upon a primary or secondary amine, or when NgOg acts upon such an amine in the absence of acid, diazo-amido-compounds result, and these readily change into amido-azo-compounds. The latter are formed directly by the action of the diazo-compounds upon tertiary amines : CgHg.N^N.Cl + NHa.CgHg = HCl + CeHgJ^^N— NH.CgHg ; ^ Y ^ Diazo-amido-benzene. CeH5.N=N.Cl + CaH5.N(CH3), = HCl + C aH,-N=N-CsH4. N(Cn,) ,. Dimethyl-amido-azobenzene. Analogous reactions also take place with the Tw-diamines and with phenols, oxy-azo-compounds being formed in the latter case, (see p. 368). The production of the orange-red dye by the action of diazo-compounds upon m-phenylene-diamine or /3-naphthol is a very delicate test for the 364 XXI. DIAZO- AND AZO-COMPOUNDS ; HYDRAZINES. presence of the former. Diazo-amido-compounds only show this reaction in acetic acid solution. The salts of the diazo-compounds are colourless and frequently crystallize well ; they often decompose with violent explosion in the air or upon being kept. Most of them are easily soluble in water, slightly soluble in alcohol, and insoluble in ether. Diazo-benzene nitrate, CgHg — N=N.(N03) (p. 361). Long needles. Diazo-benzene sulphate, C6H5.N=N.(S04H), is a syrupy mass which solidifies to prisms ; it explodes at 160°. Diazo-benzene perbromide, 06H5N=N.Br.Br2, is a dark brown oil, solidifying to yellow crystalline plates, which results upon the addition of HBr or KBr and bromine water to diazo-salts. Two of its atoms of bromine are only loosely linked. Ammonia converts it into diazo- benzene-imide, thus : When concentrated potash solution acts upon diazo-benzene nitrate, Diazo benzene-potassium oxide, CgH5N=N(0K),is formed. It crystallizes in white glancing mother-of-pearl plates, readily soluble in water and alcohol and easily decomposable, and from its aqueous solution metallic salts precipitate other metallic compounds, e.g. the very explosive Diazo-benzene-silver oxide, C6H5N=N— O. Ag. The free Diazo-benzene, C(jH5.N=N.0H, is precipitated from the potassium salt by acetic acid as a heavy oil which rapidly decomposes of itself. The diazo-amido-compounds are pale yellow crystalline substances which are stable in the air and do not combine with acids. Formation, See preceding page. Behaviour. 1. The diazo-amido-compounds behave in pretty much the same way as the diazo-compounds, since they are usually broken up in the first instance into their components, C6H5.N=N.Br + Brg = fiHs.NBr— NBr, Diazo-benzene perbromide. CeHg.NBr— NBra + NHg = C6H5.N0 II I Azoxy -benzene. Azo-benzene. Hydrazo-benzene. CgHg— NH2, Aniline. Of these the azo-compounds are the most important. 1. Azoxy-compounds. The azoxy-compounds are mostly yellow or red crystalline substances which result from the action of alcoholic potash, and especially of potassium methylate (B. 15, 865), upon the nitro-compounds. Many of them may also be obtained by the oxidation of azo-compounds. They are of neutral reaction and are very readily changed into azo-com- pounds, etc. upon reduction. HYDRAZO- AND AZO-COMPOUNDS. 367 Azoxy-benzene, (06115)2X20 (Zinin), forms pale yellow needles of M. Pt. 86°, insoluble in water but easily soluble in alcohol and ether. Concentrated sulphuric acid transforms it into the isomeric ^9- oxy-azo- benzene, C6H5N=N— C6H4OH. 2. Hydrazo-compounds. The hydrazo-compounds are colourless, crystalline and of neutral reaction, and — like the azo-compounds — they cannot be volatilized without decomposition ; for instance, hydrazo- benzene decomposes into azo-benzene and aniline when heated. They are obtained by the reduction of azo-compounds by sulphide of ammonium or zinc dust. Oxidizing agents such as ferric chloride readily transform them into azo-compounds, into which they also change slowly in the air alone. The stronger reducing agents, e.g. sodium amalgam, convert them into amido-compounds. Strong acids cause them to change into the isomeric deriva- tives of diphenyl (p. 438) ; thus from hydrazo-benzene and hydrochloric acid there results benzidine chloride (p. 439) : CeHg— NH— NH— CgH, = NH^-CeH^-CeH — NH^ Benzidine. This molecular rearrangement does not take place, or at least only with difficulty, if the hydrogen which occupies the para-position to the imido-group is replaced by other groups. Hydrazo-benzene, CgHg— NH— NH— CgHg (Hofmann),iorm^ colour- less plates of camphor-like odour, which are only slightly soluble in water, but readily soluble in alcohol and ether; M. Pt. 131°. The imido-hydrogen atoms are replaceable by acetyl- or nitroso-groups. 3. Azo-compounds. The azo-compounds are red or yellowish-red crystalline indifferent substances insoluble in water but soluble in alcohol, some of them, e.g. azo-benzene, being capable of distillation 368 XXI. DIAZO- AND AZO-COMPOUNDS ; HYDRAZINES. without change. Oxidizing agents convert them into azoxy-, and reducing agents into- hydrazo- or amido-compounds. Chlorine and bromine act as substituents. The so-called "mixed" azo- compounds, which contain a benzene radicle and an alcoholic radicle of the fatty series, are also known, e.g. Azo-phenyl-ethyl, CgHg— N=N— CgHg, a bright yellow oil. Modes of formation. 1. By the cautious reduction of nitro- or azoxy-compounds, e.g. by means of sodium amalgam, an alkaline solution of stannous oxide (B. 18, 2912), etc. 2. By distilling azoxy-benzene with iron filings. 3. By the oxidation of hydrazo-benzene. 4. By the oxidation of amido-compounds, e.g. together with azoxy-compounds by means of KMn04 • 2CeH,.NH2 + 02 = C^H — N-N— C,H, + 5. By the action of nitroso- upon amido-compounds. In this way azo-benzene is obtained from nitroso-benzene and aniline acetate : Azo-benzene, CgHg— N=N"— CgH^ (Mitscherlich, 1834), crystallizes in beautiful large red plates ; M. Pt. 66°, B. Pt. 293°. Azo-toluenes, C6H4(CH3)— N=N— C6H4(CH3). All three are known. 4. Amido-azo- and Oxy-azo- compounds. Amido-groups or hydroxyls are capable of entering into azo-benzene etc., whereby amido- and oxy-azo-benzenes are formed, thus : fiH-N=N-CeH,(NH, ) fiH,-N=N-CeH,(OH). Y ^ ^ y Amido-azo-benzene. Oxy-azo-benzene. The former are at the same time bases and azo-compounds, and the latter azo-compounds and phenols {i.e. weak acids, cf. p. 376). AMIDO-AZO- AND OXY-AZO-COMPOUNDS. 369 Formation, 1. Amido-azo-benzene is obtained from azo- benzene by first nitrating it and then reducing the resulting mononitro-azo-benzene. 2. Oxy-azo-benzene results from azoxy-benzene by warming it with concentrated sulphuric acid, (cf. p. 367). 3. Amido-azo-compounds are also formed by the molecular rearrangement of the diazo-amido-compounds, according to p. 365, i.e. in a manner indirectly by the action of diazo-benzene etc. upon primary or secondary amines. 4. The corresponding amido-compounds, whose amido- hydrogen is substituted, result directly from the action of diazo- compounds upon tertiary amines, (cf. p. 363). With m- diamines, the diazo-compounds yield diamido-azo-benzenes : CeH,.N=N.Cl+CeH,(NH2)2 = CeH,N=N-CeH3.(NH,), + HCl. ^ , ' Chrysoidin. Oxy-azo-compounds result in an analogous manner by the action of diazo-compounds upon phenols : CgH^N^N.Cl + CgH^OK = CgH^N^-N— CgH^OH + KGl. Reactions of this kind take place especially with resorcin and the phenols of the naphthalene series (p. 466). The amido- and oxy-azo-compounds are yellow, red or brown in colour and crystalline, and are mostly insoluble in water but moderately soluble in alcohol. They possess the character of dyes (azo-dyes), the chromogenic character of the azo-benzene being developed by the entrance of the salt-forming groups NH2 etc. or of OH (cf. p. 24). Thus faintly acid solutions of amido-azo-benzene colour wool and silk a beautiful yellow ("Aniline yellow"), and Chrysoidin, G-^^^^^, HCl, is an orange-red dye. To this class also belongs Vesuvine or Bismarck brown (see below). Instead of these compounds themselves, their sulphonic acids (p. 376) are generally used as dyes ; thus the so-called " fast yellow " (" Echtgelb ") is the sodium salt of amido-azo- benzene-sulphonic acid. The dyes which are derivatives of amido-azo-benzene are termed ( 506 ) 2 A 370 XXI. DIAZO- AND AZO-COMPOUNDS ; HYDRAZINES. Chrysoidines, and those which are derivatives of oxy-azo-benzene, Tropceolines. Of especial importance are those azo-dyes which contain a naphthalene radicle in the molecule. They are formed in a manner exactly analogous to the compounds mentioned above, the two naphthylamines, CioH^.NHg, and the a- and /3-naphthola, C10H7.OH, possessing respectively complete aminic and phenolic characters, and their sulphonic acids being very active chemically. They dye yellow, orange, red, brown, violet and even blue. Worthy of special mention is Orange II., C6H4(S03Na)— N =N — CioH(j(OH), which is obtained from diazo-benzene-sulphonic acid and /3-naphthol. The amido-group in amido-azo-benzene may be diazotized, as given above, and the resulting diazo-compound is now capable — like diazo- benzene chloride — of yielding azo-compounds with amines or phenols, Dis-azo- (tetrazo-) compounds, as they are termed, (B. 15, 25) ; e.g. CgHg— N=N-C6H4— N=N— C6H4.OH, (B. 9, 628). Many of the most valuable azo-dyes, such as Biebrich scarlet, Crocein scarlet etc. are derivatives of such diazo-compounds. Tris-azo- compounds also exist, (B. 16, 2028). In the formation of azo-dyes of this nature, the azo-group always takes up the para-position to the amidogen or hydroxy! if possible. Should this be already occupied, it goes into the ortho-position. This point is elucidated by the examination of the decomposition products which result upon reduction. The azo-dyes are broken up at the point of the double bond by tin and hydrochloric acid and by sulphide of ammonium, two amido -compounds resulting, thus : C6H5-N=N-C6H4N(CH3)2-f2H2 = C6H5NH2-l-C6H4(NH2)-N(CH3)2. The chemical nature of an azo-dye is thus often easily arrived at by investigating these decomposition products. Upon this reaction also depends the method of introducing new amido-groups into amines and phenols, mentioned on p. 349. For the nomenclature of the azo-compounds, see B. 13, 2023. Amido-azo-benzene, CgHg— N=N— CgH^.NHg (1 863). Beautiful yellow plates or needles. The hydrochloric acid salt crystallizes in dark violet needles and yields a red solution. METHYL ORANGE ; BISMARCK BROWN. 371 Amido azo-benzene-sulphonic acid (see p. 376) is prepared by sulphurating amido-azo-benzene, or by the combination of diazo-benzene-sulphonic acid with aniline : C6H4(S03H)— N=N-C1 + C^H^NH^ = C6H,{S03H)— N=N— CgH^— (NH2) + HCl. It has a flesh colour, it» salts being yellow. The Di-sul- phonic acid crystallizes in glittering violet needles and its salts are likewise yellow. Dimethyl-amido-azo-benzene, CgHg — — C6H4.N( 0113)2. Golden yellow plates. The chloride crystallizes in violet needles. Its mono- sulphonic acid, methyl orange, helianthin, or Orange III., is used instead of litmus as a delicate indicator in alkalimetrical titrations, its yellow solution being coloured red by traces of acids ; it is not affected either by CO2 or HgS, (B. 18, 3290). It yields amido- dimethyl-aniline and sulphanilic acid upon reduction. Diamido-azo-benzene or chryso'idiney CeHg— N"=N — C6H3.(NH2)2, (Caro, Witty 1875) ; the chloride crystallizes in large octahedra, built one upon the other. Triamido-azo-beiizene, Bismarck hrown^ CeH,(NH2)-N=N-CeH3(NH2)2 {Caro, Griess, 1866), is produced by the action of NgOg upon m-phenylene-diamine, one half of the latter being partially diazotized to CgH4(NH2) — N=N.C1 and then acting on the other half, as given at p. 363. It forms brownish-yellow crystals, readily soluble in hot water; the salts are reddish- brown. Amido-azo- toluene, from diazo-p-amido-toluene, has the constitution C6H4(CH3)-N=:N-C6H3(CH3)(NH2), (B. 17, 77). It crystallizes in orange-red needles. The alcoholic solution is turned green by hydro- chloric acid. Oxy-azo-benzene, CgHg— N=N— C6H4(OH) {Griess, 1866), results from the action of diazo-benzene chloride upon phenol and also from the molecular transformation of azoxy-benzene, (c£ p. 367). It crystallizes in brick-red rhombic prisms and is a yellowish-red dye. Dioxy-azo-benzene-sulphonic acid, C(5H4(S03lI)— N=N— C(jH3(OH)2, from diazo-benzene-sulphonic acid and resorcin, forms as sodium salt Chrysoin or Tropa3olin O. 372 XXI. DIAZO- AND AZO-COMPOUNDS ; HYDRAZINES. Orange II., (cf. p. 370). The Ponceaux and Bordeaux of commerce are mostly prepared from the xylidines and cumidines. Biebrich scarlet, C6H4(S03Na)-N=N— CgH^— N=N— CioHg.OH, (see p. 370). D. Hydrazines. The hydrazines of the benzene series {E, Fischer) entirely correspond with those of the fatty, (cf. p. 117) : CgH^-NH-NH, (CeH5)2N-NH, (CoH5)(C,H5)N-NH,. Phenyl-hydrazine. Diphenyl-hydrazine. Phenyl-ethyl-hydrazine. Hydrazo-benzene results from the entrance of phenyl into the second amidogen of phenyl-hydrazine. Phenyl-hydrazine, C^^H^ — NH — NHg, forms a colourless crystalline mass, melting at 23° to a colourless oil which quickly becomes brown from oxidation, and which boils at 233° without decomposition. It combines with hydrochloric acid to the chloride, CgH^NgHg, HCl (plates). Like all hydrazines it is characterized by strong reducing power, reducing Fehling^s solution even in the cold. It is readily destroyed by oxidation but is stable towards reducing agents ; gentle oxidation of the sulphate by means of HgO converts it into diazo-benzene sulphate. Conversely, phenyl-hydrazine is prepared: (a) By reducing diazo-benzene chloride with the calculated quantity of SnClg and HCl, (F, Meyer and Lecco, B. 16, 2976) : CeHg— N=N.C1 + 2H2 = CeH^— NH— NH2, HCl. (b) By reducing diazo-benzene potassium sulphite, CgH^— N=N.S03K (from C6H5N2CI and K2SO3), with zinc dust and acetic acid to phenyl-hydrazine potassium sulphite, CgHg — NH — NH.SO3K, which is then broken up into phenyl- hydrazine and sulphuric acid upon heating with HCl : CfiH^— NH-NH— SO3K + HCl + H^O = CgH^— NH— NH2, HCl + SO^KH, HYDRAZINES; BENZENE-SULPHONIC ACID. 373 By the action of halogen-alkyl upon phenyl-hydrazine, the imido- hydrogen atom of the latter is replaced by alkyl ; the further action of halogen-alkyl gives rise at once to ammonium compounds, without replacement of the hydrogen of the amido-group. Acid radicles may replace either one or two H-atoms. The base is an important and often an exceedingly delicate reagent for aldehydes and ketones, combining with them to hydrazones with elimination of water, (cf. pp. 135 and 143; also B. 17, 572 ; 21, 984). Most of these compounds are solid and crystalline and are therefore eminently suited for the recognition of aldehydes and ketones, and also of glucoses. Phenyl-hydrazine reacts in the first instance with the latter in the same way as it does with the former, but here (as also in the case of other aldehyde- and ketone- alcohols) a second hydrazine molecule may come into play, whereby ozazones (p. 287) result. By the reduction of the hydrazones, primary amines are formed, (B. 19, 1924) : With aceto-acetic ether, phenyl-hydrazine forms pyrazole derivatives (see antipyrine). It also reacts with lactones, (B. 19, 1706). Phenyl-hydrazine-sulphonic acid, (B. 18, 2193). Is used for the preparation of tartrazine (p. 245). Diphenyl-hydrazine, (C6Hg)2N— NHg, is an oily base which boils without decomposition and, like phenyl-hydrazine, is easily oxidized ; it only reduces Fehling's solution, however, when warmed. It is obtained by reducing diphenyl-nitrosamine, (C6Hg)2N — NO, with zinc dust and acetic acid ; mercuric oxide converts it into a tetrazone. (Cf. p. 118.) The aromatic sulphonic acids are very similar in properties to the sulphonic acids of the fatty series. Benzene-sulphonic acid, C(3H^.S03H (Mitscherlich, 1834), results upon warming benzene with concentrated sulphuric acid (see p. 306) : XXII. AROMATIC SULPHONIC ACIDS. 374 XXII. AROMATIC SULPHONIC ACIDS. As in the case of ethyl-sulphuric acid, advantage is taken of the solubility of its barium, calcium or lead salt to separate it from the excess of sulphuric acid. Small tables ( + l^H^O), deliquescent in the air and readily soluble in alcohol. The barium salt crystallizes in glancing mother-of-pearl plates. Behaviour. 1. Benzene-sulphonic acid is very stable, not being decomposed when boiled with alkalies or acids, as ethyl- sulphuric acid is. It is, however, broken up into benzene and sulphuric acid when heated with hydrochloric acid to 150°, or with water vapour at a high temperature (cf. p. 325) : CeH,.S03H -\- H^O = CeH, + SO.H^. 2. When fused with alkali, it yields phenol : CeHg.SOgK + KOH = CgH^.OH + BO,K^. 3. When it is distilled with potassium cyanide, benzo-nitrile is formed : CgHg-SOgK 4- CNK = CoHg.CN + SOgKg. 4. When it is acted upon by PCI5, its chloride, Benzene- sulphonic chloride, results : CeH^.SOgOH + PCI5 = CeH^.SO^Cl + POCI3 + HCl. The latter is an oil, insoluble in water and solidifying at 0° ; as an acid chloride it is reconverted into sulphonic acid by hot water, and into Benzene-sulphonamide, CeHg.SOo.NHg (glancing mother-of-pearl sublimable plates), by ammonia. This compound corresponds with other amides in its properties. 5. When benzene-sulphonic chloride is treated with zinc dust, benzene-sulphinate of zinc is formed : 2CfiH5.S02Cl + 2Zn = (C6H5S02)2Zn + ZnClg. Benzene-sulphinic acid crystallizes in large glancing prisms, readily soluble in hot water, alcohol and ether. It possesses reducing properties and is itself converted into thio-phenol by nascent hydrogen : CeHg.SOgH + 2H2 = CeHgSH + SHgO. The sulphone, Sulpho-benzide, (CgH5)2S02, results from the action of SO3 upon benzene, and also from the oxidation of phenyl sulphide, (CeHgjgS. It crystallizes in plates, is only sparingly soluble in water SUBSTITUTED BENZENE-SULPHONIC ACIDS. 375 but more readily in alcohol, and distils unchanged. In properties it is analogous to diethyl-sulphone. Mixed sulphones are also known, e.g. Phenyl-ethyl-sulphone, (C6H5)(C2H5)S02. Isomeric with the sulphones are the (easily decomposable) ethers of benzene-sulphinic acid, e.g. CgHg.SOglCaHg). Substitution may be effected in benzene-sulphonic acid by chlorine, bromine, and the groups NOg and NHg. The Nitro-benzene-sulphonic acids, C6H4(]Sr02).S03H, result upon nitrating benzene-sulphonic acid or upon sulphurating nitro-benzene, the m-compound preponderating. Reduction converts them into the : Amido-benzene-sulphonic acids, C(3H4(NH2).S03H. The ^-compound, which is termed Sulphanilic acid, is obtained by heating aniline with fuming sulphuric acid, or from aniline sulphate at 180° to 200° {Gerliardt, 1845); also by reducing p-nitro-benzene-sulphonic acid. It forms rhombic plates ( + H2O), rather difficultly soluble in water, which weather in the air. It combines with bases, e.g. with soda to sodium sulphanilate, C6H4NH2S03Na + 2H2O (large plates), but not with acids. The formula CgH4<^ SO.^-^ possibly expresses the constitution of sulphanilic acid. The m-acid, also termed Metanilic acid, is employed in the preparation of the azo-dye, metaniline yellow ; it crystallizes in fine needles or prisms. Diazo-benzene-sulphonic acid, CgH4<^^^''^^ (the an- hydride of C^6H5cid which is formed in largest quantity directly ; its potassium salt crystallizes beautifully. The sulphonic acids of the three xylenes, the Xylene -sulphonic acids, C6H3(CH3)2S03H, serve for the separation of these isomers from each other ; and the power of crystallization of the salts or amides of the sulphonic acids of the higher benzene homologues is frequently made use of for the recognition and separation of these hydrocarbons. As an example of a complicated aromatic sulphonic acid may be mentioned (?-Bromo-m-nitro-|?-toluene-sulphonic acid, CeH,(CH3)Br(NO,)(S03H). The above instance is sufficient to show that sulphonic acids may be obtained from the most complicated aromatic compounds. This is of especial importance if the latter are dyes whose application is hindered by their insolubility in water or by other circumstances, as in the case e.g. of indigo, amido-azo-benzene, etc. ; the sodium salts of their sulphonic acids are for the most part readily soluble in water, without the dye-character becoming weakened thereby. For sulphonic acids of the azo-dyes, see p. 370. XXIII. PHENOLS. Phenols are oxygenated derivatives of benzene which stand midway in chemical character between alcohols and acids. ^ They are derived from the benzene hydrocarbons in the same way as the alcohols of the fatty series are from the paraffins, i.e. by the replacement of hydrogen in the benzene nucleus by hydroxyl. The phenols are either liquid or solid compounds and are often characterized by a peculiar odour, e.g. carbolic acid and thymol. Most of them can be distilled without decomposition and are readily soluble in alcohol and ether; some dissolve easily in water, others with more difficulty. Many of them are antiseptics, e.g. phenol, creosol and resorcin. Phenols ; Behaviour. 377 Summary of the most important Phenols, Monatomic : Diatomic : Triatomic : CgHg.OH Phenol [41°] (183°) C6H4(CH3).OH Cresols 0- : m- : p- : [31°] (188°) [3°] (201°) [36°] (198°) C6H4(OH)2 Dioxy-benzenes 0 — Pyrocatechin [104°] (245°) m = Resorcin [118°] (276°) 7)=:Hydroquinone [169°] LQuinoneJ Trioxy-benzenes v = Pyrogallol[115°] (210°) a = Oxy-hydroquinone s = Phloroglucin (217°) C6H,(CH3)(OH)3 IVTethyl-pyrogallol C6H3(CH3)2.0H Xylenols e.g. [74°] (2ir) Cg, ^/'-Cumenols Cjo, Durenols CeH3(CH3)(C3H7).OH Thymol [50°] (222°) Carvacrol [0°] (237°) Tetratomic : aHo(CHo)(OH)o l:3:5 = Orcm[86°] (288°) 1 :3 :4 = Homo-pyro- catechin CeH,(0H)4 Tetroxy-benzene Hexatomic : Cg, Xylorcin, etc. Hexoxy -benzene Cn, Penta-methyl-phenol Cg, Mesorcin Behaviour, 1. The phenols behave like alcohols in that they are capable of forming ethers such as anisol, CgHg.O.CHg, saponifiable ethers such as phenyl-sulphonic acid, CeHg.O.SOgH, thio-compounds, etc. They can only be compared with the tertiary alcohols, since they cannot, like the primary or secondary, yield acids or ketones containing an equal number of carbon atoms in the molecule upon oxidation. Unlike the alcohols, however, the phenols are very stable as regards oxidizing agents, undergoing only substitution and not oxidation by halogens and nitric acid, and not going into hydrocarbons with elimination of water, etc. 2. The phenols possess the character of weak acids; they form salts with alkalies, etc., most of which are readily soluble in water, and which correspond with the alcoholates but are far more stable than these. Thus, the phenols dissolve in the alkalies to salts; the latter are usually decomposed, 378 XXIII. PHENOLS. however, by carbonic acid. The acid character of the phenols is considerably increased by the entrance of negative groups, especially NOg, into the molecule. (See picric acid.) 3. The phenols are true derivatives of benzene. They are capable of yielding all those varieties of derivatives which have been described as derivatives of benzene, e,g, chloro-, bromo-, nitro-, amido-, diazo- and sulpho-phenols. The ease with which chlorine, bromine, nitric acid, etc., produce such derivatives is characteristic of the phenols ; thus the former substitute even in very dilute aqueous solution, and nitro- phenols also result from the action of dilute HNO3, the concentrated acid giving rise at the same time to di- and trinitro-compounds. From the phenols having the character of weak acids, it follows that the group CgHg (phenyl) is of a negative nature, i,e. that it acts as an acid radicle. Occurrence, Many individual phenols are found in the vegetable and animal kingdoms. Constitution. The hydroxy 1 in phenol, CgH^.OH, and in the dioxy- and trioxy-benzenes, etc., containing six carbon atoms, is linked to the benzene nucleus. That this is also the case in the homologues of those compounds follows : {a) from their completely analogous reactions ; (b) from their behaviour upon oxidation. The products which hereby result from the trans- formation of the side chains into carboxyl are oxy-acids, i.e., still contain the hydroxyl. The entrance of the hydroxyl into the side chain of the benzene homologues is also theoretically possible, but in this case it is not phenols which result but true aromatic alcohols, (cf. p. 395). A. Monatomic Phenols. Modes of formation. 1. Many phenols result from the destructive distillation of the more complex carbon com- pounds, especially of wood and coal; they are therefore present in wood and coal tars. The latter contains especially MONATOMIC PHENOLS; FORMATION. 379 plienol and its homologues, cresol, etc. ; the former, among other products, the methyl ethers of polyatomic phenols, e.g. guaiacol, CeH4.(OH)(O.CH3), and its homologue creosol, CeH3.CH3(OH)(O.CH3). The phenols are isolated from coal tar etc. by shaking up with potash, in which they dissolve, saturating the solution with hydro- chloric acid, and purifying the precipitated phenols by fractional distillation. 2. The phenols result together with a sulphite upon fusion of the sulphonic acids with potash or soda, {Kekule, Wurtz, Dusart, 1867): CgH^.SOgK + 2K0H = CgHg.OK + SO3K2 + H^O. In the laboratory silver basins are used for this fusion, and on the large scale iron boilers, etc. The same dioxy-benzene, resorcin, results from all three benzene-disulphonic acids. The chlorinated sulphonic acids and the chlorinated phenols also exchange the halogen for hydroxyl upon fusion with potash : C6H4.C1(S03K) + 4K0H = C6H4(OK)2 + SO3K2 + KCl + 2H2O. 3. By boiling the diazo-compounds with water (Griess ; cf. p. 362). In this case a very dilute sulphuric acid solution is employed : CeH^CKNiN.Cl) + H^O = Ce'H^CKOH) + N2 + HCl. 4. Phenol is produced from benzene by the action of ozone or hydrogen peroxide, and also by that of the oxygen of the air in presence of caustic soda solution or of aluminium chloride. In an analogous manner di- and even tri-oxy-benzene may be obtained by fusing phenol with potash : CA.OH + O = CeH^COH)^. 5. The phenols cannot be prepared from chloro-, bromo- or iodo- benzene as the alcohols can from chloro-, bromo- or iodo-alkyl, the halogen being bound too firmly to the benzene nucleus. If, however, nitro-groups are present at the same time, an exchange of this kind can be effected by heating with potash or soda solution ; trinitro- chloro-benzene indeed reacts with water alone : C6H,C1.(N02)3 + HOH = CcH,(OH)(N02)3 + HCl. 6. Similarly the amido-group in amido-compounds may be replaced by hydroxyl upon boiling with alkalies, provided nitro-groups are 380 XXIII. PHENOLS. also present ; thus o- and p- (not m-) dinitro-aniline yield dinitro- phenols, a reaction which corresponds with the saponification of the amides, (cf. p. 318). 7. Phenols result from the dry distillation of the salts of the aromatic oxy-acids with lime, or from that of their silver salts, e,g, Gallic acid. Pyrogallol. 8. Homologues of the phenols are produced by heating phenol with alcohols and zinc chloride, e.g. ethyl and butyl phenols, (B. 14, 1845 ; 15, 150). 9. Phenols also result from the putrefaction of albumen, especially j^-cresol, Q>^^{G}1^011, Behaviour, 1, 2, and 3. For the alcoholic and acid characters of the phenols and for their substitution, see above and also on p. 383. Bromine water precipitates even very dilute aqueous solutions of phenol, with the formation of tribromo-phenol. 4. Many phenols give characteristic colourations with ferric chloride in neutral solution, e.g. phenol and resorcin violet, pyro-catechin green, and orcin blue-violet ; while pyrogallol yields a blue colour with ferrous sulphate containing a ferric salt, and a red one with ferric chloride. Chloride of lime and iodine also sometimes give particular colourations. 5. When the phenols are mixed with concentrated H2SO4 and some NaNOg, they yield intensively coloured solutions which turn to king's blue on saturation with potash, (the Liehermann reaction, p. 354). 6. The sodium and potassium salts of the phenols react with CO2 (Kolbe) or with COCI2, with formation of aromatic oxy- acids, e.g. salicylic acid : CgH^.OH + CO2 = C6H4(OH).C02H. The oxy-acids are also formed when CCI4 and NaOH are used, (B. 9, 1285), and their aldehydes by the action of CHCI3 and NaOH upon phenol, (B. 9, 824). 7. The phenols combine with diazo-compounds to form azo-dyes (p. 363); when heated with benzo-trichloride, CeHg.feCla, they yield yellow-red dyes (see aurin), and with phthalic acid, the phthaleius. PHENOL OR CARBOLIC ACID. 381 8. When heated with zinc dust, the phenols are converted into the corresponding hydrocarbons, (Baeyer) : CgHg.OH + H2 = C^Hg + H2O. 9. Upon heating with zinc- or calcium chloride and ammonia, the OH is replaced by NHg, (cf. p 343 ; also B. 19, 2901). 10. Heating with PCI5 partially converts the phenols into chlorinated hydrocarbons, and heating with PgSg into thio-phenols (p. 383). Phenol, Phenol, carbolic acid, phenyl alcohol, CgH^OH. Discovered in 1834 by Runge in coal tar. Occurs in the urine of the herbivora and in human urine as phenyl-sulphuric acid, in castoreum and in bone oil. It forms a colourless crystalline mass consisting of long needles. M. Pt. 41°; B. Pt. 183°; Sp. Gr. at 0°, 1-084. It is soluble in 15 parts of water at 16°, and itself dissolves some water, a small percentage of the latter sufficing to liquify the crystalline phenol ; alcohol and ether dissolve it readily. It is hygroscopic and acquires a reddish colour in the air, possesses a characteristic odour and burning taste, is poisonous, and acts as a splendid antiseptic. It exerts a strongly corrosive action upon the skin. Soluble in caustic potash but not in the carbonate. Ferric chloride colours the aqueous solution violet, while a pine shaving which has been moistened with hydrochloric is turned purple- red by phenol. Phenol-potassium, CgHg.OK, results upon heating phenol with KOH. It crystallizes in white needles which are readily soluble in water and which redden in the air. Phenol-calcium or carbolate of lime, (CgHg.OjgCa, is employed as a disinfectant. For the reactions of phenol and its homologues, see B, 14, 2306; 16, 1207. 382 XXIII. PHENOLS. Summary of the most important derivatives of Phenol, Substitution Products. Ethers. Compound ethers. C6H4(0H)C1 (3) Chloro-phenols. p- : [141°] (217°) C6H4(OH).N02 (3) Nitro-phenols. [45°] (214°); ^- : [114°] C6H2(OH)(N02)3 Trinitro-phenols. [e.g. 123°] C6H4(OH).NH2 (3) Amido-phenols. 0- : [170°] ; p- : [184°] C6H4(OH).S03H (3) Phenol-sulphonic acids. C«H,.0(CH3) Anisol. Liq. (152°) Phenetol. Liq. (172°) Diphenyl ether. [28°](246°) C6H4(NH2).OCH3 (3) Anisidines. p- : [56°] (245°) CeH3(NH2)(OCH3)(S03H) Anisidine-sulphonic acid. QH5.0(S0.3H) Phenyl-SLilphuric acid. C5H5.0(aH,0) Acetyl-pheiiol. (190°) Thio-compounds. CgHg.SH Thio-phenol. (172°) Phenyl sulphide. (272°) Ethers, Anisol or phenyl-methyl ether, CgH5.0(CH3), and Phenetol or phenyl-ethyl ether, CgH5.0(C2H5), are best got by heating phenol-potassium (or phenol and caustic potash) with methyl or ethyl iodide in alcoholic solution : CeHg.OK + CH3I = G,'R,.0(C}I^) + KI ; the former is also obtained by distilling anisic acid with lime. They are liquids of ethereal odour which boil at a lower temperature than phenol, just as ether boils at a lower one than alcohol. As regards behaviour, they are very stable neutral compounds of hydrocarbon character; when heated with HI to 140°, or with HCl to a higher temperature, they are decomposed backwards, thus : CgH^.O.CHs + HCl = CeH^.OH + CH3CI. Phenyl ether, di-phenyl oxide, (C6Hg)20, is formed upon heating phenol with ZnClg or AlaClg, but not with H2SO4. Long needles. Not split up by HI. PHENYL-»ULPHURIC ACID; THIO-PHENOLS. 383 Compound ethers of Phenol Phenol reacts as an alcohol with inorganic and organic acids to form compound ethers. Phenyl-sulphuric acid (also termed phenol-sulphuric acid), 0^^^.0(S0^}1), is only capable of existence in the form of salts, being immediately saponified into phenol and sulphuric acid when attempts are made to isolate it. The potassium salt, CgH5.0.(S03K) (plates, sparingly soluble in water), is found in the urine of the herbivora and also in human urine after the consumption of phenol, and it may be prepared synthetically by heating phenol-potassium with potassic pyro- sulphate in aqueous solution, (Baumann). It is very stable towards alkalies, but is saponified by hydrochloric acid. The other phenol-sulphuric acids, e.g. cresol-sulphuric acid, which occur in urine, are exactly analogous to the above. Phenol-cartoonic ether, phenyl carbonate, CO(O.C6Hg)2, is prepared from COCI2 and CeHgONa. It crystallizes in glancing needles, M. Pt. 78°, and is convertible into salicylic acid. Sodium phenyl- carbonate, CgHg. 0. COgNa, results from CO2 and CgHg.ONa, and goes into sodium salicylate upon heating. Acids decom- pose it into CO2 and phenol. Acetyl-phenol, 0^1150.031130, obtained from phenol-sodium and acetyl chloride, or from phenol, acetic acid and sodium acetate, is an easily saponifiable liquid which boils at 190°. Thio-phenols. Thio-phenol, phenyl hydrosulphide, OgHg.SH, is prepared from benzene-sulphonic chloride, OgHg — SOgOl, as given at p. 374, or by heating phenol with P2S5. It is a liquid of most unpleasant odour and of pronounced mercaptan character (see p. 94). It yields, for instance, a mercury compound, (C6HgS)2Hg, crystalliz- ing in glancing needles, and also salts with other metals. When warmed with concentrated H28O4, a cherry-red and then a blue colour- ation is produced. It is readily oxidizable to phenyl disulphide. 384 XXIII. PHENOLS. Closely related to the above are Phenyl sulphide, (0^115)28, a liquid smelling of leeks and oxidizable to Phenyl sulphone, (^6115)2802; and Phenyl disulphide, (CgH5)2S2 (glancing needles, M. Pt. 60°), which is very easily prepared by the action of iodine upon the potassium compound of thio-phenol, or by exposing an ammoniacal solution of the latter to the air. It is readily reducible to thio-phenol, and is indirectly oxidiz- able to Benzene di-sulph-oxide, (6(3115)28202. (Cf. the corre- sponding compounds of the fatty series, pp. 93 et seq,) Chloro- and Bromo-phenols, When chlorine is led into phenol, 0- and ^-Chloro-phenols are formed. These also result, together with the m-compound, by reducing and diazotizing the haloid-nitro-benzenes. Of the isomeric bi-derivatives, the ^^-compounds have the highest melthig point and the 0- the lowest ; thus o-chloro- and bromo-phenols are liquid and the p-compounds solid. When fused with caustic potash they yield dioxy-benzenes (p. 388), often with a molecular rearrange- ment. The chloro-phenols have a sharp persistent odour. All the five hydrogen atoms of phenol have been replaced by chlorine and bromine. Nitroso-phenols, As Nitroso-phenol, CgH4(0H)(N0), (1:4), is designated the compound prepared from phenol and nitrous acid {Baeyer, B. 8, 816), or by boiling nitroso-dimethyl-aniline with caustic soda solution (see p. 354) : C6H4(NO).N(CH3)2 + NaOH = CeH4(N0).0Na NH(CH3)2. It crystallizes in fine colourless needles which readily become brown, or in large greenish-brown plates. It yields a soda salt crystallizing in red needles and amorphous dark coloured salts with the heavy metals. Potassic ferricyanide in alkaline solution oxidizes it to p-nitro-phenol, while tin and hydrochloric acid reduce it to ^-amido-phenol. It gives the Liebermann reaction with phenol and concentrated sulphuric acid. Since, however, it is also formed from quinone and hydroxylamine hydrochloride, according to the equation ; NITRO-PHENOLS ; PICRIC ACID. 385 CgHA + NH2OH = C6H4(NO)OH + H2O, N(OH) its constitution is probably expressed by the formula C6H4<:^ | 0 (cf. B. 17, 213, 801). According to this it is an oxime of quinone, in agreement with which stands the fact of its being further convertible by hydroxylamine into quinone di-oxime (p. 394). Nitro-phenols. On mixing phenol with cold dilute nitric acid, 0- and p-nitro- phenols are formed, the latter preponderating if the liquid is cold, and the former if it is warm. Upon distilling with steam, the 1 : 2 compound (strongly smelling yellow prisms) volatilizes, while the 1 : 4 (colourless tables) remains behind. For their formation, see also pp. 378 and 353. 97i-Nitro- phenol results from m-nitraniline by diazotizing the latter. The acid character of phenol is so strengthened by the entrance of the nitro-group that its salts are not decomposed by COg but result from the nitro-phenols and alkaline carbonate. o-Nitro-phenol- sodium, CgH4(N02)ONa, crystallizes in dark red prisms, and p-Nitro-phenol- potassium in golden needles. Halogens and nitric acid readily substi- tute further in these (or in phenol itself), yielding two isomeric Dinitro- phenols, C6H3(N02)20H, (OH : NOg : NOg = 1 : 2 : 4 and 1:2:6, i.e. the two NOg-groups are always in the ?7Z -position). Further nitration gives : Picric acid, trinifro-phenol, CgH2(N02)3.0H, (OHiNOgi NO2 : NO2 = 1:2:4:6). This compound was discovered in 1799. It may also be prepared by the direct oxidation of 5-trinitro-benzene with KgFeCyg, and is produced by the action of concentrated nitric acid upon the most various organic sub- stances, e.g. silk, leather, wool, resins and aniline. It is a strong acid and forms beautifully crystallizing salts which explode violently upon heating or when struck. Very spar- ingly soluble in water. Crystallizes from alcohol or water in yellow plates or prisms, M. Pt. 122 5°. Can be sublimed without decomposition, but is explosive also. It is an import- ant yellow dye. Picryl chloride, C6H2(N02)3C1 (from picric acid and PCI5), resembles (506) 386 XXIII. PHENOLS. the acid chlorides (p. 318) in behaviour. Picric acid forms beautifully crystallizing addition-compounds with many hydrocarboUvS, e.(j. CeHg, CjoHg, etc. With KCN it yields Iso-purpuric acid, CgHgNuOg, whose potassium salt dyes a garnet-brown like orchilla. Isomers of picric acid are also known. Amido-phenols. The nitro-phenols go into amido-phenols upon reduction : C6H4(OH)NH2 C6H3(OH)(NH2)2 C6H3(OH)N02(NH2) C6H2(OH)(NH2)3. 0-, m-, p- Di-amido- Nitro-amido- Tri-amido- Amido-phenols. phenols. phenols. phenol. In the Amido-phenols {Hofmann^ 1857) the acid character of the phenols is neutralized by the presence of the amido-groups, so that they only yield salts with acids; but, as phenols, they are still capable of yielding derivatives (see anisidine), while on the other hand their amido-hydrogen is exchangeable in the most various ways, as in the case of aniline, but chiefly for acid radicles. The acid derivatives of the o-Amido-phenols yield, like the o-diamines, so-called anhydro-bases, e.g. methenyl-o-amido-phenol, C6H4<^q^CH, which may also be prepared directly by the action of the acid in question, e.g. formic acid, upon the amido-phenols, (cf. p. 349). The Hydrochlorides of the amido-phenols are relatively stable in the air and often capable of sublimation, the free bases (colourless plates) being on the other hand very readily oxidized in the air, with blacken- ing and the formation of resin, especially if they are impure. ^^-Amido- phenol is easily oxidized to quinone, C6H4O2, by potassic bichromate and sulphuric acid, while chloride of lime converts it into quinone chlor- imide, C6H40(NC1) ; with HgS and FegCle, compounds of the methylene- blue group result (p. 355). Amido-thio-phenols, C6H4(SH)NH2, are also known, of which the o-compound is again characterized by the ready formation of anhydro-compounds, such as Methenyl-amido-thio-phenol, C6H4<^'^^CH, isomeric with phenyl isothiocyanate {Hofmann^ B. 13, 1226). From the amido-phenols are further derived Diazo-phenols and Azo-phenols. The Anisidines, amido-anisols, methoxy -anilines^ C6H4(O.CH3).NH2, HOMOLOGUES OF PHENOL. 387 are bases similar to aniline, and are used in the colour industry, (azo-dyes). The Oxy-diphenylamines, e.g. CgHg— NH— C6H4.OH, are phenylated amido-phenols, and react accordingly (see also p. 356). Phenol-sulphonic acids, CgH4(OH)(S03H). The 0- and p- acids are obtained from phenol and concentrated H2SO4 at a moderate temperature, that is, with much greater ease than the benzene-sulphonic acids ; the ortho-acid changes into the para- on warming, even when in aqueous solution. The m-compound can be prepared indirectly by fusing m-benzene- disulphonic acid with potash. All three are crystalline. The 0- and m-acids yield 0- and m-dioxy-benzenes when fused with KOH, but the ^^-acid does not react in this way, being attacked only at temperatures over 320°, and no resorcin then resulting ; the same applies to caustic soda. o-Phenol-sulphonic acid is used as an antiseptic under the name of Aseptol," (B. 18, Kef. 506). Phenol-di- and tri-sulphonic acids are also known. Homologues of Phenol, The homologues of phenol resemble the latter very closely in most of their properties, form perfectly analogous deriva- tives, and possess likewise a disinfectant action and a peculiar odour (the cresols an unpleasant fsecal-like odour, the higher homologues one which is less marked). They differ from phenol mainly by the presence of side chains which, as in the case of toluene etc., may undergo certain transformations. In especial, when they are used in the form of alkyl or acetyl derivatives or sulphonic acids, they can be oxidized in such a manner that the side chains (methyl groups) are transformed into carboxyl, with the production of oxy- carboxylic acids. The cresols themselves cannot be oxidized even by chromic acid mixture, but are completely destroyed by permanganate of potash. Negative substituents, especially if they are present in the o-position, render such oxidation more difficult in acid, but facilitate it in alkaline solution. The Cresols, G^^{GI[,^OIL, are all three present in coal 388 XXIII. PHENOL&. tar and are also contained in the tar from pine and beech wood. o-Cresyl-sulphuric acid (analogous to phenyl-sulphuric acid) is found in the urine of horses, and the ^-compound in human urine. ^-Cresol, G^fl^(GI{^)OIi, is produced by the decay of albumen. Its dinitro-compound is a golden-yellow dye which is used as ammonium or potassium salt under the name of Victoria orange. Thymol, CioHi40,(CH3:C3H^:OH = 1:4:3) is found together with cymene, C^qH^^, and thymene, CioH^g, in oil of thyme, Thymus Serpyllum, and is used as an antiseptic. m-Xylenol, CgHisO, (CHg : CHg : OH = 1:3:4) is found in the creosote of beech-wood tar. Carvacrol, C10H14O, (CgHg : C3H7 : OH = 1:4:2) present in Origanum hirtum, is prepared either by heating camphor with iodine or from its isomer, car vol, and vitreous phosphoric acid. Carvol, C10H14O, the chief constituent of oil of cumin (from Carvum Carvi), appears to be a keto-dihydro-cymol, (B. 19, 12). For other homologues of phenol, see table, p. 377 ; Ethyl-, Propyl- and Butyl -phenols and also Penta-methyl-phenol (B. 18, 1825) have likewise been prepared. B. Diatomic Phenols. By the entrance of two hydroxyls into benzene and its homologues, the diatomic phenols are produced. These are analogous to the monatomic compounds in most of their relations, but differ from them in the same way as the diatomic alcohols do from the monatomic. They are likewise formed by methods completely analogous to those for the monatomic phenols, especially by fusion with potash (p. 374) ; instead, however, of the compound expected, an isomeride which is stable at that high temperature frequently results (see resorcin). The ^-dioxy-compounds are characterized by their close connection with the quinones. Many of the poly- atomic phenols are strong reducing agents. Pyro-catechin, CgH4(OH)2 (1:2), which was first obtained by the distillation of catechin (Mimosa Catechu), is present in PYRO-CATECHIN ; RESORCIN ; HYDROQUINONE. 389 raw beet sugar and results from the fusion of many of the resins as well as of o-phenol-sulphonic acid with potash. It crystallizes in short white rhombic prisms, which can be sublimed, and are readily soluble in water, alcohol and ether. It is prepared by heating its mono-methyl ether, Guaiacol, C6H4(OH)(O.CH3), a constituent of beech-wood tar, with hydriodic acid (see anisol, p. 382). Like most of the polyatomic phenols it is very unstable in an alkaline solution, which quickly becomes green and then black in the air. The aqueous solution is coloured green by Fe2Cl6 and then violet by NHg (reactions of the o-dioxy-compounds). It possesses reducing properties, causing separation of the metal from a solution of silver nitrate even in the cold. By boiling it with potash and potassic methyl-sulphate, it may be reconverted into guaiacol, which likewise shows the ferric chloride reaction and possesses reducing powers. Veratrol, C6H4(OCH3)2, is its di-methyl ether. Resorcin, GoH^iOR)^, (1:3) {Hlasiwetz, Earth, 1864), is obtained on fusing many resins (Galbanum, Asafoetida), also m-phenol-sulphonic acid, all three bromo-benzene-sulphonic acids, and m- and ^-benzene-disulphonic acids with potash. The last mentioned compounds are employed for its prepara- tion on the technical scale. It also results from the distillation of the extract of Brazil wood. White rhombic prisms or tables which quickly become brown in the air, dissolve easily in water, alcohol and ether, and reduce an aqueous solution of silver nitrate when warmed with it, and an alkaline solution even in the cold. With FegClg resorcin gives a dark violet colouration. It yields dyes with NgOg. When heated with phthalic anhydride it is converted into fluorescein (see eosin ; test for m-dioxy-benzenes), and it is therefore prepared on the large scale. Diazo-compounds transform it into azo-dyes, (cf. p. 369). Its trinitro-derivative is Styphnic acid, 06H(OH)2(N02)3, which is formed by the action of nitric acid upon many gum-resins. Hydroquinone, G^H^OTl)^ (1:4), (mhler, 1844). Formation. By the oxidation of quinic acid, C7II32O6, by means of Pb02, by the saponification of arbutin, and from succino-succinic ether as given at p. 429, etc. Preparation. By the oxidation of aniline with chromic acid 390 XXIII. PHENOLS. mixture, and also by the reduction of quinone with sulphur dioxide. Small monoclinic plates or hexagonal prisms, of about the same solubility as its isomers and capable of being sublimed. Ammonia colours it reddish-brown, while chromic acid, ferric chloride and other oxidizing agents convert it into quinone and eventually into quinhydrone (p. 393). Acetate of lead yields a white precipitate with a solution of pyro- catechiii, but none with resorcin, while hydroquinone is only precipi- tated in presence of ammonia. From the observed heat of neutraliza- tion, resorcin and hydroquinone behave towards soda as dibasic acids, and pyrocatechin as a weak monobasic acid. Dioxy-toluenes, C6H3(CH3)(OH)2. Among the various isomerides which have been prepared (see B. 15, 2995), there may be mentioned : 1. Orcin, (CHg : OH : OH = 1:3:5), which is found in many lichens (Rocella tinctoria, Lecanora, etc.). It results from orsellinic acid with separation of COg, e.g, upon fusing extract of aloes with potash, and it can also be prepared synthetically from toluene, (B. 15, 2992). Of especial interest is its synthesis from acetone-dicarboxylic ether (p. 244) and sodium, (B. 19, 1446). It crystallizes in colourless prisms of sweetish taste which tend to become red, and whose aqueous solution is coloured blueish-violet by FcgClg. It does not yield a fluorescein with phthalic anhydride. By the oxidation of its ammoniacal solution in the air, orcein, C7H7NO3, the chief constituent of the commercial orchil dye, is formed, a compound which is also prepared directly from the lichens named above. Related to it is the well known colouring matter litmus. 2. Homo-pyrocatecliin, C6H3(CH3)(OH)2, (CH3 : OH : OH = 1:3:4), deserves mention on account of its mono -methyl ether Creosol, C6H3CH3(OH)(O.OH3), occurring in beech- wood tar. Creosol is a liquid similar to guaiacol, boiling at 220°, and, as a derivative of pyrocatechin, giving a green colouration with FegClg. Among the other isomers are Cresorcin, Tolu-hydroquinone, etc. Homologous with the above are e.g. Xylorcin (CH3 : CH3 : OH : OH = 1:3:4:6) and Beta-orcinol (wi-dioxy-p-xylene), C6H2(CH3)2(OH)2 ; Mesorcin, C6H(CH3)3(OH)2, (CH3 : CH3 : CH3 : OH : OH = 1 : 3 : 5 : 2 : 4) (see table, p. 377) ; Thymo-hydroquinone, CioHi402, which is present in Arnica montana, etc. Eugenol, C10H12O2, = C6H3(OH)(OCH3)(CH2.CH : CH2), the chief constituent of oil of cloves, is a derivative of an unsaturated diatomic phenol. PYROGALLOL ; PHLOROGLUCIN. 391 0. Triatomic Phenols. rPyrogallol = 1:2:^ = C6H3(OH)3 j Phloroglucin = 1 : 3 : 5 = s h ^"^ee table, p. 377. vOxy-hydroquinone = 1:2:4 = aJ 1. Pyrogallol, pyrogallic acid (Scheele, 1786), is the most important of these three isomers. It is obtained, apart from synthetical reactions, by heating gallic acid, CO2 being split off: CeH2(OH)3.CO,H = CeH3(OH)3 + CO^. It crystallizes in white plates, M. Pt. 115°, readily soluble in water and capable of subliming without decomposition. It is an energetic reducing agent, e.g. for silver salts, and its alkaline solution rapidly absorbs oxygen from the air, hence it is used in gas analysis, as a developer in photography, and so on. The aqueous solution is coloured bluish-black by a solution of ferrous sulphate containing ferric salt, and purple- red by iodine. PyrogaUol dimethyl ether, C6H3(OH)(OCH3)2 {Hofmann), is con- tained in beech-wood tar, as are likewise the dimethyl ethers of the compounds C6H2(CH3)(OH)3 and CgH2(C3H7)(OH)3, homologous with pyrogallol. 2. Phloroglucin, (Hlasiwetz^ 1855), results from the fusion of various resins and of resorcin with potash or soda, by the action of alkali upon phloretin, and by fusing its tricarboxylic ether (whose synthetical formation is given on p. 321) with potash. Large prisms which weather in the air and sublime without decomposition ; M. Pt. 218°. Gives with FcgClg a dark violet colouration. Its reactions partly agree with the formula C6H3(OH)3, e.g. it forms metallic compounds and a Tri-methyl ether, C6H3(0. €113)3, insoluble in alkali ; but, on the other hand, it yields like the ketones a Trioxime, CgHg(]S.0H)3, and therefore appears readily to build up the atomic group CH2— CO— CH2— CO— CH2— CO, = Tri-keto-hexa-methylene, which is termed the secondary or pseudo-iormy in contradistinction to the first-named (the tertiary). (Cf. pp. 317 and 265 ; also B. 19, 159, 2186.) 392 XXIII. THENOLS. 3. Oxy-hydroquinone results from the fusion of hydroquinone with potash, (B. 16, 1231). Like pyrogallol it does not react with liydroxyl- amine. D. Tetra-, penta- and hexatomic phenols. Tetr-oxy-benzene, CoH^iO}!)^ (1 : 2 : 4 : 5), is prepared from succino- succinic ether, (B. 19, 23S5). It crystallizes in yellow needles and is stable when pure. Its chloro-derivative, Dichloro-tetroxy-'benzene, C6Clo(OH)4, is readily oxidizable to chloranilic acid (see p. 394). Hex-oxy-benzene, Cfi(OH)g, forms as potassium salt the so-called Potasshim carhoxide, CgOgKg. It crystallizes in colourless readily oxidizable prisms and can be converted into its quinone (tri-quinone), CeOg (p. 395). It has also been prepared synthetically, (B. 18, 499, 1833). As a pentatomic phenol of the reduced benzene, CgH.{Hg)(0H)5, is to be regarded Quercite (in Quercus), a substance which resembles maunite ; and as a hexatomic phenol, Phenose, Cg.(Hg)(OH)g, which has been prepared by treating CgHg. Clg with moist oxide of silver. E. Quinones. Quinone, CgH^Og (1838). Quinone is produced when chromic acid is added to a solution of hydroquinone. It crystallizes in yellow needles or prisms of a characteristic pungent odour something like that of nut shells, sparingly soluble in water but readily in alcohol and ether, and capable of sublimation; M. Pt. 116°. Corresponding to it we have a large number of higher homologues, etc. These also are solids mostly of a yellow colour and volatile with steam ; they result from the oxidation of the corresponding para-dioxy-com- pounds or of the higher atomic phenols, which contain two hydroxyls in the para-position. The isomeric dioxy-benzenes do not show this formation of quinone. Quinone is also produced by the oxidation of many aniline and phenol derivatives belonging to the para-series, e.g. p-amido-phenol, sulphanilic acid and jp-phenol-sulphonic acid ; further, by the oxidation of aniline itself by means of chromic QUINONE. 393 acid, (see B. 19, 14G7). It was first obtained by distilling quinic acid with manganese dioxide and sulphuric acid. Quinone readily volatilizes with steam, but at the same time much of it is decomposed. Exposure to light causes it to turn brown, and it colours the skin yellow-brown. It is easily converted into hydroquinone by reducing agents such as SO2, HI, SnClg and HCl etc., and can therefore act as an oxidizer. Chlorine and bromine act upon it as substituents, while hydrochloric acid forms Mono-chloro-hydroquinone : C6H4O2 + HCl = CgHgCUOHja. It yields sparingly soluble crystalline compounds with primary amines and also (coloured) compounds with phenols. It is soluble in alkalies, the solution decomposing rapidly. With hydroquinone it forms an addition-compound termed Quinhydrone, CgH402 + C6H4(OH)2, crystallizing in green prisms with a metallic glance, which also results as an intermediate product in the oxidation of hydroquinone or in the reduction of quinone. Constitution, Quinone is derived from benzene by the exchange of two atoms of hydrogen for two of oxygen which, from the close connection between quinone and hydroquinone, must be in the ^-position. The constitution of quinone may be explained either by assuming that these two oxygen atoms are linked together as in peroxide of hydrogen, H — 0 — 0 — H? so that the benzene nucleus remains unchanged, or that the latter experiences a partial reduction, with the formation of a derivative of CgHg, a diketo-dihydro-benzene " : CO /O HC/9\CH ^0 HC/\CH C CO According to the first of these two formulae quinone would be a peroxide, according to the second, a ketone (quinone CO = C2H2<^QQ^C2ll2). In favour of the latter view are (1) the fact that quinone can be converted into an oxime, C(N OH C2H2ns the benzene nucleus remains unaltered, (cf. p. 312, 3). Their constitution is therefore entirely analogous to that of the acids of the acrylic or propiolic series ; they contain a side chain with a double or triple carbon bond. The oxy-acids, such as the oxy-benzoic acids, which possess at the same time phenolic and acid characters, manifestly contain phenol-hydroxyl (i.e. hydroxy 1 which is linked directly to the benzene nucleus) in addition to the carboxyl group or groups ; they are capable of yielding salts either as acids or as phenols, but otherwise they correspond in many points with the alcohol-acids of the fatty series. The true aromatic alcohol-acids, such as mandelic acid (phenyl-glycollic acid), which completely correspond with the latter, manifestly contain their alcoholic hydroxyl not in the benzene nucleus but in the side chain, as is also the case with the aromatic alcohols. Nomenclature. The most rational nomenclature is the designa- tion of the aromatic acids as carboxylic acids of the original hydrocarbons in question, e.g. phthalic acid is benzene-dicar- boxylic acid. Many names, such as xylic acid, are taken from those of the hydrocarbons into which the carboxyl has entered, while others, such as mesitylenic acid, indicate the hydro- carbons from whose oxidation the acids result. An important principle as regards nomenclature depends upon the fact that aromatic acids can be derived from almost every fatty acid of any consequence by the exchange of H for CgH^, e.g. : CH3-CO2H, acetic acid ; C^H^-CHo-COgH, phenyl-acetic acid. There thus exist phenylated acids analogous to the acids of the acetic, glycollic, succinic, malic and tartaric series, etc. Atropic acid, C^Hr, — ^^qo.JI' example, may be designated a-phenyl-acrylic acid, and so on. 404 XXV. AROMATIC ACIDS. Properties, Most of the aromatic acids are solid crystalline substances, generally only sparingly soluble in water and therefore precipitable by acids from solutions of their salts, but often readily soluble in alcohol and ether. The simpler among them can be distilled or sublimed without decomposi- tion, while the more complicated, especially phenolic and poly-carboxylic acids, give up carbon dioxide when heated; e.g. salicylic acid, CgH4(OH).C02H, breaks up thus into phenol and COg. Such a separation of carbonic anhydride is effected in the case of those acids which are volatile without decom- position by heating e.g. with soda-lime; in polybasic acids the carboxyls may be split up in succession : CeH,(C02H)2 = CeH.CCO^H) + CO^ = CeH^ + 2G0^. Occurrence. A large number of the aromatic acids are found in nature, e.g. in many resins and balsams, and also in the animal organism in the form of nitrogenous derivatives such as hippuric acid. Modes of formation, A. Of the saturated acids. 1. By the oxidation of the corresponding primary alcohols or aldehydes ; e.g. benzoic acid from benzyl alcohol. 2. By the oxidation of the benzene homologues and of all the compounds which are derived from these by substitutions in the side chain; also of all the derivatives of those com- pounds which contain halogen, nitro-, sulpho-, etc. groups, liydroxyl or carboxyl in place of benzene hydrogen ; C6H5(CH3) yields CfiHglCO^H) cSicSkHj " C6H3(CH3),(C2H5) „ CeH3(CO,H)3 CeHs-CH^tNH,,) „ CeHs-CO^H CeH^CUCH,) „ C6H4C1(C02H) C6H4(N02)(C2H5) „ CeH^lNO^XCO^H) CeHjlOHj^lCHg) „ CeHsCOHj^fCO^H) CeH4(CH3)(CO,H) „ C,H4(CO,H)2 C6H5-CH=CH-C02H „ CeHj-CO^H. Should there be several side chains in the molecule, they are usually all converted directly into carboxyl by chromic acid, whereas by GENERAL MODES OF FORMATION. 405 using dilute nitric acid, this transformation can be effected step by step, e.g. : C6H4(CH3)2 yield first C6H4(CH3)(C02H) and then C6H4(C02H)2 The xylenes Toluic acids Phthalic acids. Nevertheless the three classes of isomeric benzene derivatives with two side chains comport themselves differently. The para-compounds are the most readily oxidized to acids by chromic acid mixture and then the meta-, whereas the ortho-compounds are either completely destroyed by it (p. 326) or not attacked at all. The last-named may however be oxidized in the normal manner by nitric acid or perman- ganate of potash. The entrance of a negative group (and also of hydroxyl) renders more difficult the oxidation of an alkyl-group having the o-position with regard to it (cf. p. 387). 3. By the saponification of the corresponding nitriles (p. 402). CgHg.CN + 2H2O = CgHg.COgH + NH3. These Nitriles, which can be prepared from the ammonium salts of the acids in the same manner as those of the fatty- series, result from the following syntheses : (a) By distilling the potash salts of the sulphonic acids with potassium cyanide or ferrocyanide (Merz), just as the nitriles of the fatty acids are formed from the alkyl sulphates (p. 107): CgHg.SOgK + KCN = CgHg.CN + SO,K^. Nitriles cannot as a rule be prepared from chloro-benzenes, etc. and KCN, (cf p. 333) ; the halogen is more readily replaced by cyanogen if sulpho-groups are likewise present. Or nitro-groups (in presence of halogens) can also be replaced, as in the case of the bromo-nitro-benzenes, (B. 8, 1418). Benzyl chloride, CgH^ — CHgCl, and all the haloid hydro- carbons which are substituted in the side chain, on the other hand, show the normal ready exchangeability of halogen for cyanogen : CgH^— CH2CI + KCN = KCl + C.H^— CH2.CN Benzyl cyanide. (b) By heating the mustard oils with copper or zinc dust ( Weith) : CeHg.NCS -f 2Cu = CgHgCN -f Cu^S. (c) By the molecular transformation of the isomeric iso-nitriles at a 406 XXV. AROMATIC ACIDS. somewhat high temperature : (QjHg.NC = CdHg.CN). The nitriles may be prepared indirectly from the amines by botli the last methods, and also by exchanging the diazo-group for the cyanogen one (p. 363). {d) By eliminating the elements of water from the oximes of the aldehydes (p. 134) by means of acetyl chloride : C6H5.CH=]Sr.OH = CfiHg.CN + HgO. Benzaldoxime. 4. Syntheses effected by the action of carbonic acid or its derivatives : (a) Benzoic acid, etc. is produced by the action of carbon dioxide upon mono-bromo-benzene, etc. in presence of sodium, {KekuU) : C^H.Br + CO2 + 2Na = C^H^.COgNa + NaBr. {h) By the action of phosgene, COClg, or also of COg, upon benzene and its homologues in presence of AlgClg (Friedel and Crafts) : CgHg + COCI2 = CgH^.COCl + HCl. Acid chlorides are first formed here, which are then to be decomposed by water. By the further action of these chlorides upon benzene in presence of AlgClg, ketones result (see benzophenone. ) COCI2 acts with particular ease upon tertiary amines : C6H5.N(CH3)2 + COCI2 = C6H4[N(CH3)2].C0C1 + HCl. (c) By the action of carbamic chloride, CI — CO.NHg, upon benzene in presence of AlgClg, there result in an analogous manner the amides of the aromatic acids, (Gatterman and Schmidt, B. 20, 862) : CgH^CCHs) + CI-CO.NH2 = CeH4{™3^jj^ + HCl. {d) By the action of sodium upon a mixture of brominated benzenes and chloro-carbonic ether (Wurtz); in this case the compound ethers are first formed, but these are easy to saponify : CgH^Br + C1.C02(C2H5) + 2Na = C6H5.C02(C,H5) + NaBr + NaCl. (e) The phenolic acids are produced by passing carbon dioxide over heated sodium phenate, (Kolbe; see p. 419) : CeHg.ONa + COg = C6H4(OH).C02Na. GENERAL MODES OF FORMATION. 407 In the case of the phenols of higher atomicity, e.g. resorcin, it often suffices merely to heat with a solution of ammonium carbonate or potassium bicarbonate, (B. 13, 930). Chlorocarbonic ether acts in a similar way. (/) i?-Oxy-acids are formed by the action of carbon tetra- chloride upon phenols in alkaline solution, (B. 10, 2185) : CeH.ONa + CCI4 = C6H,(OH).CCl3 + NaCl. C6H4(OH).CCl3 + 4NaOH = CeH4(OH).C02Na + 3NaCl + 2H2O. When chloroform is employed, the aldehydes of these (0- and p') oxy-acids result in an analogous manner : CeHg.OH + CHCI3 + 3NaOH = C6H4.(OH)CHO + 3NaCl + 2H2O. Methylene chloride, CHgClg, also shows a similar behaviour, with the formation of aromatic oxy-alcohols. {g) By heating the sulphonates with sodium formate ( F. Meyer) : CeHg.SOsK + HCO2K = C6H5.CO2K + HSO3K. 5. Aceto-acetic ether and malonic ether syntheses, etc. {a) For the formation of phloroglucin-tricarboxylic ether from sodio- malonic ether, see p. 321. (b) Sodio-aceto-acetic ether yields a complicated benzene derivative in an analogous manner, (B. 18, 3460). (c) For the production of hydroquinone-dicarboxylic ether, etc. from ethyl succinate or from brom-aceto-acetic ether, see p. 321. (d) For the action of aceto-acetic ether upon phenols, see p. 408. (e) Aceto-acetic ether acts upon the haloid derivatives which are substituted in the side chain, e.g. benzyl chloride, exactly as in the fatty series, with the formation of the more complicated ketonic acids, which again are capable of undergoing either the " acid decomposition " or the " ketone decomposition " (p. 225), e.g. : CgH^— CH2CI + CH3— CO— CHNa— CO2R = CH3— CO— CH(C7H7)-C02R + NaCl. ^ , ' Benzyl-aceto-acetic ether. CH3— CO— CH(C7H^)— CO2R + H2O = CgHs— CH^— CHg- CO,R + CH3.CO2H. Phenyl-propionic ether. 408 XXV. AROMATIC ACIDS. 6. Alcohol -acids and ketone-acids are formed by exactly the same methods as in the fatty series (p. 207), e.g. mandelic acid by the com- bination of hydrocyanic acid with benzaldehyde, and saponification of the resulting nitrile, (B. 14, 239, 1965) : CgHg— CHO + HCN = CgHs-CHlOH)— CN; or, from a-chlorophenyl-acetic acid, (B. 14, 239) : CeHg-CHCl-COgH + KOH = C6H5-CH(OH)-C02H + KCl. 7. Hydro-^-cumai'ic acid, hydrocinnamic acid, ^-oxyphenyl- acetic acid, etc. are produced by the decay of albumen, (B. 16, 2313). B. Of the unsaturated acids. 1. From the mono-haloid substitution products of the saturated acids in the normal manner (p. 164); similarly from the corresponding nitriles, primary alcohols, etc., as in the case of the saturated compounds. 2. According to the so-called Ferkin reaction, by the action of aromatic aldehydes upon fatty acids. Thus, when benzalde- hyde is heated with acetic anhydride and sodium acetate, cinnamic acid is formed : CeH5.CHO + CH3.C02Na = CgH^— CH=CH— C02Na + HgO. The acetic anhydride only acts as a dehydrating agent in this instance, the reaction taking place between the sodium acetate and the aldehyde, (cf. A. 216, 9). Oxy-acids are formed as intermediate products here by a reaction similar to "aldol condensation" (p. 134); in the above case, for instance, /3 -phenyl -hydracry lie acid, CgHg— CH(OH)— CHg— COgH. This reaction also takes place with the oxy- aldehydes, with the homologues of acetic acid, and also with dibasic acids, e.g. malonic. 3. Cinnamic acid results in an analogous manner by the action of benzal cloride upon sodium acetate (Caro) : CeHs-CHClg + CHg— CO2H = CgHg— CH=CH— COgH + 2HC1. 4. By the action of aceto-acetic ether upon the phenols in presence of concentrated H2SO4, there are formed unsaturated phenolic acids or their anhydrides (B. 16, 2119 ; 17, 2191), e.g.: WOH) H- (0H).C(CH3)=CH ^ C(CH3)=CH ^ ^ HO~CO ^0 —CO ^ ^ ^ Aceto-acetic ether. Methyl-cumarin. MONOBASIC AROMATIC ACIDS. 409 4a. Malic acid acts upon phenols in presence of H2SO4 in an analogous manner, reacting here probably as the half-aldehyde of malonic acid, CHO-CH2— CO2H ( = malic acid, C2H3(OH)(C02H)2, -CO2H2 [see p. 222]), {v, Pechmann, B. 17, 929) : PH OH + 0=CH-CH2 _ /CH^CH Malonic aldehyde-acid. Cumarin. A. Monobasic Aromatic Acids. (See table, p. 410.) Constitution and Isomers. The cases of isomerism in the aromatic acids are easy to tabulate. An isomer of benzoic acid is neither theoretically possible nor actually known. Carboxylic acids of the formula CgHgOg may however be derived from toluene by the entrance of carboxyl either into the benzene nucleus or into the side chain, thus : C6H,(CH3)(C02H) CeH5.CH2.CO2H (3) Toluic acids. Phenyl-acetic acid. The behaviour of these acids upon oxidation yields proof of their constitution, the former going into the phthalic acids and the latter into benzoic. Of acids CgH^oOg, a large number of isomers are already known (see table). Hydrocinnamic acid and hydratropic acid are phenyl-propionic acids, the former /5- and the latter a-, corresponding to the lactic acids ; the isomeric relations of the fatty acids thus repeat themselves here also. The a-xylic acids, CH C H Q^l^^<^^Yi CO2H' ethyl-benzoic acids, ^Q^4CO + H2O. Such a formation of intramolecular anhydride is of very frequent occurrence in ortho-compounds of this kind, in contradistinction to the m- and 2>compounds (see Indole). Theoretically it may take place in the above instance in two difierent ways, viz., either by the elimination of a hydrogen atom of the amidogen together with OH, or of both of the amidogen H-atoms with 0. These two cases are distinguished by Baeyer 3i& " Lactame formation " and *' Lactime formation," Oxindole is a lactame, while isatin, CgH4<^^Q^C.0H (p. 433), is a lactime of o-amido-phenyl-glyoxylic acid (p. 424). Both lactames and lactimes contain hydrogen which is readilj replaceable ; in the former case it is present in the amido-group and in the latter in the hydroxyl. If the compounds which result from the replacement of hydrogen by alkyl are very stable, the alkyl in them is linked to the nitrogen and they are derivatives of the lactames ; if on the contrary they are easily saponifiable, the alkyl is linked to oxygen and they are ethers of the lactimes. Acids, CgHjoOg. 1. Dimethyl-benzoic acids, xylene-carhoxylic acids, CgH3(CH3)2(C02H). Of these six are possible and four are known. Mesitylenic acid, (COgH : CH3 : CH3 = 1:3:5), results from the oxidation of mesitylene, and the two isomeric Xylic acids (1 : 2 : 4) and Paraxylic acid (1:3:4, see table, p. 410) from that of pseudo-cumene. Isomeric with them are : 2. a-Xylic acid, GQ^^[Qn^)—{CIL^—QO^B.) (1:4), and the Ethyi benzoic acids, C6H4(C2H5)C02H, both of which are bi-derivatives of benzene, (cf. p. 409 and also the table). HYDROCINNAMIC ACID; CINNAMIC ACID. 417 3. The Phenyl-propionic acids, C^jH^— C2H4- -CO^H. These may be either a- or ^-derivatives of propionic acid. ^-Phenyl-propionic acid or Hydrocinnamic acid, CgH^ — CH2 — CH2 — CO2H, results from the action of sodium amalgam upon cinnamic acid and from the decay of albuminous matter. Fine needles ; M. Pt. 47°, B. Pt. 280^ Many substitution products etc. of this acid are known, among which may be mentioned o-Nitro-cinnamic dibromide, C6H4<^^g^^_^jj-g^_QQ jj, a compound nearly related to indigo (p. 431); further, Phenyl-a-amido-propionic acid (phenyl-alanine), CeHg— CHg— CHtNHg)— COgH, and Phenyl-jS-amido-propionic acid, CgHg — CH(NH2) — CH2 — CO2H, both of which can be prepared syntheti- cally, the former being likewise produced by the decay of albumen and by the germination of {e.g.) Lupinus luteus. NH The isomeric o-Amido-liydrocinnamic acid, C6H4<^^ —CO H not stable, but goes immediately into its lactame, hydro-carbostyril, C9H9ON, a quinoline derivative. Hydratropic acid, CgHg — CH(CH3)— CO2H, is obtained — as its name implies — by the addition of hydrogen to atropic acid. It is liquid and volatile with steam. Acids, C1QH12O2. Among these may be mentioned Cumic acid or p-isopropyl- benzoic acid, CgH4(C3H.jr)(C02H), which is obtained by oxidizing Roman oil of cumin with permanganate of potash; (this oil contains — in addition to cymene — its aldehyde, cumic alde- hyde). It also results from the oxidation of cymene in the animal organism, the propyl group being here changed into the isopropyl one. It crystallizes in plates, boils without decomposition, and yields cumene when distilled with lime. The isomeric normal Propyl-benzoic acid has also been prepared (see p. 330). 2. Monatomic unsaturated acids. 1. Cinnamic acid, GgEfi^, = CgH^— CH-.CH-CO2H, ( 506 ) 2 D " 418 XXV. AROMATIC ACIDS. {Trommsdorfy 1780), occurs in Peru and Tolu balsams and also in storax, and may be prepared as given at p. 408. It crystal- lizes in needles or prisms, readily soluble in hot water ; M. Pt. 133°, B. Pt. 290°. When fused with potash, it is split up into benzoic and acetic acids, going into the former also upon oxidation. It yields salts, compound ethers, etc. ; also HC1-, HBr-, HI-, ClOH-, \jv^- etc. addition compounds, e.g. cinnamic dibromide (phenyl-dibromo-propionic acid), CgH^ — CHBr — CHBr — CO2H. Further, the hydrogen in the benzene nucleus may be replaced by CI, Br, NOg, NHg, etc.; thus, upon nitrat- ing cinnamic acid we obtain : 0- and ^-Nitro-cinnamic acids, ^6H4CH2) .CH-CH-CH^CH-CO^H, a decomposition product of piperine (p. 488), which crystallizes in long needles. 428 XXV. AROMATIC ACIDS. Trioxy-cinnamic acids. 0 —CO ^sculetin, C6H2{OH)2<^^jj_^^jj, and its isomeride Daplmetin are dioxy-cumarins, their glucosides (/Esculin and Daphnin) occurring respectively in the horse chestnut and in Daphne varieties. Like the dioxy-cinnamic acids they may also be prepared synthetically, (B. 17, 2191). B. Dibasic Acids. The dibasic acids occupy exactly the same position in the aromatic series as the dibasic acids Ci,H2n_204 do in the fatty ; they form two series of each derivative (compound ethers, chlorides, amides, etc.). The two carboxyl groups, which according to theory they contain, may either both be in the nucleus or in the side chain or chains, or be divided between them. Dibasic phenolic acids can of course occur here also. Benzene-dicarboxylic acids^ CgH4(C02H)2. 1. Phthalic acid, GQii^iCO^Il)^ (1 : 2), (Laurent, 1836), results when any o-di-derivative of benzene, which contains two carbon side chains, is oxidized by HNO3 or KMnO^, but not CrOg (cf. p. 326) ; it is formed in especial by the oxidation of naphthalene by nitric acid, and also of anthracene deriva- tives. In preparing it on the large scale the naphthalene is first converted into its tetra-chlor-addition product, C^oHgCl^, and this then oxidized. It crystallizes in short prisms or plates, M. Pt. 184°, readily soluble in water, alcohol and ether. When heated above its melting point, it goes into the anhy- dride (see below). It loses one mol. COg when heated with a little lime, and two mols. when heated with excess, yielding benzoic acid or benzene. Chromic acid disintegrates it com- pletely, while sodium amalgam converts it into hydro-phthalic acid, CgH4.H2.(C02H)2. Its barium salt, CgH^(C02)2Ba, is difficultly soluble in water. PHTHALIC AND OXY-PHTHALIC ACIDS. 429 Phthalic anhydride, GqH^<^^q^O, crystallizes in magni- ficent long prisms which can be sublimed ; M. Pt. 128°, B. Pt. 284°. It is used in the preparation of eosin dyes (see fluorescein). The chloride, Phthalyl chloride, which results from the action of PCI5 upon the acid, appears strangely enough not to have the constitution 06H4(OOCl)2 but that of C6H4<^q 2\.o, as it yields, for instance, phthalo-phenone, CgH^ with benzene and Al2Clg. Sodium amalgam transforms it into phthalide. 2. Isophthalic acid (1:3) crystallizes in fine long needles from hot water, in which it is only sparingly soluble ; it sublimes without forming an anhydride, and is reduced by nascent hydrogen to tetrahydro-isophthalic acid. The barium salt is readily soluble in water. 3. Terephthalic acid (1:4) results from the oxidation of jp-xylene, cymene etc., and especially of oil of turpentine or oil of cumin. It forms a powder almost insoluble in alcohol and water, and sublimes unchanged. Nascent hydrogen con- verts it into tetra- and hexahj^dro-terephthalic acids. The barium salt is only sparingly soluble. A large number of substitution products of the phthalic acids are known, e.g. chloro- and bromo-phthalic acids (which are used in the eosin industry), nitro-, amido-, oxy- and sulpho-phthalic acids, etc. Oxy-phthalic Acids, The six Oxy-phthalic acids, C6H3(OH)(C02H)2, are of theoretical interest, (cf. p. .314). Dioxy-terephthalic acid, hydroquinone-p-dicarboxylic acid, C8H(.0(5, = C6H2(OH)2(C02H)2, in which both the hydroxyls and the carboxyls are respectively in the p-position to one another, results as ethyl ether by the action of bromine upon succino-succinic ether, or of sodium ethylate upon dibromo-aceto-acetic ether. The free acid breaks up into hydroquinone and CO2 when distilled, and is converted by 430 XXV. AROMATIC ACIDS. nascent hydrogen into siiccino-succinic acid, i.e. the benzene nucleus is reduced" to a hexa-methylene derivative. Succino- succinic ether, whose constitution is given on p. .320, crystallizes in triclinic prisms which melt at 126°, and dissolve in alcohol to a bright blue fluorescent liquid which is coloured cherry-red by ferric chloride. It contains two replaceable H -atoms (in the methine groups), being analogous to aceto-acetic ether. The free acid changes, on losing COg, into quinone-tetrahydro-carboxylic acid, formerly termed succino-propionic acid (see p. 425), and then into quinone-tetrahydride, ^^<^Ch'— CH^^^^ (colourless prisms, M. Pt. 75°; A. 211, 322). Succino-succinic acid and many of its derivatives behave partly as quinones and partly as phenols, and are sometimes coloured (yellow or yellow-green), sometimes colourless. Certain relations have been made out between behaviour and colour which are of service in drawing conclusions as to the constitution of the compounds in question. The phenomenon of desmotropism (p. 266) has been closely investigated here, (B. 20, 2801). Hemipinic acid is a dimethyl ether of the isomeric pyrocate- chin-o-dicarboxylic acid, while the half-aldehyde of the latter is Opianic acid, and the corresponding alcohol-acid is Meconinic acid C6H2(O.CH3)2(C02H)(CH2.0H) ; all these compounds are nearly related to pyrocatechuic acid and can be prepared from narcotine. For the constitution of opianic acid, of. also B. 19, 2275. 0. Tri- to Hexabasic Acids. Benzene-fricarboxylic Acids, CgH3(C02H)3. 1. Trimesic acid (1:3:5). From mesitylene. 2. Trimellitic acid (1:2:4). From colophonium. 3. Hemimellitic acid (1:2:3). Benzene-tetracarhoxylic Acids, CgH2(C02H)4. 1. Pyromellitic acid, 2. Prehnitic acid, 3. Mellophanic acid. The above six acids have been prepared from mellitic acid or its hydro-derivatives by the partial separation of CO2. They readily yield (tetra-) hydro-acids with sodium amalgam. 4. Hydroquinone- and quinone-tetracarboxylic acids. See B. 19, 516. INDIGO GROUP; INDIGO. 431 Benzene-;pentacarhoxylic Acid, CgH(C02H)5. Only one modification is theoretically possible and only one is known. Benzene-hexacarhoxylic Acid, Cg(C(32H)g. Mellitic acid, Ci2HgOj2> occurs in peat as aluminium salt or honey-stone, G^^kl^O^^^ which crystallizes in octahedra, and it results from the oxidation of lignite or graphite with KMnO^. It forms fine silky needles of great stability. It can neither be chlorinated, nitrated nor sulphurated, but is readily reduced by sodium amalgam to Hydromellitic acid, G-^^^^fi^^, and yields benzene when distilled with lime. XXVI. INDIGO (OR INDOLE) GROUP. (Cf. the arrangement of Baeyer's researches, which are cited below, in R. Meyer's Theerfarbstoffe," Vieweg und Sohn.) Indigo, which is obtained from the indigo plant (Indigofera tinctoria), and from woad (Isatis tinctoria), has been known for thousands of years as a valuable blue dye, especially for woollen fabrics. In addition to indigo blue (indigotin), commercial indigo contains indigo-gelatine, indigo-brown and indigo-red, all of which can be extracted from it by solvents. The colouring matter is not present as such in the indigo plant, but as the glucoside " Indican," from which it can be separated either by dilute acids or by the action of the air in presence of water. It forms a dark blue coppery and shimmering powder or, after sublimation, copper-red prisms, insoluble in most solvents (including the alkalies and dilute acids), but dissolving to a blue solution in hot aniline and to a red one in paraffin, from either of which it may be crystalhzed. Its vapour is dark red. The formula CigH^QN202 is confirmed by the vapour density. It is converted by reducing agents, such as ferrous sulpliate and caustic soda solution or grape sugar and soda, into Indigo 432 XXVI. INDIGO GROUP. white, CigH^2-^2^2' ^ white crystalline powder soluble in alcohol and ether, also in alkalies and in phenol ; the alkaline suhition quickly becomes oxidized by the oxygen of the air, with the separation of a blue film of indigo. It yields an acetyl compound which crystallizes in colourless needles. Warm concentrated or fuming sulphuric acid dissolves indigo to Indigo-mono-sulphonic and di-sulphonic acids, the former of which (termed phoenicin-sulphonic acid) is difficultly soluble in water but the latter readily so ; the sodium di- sulphonate is the indigo carmine of commerce. Nitric acid oxidizes indigo to isatin, while distillation with potash yields aniline, and heating with manganese dioxide and a solution of potash, anthranilic acid. Indigo has been prepared synthetically by Baeyer, (B. 14, 1741; 15, 775, 2093, 2856; 16, 1704, 2188, etc.). 1. From isatin chloride. 2. By warming o-nitro-phenyl-propiolic acid with (e.g.) grape sugar in alkaline solution : 2C6H4(N02)C=C.C02H + 2H2 - CigHioN202+ 2CO2 + 2H2O. 3. From o-nitro-phenyl-acetylene (p. 332), by converting it into o-dinitro-diphenyl-diacetylene, C6H4(N02)C=C— C=C— C6H4(N02) (p. 459), treating the latter with H2SO4, and finally reducing. 4. By the action of dilute alkalies upon a solution of o-nitro- benzaldehyde in acetone : 2C6H4(N02)CHO + 2C3H60 = C^,R^,-Nfi^ + 2G^}ifi^ + 2}ifi. There is formed as intermediate product in this reaction **o-nitro- phenyl-lacto-methyl-ketone,"C6H4(N02)— CH(OH)— CH2— CO— CH3. 5. By the oxidation, etc., of indoxylic acid and indoxyl. The constitution of indigo is very probably : The following are isomerides of indigo : indigo red (in the indigo of commerce), indirubin (also called indigo-purpurin), and indin ; the last two of these have been prepared synthetically. There have also been prepared dichlor-, dibrom-, tetrachlor-, diethyl-. ISATIN. 433 etc. substitution products of indigo, also indigo-carboxylic acid, (B. 12, 458). Derivatives of Indigo. CoH.NO. C6H4<^>C(OH) C6H4CO <^6H4CH C8He(CH3)N (and its isomers) 1. Isatin, CgH4<^QQ^0(OH),is easily prepared by oxidizing indigo with nitric acid {Erdmann and Laurent, 1841 ; cf. also B. 17, 976). It likewise results from the oxidation of dioxindole, of oxindole (indirectly), and of indoxyl (Baeyer) \ also by boiling o-nitro-phenyl-propiolic acid with alkalies. It crystallizes in reddish-yellow monoclinic prisms, which are only sparingly soluble in cold water, but more readily in hot water and in alcohol to a brownish-red solution. Caustic potash dissolves it at first to a violet solution, with the formation of the compound CgH^NO.OK, but this changes into potassium isatate, CgH4(NH2) — CO — COOK, upon warm- ing (p. 424). Isatin is the lactime of isatic acid (o-amido- benzoyl-formic acid), (p, 416). For its synthesis from o-nitro-benzoyl-formic acid, see p. 424, and for its reaction with thiophene, p. 298. Chloro-, Bromo- and Nitro- isatins are also known. As a ketone, isatin forms with ammonia Imesatin, CgHgNOlNH)", by the exchange of O for NH ; and with ( 506 ) 2 E 434 XXVI. INDIGO GROUP. hydroxylamine, Isatoxime, C6H4<^Qj_jq. qjjj^C.OH (yellow needles), which also results from oxindole and nitrous acid. The homologous Methyl-isatin can be obtained from p-toluidine and dichlor-acetic acid, a tolyl derivative of Methyl -ime satin being formed here in the first instance, (B. 18, 190). Chromic acid oxidizes isatin to Isatoic acid CO (anthranil-carboxylic acid), CsHgNOg, = C6H4<^ • (cf. p. 414). ^ — 002tL Isatin yields a methyl ether, Methyl-isatin, C6H4<^^^C. 0. CHg, which is prepared from isatin-silver (a red powder) and methyl iodide, and forms blood-red crystals ; it dissolves in alkali to isatic acid and methyl alcohol, i.e. the water abstracted in the formation of lactime is again taken up, and the methyl ether is saponified. From this reaction the above constitutional formula of isatin follows. An isomeric compound, Methyl-pseudo -isatin, is derived from an unknown isomer of isatin, pseudo-isatin, C6H4<^qq^CO, the lactame of amido-benzoyl-formic acid. This results e.g. by the action of sodium hypobromite upon methyl-indole and subsequent boiling with alcoholic potash ; since it dissolves at once in alkali to Methyl- isatic acid, C6H4(NH.CH3) — CO — CO2H, it has the constitution C6H4<^gJ^3)>cO, (B. 17, 559). CO Isatin chloride, C6H4<^ ^C. CI (from isatin and PCI5), crystallizes in brown needles which are soluble in alcohol and ether with a blue colour. It goes into indigo when treated with hydriodic acid, or with zinc dust and glacial acetic acid (synthesis of indigo, Baeyer) : 2C8H4NOCI + 2H2 = C16H10N2O2 + 2HC1. 2. Dioxindole^ C6H4<^^'^^"^'^CO, is the intra-molecular anhydride of the unstable o-amido-mandelic acid (p. 423). It is obtained from the reduction of isatin (into which it is again easily oxidized) with zinc dust and hydrochloric acid. Readily soluble colourless prisms, M. Pt. 180°. It possesses both basic and acid properties (two H-atoms being replaceable), and forms a nitroso-compound, acetyl derivative (the acetyl being joined to the N), etc. TVTTT 3. Oxindole, CgH4<^Qjj ^CO, the lactame of (?-amido- phenyl-acetic acid, is formed by the reduction of o-nitro- phenyl- acetic acid (p. 416); also by that of dioxindole with tin and hydrochloric acid. Colourless needles, readily OXINDOLE ; INDOXYL. 435 oxidizable to dioxindole, and therefore of faintly reducing character. Oxindole is at the same time an acid and a base, dissolving both in alkalies and in hydrochloric acid. Baryta water at a somewhat high temperature transforms it into ^?-amido-phenyl-acetate of barium. The imido-hydrogen is exchangeable for ethyl, acetyl, the nitroso-group, etc. 4. Isomeric with oxindole is : Indoxyl, CgH4<^Q^Qjj^^CH, which is obtained by the separation of COg from indoxylic acid, and which is often present in the urine of the carnivora as potassium indoxyl- sulphate or urine-indican, CgHgN.0.(S03K). It is a thick liquid, moderately soluble in water with yellow fluorescence, and not volatile with steam. It dissolves in concentrated hydrochloric acid to a red solution. It is very unstable, quickly becoming resinous, and readily changing into indigo when its ammoniacal solution is exposed to the air, or when ferric chloride is added to its solution in hydrochloric acid. It yields a Nitroso-compound, C6H4<^q^^^^^^CH, of the same character as the nitrosamines, and therefore it contains an imido- group ; further, its relation to indoxyl -sulphuric acid shows that it contains an alcoholic hydroxyl, from which its constitution follows. Potassium indoxyl- sulphate is prepared synthetically by warming indoxyl with potassium pyrosulphate ; it crystallizes in glancing plates and breaks up again backwards when warmed with acids. Ethyl-indoxyl results from indoxyl by the exchange of the hydroxylic hydrogen for CgHg. Derivatives of the hypothetical Pseudo-indoxyl, C6H4<^^Q^CH2, are also known, some of them being convertible into indigo derivatives (e.g. diethyl-indigo). Indoxylic acid, C6H4<^^|q jj^^C— COgH, the carboxylic acid of indoxyl, forms white crystals, is converted into indigo by ferric chloride, and breaks up into indoxyl and COg when fused. It is obtained from its ether : Ethyl indoxylate, by fusing with soda. The latter compound, which crystallizes in thick prisms, M. Pt. 120°, also results — among other methods — from the reduction of ethyl-o-nitro-phenyl-propiolate with ammonium sulphide. The mother substance of the whole indigo group is : 436 XXVI. INDIGO GROUP. 5. Indole, C6H4<§2>CH {Baeyer, 1868), which is ob- tained by distilling oxindole with zinc dust; by heating o-nitro-cinnamic acid with potash and iron filings ; by the action of sodium alcoholate upon o-amido-chloro-styrene (from (?-nitro-cinnamic acid +CIOH-CO2) (B. 17, 1067): C6H4<^^!^(.jj(.l + NaO.C2H5 = C6H4<^^>CH + NaCl + C2H5OH ; by the pancreatic fermentation of albumen; together with skatole by fusing albumen with potash; and by passing the vapours of various anilines, e.g. diethyl-o-toluidine, through red-hot tubes, etc. It crystallizes in glancing plates, M. Pt. 52°, volatilizes readily with steam, and has a peculiar faecal- like odour. It is weakly basic, colours a pine shaving which has been moistened with HCl cherry-red, gives a red precipi- tate of nitroso-indole with N2O3 (a delicate reaction), and yields acetyl-indole when acetylated. These last reactions show that indole contains an imido-group. Indole may be looked upon as pyrrol which has two C-atoms in common with a benzene nucleus, as in the case of naphthalene : NH CH (a) Ch/\J/\cH j^jj (/3) ChLJ^^CH' = CeH<^jj>CH. CH A large number of derivatives spring from indole by the replacement either of the imido-hydrogen, or of the hydrogen atoms marked (a) and (/3), or of those of the benzene nucleus. These result synthetically e.g. by the condensation of the aromatic primary or secondary hydrazines either with pyroracemic acid or with certain ketones or aldehydes, and treatment of the resulting hydrazides with dilute HCl or ZnClg [E. Fischer, B. 17, 559 ; 19, 1563) ; thus acetone-phenyl-hydrazine, for instance, yields a-methyl-ketole, C^^<^q^^Q—CK^, propyl aldehyde- phenyl-hydrazine yields skatole, and so on. Skatole, p-methyl-indole, ^6^4.'^(j,^qjj^ ^^CH, is found in faeces, and is produced together with indole e.g. by the decay of albumen or by fusing it with potash. Colourless plates of a strong faecal odour, M. Pt. 95°. Nitrous acid does not colour it red. It takeii up two atoms of hydrogen to form a hydro-compound. DERIVATIVES OF INDOLE. 437 Methyl-indole, CqH^<^^^^^^^^^CH, results from phenyl-methyl- hydrazine (p. 372) and pyroracemic acid, at first in the form of the carboxylic acid. It is an oil, B. Pt. 239°. Just as furfurane and thiophene are related to pyrrol, so there are compounds analogous to indole which contain oxygen or sulphur in place of the imido-group. We know, for example, a hydroxyl-deriva- S tive of Thio-naphthene, CqR4<^qj^C1I [a compound as yet but little known, (B. 19, 1432, 1667)], viz. Oxy-thio-naphthene (B. 19, 1617), which resembles a-oxy-naphthalene (a-naphthol) in the same degree as thiophene does benzene. Cf. pp. 297 et seq, ; also B. 19, 1290, 1300, 2927. The compounds of the aromatic series which have been treated of up to now are derived, with the exception of indigo, from one molecule of benzene, i.e. they contain one benzene nucleus. There are however a vast number of compounds known which contain two or more benzene nuclei. 1. When two phenyl groups are joined together directly, there results Di-phenyl, GqR—GqH^ (Group XXVII.). 2. When a methylene group, i.e, a carbon atom, connects two phenyl groups, we obtain Diphenyl-methane, CqH.^ — CHg — CgH^ (Group XXVIII. ). 3. Should three benzene residues be joined in a similar manner to methine, Triphenyl-methane, ^{(GqR^)^, is formed (Group XXIX.). 4. Benzene nuclei may likewise be connected through two or more carbon atoms, as in Di-benzyl, CgH^ — CHg — CHg — CgH^ (Group XXX). 5. Lastly, the benzene nuclei may be so grouped together that two carbon atoms are common to two of them, as in anthra- cene and naphthalene, etc. (Group XXXI. etc.). From all the hydrocarbons mentioned under the above para- graphs 1-4, homologues are derived ; all of these with the exception of diphenyl (which possesses the benzene character only) have like toluene partly a benzene and partly a 438 XXVII. DIPHENYL GROUP. methane character, and yield completely analogous derivatives, like the benzene hydrocarbons in the narrower sense of the term. XXVII. DIPHENYL GROUP. Summary. 1. Diphenyl, C.YLr-C.H,, = C^^B.^,. 29-Chloro-diphenyl . 0-, p-Nitro-diphenyl Amido-diphenyl . , Diphenylol . Cyano-diphenyl . . Diphenyl-carboxylic acid C12H9CI CisHolOH) CisHglCOgH) p-^^-Dichloro-diphenyl 'a = 'p-p-YDinitYO- j3 = o-p-j diphenyl ip-p-) = Benzidine ( o-p-) = Diphenyline Carbazole Diphenols . . . Diphenylene oxide Dicyano-diphenyl Diphenyl-dicarboxylic acid C12H8CI2 C,2H8(NO,)2 6:h:>nh Cj^HslOH), Ci2H8(CN)2 Ci2ll8(C02H)2 2. Phenyl- tolyls, C6H5--C6H4. CH3. 3. Ditolyls, C6H4(CH3)-C6H4(CH3), etc. 4. Diphenyl-benzene, C6H4(C6H5)2. 5. Triphenyl-benzene, C6H3(C6H5)3. Diphenyl, C-^^^io {P^^^Wi 1862). When bromo-benzene in ethereal solution is treated with sodium, a synthesis of diphenyl, analogous to the Fittig reaction (p. 324), is effected : 2C6H5Br + Nag C^H.-CeH^ + 2NaBr. Diphenyl also results when the vapour of benzene is led through a red-hot tube, this being the most convenient mode of preparing it. It is contained in coal tar. Large colourless DIPHENYL; BENZIDINE. 439 plates, readily soluble in alcohol and ether; M. Pt. 71°, B. Pt. 254°. Chromic acid oxidizes diphenyl to benzoic acid, one of the two benzene nuclei being destroyed, thus leaving only one carbon atom joined to the other benzene residue. From this and from its synthesis, the constitutional formula of diphenyl follows as CgHg — CgHg. Derivatives. (See Summary ; also Schultz, A. 207, 311). Like benzene, diphenyl is the mother substance of an extended series of derivatives. Even the entrance of only one substituent produces isomers, since the latter may stand either in the o-, m-, or ^-position to the point of junction of the two benzene residues. The same thing applies in still greater degree to isomeric di-derivatives, of which o-o-, p-p-y o-p- etc. compounds can exist. The constitution of these is elucidated either from their syntheses or from their products of oxidation ; thus a chloro- diphenyl, C12H9CI, which yields p-chloro -benzoic acid when oxidized by chromic acid, is obviously p-chloro-diphenyl. The substituents take up the ^-position for choice ; in di-derivatives the p-p' (and to a lesser extent the o-p-) position. C H NH Di-p-diamido diphenyl, benzidine^ CiQHg{NH2)2, = p^tt^ mtt^ (Zinin, 1845), results from the reduction of di-j?-dinitro- diphenyl (the direct nitration product of diphenyl); also, together with diphenyline, by the action of acids upon hydrazo-benzene, the latter undergoing a molecular transfor- mation : CeHj-NH-NH-CeH, = NH^-CeH^-CgH -NH^ ; it is consequently formed directly from azo-benzene by treating it with tin and hydrochloric acid. Benzidine is a diatomic base which crystallizes in colourless silky plates, readily soluble in hot water and alcohol and capable of sublimation ; M. Pt. 1 22°. It is characterized by the sparing solubility of its sulphate, Cj2H^q(NH2)2.S04H2, and by various colour reactions. Like its homologues (tolidine, 440 XXVII. DIPHENYL GROUP. etc.), it is of special importance in the colour industry, since, by coupling its diazo-compound (tetrazo-diphenyl chloride) with naphthol and the naphthylamine-sulphonic acids, etc., colours are produced which dye unmordanted cotton directly, the so-called substantive " or cotton dyes. To this class belongs the dye ConffO C„H,-N=N-C,„H,(NH,)(S03Na) belongs the dye Congo, c,H -N=N-CioH,(NH2)(S03Na)' prepared by means of naphthionic acid (p. 465). (4) C6H4-NH2 The isomeric Diphenyline, | (i) (2) , results from o-?9-dinitro- C6H4-NH2 diphenyl, and also as a bye-product in the preparation of benzidine from azo-benzene. Needles, M. Pt. 45°. Its sulphate is readily soluble. C H Carbazole, C12H9N, = -^^^NH, the imide of diphenyl, is con- tained in coal tar and in crude anthracene. It is formed e.g, by passing the vapour of diphenylamine or of aniline through red-hot tubes, just as diphenyl is obtained from benzene : (C6H5),NH = (CeHJ^NH + H^. It crystallizes in colourless plates sparingly soluble in cold alcohol, M. Pt. 238°. It distils unchanged and is characterized by its great capability of sublimation. Concentrated sulphuric acid dissolves it to a yellow solution, and it forms an acetyl- and a nitro-compound, etc. The nitrogen in it very probably occupies the di-ortho-position, which would make it a pyrrol derivative (see indole). The Dioxy-diphenyls, Ci2H8(OH)2, of which four isomeric modifica- tions are known, result partly by diazotizing benzidine, partly by fusing diphenyl-disulphonic acid with potash, and partly by fusing phenol with potash ; in the last case hydrogen is separated and two benzene residues join together. C H Diphenylene oxide, %^^^0, is obtained by distilling phenol with oxide of lead ; it crystallizes in plates which distil without decomposi- tion. Hexoxy-diphenyl, Ci2H4(OH)6 (silvery glancing plates), which dis- solves in potash with a beautiful violet-blue colour, is the mother sub- stance of Coerulignone or Cedriret, CieHigOg, a violet-coloured compound which is formed when crude pyroligneous acid is purified with chromate of potash, and also from the oxidation of the dimethyl-pyrogallol of beech-wood tar by means e.g. of potassic ferricyanide; in the latter case there is not only a joining together of the two benzene nuclei, but also COERULiaNONE ; DIPHENIC ACID. 441 a separation of hydrogen, with the production of a linking of somewhat the same nature as in superoxides : Coerulignone crystallizes in fine steel-grey needles soluble in con- centrated sulphuric acid with a blue colour. Tin and hydrochloric acid convert it into Hydro -coerulignone, = tetramethyl-hexoxy-diphenyl, which is split up into methyl chloride and hexoxy-diphenyl on warming with concentrated hydrochloric acid {Liehermann). The carboxylic acids of diphenyl are obtained from the correspond- ing cyanides, which on their part are prepared by distilling the sulphonic acids of diphenyl with KCN. Di-^^-diphenyl-dicarboxylic acid, C22H8(C02H)2, a white powder insoluble in water, alcohol and ether, is an oxidation product of phenanthrene and similar compounds ; Diphenic C H CO H acid, A^TT^Virk^TTj ^ di-ortho-compound, crystallizes in needles or plates 06x14. CO2H which are readily soluble in the solvents just mentioned ; M. Pt. 229°. Both of these are dibasic acids, which yield diphenyl when heated with soda-lime. The homologues of diphenyl are, like the latter, obtained by means of the Fittig reaction. Analogous to benzidine is o-Tolidine, 012116(0113)2(^112)2, M. Pt. 128°, which is likewise used in the manufac- ture of cotton dyes, e.g. Azo-blue and Benzo-purpurin. It is combined in the former with naphthol-sulphonic, and in the latter with naph- thionic acid. Appendix. By the action of sodium upon a mixture of ^-dibromo- benzene and bromo-benzene, there is formed Diphenyl-benzene, 05114(06115)2 (flat prisms, M. Pt. 205°), which is oxidizable to diphenyl- monocarboxylic and terephthalic acids. When hydrochloric acid gas is led into acetophenone, O^Hg.OO.OHg, a reaction analogous to the formation of mesitylene from acetone ensues, and there is produced Triphenyl-benzene, 06H3(06Hg)3 (1 : 3 : 5 ; rhombic plates). 442 XXVIII. DIPHENYL-METHANE GROUP. XXVIII. DIPHENYL-METHANE GROUP. Summary, (^'6^5)2=^112 Diphenyl-methane. (96^5)2=CH-CH3 Diphenyl-ethane. Diphenyl-acetic acid. Phenyl-tolyl-methanes. CfiH5-CH2-C6H4-C02H Benzyl-benzoic acids, etc. (C6H5),=CH.OH Benzhydrol. in XT X -(VC\Tf\_cn "FT Benzylic acid. ' C6H5-CH(OH)-C6H4-CH3 Phenyl-tolyl carbinols. C6H5-CH(OH)-C6H4-C02H Benzhydril-benzoic acids. (C6H,),=C0 Benzophenone. CgIl5-CO-CgH4-CH3 Phenyl-tolyl ketones. C6H5-CO-C6H4-CO2H Benzoyl-benzoic acids. Fluorene. 9;JJ;>cH.oH Fluorenyl alcohol. Diphenylene ketone. Diphenyl-methane is derived from methane by the substitu- tion of two hydrogen atoms by two phenyl-groups, just as toluene is by the substitution of one. It consequently resembles the latter hydrocarbon in most of its relations, with this important difference that, as it no longer contains a CHg-group, it cannot yield an acid containing an equal number of carbon atoms in the molecule upon oxidation ; combination with oxygen produces benzhydrol and benzo- phenone. As soon, however, as more carbon atoms are made to enter the molecule, the same conditions repeat themselves as in the case of toluene, xylene, etc., and the most various acids, alcohol-acids, ketone-acids, etc. can be obtained from the resulting homologues. Formation of diphenyl-methane and its derivatives. 1. Diphenyl-methane is produced by the action of benzyl MODES OF FORMATION. 443 chloride upon benzene, in presence of zinc dust (Zincke, A. 159, 374), or of aluminium chloride (Friedel and Crafts) : CeH-CH^Cl + C„He = C,H -CH^-CeH^ + HCl. The homologues of benzene, and also the phenols and tertiary amines, may be used here instead of benzene itself. In an exactly analogous manner diphenyl-methane results from the action of methylene chloride, CH2CI2, upon benzene in presence of chloride of aluminium : CH2CI2 + 2C6H, = CH^lCeHg)^ + 2HC1. 2. Diphenyl-methane hydrocarbons are formed by the action of the fatty aldehydes, e.g. acetic or formic aldehyde, upon benzene, etc. in the presence of concentrated sulphuric acid (Baeyer, B. 6, 221) : CH3— CHO + 2C,He = CH3— CH(C6H5)2 + H^O. V y Y Diphenyl-ethane. The acetic and formic aldehydes are employed here in the form of para-aldehyde and methylal. When aromatic aldehydes are used, triphenyl-methane derivatives result (p. 446). 2\ Aromatic alcohols react with benzene and sulphuric acid in an analogous manner ( V. Meyer) ; C6H5-CH2.OH + CeH^ = CeHg-CH^-CeHs + H^O. Similar reactions have also been brought about by means of ketones, aldehyde-acids and ketone-acids on the one hand, and phenol and tertiary anilines on the other. 3. Benzophenone is produced by the action of benzoic acid upon benzene in presence of P2^5 (^^^-^j B. 6, 536) : C,H,-CO.OH + G,U, == CeH^-CO-C.H, + H^O. 4. Benzophenone and the analogous ketones result upon heating the mixed calcium salts of the aromatic acids, accord- ing to the general mode of formation 2 of the ketones ; thus calcium benzoate heated alone yields benzophenone : CgHg.COgCa + CeH5.C02ca = C^jH^.CO.CgHg + CaCOg. Mixed ketones (p. 139) can be prepared in the same way. 5. Ketones are likewise produced by the action of benzoyl- 444 XXVIII. DIPHENYL-METHANE GROUP. chloride, CgH^CO.Cl, etc. upon benzene, etc. in presence ol AlgClg (Friedel and Crafts; also Ador, B. 10, 1854) : C,H,.C0.C1 + C,H, = G,Yl,.GO.C,R, + HCl. In this case also, as in method 3, phenols (or, better, phenolic ethers) or tertiary amines may be employed in place of the benzene hydro- carbons. 5*. Since the acid chlorides are formed from the benzenes with cobalt chloride and zinc chloride, these reagents may be used directly for the production of ketones, under suitable conditions. The above ketones are, like all others, converted into their cor- responding hydrocarbons by distilling over zinc dust, or by heating with hydriodic acid and phosphorus, etc. (cf. p. 38). 1. Diphenyl-methane, {G(^fl^)2GB.^, is most conveniently prepared from benzyl chloride, benzene and AlgCl^. It crystallizes in colourless needles of very low melting point (26°), is readily soluble in alcohol and ether, has a pleasant odour of oranges, and distils unaltered; B. Pt. 272°. It yields nitro-, amido- and oxy-derivatives. By the action of bromine, aided by warming, Diphenyl-bromo -methane, (C6H5)2CHBr, is obtained, and when this latter is heated with water to 150°, it goes into : Benzhydrol, diphenyl-carbinol, (C6H5)2CH.OH, which also results from benzophenone and sodium amalgam. It crystallizes in glancing silky needles, possesses in every respect the character of a secondary alcohol (forming compound ethers, amines, etc.), and is readily oxidiz- able into the corresponding ketone. Benzophenone, diphenyl-ketone, {GqH.^)^GO. This compound is prepared by distilling benzoate of lime (Feligot, 1834), and also results directly from the oxidation of diphenyl-methane with chromic acid. It is the simplest pure aromatic ketone, and possesses the ketonic character in its entirety, being reducible to benzhydrol, yielding with PCI5 a dichloride, (CgH5)2C=Cl2, and combining with phenyl-hydrazine, etc. It is characterized by being dimorphous, crystallizing in large rhombic prisms, M. Pt. 49° (stable), and also in rhombohedra, M. Pt. 27° (unstable) ; B. Pt. 297°. Fused potash decomposes it into benzoic acid and benzene, while red-hot zinc dust regenerates diphenyl- methane. Among its derivatives may be mentioned Di-jp-diamido-benzophenone, CO(C6H4.NH2)2, whose tetra-methyl compound, Tetramethyl-diamido- BENZILIC ACID; BENZOYL-BENZOIC ACIDS. 445 benzophenone, CO[C6H4Nr(CH3)2]2, results from the action of COCI2 upon dimethyl-aniline : COCI2 + 2C6H5.N(CH3)2 = CO[C6H4N(CH3)2]2 + HCl. It is nearly related to certain dyes, being converted into methyl violet (p. 452) upon further treatment with dimethyl-aniline, and into Auramine or its derivatives (beautiful yellow dyes) by ammonia or amine bases respectively. The ^-position of the amido-groups has been proved. jo-Dioxy-benzophenone, [C6H4(OH)2]CO, results among other methods from the decomposition of complicated benzene dyes, such as rosaniline and aurin, by heating these with water or with alkalies. It can be prepared synthetically from anisaldehyde (B. 14, 328), and therefore contains the hydroxy Is in the _p-position. Homologues of Diphenyl-methane ; Fluorene, 2. Diphenyl- ethane, (C6Hg)2CH — CH3 (unsymmetrical, see p. 457)> is obtained from benzene and para-aldehyde as given on p. 443. It is a liquid which boils without decomposition and which is oxidized to benzophenone by chromic acid. From it is derived : Benzilic acid, diphenyl-glycollic acid, (C6H5)2=C(OH)— COgH, which results by a molecular transformation upon fusing benzile (p. 458) with potash. It crystallizes in needles or prisms, soluble in H2SO4 with a blood-red colour, and is reduced by hydriodic acid to : Diphenyl-acetic acid, (C6Hg)2=CH — COgH (needles or plates), which on its part is obtained synthetically from phenyl-bromacetic acid, CgHg — CHBr — CO2H, benzene and zinc dust, according to mode of formation 1, p. 442; this yields proof of its constitution. Both sub- stances yield benzophenone upon oxidation ; here, therefore, as in the simpler cases, all the carbon is separated which is not directly linked to the benzene nuclei. 3. Phenyl-tolyl-methanes, CgHg— CHg— C6H4— CH3. The p- and o- compounds are obtained from benzyl chloride and toluene, as given at p. 443. They yield on oxidation the corresponding Phenyl-tolyl- ketones, CgHg — CO — C6H4 — CH3, and finally the Benzoyl-benzoic acids, CgHs— CO— C6H4— CO2H (B. 6, 907). Of these, the o-acid, for example (M. Pt. 127°), has also been prepared synthetically by heating phthalic anhydride with benzene and Al2Clg. They are reducible to benzhydril-benzoic acids (or anhydrides) and benzyl-benzoic acids respectively. When the o-acid is heated with P2O5 to 180°, it yields anthraquinone, various transformations into the anthracene scries having been effected from o-phenyl-tolyl-methane and -ketone. 446 XXIX. TRIPHENYL-METHANE GROUP. 4. Ditolyl-methane, (CH3.C6H4)2CH2. C H 5. Fluorene, diphenylene-methane, -^^^CHg, stands in the same relation to diphenyl-methane as carbazole (p. 440) does to diphenyl- amine; it is at the same time a diphenyl and a methane derivative. It is contained in coal tar and crystallizes in colourless plates with a violet fluorescence; M. Pt. 113°, B. Pt. 295°. The corresponding ketone, Diphenylene ketone, CioHg^CO (yellow prisms, M. Pt. 84°), is obtained e.g. by heating phenanthrene quinone with lime, and is converted into fluorenyl alcohol by nascent hydrogen and into diphenyl-carboxylic acid, CgHg — C6H4 — COgH, by fusion with potash. XXIX. TRIPHENYL-METHANE GROUP. Triphenyl-methane, CH(CgH5)3, results from the entrance of three phenyl groups into the methane molecule; among its homologues are e.g. Diphenyl-tolyl-methane, CH^^ |j ^^jj , Phenyl-ditolyl-methane, CH-<^^p^»§^^pTT \ , etc. These hydrocarbons are of especial interest as being the mother substances of an extensive series of dyes. Their formation is effected in a manner analogous to that of the diphenyl-methane derivatives, i.e. by the aid of zinc dust or aluminium chloride when chlorine compounds are used, or by the aid of phosphoric anhydride when oxygen compounds are employed. Thus, triphenyl-methane results : 1. From benzal chloride and benzene : C6H5.CHCI2 + 2C6H6 = CH(C6H5)3 + 3HC1 ; 1*. from benzaldehyde, benzene and zinc chloride (see p. 339) ; 2. from chloroform and benzene by means of AlgClg : SCcHg + CHCI3 = CH(C6H5)3 + 3HC1 ; 3. from benzhydrol and benzene : (C6H,),=CH.0H + CeH, = {C,U,),=Q11.(0,^,) + H,0. The leuco-base of bitter-almond-oil green (cf p. 448) results from benzaldehyde and dimethyl aniline. TRIPHENYIrMETHANE. 447 By using other amine bases and also phenols, a series of allied com- pounds (which are often dyes) is obtained, the separation of water being facilitated by the addition of zinc chloride, concentrated sulphuric acid, or anhydrous oxalic acid. 1. Triphenyl-methane, CigH^g, = CH(C6H5)3 {KekuU and Franchimont, B. 5, 906). This compound may be prepared from chloroform and benzene by the Friedel-Crafts reaction (cf. A. 194, 152), diphenyl-methane being produced at the same time; also by diazotizing jp-leucaniline, C^9H;l3(NH2)3, i.e. by eliminating the amido-groups from it. It crystallizes in beautiful white prisms, insoluble in water and only slightly soluble in cold alcohol, but readily soluble in hot alcohol, ether and benzene; M. Pt. 93°, B. Pt. 359°. It crystallizes from benzene with one molecule of " benzene of crystallization," which is also the case with many triphenyl-methane derivatives. When triphenyl-methane is treated with bromine in a solution of .carbon bisulphide, the methane hydrogen atom is exchanged for bromine with the formation of : Triphenyl-methane bromide, (06115)3. CBr, which, when boiled with water, goes into : Triphenyl-carbinol, (CgH5)3C.(OH). This crystallizes in glancing prisms, M. Pt. 157°, and can be sublimed unchanged; it may also be prepared directly by oxidizing a solution of triphenyl-methane in glacial acetic acid with chromic acid. Fuming nitric acid acts upon triphenyl-methane to form Trinitro- triphenyl-methane, (C6H4.N02)3.CH (yellow scales), which is in its turn converted into : Trinitro-triphenyl-carbinol, (C6H4.N02)3C(OH), by chromic acid. The latter gives para-rosaniline, (C6H4.NH2)3C.OH, when treated with zinc dust and glacial acetic acid, and the former, para-leucaniline (p. 450). Homologous with triphenyl-methane are the : 2. Diphenyl-tolyl-methanes, {G^'H,)^=CB.—G,'H,{m,), From these also dyes are derived, especially from Diphenyl- m-tolyl-methane (in which the CH3 occupies the mcta-position with regard to the methane carbon atom), which can be pre- 448 XXIX. TRIPHEN^METHANE GROUP. pared by diazotizing ordinary leucanilinej it crystallizes in small prisms, M. Pt. 59-5°. Triphenyl-methane Dyes. Of the derivatives of triphenyl-methane and of diphenyl- tolyl-methane, those are especially interesting which result from them by the entrance of amidogen or hydroxyl (or also carboxyl). The entrance of three amido- or hydroxyl-groups converts them into the leuco-compounds of dyes, some of which latter are of great value. Two amido-groups suffice for the full development of the dye character only when the amido-hydrogen atoms are replaced by alcoholic radicles. We distinguish between the following groups : 1. that of diamido-triphenyl-methane (the bitter-almond-oil green group) ; 2. that of triamido-triphenyl-methane (the rosaniline group) ; 3. that of trioxy-triphenyl-methane (the aurin group) ; 4. that of triphenyl-methane-carboxylic acid (the eosin group). Leuco-bases or Leuco-compounds of dyes are compounds which result from the reduction of the dyes themselves (in most cases by the addition of two atoms of hydrogen) ; they are colourless, but are converted into the dyes by oxidation. All the dyes of the triphenyl-methane group, and also indigo, methylene blue, safranine, etc. are capable of yielding such leuco-compounds (mostly by the action of zinc and hydro- chloric acid, stannous chloride, or ammonium sulphide). The oxidation of the leuco-compounds is often quickly effected by the oxygen of the air (e.g. in the cases of indigo white and of leuco- methylene blue) ; in the triphenyl-methane group it is slower and frequently more complicated. Leuco-bitter-almond-oil green readily goes into the corresponding colour-base when treated with PbOg in acid solution, and leucaniline does the same when warmed with chloranil in alcoholic solution, or when its hydrochloride is heated either alone or with a concentrated solution of arsenic acid, or with metallic hydroxides such as Fe2(0H)g. BITTER-ALMOND-OIL GREEN, ETC. 449 1, Diamido-triphenyl-methane Group. Diamido-triphenyl-methane, CgHg — CH(C6H4.NH2)2, is prepared by the action of zinc chloride or of fuming hydrochloric acid upon a mixture of benzaldehyde and aniline sulphate or chloride : CeHs.CHO + 2C6H5NH2 = C6H5.CH=(C6H4.NH2)2 + H^O. It crystallizes in glancing prisms. The colourless salts yield an unstable blue-violet dye, Benzal violet, upon oxidation. Methylation converts the base into : Tetramethyl-di-p-amido-triphenyl-methane, leuco -malachite green, CeHg — CH=[C6H4.N(CH3)2]25 which is prepared on the technical scale by heating benzaldehyde and dimethyl-aniline with zinc chloride or anhydrous oxalic acid (p. 399 ; 0. Fischer^ A. 206, 103). It forms colourless plates or prisms. As a diatomic base it yields colourless salts, and is slowly converted by the air, but immediately by other oxidizing agents, such as Pb02 + H2SO4, into (the salts of) : Tetramethyl-diamido-triphenyl-carbinol, C6H5.C(OH)— [C6H4N(CH3)2]2. The free base is obtained by precipitating the salts with alkali. It crystallizes in colourless needles and dissolves in cold acid to a colourless solution; upon warming, however, the intensive green colouration of the salts is produced. (For an explanation of this, see p. 451). The double salt with zinc chloride or the oxalate of this base is the valuable dye Bitter-almond-oil green, malachite green or Victoria green, which forms green plates, readily soluble in water. This can also be prepared directly by heat- ing benzo-trichloride with dimethyl-aniline and chloride of zinc {Doebner). Brilliant green is the corresponding ethyl compound. If, instead of benzaldehyde, o-, m- or ^^-nitro-benzaldehyde is used, nitro-derivatives of (leuco-) malachite green are obtained. The analogous ^^-Nitro- diamido-triphenyl-methane, C6H4(N02)-CH(C6H4.NH2) 2, can be prepared from p-nitro-benzalde- hyde, aniline sulphate and sulphuric acid. It goes into para-leucaniline upon reduction. The reduction of the isomeric m- and o-compounds yields isomers of leucaniline (Pseudo- and Ortho-leucanilines), which give violet and brown dyes upon oxidation. (506) 2F 450 XXIX. TRIPHENYL-METHANE GROUP. 2. Rosaniline Group. Fuchsine was first obtained in 1856 by Natanson [who noticed the formation of a red substance, in addition to that of aniline hydrochloride and ethylene-aniline, when ethylene chloride was allowed to act upon aniline at a temperature of 200° (A. 98, 297)], and shortly afterwards by ^. W. Hofmann (by the action of carbon tetrachloride upon aniline), and was first prepared on the technical scale in 1859. Hofmann' s scientific researches on this subject date from 1861. The chemical constitution was made clear by Emil and Otto Fischer in 1878 (A. 194, 172). (Cf. also Garo and Grcehe, B. 11, 1117.) The rosaniline dyes are derived partly from triphenyl- methane and partly from diphenyl-m-tolyl-methane ; in the former case they are often designated para-cofnpounds {e,g, *'para-rosaniline," because it is prepared from aniline and para-toluidine ; " para-rosolic acid "). Para-leucaniline, CigH^gNg, and Leucaniline, C20H21N3, result from the reduction of the corresponding trinitro- compounds and also of the corresponding dyes, para-rosaniline and fuchsine j the first named likewise from the reduction of p-nitro-diamido-triphenyl-methane. The free leuco-bases are thrown down by ammonia from solutions of their salts as white or reddish flocculent precipitates, and crystallize in colourless needles or plates; they melt at 148° and 100° respectively. As triatomic bases they form colourless crystal- line salts. Para-rosaniline, C^gH^gNgO, and Rosaniline, CgoHgiNgO, are the bases of the fuchsine dyes. They are obtained by precipitating solutions of their salts with alkalies, and crystallize from hot water or alcohol in colourless needles or plates. Both are triatomic bases, stronger than ammonia. They yield tri-diazo-compounds with nitrous acid, compounds which go into the corresponding phenol dyes (aurin and rosolic acid) when boiled with water ; they are therefore primary. Constitution. The relations between the rosanilines and triphenyl- methane have been made clear by the transformation of leucaniline (by diazotizing it) into diphenyl-tolyl-methane, and the analogous con- version of para-leucaniline into triphenyl-methane {E. and 0. Fischer ^ loc. cit.). Para-leucaniline is thus triamido-triphenyl-methane, while leucaniline PARA-ROSANILINE AND ROSANILINE. 451 is triamido-diphenyl-tolyl-methane. The dye-bases belonging to them are the corresponding carbinols, e.g. rosaniline is triamido-diphenyl- tolyl-carbinol. The three amido-groups can be introduced synthetically, as given at p. 448. They are distributed equally among the three benzene nuclei, as is clear from the synthesis of para-leucaniline by means of p-nitro-benzaldehyde (p. 449). We have therefore e.g. the following formulae : , /C6H4.NH2 /C6H4.NH2 \C6H4.NH2 \C6H3(CH3).NH2. Para-leucaniline. Kosaniline. The para-position of the NHg-groups with regard to the methane carbon atom is proved as follows : (1) Para-rosaniline yields p-dioxy- benzophenone (p. 445; B. 11, 1434) when heated with water, while rosaniline gives p-diamido-methyl-benzophenone (B. 16, 1928 ; 19, 107). (2) Diamido-triphenyl-methane (from benzaldehyde and aniline) is a di-p- compound, because it is likewise convertible into di-p-oxy- benzophenone (B. 12, 1466). Para-leucaniline (from ^^-nitro-benzalde- hyde and aniline, B. 15, 101) is therefore a tri -^-compound. The salts of rosaniline and para-rosaniline, Fuchsine, C20H20N3CI, Rosaniline nitrate, C2oH2oN3(N03), Rosaniline acetate, €201120^3(^^211302), etc. are the actual dyes. While they possess a magnificent fuchsine-red colour in solution, and have intense colouring power (dyeing wool and silk without a mordant), their crystals are of a brilliant metallic green with cantharides glance, i.e. of nearly the complementary colour. They are fairly soluble in hot water and alcohol. In the formation of the salts water is separated, a peculiar nitrogen- carbon linking being manifestly brought about, thus : /C6H4.NH2 C(OH)(C6H4.NH2)3 + HCl = C^C6H4.NH2 + H.O. I \C6H4.NH, HCl An analogous separation of water is also observed in the formation of salts of the malachite green base, but this only takes place upon warming, as is proved by the fact that it dissolves without colour in cold acids, and that the intense colouration of the salts first becomes apparent after warming the solution. In addition to the above salts there also exist acid ones, e.g. C20H20N3CI + 2HC1 (which yields a yellow-brown solution, not a fuchsine-coloured one) ; these dissociate into the neutral salts and free acid upon the addition of much water. In the manufacture of fuchsine either a mixture of aniline with 0- and ^-toluidine is oxidized by syrupy arsenic acid, or a mixture of nitro-benzene with aniline and toluidine is 452 XXIX. TRIPHENYL-METHANE GROUP. heated with iron filings and hydrochloric acid (Courier). For the preparation of the higher homologues, o- and ^-nitro- toluenes may be employed instead of nitro-benzene. Instead of arsenic acid, stannic chloride or mercuric chloride or nitrate, etc. may be used for the oxidation. If o-toluidine is present in the mixture to be oxidized, rosaniline is formed, and if it is absent, para-rosaniline. When pure aniline is oxidized alone, it yields no fuchsine at all, but products of the nature of indulin. This is ex- plained by the fact that for the formation of fuchsine a carbon atom is required which shall serve to link the benzene nuclei together, a so-called ^* methane-carbon " ; in the action of carbon tetrachloride upon aniline, this carbon originates from the tetrachloride, and in the oxidation of a mixture of aniline and toluidine, from the methyl group of the latter, as is shown in the following equation : H3C + C6H5.NH2 - 3fT2 = C^CeH^.NH^. + CgHg.NH^ I \C6H4.NH When rosaniline is heated with hydrochloric or hydriodic acid to 200°, it is split up into aniline and toluidine ; when superheated with water, para-rosaniline yields j9-dioxy-benzo- phenone, ammonia and phenol. A solution of fuchsine is decolourized by sulphurous acid, an addition product, fuchsine- sulphurous acid, being formed. This solution is a delicate reagent for aldehydes, which colour it violet-red (see p. 135.) For the homologues and isomers of rosaniline, see B. 15, 1453. Derivatives of Rosaniline. 1. Methylated rosanilines (Hofmann, Lauth). The red colour of para-rosaniline and of rosaniline is changed into violet by the entrance of methyl or ethyl, the intensity of the latter colour increasing with an increasing number of these groups. The salts of Hexamethyl-para-rosaniline have a magnificent bluish-violet shade. In the manufacture of these "Methyl-violets" one may either (1) methylate rosaniline (by means of CH^Cl or CH3I); or (2) oxidize, instead of aniline, a methylated aniline such as dimethyl-aniline (e.g. by means of cupric salts), whereby para-rosaniline derivatives result ; or, (3) allow phosgene to act upon dimethyl-aniline (or DERIVATIVES OF ROSANILINE. 453 the latter to act upon the tetramethyl-diamido-benzophenone at first produced) (cf. B. 17, Eef. 339) : COCI2 + 3C6H5.N(CH3)2 = C(OH)[CeH4.N(CH3)2]3 + 2HC1. In the last case hexamethyl-violet, termed " Crystal violet " on account of the beauty of its crystals, results, while the methyl-violets prepared by other methods are mixtures of hexa-, penta- and tetra-methyl-rosanilines and are amorphous. The hydrochloride of the hexamethyl dye has manifestly the con- stitution : Vo c.h.C(c:h:(OH)>o)>; Phenol-phthalein. Fluorescein, in the latter case a molecule of water is split off from two hydroxyls of the two resorcin residues. Phthalems of this kind (being oxy-phthalophenones) are converted by reduction into the oxy-derivatives of triphenyl-carboxylic acid, which are termed Fhthalines e.g phenol-phthalein into dioxy- triphenyl-methane-carboxylic acid (i.e, phenol-phthaline), CH^^^^^^^^^2^. The phthalines are colourless, and are to be looked upon as leuco-compounds of the phthaleins. The phthalems include among themselves many dyes which are of technical value, e.g. the eosins {Caro, Baeyer^ 1871). 456 XXIX. TRIPHENYL-METHANE GROUP. Phenol-phthalein, C20H14O4, is prepared by heating phthalic an- hydride with phenol and sulphuric acid or, better, stannic chloride (or oxalic acid) to 115-120°. It also results upon nitrating diphenyl- phthalide, reducing the two substituting nitro-groups to amido-ones, and transforming these into hydroxyl by diazotizing (A. 202, 68). It crystallizes from alcohol in colourless crusts ; in water it is nearly insoluble, but it dissolves in alkalies with a beautiful red colour which vanishes again on the addition of acids ; it is thus a valuable indicator (B. 17, 1017, 1097). It yields a Di-acetyl derivative and is reduced by potash and zinc dust to : Phenol-phthaline (colourless needles), which dissolves in alkali to a colourless solution, but is readily reoxidized in this solution to phthalein. riuorescein or resorcin-pMhalein, C^qH^cP^ + HgO, is pre- pared by heating phthalic anhydride and resorcin to 200°. It forms a dark red crystalline powder, and dissolves in alcohol with a yellow-red colour, and in alkalies with a red colour and splendid green fluorescence. It is reducible to the phthaline " Fluorescin," and yields with bromine red crystals of tetra- bromo-fluorescein, whose potassium salt, CgoHgBr^O^Kg, is the magnificent dye Eosin. Fluorescing dyes are likewise formed in an analogous manner from all the derivatives of 1 : 3-dioxy- benzene, in which position 5 is unoccupied. Instead of phthalic acid itself, chlorinated or brominated, etc. phthalic acids may be employed, so that, by gradually increasing the amount of halogen present, a whole series of yellow-red to violet-red eosins can be prepared, e,g, tetrabrom-iodo-eosin ; these are known under the names of Erythrosin, Eose de Ben gale, Phloxin, etc. It is worthy of note here that many other dibasic acids, e.g. succinic and maleic, are capable of yielding fluorescing compounds. Further, m-amido-phenol and m-dimethyl-amido-phenol show a behaviour towards phthalic anhydride similar to that of resorcin. The dye Rhodanin, C2oHio03[N( 0113)212, which is prepared from m-dimethyl- amido-phenol, is derived from fluorescein by the exchange of both of the two hydroxyls for two N'(CH3)2-groups, and is therefore not a phenol but a basic dye of beautiful shade. Gallein, C20H10O7, is obtained in an analogous manner from pyro- gallol and phthalic anhydride ; it dissolves in alkalies with a blue colour. Gallein contains two atoms of hydrogen less than the normal phthalein of pyrogallol ; as in the case of coerulignone, two " super- oxide " oxygen atoms are assumed here. Its phthaline, Gallin, C20HJ4O7, is transformed by concentrated dibenzyl; stilbene. 457 sulphuric acid into the phthalidine " Coerulin, CgoHigOg, which yiehls the " phthalidein" Coerulein, CsoHgOg, a valuable olive-green dye, upon oxidation. The mother substance of both the latter compounds is phenyl-anthranol (p. 473). For details, see A. 209, 249. XXX. DIBENZYL GROUP. The modes of formation, etc. of the members of the dibenzyl group show that the two benzene nuclei in them are connected together by two carbon atoms ; all of them are transformed into benzoic acid upon oxidation. Summary. CgHg — CH2 — CH2 — CgHg CgHg — CH=CH — CgHs CgHg — C=C — CgHg Dibenzyl. Stilbene. Tolane. CeHg— CH2-CO— CfiHg C6H5-CH(OH)— CH(OH)— CgHg Desoxy-benzoin. Hydrobenzoin. C6H5-CH(OH)-CO— CgHg CeHg— CO— CO— CgHg Benzoin. Benzile. Dibenzyl may be designated as symmetrical diphenyl-ethane (for the unsymmetrical compound, see p. 445), stilbene as 5-diphenyl-ethylene, and tolane as diphenyl-acetylene. Dibenzyl, C14H14. When benzyl chloride (2 mols.) is treated with sodium, the two liberated residues CgHg — CHg — (benzyl) join together with the formation of dibenzyl, a hydrocarbon which is isomeric with ditolyl and with phenyl-tolyl-methane. It crystallizes in needles or small plates, M. Pt. 52°, and sublimes unchanged. Stilbene, diphenyl-ethylene, C14H12, forms monoclinic plates or prisms, M. Pt. 126°, which also boil without decomposition. It may be pre- pared e.g. by the action of sodium upon benzal chloride or oil of bitter almonds, or by passing the vapour of toluene or dibenzyl over heated oxide of lead, and possesses the full character of an olefine, giving — for instance — a dibromide, O^^r^ — CHBr — CHBr — CgHg, with bromine, and being converted into dibenzyl by hydriodic acid. ;9-Diamido- stilbene, Ci4EI]o(N 112)2, disulphonic acid are, like benzidine, mother substances of cotton dyes" (see p. 440). Just as ethylene 458 XXX. DIBENZYL GROUP. bromide yields acetylene when boiled with alcoholic potash, so does stilbene dibromide yield : Tolane, C14H10, which crystallizes in prisms or plates, M. Pt. 60°. Tolane corresponds with acetylene in its properties in so far that it combines with chlorine to a dichloride and a tetrachloride, and so on, but it does not yield metallic compounds since it contains no " acetylene hydrogen. " When stilbene dibromide is treated with silver acetate and the resulting acetic ether acted upon by alcoholic ammonia, one obtains two isomeric substances of the composition : C14H14O2, = CoH5-CH(OH)-CH(OH)-C6H5, Hydrobenzoin and Iso-hydrobenzom. These likewise result , from the action of sodium amalgam upon oil of bitter almonds. The former crystallizes in rhombic plates, M. Pt. 133°, and the latter in four-sided prisms, M. Pt. 119°, which are the more soluble of the two. Their di-acetyl ethers are also different. The reason of the isomerism of hydrobenzoin and iso-hydrobenzoin is not yet clear ; possibly they are only physically isomeric (see A. 198, 191 and 115). The compounds Benzoin, Benzile and Desoxy-benzoin, which have already been referred to in the summary, are closely related to one another as their formulae show, and can also be prepared from bitter almond oil. The latter condenses" (p. 133) in alcoholic solution, under the influence of potassium cyanide, to benzoin (2C7HgO, = Ci4Hi202), which forms beautiful glancing prisms ; nascent hydrogen reduces it to hydrobenzoin, from which it also results upon oxidation. It reduces Fehling's solution even at the ordinary temperature, with the formation of benzile. Benzile, CgHg— CO — CO — CgHg, is obtained by oxidizing benzoin by means of nitric acid. It crystallizes in large six-sided prisms, M. Pt. 90^ It reacts as a double ketone with hydroxylamine, is oxidized to benzoic acid by CrOg, and reduced by nascent hydrogen — according to the conditions— either to benzoin or to : Desoxy-benzoin. The latter forms large plates, M. Pt. 55°, and can be sublimed or distilled unchanged. It can be prepared by the action of benzene and aluminic chloride upon the chloride of phenyl-acetic acid (CgHg — CHg — CO. CI), which is a proof of its constitution, and yields di-benzyl with hydriodic acid. Benzilic acid, (C6H5)2=C(OH)— CO2H (p. 445), results upon heating benzile with alcoholic potash, by a peculiar molecular transformation similar to that by which pinacoline is formed (p. 192). A series of compounds homologous with di-benzyl, stilbene, etc. is also known. Carboxyl groups can likewise substitute in di-benzyl and stilbene, with the formation of phenyl-cinnamic acid, diphenyl- SQccinic acid, stilbene-dicarboxylic acid, etc. DIPHENYL-DIACETYLENE, ETO. 459 Appendix. Further, two or more benzene nuclei may be connected together through more than two carbon atoms. In indigo, for example, the two benzene residues are linked together by four carbon atoms, and the same holds good for the hydrocarbon which is its basis, viz., Diphenyl-diacetylene, CgHg — C=C— C=C — CgHg {Baeyer). This last compound results from the oxidation of copper phenyl-acetylene, CfiHg — C=C — Cu, with a solution of potassium ferricyanide, crystallizes in long needles which melt at 88°, and combines with eight atoms of bromine to an octo-bromide. Its o-Dinitro-derivative, which is pre- pared in an analogous manner from o-nitro-phenyl-acetylene, yields indigo when treated first with sulphuric acid and then with sulphide of ammonium (see p. 432; also B. 15, 53). In Dibenzoyl- acetic acid, (CgH5.CO)2=CH— COgH, a di-ketonic acid, whose ether is obtained by treating benzoyl-acetic ether with benzoyl chloride, two benzene residues are connected together by three carbon atoms. The free acid, which crystallizes in needles, M. Pt. 109°, is split up into COg and the di-ketone Dibenzoyl-methane, {0^11^0)2=012, when boiled with water. In the latter, a solid substance which boils without decomposition, the hydrogen of the methylene group is re- placeable by metals (through the influence of the two carbonyls), so that the compound dissolves in alkalies and is again thrown down by acids. By the further action of benzoyl chloride upon its sodium compound, we obtain Tribenzoyl-methane, (C6H5.CO)3CH. Vulpic acid, C19H14O5, a lichen acid, is related to the above compounds. Tetraphenyl-ethane, {CqI15)2=CR—CB.=(CqHq),2 (large prisms), and Tetraphenyl-ethylene, (C6H5)2=C=C=(C6Hg)2 (fine needles), are also related to dibenzyl ; both of these go into benzophenone upon oxidation. COMPOUNDS WITH CONDENSED BENZENE NUCLEI. That portion of coal tar which boils at a high temperature contains a number of higher hydrocarbons, among which may be especially mentioned naphthalene, C^^^Hy, anthracene. 460 XXXI. NAPHTHALENE GROUP. Cj^HjQ, and its isomericle phenanthrene, G-^Ji-^Q. The first- named is found in the fraction between 180-200°, and the two latter in that between 340-360°. These compounds are of more complex composition than benzene, the molecule of naphthalene differing from that of the latter by C^Hg, and those of anthracene and phenanthrene from that of naphthalene by the same increment. They show however the most complete analogy to benzene as regards behaviour, so that almost exactly the same varieties of com- pounds may be derived from them as from benzene itself. As a matter of fact they are undoubtedly benzene deriva- tives, anthracene yielding benzoic acid upon oxidation, naphthalene phthalic acid, and phenanthrene diphenic acid. From their modes of formation and behaviour it follows that in the building up of their molecules the benzene residues combine together in such a manner that 2 or (2 x 2) contiguous carbon atoms are common to both. For further details see pp. 461 and 470, XXXI. NAPHTHALENE GROUP. Naphthalene. Naphthalene, Ci^Hg, was discovered by Garden in 1820. It is contained in coal tar and crystallizes out from the fraction which distils over between 180-200°. Formation. 1. By exposing a large number of carbon com- pounds to a red heat; thus, together with benzene, styrene, etc., by passing the vapours of methane, ethylene, acetylene, alcohol, acetic acid, etc. through red-hot tubes. 2. By leading the vapour of phenyl-butylene dibromide, CgHg— CH2— CH2— CHBr— CHgBr, over quick-lime raised to a low red heat (Aronheim) : CioHi2Br2 = CioHg + 2HBr + Hg. 3. By the action of o-xylylene bromide (p. 332) upon the sodium compound of acetylene-tetracarboxylic ether (see ethane- tetracarboxy lie NAPHTHALENE. 461 ether, p. 247), there results " Hydronaphthalene-tetracarboxylic ether" thus : p ^ /.CH^Br ^ Na-C(C02R)2 ^6^4<\CH2Br + Na-C(C02R)2 C6H4<^ CH2— C(C02R)2 CH2-C(C02R)2 + 2NaBr ; and from this latter, by the separation of the carboxyl groups and the excess of hydrogen, naphthalene (Baeyer and PerJcin, B. 17, 448). 4. a-Naphthol, CiqH^.OH, is produced by the separation of water from phenyl-isocro tonic acid (Fittig and Erdmann, B. 16, 43), and yields naphthalene when heated with zinc dust. For further details, see below. Constitution. That naphthalene contains a benzene nucleus, in which two hydrogen atoms occupying the ortho-position are replaced by the group (CgH^)", follows not only from its oxidizability to phthalic acid, but also (e.g.) from its formation from o-xylylene bromide. And that the four carbon atoms of this group are linked to one another without branching is shown by the formation of a-napthol (as given above), from which it follows at the same time that the end C-atom of the side chain takes hold of the benzene nucleus already present, with the production of a new six-cornered ring : HC CH CH /\^/\cH HC va:..../ HC l^^OiC (OH) CH Hi HC HC CH CH ^C HC C (OH) CH CH Phenyl-isocrotonic acid. a-Naphthol. That there are actually two so-called " condensed " benzene nuclei present in the naphthalene molecule is a necessary con- sequence of the fact that phthalic acid or its derivatives ensue on the breaking up of the compound, not only from one but from both of the six-cornered rings. For instance, a-nitro-naphthalene (p. 464) allows itself to be oxidized to nitro-phthalic acid, C(.H3(N02)(C02H)2 ; consequently the benzene ring to which the nitro-group is linked remains intact. But, on reduc- ing the nitro-naphthalene to amido -naphthalene and oxidizing the lattei, 462 XXXI. NAPHTHALENE GROUP. no amido-phthalic acid nor any oxidation product of it is obtained, but phthalic acid itself, a proof that this time the benzene nucleus which binds the amido-group has been destroyed, and that the other has remained intact {Graebe, 1880 ; for an analogous proof by him, see A. 149, 20). Naphthalene therefore receives the constitutional formula (Erlenmeyer y : H H The behaviour of the isomeric tetrahydro-naphthylamines upon oxidation (p. 464) is also of great interest with regard to the constitu- tion of naphthalene. Properties, Naphthalene crystallizes in glancing plates which are insoluble in water, sparingly soluble in cold alcohol and ligroi'n, but readily soluble in hot alcohol and ether ; M. Pt. 80°, B. Pt. 217°. It has a characteristic tarry smell, and is distinguished by the ease with which it sublimes and volatilizes with steam. It yields a molecular compound, crystallizing in yellow needles, with picric acid, and takes up hydrogen far more readily than benzene does to form Naphthalene dihydride, CioHg.Hg, and -tetrahydride, C10H8.H4, both of these being liquids of pungent odour which regenerate naphtha- lene again when heated. By the intensive action of hydriodic acid and phosphorus, the second benzene nucleus can also be made to take up hydrogen, so that a hexahydride, CioHs-^e) ^^^^ finally a dekahydride, CioHg.HiQ result. It likewise yields addition-products with chlorine more readily than benzene does, e.g. Naphthalene dichloride, CioHg.Cla, and -tetrachloride, C10H8.CI4 (M. Pt. 184°); the latter is oxidized to phthalic acid more easily than naphthalene itself, hence that acid is prepared from it on the large scale. Naphthalene is principally used for the preparation of phthalic acid (for eosin, etc.), and of naphthylamines and naphthols (for azo-dyes) ; also for the carburation of illumin- ating gas. It is a powerful antiseptic. or 6 3 NAPHTHALENE COMPOUNDS. 463 Derivatives of Naphthalene. The substitution products etc. of naphthalene may be mono- or di-derivatives, etc. The mono-derivatives invariably exist in two isomeric forms^ the a- and l3-compounds, thus : C10H7CI ^"j^Chloro-naphthalene. C10H7NH2 j^^lNaphthylamine. C10H7OH ^;|Naphthol. C10H7CH3 I Methyl-naphthalene. As in the case of the benzene compounds, the existence of two series of mono-derivatives here has not only been established empirically, but it has also been proved (in a manner similar to that given on pp. 307 et seq. ) that the four hydrogen atoms of each of the two groups have an equal value as regards one another, but not as regards the atoms of the other group, so that (e.g.) the a-position occurs four times in the molecule, i.e. twice in each of the benzene nuclei {Atterberg). The above constitutional formula for naphthalene satisfies these con- ditions admirably, since, according to it, the positions 1, 4, 5 and 8 are severally equal and also the positions 2, 3, 6 and 7, but not the positions 1 and 2. The conception that in the a-compounds the position 1, 4, 5 or 8 is occupied : is due to Liebermann (A. 163, 225), Eeverdin and Nolting (B. 13, 36), and Fittig and Erdmann (cf. the formation of a-naphthol, given above). With regard to the di-derivatives of naphthalene, a considerable number of isomerides of a good many are known ; according to the naphthalene formula, ten are theoretically possible in each case when the two substituents are the same, and fourteen when they are different. Bromo-na^hthalenes, a-Bromo-naphthalene, which can be prepared directly, goes partially into the /3-compound when heated with chloride of aluminium. 464 XXXI. NAPHTHALENE GROUP. Nitro-naphthalenes, a-Nitro-naphthalene, CioHy.N02 (Laurent, 1835), results from the direct nitration of naphthalene. It forms yellow prisms, M. Pt. 6 1 °, boils without decomposition, and goes into di-, tri- and tetra-nitro-naphthalenes upon further nitration. On reduction it is converted into a-naphthylamine. The isomeric /3-Nitro-naphthalene can be obtained indirectly by diazotizing /3-naphthylamine, and acting on the product with sodium nitrite in presence of cuprous oxide (see p. 337) ; it crystallizes in bright yellow needles. Naphthylamines ; Naphthalene-sulphonic acids. a-Naphthylamine, CiqH^.NH2 (Zinin), forms colourless needles or prisms readily soluble in alcohol; M. Pt. 50°, B. Pt. 300°. It can also be easily prepared by heating a-naphthol with the double compound of chloride of calcium and ammonia (while aniline can only be got from phenol in a similar manner with difficulty) : CioH^.OH + NH3 = CioH^.NH^ + H^O. It possesses a disagreeable fsecal-like odour, sublimes readily, and turns brown in the air. Certain oxidizing agents, such as ferric chloride, produce a blue precipitate with solutions of its salts, while others give rise to a red oxidation product; chromic anhydride oxidizes it to a-naphthoquinone. In other respects it is very like aniline. The isomeric ^-Naphthylamlne, CjQH^.NHg (Liehermann, 1876), is most conveniently prepared by heating /5-naphthol either in a stream of ammonia or with the double compound of zinc chloride and ammonia. It crystallizes in glancing mother-of-pearl plates, M. Pt. 112°, and has no odour. It is more stable than a-naphthylamine and is not coloured by oxidizing agents. Both of these naphthylamines can be converted into tetrahydro- compounds by the action of sodium and amyl alcohol [i.e. nascent hydrogen) upon them. While, however, Tetrahydro- a-naphthylamine NAPHTHYLAMINES. 465 still resembles its mother substance closely in most of its properties, Tetrahydro-/3-naphthylamine possesses a character somewhat like that of ethylamine. The latter is very strongly basic, has an affinity for carbonic acid and cannot be diazotized, yielding on the contrary a very stable nitrite. The a-compound is oxidizable to adipic acid (p. 228), and the ^-compound to carbo-hydrocinnamic acid," C6H4<^^2— COgH^ -p^^^ justified in concluding that in the jS-compound it is the benzene nucleus to which the amido- group is joined which has taken up hydrogen, but in the a-compound, on the contrary, the other benzene nucleus [Bamberger and Midler, B. 21, 847, 1112, etc.). From both naphthylamines there are derived, as in the benzene series, Methyl- and Dimethyl-naphthylamines, Phenyl-a- and -j8-naph- thylamines (which are of technical importance), Nitro -naphthylamines, Diamido-naphthalenes or Naphthylene- diamines, CioH6(NH2)2, Diazo- compounds (which are in every respect analogous to the diazo-com- pounds of benzene, especially in their capability of yielding azo-dyes), Diazo-amido-compounds, etc. The Diazo-amido-naphthalene, C10H7 — 1^=]^ — NH— C10H7, which results from the action of NgOg upon a-naphthylamine, readily under- goes a molecular transformation (like the corresponding benzene compound) into Amido-azo-naphthalene, C10H7 — N=N — CioHg.NHg. This latter compound crystallizes in brownish-red needles with a green metallic glance, and can be diazotized, its diazo- compound yielding a -Azo -naphthalene, C10H7 — N=N — O^qK,^ (red to steel-blue glancing prisms), when boiled with alcohol. This last, which can either not be prepared at all or only with great difficulty by the methods which hold good for azo-benzene, is in its turn capable of forming a hydrazo- compound, Cn)H7— ^^H — NH — C10H7, which undergoes a molecular transformation with acids into bases of the nature of benzidine, e.g, Naphthidine, (CioH6)2(NH2)2, etc. The two Naphthalene- sulphonic acids, CioH7(S03H), which are crystalline hygroscopic substances obtained by heating naphthalene with concentrated H2SO4, and of which the a-acid changes into the /5-one when warmed with sulphuric acid, yield the two naphthols when fused with alkalies, and the two Cyano -naphthalenes, C10H7. CN, when heated with potassium cyanide; these last are crystalline com- pounds which distil unchanged. Naphthylamine-sulphonic acids, e.g. G^^q(1^'R^{^0^\ are known in large number. Naphthionic acid (NH2 : SO3H -1:4) results upon sulphurating a-naphthylamine ; it is employed in the preparation of azo-dyes. (506) 2G 466 XXXI. NAPHTHALENE GROUP. Najphthols, a- and /5-Naphthols, CjqH^.OH, which are present in coal tar, can be easily prepared, not only from the naphthalene- sulphonic acids as above, but also by diazotizing the naphthyl- amines. They crystallize in glancing plates of a phenolic odour, and are readily soluble in alcohol and ether but only sparingly in hot water. a-Naphthol (Griess, 1866) has the M. Pt. 95' and B. Pt. 279^ while /3-naphthol (Schdffer, 1869) has the M. Pt. 122° and B. Pt. 286° ; both of them are readily volatile. They possess a phenolic character but nevertheless resemble the alcohols of the benzene series more than the phenols, their hydroxyl groups being far more capable of reaction than those of the latter, e.g. being readily exchange- able for NHg (see above). Both of the naphthols yield Ethyl ethers, CioH^.O.CgHg, Acetyl- naphthols, CioHy.OlCgHsO), etc. Ferric chloride oxidizes both, with the production of a violet (a) or green (jS) colour, to Dinaphthols, C2oHi2(OH)2, which correspond to the diphenols (p. 438) and are derivatives of dinaphthyl. From the naphthols, as from the phenols, there are derived Nitro-, Dinitro-, Trinitro- and Amido-compounds, etc. The calcium salt of Dinltro-a-naphthol, CioH5(N02)2.0H, is known as Martins^ yellow or naphthalene yellow, and its sulphonic acid, Naphthol yellow S or fast yelloiv, is also a valuable yellow dye. Amido-naphthols, CioH6(NH2)(OH), result from the nitro-naphthols upon reduction ; like the amido-phenols they are readily oxidized in the air. (NH2 : OH in the a -compound = 1 : 4, in the jS- compound = 1:2.) The dyes (e.g. Orange II.) which are obtained by the action of diazo -compounds upon the naphthols, have been already mentioned at p. 370. Other azo-dyes contain only naphthalene residues, e.g. Fast red (" Echtroth "), CioH6(S03Na)— N=N— CioHg.ONa, which results from the action of diazo-naphthalene-sulphonic acid (a compound analogous to diazo-benzene-sulphonic acid) upon /5-naphthol. For the composition of Biebrich scarlet, etc. see p. 372. A series of Naphthol-mono-, -di- etc. sulphonic acids, which are of great technical value for the preparation of azo-dyes, are known. NAPHTHOQUINONES. 467 Dioxy-naphthalenes ; Naphthoquinones, Various Dioxy-naphthalenes, CioH6(OH)2, are known. Two of them, the hydro-naphthoquinones, are oxidizable by chromic acid to compounds of a quinonic nature (p. 392), the naphthoquinones, just as hydro- quinone itself is. a-Naphthoquinone, CioHgOg, also results from the oxidation of naphthalene, a-naphthylamine, a-amido-naphthol, etc. by chromic acid. It crystallizes in yellow rhombic tablets, M. Pt. 125°, and is the com- plete analogue of ordinary quinone, having a similar odour and being volatile with steam. j8-Naphthoquinone, which crystallizes in yellow-red plates and blackens when heated to 115-120°, has no odour and is not volatile, being thus more like phenanthrene-quinone. These two compounds receive the formula : and CO j8-Naphthoquin one (see Schultz, " Theerf arben, " 1 Aufl. S. 861 u. 862), since they react with hydroxylamine to form oximes, the so-called Iso-nitroso-naphthols, compounds which are also obtained by the action of nitrogen trioxide upon the naphthols themselves. Oxy -naphthoquinones, CjoHgOglOH), are likewise known. The ordin- ary oxy-naphthoquinone is a hydroxyl derivative of a-naphthoquinone (0:0: OH = 1:4:2); Juglone (yellow needles) is an isomeric oxy- naphthoquinone (0:0: OH = 1:4:5) which occurs in nut shells and has also been prepared artificially (B. 20, 934). A Dioxy-naphthoquinone, CioH402(OH)2, is the naphthazarin " or alizarin black" of commerce, a valuable dye which is prepared by acting upon a-dinitro-naphthalene with zinc and sulphuric acid, and which comports itself like the alizarin dyes ; it is the "alizarin " of the naphthalene series (see p. 474). Homologues of Naphthalene and Hydrocarbons related to it ; Carhoxylic Acids. a- and /^-Methyl-naphthalenes, CioH^.CH^, and also the Dimethyl-naphthalenes, G^^^q{GE.^c^, are present in coal tar. 468 XXXI. NAPHTHALENE GROUP. They may be prepared synthetically by methods analogous to those applicable to the homologues of benzene. The Naphthoic acids, CioH7.(C02H), can be obtained by saponifying the cyano-naphthalenes and also by the other synthetical methods given on pp. 404 et seq. ; they crystallize in fine needles sparingly soluble in hot water, and break up into naphthalene and COg when distilled with lime. Among the Naphthalene -dicarhoxylic acids, CioHg(C02H)2, which are known may be mentioned Naphthalic acid, which at a some- what high temperature yields an anhydride similar to phthalic anhyd- ride. The positions a-a'" (= 1:8) are ascribed to its carboxyls, this being termed the "peri "-position. Phenyl-naphthalene, Cif^^jiC^R^)^ has also been prepared ; it is a compound built up of a naphthalene and of a benzene nucleus, and is therefore analogous to diphenyl, CgHg — CgHg. The same applies to : Di-naphthyl, C10H7 — C11H7, which yields derivatives [e.g. the di- naphthols and naphthidines) analogous to those of diphenyl. Three modifications, the a-a-, /3-/3- and .a-/3- compounds, are theoretically possible. Another derivative of naphthalene is Acenaphthene, C12H10, CH = CioH6^6H4 + 4Na = 0,^,CeH, - H, = CeH,<^JJ>C,H,. 5. By heating benzene with symmetrical tetrabromo-ethane and aluminic chloride (B. 16, 623) : BrCHBr + ^""^ " ^^^^^^^CH" 6. When phthalic anhydride is heated with benzene and 470 XXXII. ANTHRACENE AND PHENANTHRENE GROUPS. chloride of aluminium, o-benzoyl-benzoic acid results, and from this, on heating with phosphoric anhydride, anthraquinone {Behr and v. Dorp, B. 7, 578) ; the latter goes into anthracene upon reduction with zinc dust : 7. From alizarin by means of zinc dust (see p. 474). Constitution. From the above modes of formation and from its relation to anthraquinone, whose constitution follows e.g. from mode of formation 6, the anthracene molecule is seen to contain two benzene nuclei, CgH^, joined together by a middle group, CgHg. The carbon atoms of this middle group are like- wise linked together, as is seen from mode of formation 5, and take up the o-position with regard to each other on one or other of the benzene nuclei (on one nucleus according to methods of formation 2 and 6, and on the other according to method 4 ; for further proofs of this, see e.g. v. Pechmann, B. 12, 2124). The constitution of anthracene is thus the follow- ing (Graebe and Liebermann, A. Suppl. 7, 313) : HC HC H C c H H C c H H C C H CH CH The two carbon atoms of the middle group thus form a new hexagon- ring with the carbon atoms of the benzene nuclei to which they are linked, so that anthracene may also be looked upon as being built up by the conjunction of three benzene nuclei. Properties and Behaviour. Anthracene crystallizes in colour- less plates which show a magnificent blue fluorescence. It is insoluble in water and only sparingly soluble in alcohol and ether, but readily so in hot benzene; M. Pt. 213°, B. Pt. DERIVATIVES OF ANTHRACENE. 471 above 360°. With picric acid it yields an addition compound crystallizing in beautiful red needles. Anthracene is transformed by sunlight into (the polymeric ? ) Para- anthracene, (Ci4Hio)x. It takes up in the first instance two atoms of hydrogen when reduced {e.g. by hydriodic acid and phosphorus), with the formation of Anthracene dihydride, Ci4H^o-H2 (see above, mode of formation 4). This latter crystallizes in white plates, readily soluble in alcohol, M. Pt. 107° ; it sublimes easily and distils without decom- position, but goes back into anthracene at a red heat or when warmed with concentrated sulphuric acid. It has the constitution : A Hexa-hydride, Ci4Hio.Hg, is also known. Derivatives of Anthracene. Theoretically three isomeric mono-derivatives are possible in each case, viz., the a-, and y-compounds : a" y' a' since, in the graphical formula given on the preceding page, 1 = 4 = 5 = 8 = a, 2 = 3 = 6 = 7 = y8, and 9 = 10 == y. The observed facts are in complete accordance with this. The position of the substituting group can usually be determined either by the behaviour of the substance in question upon oxidation, e.g, if it be in the 7-position it will be eliminated with the formation of anthraquinone ; or it is arrived at from the synthesis of the compound, e.g. in the case of alizarin, whose formation from pyrocatechin and phthalic acid shows that its two hydroxy Is are contained in one and the same benzene nucleus. Anthraquinone, GqHl^(C0)2Gq}1^, in which the hydrogen atoms 9 and 10 are replaced by two atoms of oxygen, only yields two isomeric mono-derivatives in each case. Isomeric di-derivatives may exist in very large number. 472 XXXII. ANTHRACENE AND PHENANTHRENE GROUPS. Summary of the most important derivatives of Anthracene. C^^H^Cl l^'l^lo^o-, Dichloro-, and ^i4„8 2 I Dibromo-anthracenes C14H9.NO2, unknown. C„H,<^^>CeH3.0H "jAnthrol. C14H9.NH2, Anthramine 1^ ^' ^ \ onic acid. r TT ^QH TT\ j3-Anthracene- Oi4n8i^U3ti)2| disulphonic acids. Ci4H9(OH), Oxy -anthracenes : CH C6Er4<^^Qjj^>C6H4, Anthranol (7). Hydro-compound : CQR4<.Q^lQ^y>^6^^^ ^oUy)!^ Ci4H8(OH)2, Dioxy -anthracenes : C6H4<^ • J ^C6H4, Anthra-hydroquinone ( isomers C14H8O2, Anthraquinone : Rufol, FlavolA Chrysazol. / r« Tin /Qr» TT\ fAnthraquinone- Oi4±i6U2(bU3±l)2 pjjQ^.^ ^^^^^ C6H4<^^(^^KC6H4, Oxanthranol. Ci4H702(OH), Oxy-anthraquinones : C6H4(CO)2C6H3(OH) : a = Erythro-oxy-, /3 = Oxy-anthraquinone. Ci4H602(OH)2, Dioxy -anthraquinones : C6H4(CO)2C6H2(OH)2 ; = Alizarin, aa' = Quinizarin, a^' = Purpuro- xanthine, etc. C6H3(OH)(CO)2C6H3(OH) : Anthraflavic acid, Iso-anthraflavic acid, Anthra- rufin, Chrysazin, etc. Ci4H502(OH)3, Trioxy -anthraquinones : C6H4(CO)2C(5H(OH)3 : a^a' = Purpurin. Isomers : Flavo-purpurin, Anthra-purpurin, etc, Tetroxy-anthraquinones : Anthrachrysone, Rufiopin. Hexoxy -anthraquinone : Rufigallic acid. Ci4H9(CH3), Methyl-anthracenes. Ci4H9(C6H6), Phenyl-anthracene, etc. p -p. /CH2 TT Alkybhydro- ^6J=i4<\CHR-^^6^4' anthracenes. p/rvTTv Phenyl- Ci4H8(CH3)2, Dimethyl-anthracenes. XT /nri TT\ fAnthracene-carboxylic Oi4H9(C02H),| acids(a, ft 7). CR(OH) ^6H4<^6^4» nol (Phthalideins), DERIVATIVES OF ANTHRACENE; ANTIIRAQUINONE. 473 Substitution products are obtained directly from these compounds ; they yield antliraquinone upon oxidation, and therefore contain the halogen in the 7-position. jS-Anthramine, C14H11N, is obtained from /3-anthrol, C^JIiqO, and ammonia, anthrol from anthracene-sulphonic acid and potash, and the last-named acid by the reduction of /3-anthraquinone-mono-sulphonic acid, a- and j8-Dioxy-anthracenes are prepared by fusing the sulphonic acids with potash, and the following substances, which stand midway between hydro-anthracene and anthraquinone, viz. hydranthranol, oxanthranol, anthranol and anthra-hydroquinone [Liebermann), by the more or less energetic reduction of anthraquinone. The oxy-anthracenes appear to be also present in coal tar. The phthalidines result from the action of concentrated sulphuric acid upon the phthalines (p. 455 ; cf. also B. 18, 2150), thus : C6H4CeH, Triphenyl-methane-carboxylic acid. Phenyl- anthranol ; they are oxidizable to the phthalideins, e.g. Coerulein (p. 457). 7-Alkylated anthracenes are also produced by the elimination of the elements of water from the alkylated hydranthranols, which in their turn are obtained from hydranthranol by acting upon it with alkyl iodide and potash ; while 7-phenyl-anthracene is got by heating phenyl- anthranol (a phthalidine) with zinc dust. For isomeric alkyl-anthra- cenes, see below. Anthraquinone and its oxy-compounds are of especial importance. Anthraquinone, Ci^HgOg (Laurent, 1834). Formation as given above. It is easily obtained by oxidizing anthracene with chromic acid mixture (which is the method followed on the large scale), or with chromic anhydride and glacial acetic acid, and is also produced when calcium benzoate is distilled. It crystallizes in yellow prisms or needles which are soluble in hot benzene, sublime with great readiness, and are ex- ceedingly stable as regards oxidizing agents ; M. Pt. 277°. Hydriodic acid at 150° reduces it either to anthracene or its di-hydride, while fusion with potash converts it into benzoic acid. It possesses more of a ketonic than of a quinonic character (Zincke, Fittig), not being reduced by sulphurous acid, and it gives an oxime with hydroxylamine. 474 XXXII. ANTHRACENE AND PHENANTHRENE GROUPS. It yields (mono- and di-) bromo-, nitro- and sulpho- compounds. Anthraquinone-j8-mono-sulphonic-acid crystallizes in yellow tablets ; of the Di-sulpho-acids we are acquainted with two which are formed directly from anthraquinone, and two which are produced by the oxidation of the anthracene-disulphonic acids. Fusion of the sulphonic acids with potash does not generally yield the analogous oxy-compounds in theoretical quantity, oxygen being usually absorbed from the air at the same time ; thus the mono-sulphonic acids yield mono- and dioxy-, and the di-sulphonic acids di- and trioxy- anthraquinones. In practical working the amount of chlorate of potash required is added to the "melt." Prolonged fusion with potash gives rise to decomposition into (oxy-) benzoic acids. Various Oxy-anthraquinones can also be prepared by the synthetical mode of formation 6, p. 469, which applies in the case of anthraquinone, viz., from phthalic anhydride and the mono- or dioxy-benzenes (Baeyer and Caro, B. 7, 792 ; 8, 152), e.g, : C6H4^ + C,Il,(OK), ^ C6H4CeH2(OH)2 + H^O ; phenol yields by this method the two oxy-anthraquinones (yellow needles), pyro-catechin (1:2) yields alizarin, hydroquinone yields quinizarin, and so on. They are further produced by fusing chloro- and bromo-anthraquinones with potash, while m-oxy-benzoic acid can be converted directly by sulphuric acid into anthraflavic acid, water being separated (see Summary). Alizarin, C^Jifi^, is the most important constituent of the • beautiful red dye of the madder root (Rubia tinctorum), which has been known for ages, being present in the latter as the readily decomposable glucoside, Ruberythric acid, G2qH.28^u (p. 513); in addition to alizarin, madder also contains purpurin. The preparation of alizarin from anthracene, with the inter- mediate formation of anthraquinone-mono-sulphonic acid or of dichloro-anthraquinone, which was first introduced in 1871 (Graebe and Liebermami, Caro, Perking B. 3, 359 ; A. 160, 130), depends upon an observation made by Graebe and Liebermann in 1868 (B. 1, 49; A. Suppl. 7, 297) that alizarin is reduced to anthracene when strongly heated with zinc dust. It crystallizes in magnificent red prisms or needles of a glassy glance, which melt at 282** and can be sublimed, dis- solves readily in alcohol and ether, only sparingly in hot water, but, as a phenol, very easily in alkalies to a violet-red solution. It yields insoluble coloured compounds — the so-called "lakes'^ PURPURIN, ETC. ; PHENANTHRENE. 475 — with metallic oxides, the alumina and tin lakes being of a magnificent red colour, iron lake violet-black, and lime lake blue. In the Turkey Red manufacture, for instance, the materials to be dyed are previously mordanted with acetate of alumina or with " ricinoleic-sulphuric acid" (see p. 167). Nitrogen tetroxide, N2C^4» converts alizarin into /3-Nitro-alizarin or Alizarin orange, Ci4H7(N02)04, a yellowish-red dye ; and this latter, when treated with glycerine and sulphuric acid (the Skraup reaction, p. 492), yields Alizarin blue, C17H9NO4 (see quinoline), which is likewise a valuable blue dye, being used chiefly in the form of the NaHSOs-com- pound. Purpurin, Anthrapurpurin and riavopurpurin are also valuable dyes which are manufactured on a large scale. The colouring power of these compounds is connected with the pre- sence of two hydroxy Is in the ortho-position to one another. Closely related to the anthracene dyes in properties is Galloflavin, CisHgOg, which is obtained by exposing an alkaline solution of gallic acid to the action of the air (Bohn and Graehe, B. 20, 2327). Eomologues of Anthracene. There are also present in coal tar : 1. Methyl-anthracene (either a- or jS-), C14H9.CH3, which resembles anthracene and is oxidizable to methyl-anthraquinone ; M. Pt. 199°. 2. Dimethyl-anthracene, Ci4H8(CH3)2, M. Pt. 224-225°; isomers of this compound have been prepared synthetically. The three Anthracene-monocarboxylic acids which are theoretically possible and also some Anthracene-dicarboxylic acids are likewise known. B. Phenanthrene. Phenanthrene, Ci^H^o [Fittig and Ostermeyer (1872), A. 166, 361]. This hydrocarbon is found accompanying anthracene in coal tar. It crystallizes in colourless glancing plates, and dissolves in alcohol more readily than anthracene (with a blue fluorescence); M. Pt. 100°, B. Pt. 340°. It may be separated from anthracene by partial oxidation, the latter being the first .4 47G XXXII. ANTHRACENE AND PHENANTHRENE GROUPS. to be attacked, and subsequent distillation. Oxidizing agents convert it into diphenic acid (p. 441). It is employed in the manufacture of printer's black. Formation. 1. By. leading the vapour of toluene, stilbene, dibenzyl or o-ditolyl through a red-hot tube, thus : C6H4— CH3 _ C6H4— CH ^ C6H4 — CH3 C'gH4 — CH ^ o-DitoIyl. Phenanthrene, 2. Together with anthracene from o-bromo -benzyl bromide and sodium. 3. By distilling morphine with zinc dust. - Constitution. The formation of phenanthrene from o-ditolyl, and its oxidation to diphenic acid, nr^xi^ show that it is a diphenyl Cgri4 — 002^1 derivative and that it contains one C-atom linked to each benzene nucleus ; this carbon atom is joined to the corresponding one by a double bond, as is shown e.g. by its formation from stilbene, ^6^5 — CH CgHg — CH diphenyl from benzene. Since diphenic acid is a di-ortho-diphenyl- dicarboxylic acid {Scliultz, A. 196, 1 ; 203, 95), phenanthrene is also a di-ortho-derivative and possesses the following constitution : CH CH C6H4-CH CgH4 — CH According to the above formula, the two CH-groups form a new hexagon ring with the two carbon atoms of both benzene nuclei of the diphenyl to which they are linked, so that phenanthrene — like anthra- cene — may be looked upon as the product of the coalition of three benzene nuclei, or of one naphthalene and one benzene nucleus. We are likewise acquainted with addition and substitution products of phenanthrene, e.g. a tetrahydride, nitro-, amido-, cyano- and oxy- compounds, and sulphonic and carboxylic acids. Phenanthrol, Ci4H9(OH), is an oxy-phenanthrene, and Phenanthrene-hydroquinone, Ci4H8(OH)2, a dioxy-compound which goes upon oxidation into : PHENANTHRENE COMPOUNDS; FLUORANTHENE, ETC. 477 Phenanthrene-quinone, i ^ ^ i , which latter may also CgH^ — CO be prepared directly from phenanthrene and chromic acid. It crystallizes in odourless orange needles which distil un- changed, but are not volatile with steam; M. Pt. 198°. Phenanthrene-quinone possesses the character of a di-ketone, reacting with hydroxylamine, sodium bisulphite, etc., but it can be reduced to the corresponding hydroquinone by sul- phurous acid. It gives a bluish-green colouration with toluene containing thio-tolene, glacial acetic acid and sulphuric acid, which changes to violet after dilution and addition of ether, i.e. the ether becomes violet-coloured; this is the Lauhenheimer reaction (see p. 298, also B. 17, 1338). With o-diamines, members of the phenazine group result (p. 501). O. Hydrocarbons of more complex nature. Fluoranthene, CigHio, Pyrene, CiqHiq, Chrysene, CjgHia, and Retene, CisHiS) are hydrocarbons which have been isolated from that portion of coal tar which boils at above 360°. Phenanthrene, pyrene and fluoranthene are also found in *'Stupp" fat, i.e. the fat obtained as a bye-product from the working up of mercury ores in Idria. They all crystallize in white plates, sublime without decomposition, and are converted into the corresponding ketones upon oxidation. Their constitution is expressed by the following formulae (with regard to that of pyrene, see Bamberger , A. 24 O, 147) : C6H4^^ Cg H4 — CH Q^S.^- — CH C'eHs^Qjj^CH CioHg — CH ^^jl^^CgHg— CH Fluoranthene. Chrysene. Retene. Naphtho-anthracene, which has been prepared synthetically, is isomeric with chrysene (B. 10, 2209). 478 TRANSITION TO THE PYRIDINE GROUP. PYRIDINE DERIVATIVES, ALKALOIDS AND COMPOUNDS RELATED TO THEM. The aromatic compounds which have been described up to now are derived from the mother hydrocarbons : Benzene, CgHg, Naphthalene, C-^qH.^, Anthracene, Ci^H^q, etc. But alongside of them we have to place several groups of very important nitrogenous compounds, which are derived from the mother substances : Pyridine, C^H^N, Quinoline, CgH^N, Acridine, C^gHgN, etc. in precisely the same manner as the former are from benzene, etc., i.e. through the replacement of hydrogen by halogen, NO2, NH2, SO3H, OH, CH3, CO2H, etc. The difference in composition between these bases (among one another) is C4H2, this being the same as the difference between the mother hydrocarbons, from which they may be considered as being derived by the exchange of CH for N, thus : CeHg - CH + N = C5H5N. Just as naphthalene and anthracene are benzene derivatives, so are quinoline and acridine derivatives of benzene on the one hand and of pyridine on the other ; the latter is thus the mother base of all the classes of compounds which are now about to be described. It may be compared with benzene in many points : 1. It is even more stable than benzene, and is further distinguished from the latter by a greater indifference towards the substituting reagents sulphuric and nitric acids and the halogens. The first of these sulphurates only at very high temperatures ; nitro-pyridines are as yet unknown, as are also iodo-pyridines ; while chloro- and bromo-pyridines have so far only been prepared in small number. Neither pyridine nor its carboxylic acids are affected by nitric acid, chromic acid, or permanganate of potash. TRANSITION TO THE PYRIDINE GROUP. 479 2. The behaviour of its derivatives is on the whole very like that of the derivatives of benzene. Thus its homo- logues (and also quinoline, etc.) are transformed into pyridine- carboxylic acids upon oxidation, and these acids yield pyridine when distilled with lime, just as benzoic acid yields benzene. 3. The isomeric relations are also precisely similar to those of the benzene derivatives. Thus the number of the isomeric mono-derivatives of pyridine is the same as that of the isomeric bi-derivatives of benzene, viz., three ; and the number of the bi-derivatives of pyridine, with two atoms of one and the same substituent, the same as that of the benzene derivatives CgHgXXX', viz., six, and so on. 4. The products of reduction are likewise analogous. Just as hexahydro-benzene results from benzene, so do we obtain from pyridine (but more easily) hexahydro-pyridine or piperi- dine, CgH^jN ; further, just as naphthalene yields tetrahydro- naphthalene, so does quinoline (readily) tetrahydro-quinoline, CgHjjN, and acridine (readily) (di-) hydro-acridine, C^gH^^N, which last is analogous to anthracene di-hydride. Here also, as in the case of the hydrides of the benzene series, further combination with hydrogen may take place, but there is like- wise here a tendency to the reproduction of the original bases. Consequently the constitution of these compounds is very similar to that of the benzene hydrocarbons. (For further details, see pp. 483 and 494.) In contradistinction to the neutral benzene hydrocarbons, pyridine and its homologues, etc., are strong bases, most of them having a pungent odour ; pyridine is readily soluble in water but quinoline only slightly so. They distil or sublime without decomposition, and form salts with hydrochloric and sulphuric acids which are for the most part readily soluble, while those with chromic acid, though often characteristic, are usually only sparingly soluble; also double salts with the chlorides of platinum, gold and mercury, most of which dissolve with difficulty, and so on. [Continued on p. 480. 480 TRANSITION TO THE PYRIDINE GROUP. Summary of several Pyridine and Quinoline Derivatives. Pyridine Chloro-pyridine, etc. Pyridine-sulphonic acid (jS-) . . . Oxy -pyridines (3) . Methyl-pyridines . (Picolines) (3) Dimethyl-pyridines (Lutidines) Trimethyl-pyridines Propyl-pyridines . Pyridine-carhoxylic acids (3) . . . . Pyridine-dicarboxylic acids (6) . . . . Picoline-carboxylic acids Di-pyridine . . . Di-pyridyl . . . Phenyl-pyridines . Piper idine . . . C5H5N C5H4NCI CsH^NCOH) CsH^NlCHs) CsHsNlCHa)^ C5H2N(CH3)3 CsH^NlCsHy) C6H4N(C02H) C5H3N(C02H)2 C5H3N(CH3)(C02H) C10H10N2 O5H4N-C5H4N OsH^NlCeHs) Quinoline Chloro-quinoline, etc. Amido-quinolines . . Quinoline-sulphonic acids Oxy-quinolines . . Methyl-quinolines . (Quinaldine, etc.) Dimethyl-quinolines Trimethyl-quinolines etc. Quinoline-carhoxylic acids Quinoline-dicarboxylic acids Quinaldine-carboxylic acids Di- quinoline .... Di-quinolyline . . . Phenyl-quinolines . . Tetrahydro-quinoUne . C9H7N CgHgNCl CoHoNlNHs) CgHeNlSOaH) CgHeNlOH) CgHeNlCHs) CANlCHsla C9H4N(OH3)3 C9H6N(C02H) C9H5N(C02H), CgHsNlCHsllCO: C18H14N2 C9HeN(C6H5) CgHnN As bases they are tertiary, and therefore cannot {e.g.) be acetylated; they combine with methyl iodide to quaternary compounds. Pyridine, quinoline and many of their homologues (and also acridine) are found in coal tar and in bone oil (oleum Dippelii animale), from which they can be separated by the addition of acids ; nevertheless they cannot, speaking generally, be obtained chemically pure even by repeated ALKALOIDS; PYRIDINE GROUP. 481 fractionation. To prepare them pure, therefore, recourse must often be had to synthetical methods. The quinoline and also the pyridine bases result from the distillation of most of the alkaloids which occur in nature, e.g. quinine, cinchonine and strychnine, with caustic potash, etc., and their carboxylic acids from the oxidation of these alkaloids. It follows from this that most of the latter are pyridine deriva- tives. The Alkaloids are vegetable bases, most of which exert an intensely poisonous or curative action ; they are therefore of great medicinal importance. They will be treated of shortly here, partly under the pyridine derivatives, and partly (where their relation to the latter is as yet only slightly known) in an appendix. Certain alkaloids {e.g. caffeine, p. 284, and choline, p. 196) belong moreover to other classes of com- pounds. The designation "alkaloids" is now becoming limited to the vegetable bases which are derived from pyridine. XXXIIL THE PYRIDINE GROUP, CAn-sN. The pyridine group comprises pyridine itself, together with its homologues, carboxylic acids and more nearly allied deriva- tives. The homologues of pyridine which are obtained from coal tar and bone oil are known as Picoline (CgH^N), Lutidine (C^), Collidine (Cg), Parvoline (Cg), Coridine (C^q), etc. ; the fractions, however, whose empirical analyses agree with these formulae, do not represent chemical individuals, but are mixtures of isomeric and also in part of homologous bases. All the homologues .of pyridine are distinguished from pyridine itself, as those of benzene are from the latter, by the readiness with which they are oxidized to pyridine-carboxylic acids : C,H3N(OH3)(C2H,) yields C,H3N(C0,H),. (606) 2H 482 XXXIII. PYRIDINE GROUP. Formation. 1. The pyridine bases result from the destruc- tive distillation of many nitrogenous organic substances, hence their presence in coal tar. 2. Lutidine is obtained, together with other bases, on distil- ling cinchonine with potash. 3. Pyridine is got by oxidizing quinoline to quinolinic acid, C3H3N(C02H)2, and then breaking up the carboxylic groups. 4. /?-Methyl-pyridine results on distilling acrolein-ammonia (p. 138), and collidine in an analogous manner from crotonic aldehyde-ammonia or aldehyde-ammonia (p. 132) {Baeyer^ A. 155, 283, 297). Aldehydine, CgHiiN, is produced by heating ethylidene chloride or bromide with alcoholic ammonia, and /3-methyl-pyridine by heating glycerine with acetamide and phosphoric anhydride. 5. When potassium-pyrrol, C4H4NK, is heated with CHCI3, chloro- pyridine, C5H4CIN, results ; and when with CHgClg, pyridine. 6. Pyridine is also obtained by heating hexahydro-pyridine (piperidine) with concentrated sulphuric acid to 300° (Konigs): 7. When the hydrochloride of penta-methylene-diamine, C5Hi(,(N 112)2, is heated rapidly, piperidine is produced {Laden- burg, B. 18, 2956, 3100) : C,H,o(NH2)2, HCl = C,H,,N + NH.Cl. 8. The compounds of the pyridone group (p. 491) are transformed into pyridine derivatives by the action of ammonia. The amides of citric acid, e.g. the monamide, CeHyOeCNHg), yield citrazinic acid [dioxy-pyridine-7-carboxylic acid {HofmanTi)] when heated with H2SO4, while acetone-dicarboxylic acid yields trioxy-pyridine (B. 19, 2694). 9. When aceto-acetic ether is warmed with aldehyde-ammonia, the ether of " Dihydro-collidine-dicarboxylic acid," i.e. a dihydride of tri- methyl-pyridine-dicarboxylic ethyl ether, is produced (Hantzsch) : 2C6H10O3 + CH3.CHO + NH3 = C5N(H2)(CH3)3(C02R)2 + 3H2O. This loses its two ' hydro- ' hydrogen atoms when acted on by ^303, and goes into collidine-dicarboxylic ether, C5N(CH3)3(C02R)2, from which collidine results on saponification and elimination of COg. If, instead of aldehyde-ammonia, the ammonia compounds of other aldehydes are used, one obtains analogous bases of the formula : C5H2N(CH3)3(CnH2„+l). pyridine; formation and constitution. 483 In the above reaction also a molecule of aceto-acetic ether may be replaced by one of aldehyde, when the mono-carboxylic ethers of dimethyl- etc. pyridine are formed, thus : CoHioOg + 2CH3.CHO + NH3 = C5H2NH2(CH3)2.C02R + 3H2O. This is a very important synthetical method (JIantzsch, A. 215, 1, etc.). 10. Trioxy-pyridine results from acetone-dicarboxylic ether and ammonia. 11. Pyridine is further produced by oxidizing its homologues to carboxylic acids and eliminating CO2 from the latter. 12. Conversely, the homologues of pyridine are formed by heating the latter with alkyl iodide to 300° {Ladenhurg), a reaction analogous to the production of toluidine from methyl-aniline. Constitution. The constitution of piperidine and pyridine is expressed by the following formulae : H2 H C C H2C/\CH2 HC/\|CH and (1.) HaC'v yCHa HCsl ^ICH N N H Piperidine, Pyridine. That of piperidine follows from its formation from penta- methylene-diamine : CH.NH + NH, Piperidine therefore contains a hexagon ring made up of one imido- and five methylene groups, and is a complete analogue of hexa-methylene ; it may be designated penta- methylene-imine. The constitution of pyridine follows: 1. from its near relation to piperidine ; 2. from the formation of pyridine-dicarboxylic acid by the oxidation of quinoline (see above) : C9H7N + 09 = C5H3N(002H)2 + H2O + 2CO2, in conjunction with which are to be taken the proofs of the constitution of quinoline (p. 494) ; 484 XXXIII. PYRIDINE GROUP. 3. from the perfect agreement with theory of the observed isomeric relations (see below) ; 4. from the transformation of ethyl -pyridine into ethyl-benzene upon heating pyridine with ethyl iodide (A. 241, 14). The above constitutional formula of pyridine was first proposed by Korner, The formation of collidine-dicarboxylic ether (p. 482) thus proceeds as follows (B. 18, 1744): I OCH ^ \ COgR— CH2 HgC— CO2R COgR— C C— CO2B I I = I II +3H2O + H2. CH3— CO OC— CH3 H3C— C C— CH3 NH3 Three isomeric mono-derivatives of pyridine are known in each case (p. 479). This agrees with the regarding of pyridine as a kind of mono-derivative of benzene in which, instead of H, a CH-group is replaced by N; the mono-derivatives of pyridine are thus comparable with the bi-derivatives of benzene, and are therefore three in number. They are designated as a-, fS- and y-derivatives of pyridine, as is shown in the following graphical formula : a'\ /a (II.) In order to determine the position of any given group, it is sought to exchange it for carboxyl ; should picolinic acid result, it fills the a-position, and should nicotinic or iso-nicotinic, then it fills the p- or 7-position respectively, since in these acids the a-, /5- and 7-positions of the carboxyl have been determined by special means. (See Monatsh. f. Chemie, 1, 800; 4, 437, 453, 595; B. 17, 1518; 18, 2967; 19. 2432). Di-derivatives of pyridine containing in the molecule two atoms of one and the same substituent can exist theoretically in six isomeric forms. As a matter of fact the six dicarboxylic acids, for example, are known [aa'-, a(3-, ay-, a^S'-, ^y- and /3/3'- ; see p. 488). The above pyridine formula (II.) has the advantage over (I.) that it gives expression to the linking in ring form of the five carbon atoms and of the nitrogen, without rendering it necessary to take specially into PYRIDINE. 485 account the mode in which the fourth affinity of each carbon and the third affinity of the nitrogen are used (analogously to the hexagon formula of benzene, p. 312). Besides Korner's formula, Dewar's (1871) is now frequently adopted ; it is : The isomerism of picoline, CgH^N, with aniline, CgHg.NHa, which repeats itself in their homologues, is also worthy of notice. Pyridine, C^H^N {Anderson, 1846), may be prepared from bone oil, and can be obtained chemically pure by heating its carboxylic acid with lime; the ferrocyanide is especially applicable for its purification, on account of its sparing solu- bility in cold water. It is also found in the ammonia of com- merce. Pyridine is a liquid of very characteristic odour, miscible with water and boiling at 114°. When sodium is added to its hot alcoholic solution, hydrogen is taken up and piperidine, C5Hj;,^N, formed (Ladenburg and Both, B. 17, 513 ; see also p. 488). When heated strongly with liydriodic acid, pyridine is converted into normal pentane. The ammonium iodides, e.g. C5H5N, CH3I, give a characteristic pungent odour when heated with potash, a fact which may be made use of as a test for pyridine bases ; it depends upon the formation of alkylated dihydro-pyridines, e.g. Dihydro-methyl-pyridine, C5H4.H2.N(CH3) [Hofmann, B. 14, 1497). Pyridine is polymerized by the action of metallic sodium to Dipyri- dine, CioHjoNg (an oil, B. Pt. 286-290°), with the simultaneous production of 25-Dipyridyl, CioHgNg, = C5H4N— (long needles, M. Pt. 114°), a compound corresponding to diphenyl (p. 438) ; both of these yield iso-nicotinic acid upon oxidation. An isomeric m-Dipyridyl has also been prepared, which gives nicotinic acid when oxidized. Pyridine car* be brominated but not nitrated ; it can also be sulphur- (III.) N Pyridine. 486 XXXIII. PYRIDINE GROUP. ated, with the formation of /3-pyridine-sulphonic acid, C5H4N.(S03H), from which potassium cyanide produces Cyano-pyridine, C5H4N.CN, and fusion with potash /3-oxy-pyridine. The three Oxy-pjnridines, C5H4N"(OH) (a-, /3-, 7-), are best prepared by the separation of COg from the respective oxy-pyridine-carboxylic acids, a- : M. Pt. 107° ; ^- : M. Pt. 123° ; 7- : M. Pt. 148°. They possess the character of phenols and are coloured red or yellow by ferric chloride. As in the case of phloroglucin, so here also there is a tertiary as well as a secondary form to be taken into account, the former reminding one of the lactames and the latter of the lactimes ; for instance, 7-oxy-pyridine may either have the formula C2H2<^'^^'>C2H2 or C2H2<^g>C2H2, the latter of the two repre- senting a keto-dihydro-pyridine ('^ pyridone "). Both of the methyl derivatives, Methoxy-pyridine and Methyl-pyridone, which result from these two forms by the exchange of H (of the OH or NH respectively) for CH3, are known (B. 19, 19 ; 20, 956). Trioxy-pyridine, C5H5NO3. By the condensation of acetone-dicar- boxylic ether with ammonia there is produced Glutazine, C5HgN202 (colourless plates soluble in alkali), which is converted by boiling hydrochloric acid into ammonia and trioxy-pyridine (yellowish micro- scopic prisms or needles). For its constitution see B. 19, 2694 ; 20, 2655.) Homdlogues of Pyridine. (Cf. Ladenhurg, A. 247, 1.) Methyl-pyridines or Picolines, C5H4N(CH3). All the three picolines are contained in bone oil and probably also in coal tar. The /3-compound results from acrolein-ammonia (p. 482) and also upon heating strychnine with lime. They are liquids of unpleasant piercing odour resembling that of pyridine, and they yield a-, /S- or 7- pyridine-carboxylic acid when oxidized, a-: B. Pt. 120°; ft-: B. Pt. 142-144°; 7-: B. Pt. 142-145°. Ethyl-pyridines, CgH4N(C2H5), are also known, a-Ethyl-pyridine (B. Pt. 148*5°) being obtained by the breaking up of tropine. Propyl- and Isopropyl Pyridines, C5H4N(C3H7), have been carefully investigated on account of their near relation to conine. They are prepared as given at p. 483, 12. Conyrine, CgHjiN (liquid, B. Pt. 166-168°), which results upon heating conine, C8H17N, with zinc dust, and which goes into conine again when treated with hydriodic acid, is a-normal propyl-pyridine. HOMOLOGUES AND OAKBOXYLIC ACIDS OF PYRIDINE. 487 a-Allyl-pyridine, C5H4N(C3H5), is produced when a-picoline is heated with aldehyde : C5H4N.CH3 + OHC-CH3 = C5H4N.CH=CH— CH3 + HgO. Reduction transforms it into inactive conine (B. Pt. 189-190°). Dimethyl-pyridines or Lutidines, C5H3N( 0113)2. The presence of the three lutidines has been proved in bone oil and coal tar. For their synthetical formation see p. 483. a-7-Lutidine boils at 157°, and the aa'-compound at 142-143°. The CoUidines, CgH^iN, are isomeric with the propyl-pyridines. Some of them are present in bone oil and can be prepared from cin- chonine by distilling the latter with caustic potash (p. 482). The collidine {a-a'-y) which is obtained from aceto-acetic ether and aldehyde- ammonia (p. 482), boils at 171-172°. Aldehydine " (from aldehyde, p. 482) is ^'-ethyl-a-methyl-pyridine (B. 21, 294). a- and jS-Phenyl-pyridines, C5H4N(C6H5), are analogous to diphenyl. (See Monatsch. f. Chemie, IV., 456, 472.) Pyridine-carboxylic acids, (See Summary, also A. 241, 1.) The Pyridine-mono-carboxylic acids, C5H4N(C02H), result from the oxidation of all the pyridine derivatives which con- tain only one (carbon-containing) side-chain, i.e. from methyl-, propyl-, phenyl-, etc. pyridines; also from the pyridine-dicar- boxylic acids by the breaking up of one of the carboxyls, just as benzoic acid results from phthalic. It is the carboxyl which stands nearest to the nitrogen which is first eliminated here. Nicotinic acid is also produced by the oxidation of nicotine. They unite in themselves the characters of the basic pyridine and of an acid, and are therefore comparable with glycocoll. They yield salts with HCl, etc. and double salts with HgCl2, PtCl4, etc. ; on the other hand they also form salts as acids, those with copper being frequently made use of for the separa- tion of the acid. The a- acid is Picolinic acid; needles, M. Pt. 135°. The /?- „ Nicotinic acid; needles, M. Pt. 231°. The y- „ Iso-nicotinic acid; needles, M. Pt. about 305°. It is noteworthy that the a- and /3-acids (and also e.g. the /3-7-dicarb- 488 XXXIII. PYRIDINE GROUP oxylic acid) readily yield up their nitrogen as ammonia when acted upon by sodium amalgam, being thereby transformed into unsaturated acids of the fatty series. Pyridine- dicarboxylic acids^ C5H3N(C02H)2. a-jS- = Quinolinic acid, M. Pt. about 223°. a-7- = Lutidinic acid, M. Pt. 235°. a-a'- = Dipicolinic acidy M. Pt. 226°. a-j3'- = Iso-cinchomeronic acid, M. Pt. 236°. /3-j3'- = Dinicotinic acid, M. Pt. over 285 . p.y. = Cinchomeronic acidj M. Pt. over 250°. Quinolinic acid (short glancing prisms), the analogue of phthalic acid, results from the oxidation of quinoline, just as phthalic acid does from naphthalene ; cinchomeronic and iso-cinchomeronic acids from the oxida- tion of cinchonine and quinine. The constitution a-jS- follows for quinolinic acid from its mode of formation (p. 483). The pyridine-mono- and di-carboxylic acids, which contain a carboxyl in the a-position, give a reddish-yellow colouration with ferrous sul- phate. Pyridine-tricarboxylic acids, C5H2N(C02H)3, are obtained in a similar manner by the oxidation of quinine, cinchonine (Carbo- cinchomeronic acid), berberine (Berberonic acid), etc. Pyridine-pentacarboxylic acid (from coUidine-dicarboxylic acid) has no longer basic properties ; it readily gives up COg. Hydro-derivatives of Pyridine, Piperidine, C^H^^N {Wertheim, Bochleder, 1850), is a colour- less liquid of peculiar odour slightly resembling that of pepper, and strongly basic properties, readily soluble in water and alcohol; B. Pt. 106°. It forms crystalline salts. It occurs in pepper in combination with piperic acid, C12H10O4 (p. 427), in the form of the alkaloid Piperine, CigHigNOg, = CgHjolS" — C12H9O3. i.e. piperyl-piperidine, which crystallizes in prisms, M. Pt. 129°; from this latter it may be prepared by boiling with alkali. For its formation from pyridine and from penta-methylene-diamine, see p. 482. Piperidine is a secondary amine ; its imido-hydrogen is replaceable by alkyl and by acid radicles. According to theory, Di- and Tetra-hydro-pyridines and derivatives of these may exist. Tetrahydro-pyridine derivatives, ** Piperideins," e.g. a-Pipecolein, CgHiiN, have been prepared by Ladenhurg, by the action of bromine and caustic soda upon the piperidines (B. 20, 1645). PIPERIDINE; CONINE. 489 The homologues of piperidine have been designated by Lademhurg Pipecolines, C5HioN(CH3), Lupetidines, 05119^(0113)2, Oopellidines, Or,H3N(OH3)3, etc. The most interesting among them are the a-, /3- and 7-Propyl- and Isopropyl-piperidines, OgHioNCOgHy), on account of their near relation to conine. Conine, dextro-rotatory a-normal-propyl-piperidine^ CgH^^N, = C5HjQN(C3H.jr), is the poisonous principle of hemlock (Conium Maculatum). It is a colourless dextro-rotatory- liquid of stupefying odour, slightly soluble in water ; M. Pt. 167-168°. Hydriodic acid at a high temperature reduces it to normal octane, while nitric acid oxidizes it to butyric acid, and potassium permanganate to picolinic acid (hence the a-position). Ladenhurg has prepared it synthetically by reducing a-allyl-pyridine in alcoholic solution by means of sodium (B. 19, 2578) : C5H4N(C3H5) + 4H, = C^HioNiCsH,). In this reaction there is first formed the optically inactive a-normal- propyl-piperidine, which is broken up, by crystallization of the tartrate, into conine (dextro-conine) and a Itevo-conine which resembles the other closely. The relations of these two bases to one another and to the inactive modification are the same as that of dextro- to Isevo-tartaric acid and of both of these to racemic acid (cf. B. 19, 2584). Analogous relations hold good with regard to the ethyl-piperidines. a-, jS- and 7-Coniceins, OsHigN, are peculiar bases which result from the (indirect) separation of hydrogen from conine. Conydrine, O18H17NO, an oxy -derivative, occurs along with conine in hemlock ; it crystallizes in plates, M. Pt. 120°, B. Pt. 240°. As secondary bases, piperidine and conine yield in the first instance tertiary bases, Methyl- piperidine and -conine, upon methylation, e.g. CqRiqN{CB.^), These unite further with methyl iodide, the resulting ammonium iodides being convertible into hydroxides; the latter how- ever do not again break up into their components upon distillation, but yield Dimethyl-plperidine, 05H9N(OH3)2 and Dimetliyl-conine, C8Hi5N(OH3)2, the ring being broken (see B. 19, 2628). If these in their turn are made to combine with OII3I, there result ammonium iodides which give off their nitrogen as tri-methylamine when distilled with alkali, and yield the hydrocarbons Piperylene, OgPIg, and Oonylene, CsHh (p. 57), respectively {HofmaiiTi's method of breaking up the piperidine bases, B. 16, 2058). Tropidine, OgHigN, an o.ly base (B. Pt. 162°), is related to conine ; it results from the action of concentrated hydrochloric acid upon 490 XXXIII. PYRIDINE GROUP. tropine, and is probably a derivative of a tetrahydro -pyridine (B. 16, 1142). Tropine, CgHj^NO, is obtained by decomposing atropine (see below). It is a base crystallizing in plates ; M. Pt. 62°, B. Pt. 229°. Very probably it is an Oxy-ethyl-methyl-tetrahydro-pyridine, C,U,.Il,.(G,Y[,OH.y—l^{CR,), (B. 15, 1029; 20, 1647). It reacts with methyl iodide in the same way as piperidine and Conine do, yielding tropilidene, CyHg (p. 58). Atropine, Hyoscyamine and Hyoscine are three isomeric bases of the formula Cj^HggNOg, which can be respectively prepared from Atropa Belladonna, Datura Strammonium and Hyoscyamus niger, and which are remarkable for their mydriatic action (power of dilating the pupil of the eye). Baryta water breaks up atropine into tropic acid and Tropine, CgHjgNO, and hyoscine in an analogous manner into tropic acid and the isomer of tropine, Pseudo-tropine. Tropic acid and tropine reunite again to atropine when their dilute hydro- chloric acid solutions are evaporated together. If, instead of tropic acid itself, a homologue is employed, homologous bases, the '^Tropeines " are obtained ; thus mandelic acid yields Homa- tropine, CieHgiNOg, which exerts like atropine a mydriatic action, although a less lasting one {Ladenhurg, A. 217, 82). Belladonnine, which likewise occurs in Atropa Belladonna, can be split up into tropic acid and Oxytropine, CgH^j^NOg. An Iso-tropine results from the distillation of benzoyl-ecgonine (p. 501). Nicotine, CioH^^Ng, = CioHg(He)N2, the poisonous con- stituent of tobacco and the tobacco plant, is a hexahydro- dipijridyl. It is a strong diatomic base, oily, readily soluble in water, alcohol and ether, and of a stupefying odour. It can be distilled unchanged in an atmosphere of hydrogen, but becomes rapidly brown in the air; B. Pt. about 250°. It yields Iso-dipyridyl, CioHgNg (p. 485), by the separation of hydrogen, and Di-piperidyl, CioHgoNg, by taking more hydrogen up. The two dipyridyls [p- and ??i-), which are known, combine with hydrogen to form iso-nicotine and nicotidine, bases isomeric with nicotine. Permanganate of potash oxidizes nicotine to nicotinic acid. QUINOLINE AND ACRIDINE GROUPS. 491 consequently the two pyridine residues of which the former is built up are in the /3-position to one another. Appendix : Pyrone Group ; Ketines. The hypothetical substance Pyrone," C2H2<^ q ^CgHg, would be an oxygenated compound of ketonic nature nearly related to pyridine. Although not known itself, derivatives of it are, e.g. Chelidonic acid, C7H4O6 (present in cellandine), is one of its dicarboxylic acids ; further, Meconic acid, C7H4O7 (present in opium), P3n:omeconic acid, C6H4O5, which can be prepared from the latter, and Cumalic acid, C6H4O4, which is obtained as given at p. 239, all belong to this group. These compounds are of especial interest because they are readily trans- formed into pyridine derivatives by ammonia, e.g. cumalic acid yields in this way oxy -nicotinic acid (B. 17, 2384). For the synthesis of com- pounds of this nature, see B. 19, 19 ; 20, 154. If two methine groups in benzene are replaced by two atoms of nitrogen, one arrives at the formula : N N It appears as if the so-called Ketines were homologues of the above hypothetical substance (which is termed ^*Pyrazine" or "Aldine"), the ketines being bases obtained by the reduction of isonitroso-acetone and analogous compounds (see p. 143; B. 16, 3073; 19, 2526; 21, 19). XXXIV. THE QUINOLINE AND AORIDINE GROUPS. A. Quinoline Group, CnHgn-nN. The quinoline group comprises quinoline, its substitution products, homologues, carboxylic acids, etc., all of which remind one of the corresponding compounds of the pyridine group in their behaviour (cf. Summary, p. 480). Quinoline stands to pyridine as naphthalene does to benzene. 492 XXXIV. <;)UINOLINE AND ACRIDINE GROUPS. Formation. 1. By the dry distillation of nitrogeneous organic substances, and from alkaloids as given at p. 481. Cinchonine yields quinoline itself when heated with potash (Gerhardty 1842), and quinine gives methoxy-quinoline (p. 496). 2. Quinoline is produced when aniline is heated with glycerine and sulphuric acid in presence of nitro-benzene (Skraup, B. 14, 1002; Monatsh. f. Chemie, I. 316; II. 141) : r H + CH,(OH)-CH(OH) . ^ ^ ^ „ .CH=CH Aniline. Glycerine. Quinoline. The nitro-benzene simply acts as an oxidizing agent ; the formation of acrolein as intermediate product is to be assumed here, the latter combining in the first instance with aniline to acrolein-aniline. The homologues and analogues of aniline yield homologues and analogues of quinoline by corresponding reactions ; when naphthylamine is used, the more complicated naphtho-quinolines result (see below). 3. Quinoline is formed by the separation of the elements of water from o-amido-cinnamic aldehyde (Baeyer and Drewson, B. 16, 2207) : /CH-CH— CHO XH=CH ^ ^^NHg ' N=CH ' Carbostyril (a-oxy-quinoline) results in an analogous manner from o-amido-cinnamic acid (Baeyer) : XH=CH XH-CH ' NH2CO.OH ' N=C.(OH) ' Of historical interest is a partly analogous synthesis of quinoline by the action of phosphorus pentachloride upon hydro-carbostyril (p. 417), and reduction of the resulting dichloro-quinoline, C9H5NOI2, by means of hydriodic acid {Baeyer, B. 12, 1320). 4. When aniline is heated with aldehyde (para-aldehyde) and hydrochloric acid, a-methyl-quinoline (quinaldine) is obtained (Doebner and v. Miller) : CeH^-NH, + 2C2H4O + 0 = CioH,N + SH^O. In this reaction aldol is formed as intermediate product, thus : OHC--CH2 ^ ^ .CH=CH Aniline. Aldol. Quinaldine. FORMATION OF QUINOLINE DERIVATIVES. 493 Here, again, various other primary aromatic amines may be used instead of aniline; and other aldehydes (B. 18, 3361) or ketones [e.g. B. 19, 1394) instead of para-aldehyde. 5. Aniline and aceto-acetic acid combine together at temperatures above 110° to aceto-acetanilide, CHg — CO — CHg — CO.NH.CgHg, from which 7-methyl-a-oxyquinoline (*' methyl-carbostyril " or "a-oxy-7- lepidine") results on the elimination of water {Knorr, A. 2 36, 75) : CH3 CH3 Aceto-acetanilide. 7-Methyl-carbostyril. Aniline can also react with aceto-acetic ether (under 100°), with the formation of jS-Phenyl-amido-crotonic ether, CgHg— NH— C(CH3)=CH— CO2C2H5, which yields v-oxy-quinaldine when heated {Conrad and Limpach, B. 20, 944) : • ^ ^ /C(OH)-CH CeH, CO-CH = CeH< ' + C.Hfi, ^NH— C-CH3 ' Analogously to aceto-acetic ether (which is the ether of a jS-ketonic acid), the jS-diketones likewise -condense with aniline ; further, also, mixtures of ketones and aldehydes, or mixtures of aldehydes which would yield /3-diketones or j8-ketonic aldehydes if condensed together (C, Beyer f B. 20, 1767). With acetyl-acetone we obtain (e.g.) a-y- dimethyl-quinoline : CO-CH3 ~" '"^N^C-CHg These reactions are nearly allied to those already spoken of under 4. 6. o-Amido-benzaldehyde undergoes condensation with aldehydes and ketones under the influence of dilute caustic soda solution, with the formation of quinoline derivatives {Friedldnder, B. 15, 2574; 16, 1833). With aldehyde quinoline itself results, and with acetone quinaldine : C6H4(NH2).CHO + CsHgO = C10H9N + 211^0; or, generally : XHO CHo— R .CH=C— R ^ ^^NH^ CO-ir ^ ^ N=C— R' ' Acetophenone, aceto-acetic ether and malonic ether also react in a similar way. 4:94 XXXIV. QUINOLINE AND ACRIDINE GROUPS. 7. Quinoline is produced when the vapour of allyl-aniline is led over heated oxide of lead {Konigs) ; 8. Also by oxidizing acridine to acridinic acid, C9H5N(C02H)2 (p. 497), and eliminating the carboxyls. 9. For further syntheses see B. 18, 632, 1460, 2632, 2975. Constitution. The above modes of formation (especially 3 and 5) show that quinoline is an ortho-di-derivative of benzene, and that it contains its nitrogen linked directly to the benzene nucleus ; they also show that the three C-atoms, which enter the complex, form a new hexagon (pyridine) ring with this nitrogen and with two carbon atoms of the benzene ring. The latter point also follows from the oxidation of quinoline to pyridine-dicarboxylic acid (Hoogewerff and van Dorp) : CO2H— CH— CH=CH CO2H— CH— N =CH Quinolinic acid. We have thus the following constitutional formula : CH CH ^ _ XH=CH N=CH Quinoline. 0, + 2CO2 + HnO. HC HC CH CH HC N The second of these two modes of writing the formula possesses this advantage over the first that it is independent of special assumptions with regard to the mode in which each fourth carbon- or third nitrogen- affinity is taken up. One may also assume here a mode of linking corresponding to that of the pyridine formula III. (p. 485). Quinoline is thus constituted in a manner perfectly analogous to naphthalene, and may be looked upon as being derived from the latter by the exchange of CH for N, or by the condensa- tion of a pyridine and a benzene nucleus. When quinoline derivatives are oxidized, the benzene residue usually proves itself to be less stable than the pyridine one. This is shown in the case of quinoline itself, the benzene nucleus being destroyed upon its oxidation to pyridine-dicarboxylic acid (p. 488). a-Methyl-quinoline gives, on the other hand, acetyl-o-amido-benzoic acid when oxidized : CONSTITUTION OF QUINOLINE. 495 C6H4< ,CH-CH + 0, = C,H,<. CO.OH NH— CO.CH. 3 + CO. The pyridine nucleus of quinoline takes up hydrogen more readily than the benzene one ; thus quinoline is easily converted (even by tin and hydrochloric acid) into tetrahydro-quinoline, although it can be reduced further only with difficulty. The three H-atoms of the pyridine nucleus, counting from the N, are designated as a-, P- and y-, and the four H-atoms of the benzene nucleus as o-, m-, p- and a- (ana-) hydrogen atoms; or the former as Py- 1,1 and 3, and the latter as B-1, -2, -3 and 4 atoms {BaeyeVy B. 17, 960). Since no one of these H-atoms is linked symmetrically to another, seven mono-deriv- atives of quinoline are in each case theoretically possible. As a matter of fact all seven quinoline-monocarboxylic acids have been prepared. The position of the substituents follows : {a) from the nature of the products which result upon oxidation, e.g. B-quinoline-carboxylic acid {i.e. one whose carboxyl is linked to the benzene nucleus) yields a pyridine-dicarboxylic acid, while a Py-quinoline-carboxylic acid (whose carboxyl is linked to the pyridine nucleus) yields a pyridine- tricar- boxylic acid ; {b) from the synthesis of the compound in question. The methyl-quinoline, for instance, which results from o-toluidine by the Skraup synthesis must be a B-1 -compound : whilst m-toluidine must yield aB-2-orB-4-, and ^-toluidine aB-3-methyl- quinoline (a tolu-quinoline "). Quinoline, leucoUne, C^H^N {Runge^ 1834), is also found in Idrian ^^Stupp" fat (see p. 477). It is a colourless strongly refracting liquid of a peculiar and very characteristic odour; B. Pt. 236°. Quinoline is a monatomic base. It forms a difficultly soluble bichromate, (C9H^N)2, CrgO^Hg. Is used as an antifebrile. Quinoline. 496 XXXIV. QUINOLINE AND ACRIDINE GROUPS. Nascent hydrogen transforms it first into Dihydro - quinoline, C9H9N (M. Pt. 161°), and then into Tetrahydro- quinoline, CgH^N, = ^6H4<^jj (liquid, B. Pt. 245°). Since both of these yield nitrosamines and can be alkylated, they are secondary bases. The tetrahydro-compound exerts a stronger antifebrile action than the mother substance, especially in the form of its ethyl-derivative, Cairolin (B. 16, 739). When quinoline is heated vi^ith sodium, a Diquinolyline, CgHgN-CgHgN, analogous to diphenyl or dipyridine, is formed ; it crystallizes in small plates or needles. Quinoline also yields Diquinoline, (C9H7N)2 (yellow needles), by polymerizing. Halogen derivatives of quinoline and nitro-quinolines have been prepared by the Skrmip reaction, etc. ; and, from the reduction of the latter, amido-quinolines, C9HgN(NH2). The quinoline-sulphonic acids yield cyano-quinolines when heated with potassium cyanide, and oxy- quinolines when fused with potash. Certain of the last-named com- pounds likewise result from the amido-phenols by the Skrauj) reaction, these containing the hydroxyl in the benzene nucleus. p-Methoxy- quinoline, C9HgN(O.CH3), is the anisol of the quinoline series and resembles quinoline closely. For its formation from quinine, see p. 492. a-Oxy-quinoline, carbostyril, CgH4(C3H2N.OH), is a quinoline hydroxylated in the pyridine nucleus (see p. 492, mode of formation 3). It crystallizes in white needles and is soluble in alkali, from which it is again thrown down by carbonic acid; M. Pt. 198-199°. Its constitution follows from its formation from (?-amido-cinnamic acid (p. 492). Homologues of Quinoline; condensed Quinolines. Quinaldine, a-methyl-quinoline, O^^qHqN, is contained in coal tar. It is a colourless liquid of quinoline odour, which boils at 138°, and whose oxidation yields either a benzene or a quinoline derivative, according to the nature of the oxidizing agent (see p. 494). The hydrogen of the methyl group readily enters into reaction ; quinaldine reacts with phthalic anhydride to produce a beautiful yellow dye, Quinoline-yellow, CioH7N(CO)2C6H4 (B. 16, 2602). In presence of quinoline quinaldine is transformed into the (unstable) blue dyes, the Cyanines, when alkylated and treated with caustic potash. HOMOLOGUES OF QUINOLTNE, ETC. 497 7-Methyl-quinoline, lepidine, cincho-Upidine^ Ci)HgN(CHo), is obtained by distilling cinchonine with oxide oilead ; B. Pt. 264°. The methyl-quinolines are isomeric with the naphthylamines. The homologiies of quinoline which have been isolated from coal tar and bone oil are known as Lepidine or Iridoline, CjoH^N, Cryptidine, CiiHiiN, etc. Tetramethyl-quinoline, M. Pt. 64°, B. Pt. 284° (B. 19, 1394). Phenyl- quinoline, CgHeN— CgHg. Py-3-phenyl-quinoline, C6H4<^ ^ is to be regarded as the mother substance of the cinchona alkaloids {Konigs and iVe/, B. 10, 2427). Flavaniline, C16H14N2, a beautiful yellow dye, which results upon heating acetanilide with zinc chloride, is an a-amido-phenyl-7-methyl- quinoline (B. 15, 1500). Naphtho-quinolines, C13H9N. These compounds (solid bases), which are derived from phenanthrene by the exchange of CH for N, are obtained by subjecting the two naphthylamines to the Skraup reaction. They are isomeric with acridine (p. 498). Anthr a- quinoline, CiyH^gN, is formed in an analogous manner from anthramine (p. 473). It crystallizes in colourless plates and is the mother substance of alizarin blue (p. 475). QuiiwUne-carloxylic Acids, All the seven mono-carboxylic acids of quinoline, which are possible according to theory, are known. Quinoline-benz-carboxylic acids are those which contain the carboxyl group in the benzene nucleus. Cinchoninlc acid, CgHgNlCOgH), which results from the oxidation of cinchonine by permanganate of potash and crystallizes in needles or prisms, M. Pt. 254°, is 7-quinoline-carboxylic acid. From it is derived V 7 Quininic acid, C9H5N(OCH3).C02H, which is obtained by oxidizing quinine with chromic acid ; it forms yellow prisms, M. Pt. 280°. a-/3-Qulnoline-dicart>oxylic acid or acridinic acid, results from the oxidation of acridine. Bases related to Quinoline, Iso-quinoline, an isomer of quinoline, occurs along with the latter in coal tar (B. 18, Ref. 384). It is a solid ; M. Pt. 20-22°, B. Pt. 240 5°. Since oxidation converts it into cinchomeronic acid (j8-7-Py-dicarboxylic (506) 21 498 XXXIV. QUINOLINE AND ACRIDINE GROUPS. acid) on the one hand and phthalic acid on the other, it possesses the constitution : | I tst- synthesis, see B. 19, 1653, 2354. Basee related to quinoline, which contain in the molecule two atoms of N instead of (CH) and N, and which have the formula C6H4(C2H2N2), have recently been prepared in considerable number, either themselves or in the form of derivatives ; among these are the Cinnoline-^ Quinazole- etc. compounds and the QuiiioxalineSy (B. 16, 677; 17, 319, 724; 19, 1604 ; 20, Ref. 630). Quinoxaline or quinazine, CqH^C6H4 + 2H2O. Among the analogues of phenazine is Naphthazine (see naphtho- acridine), which contains two naphthalene residues linked together by When one amido-group substitutes in such azines," there are formed the Eurhodines (B. 19, 441), sublimable dyes of a colour varying from j^ellow to red ; and when two amido- groups, the dyes of the toluylene red group. Toluylene red. Toluylene red, C15H16N4 ( Witt) . When jp-amido-dimethyl-aniline is oxidized in the cold along with m-toluylene-diamine, the beautiful blue compound Toluylene blue, an indamine (p. 356), results, which gives up hydrogen and goes into toluylene red when boiled : nh/ Amido-dimethyl-aniline. Toluylene-diamine. = (CH3)2N-C,H3<|>CeH,(CH3)-NH2 + SH^O. Toluylene red. Other similar compounds can be prepared in an analogous manner. The simplest toluylene red, which results from 29-phenylene-diamine and m-toluylene-diamine and which contains NHg in place of N(CH3)2, yields Methyl-phenazine, CgH4{N2}C6H3(CH3), when diazotized ; it con- tains therefore two primary amido-groups. Toluylene red is used on the technical scale as " Neutral red." PHENO- AND TOLU-SAFRANINES, ETC. 503 Safranines, The Safranines are related to toluylene red. They are produced by oxidizing an aqueous solution of a mixture of the sulphates of ^-phenylene-di amine (1 mol.) with a primary monamine (1 mol.) and a second monamine in which the ^-position is unoccupied (1 mol.). The simplest safranine is Pheno-safranine, CigHi^N^Cl [from CeH4(NH2)2 + SCoH^.NHJ, while the ordinary safranine of commerce consists principally of Tolu-safranine, C^iH^oN^ [from C6H3(CH3)(NH2)2 (1:2:4) and 2C6H4(CH3)NH2]. See B. 16, 472, etc. The requisite mixture of mono- and diamines is attained in practical working by the reduction of amido-azo-compounds (see p. 370). The safranines are beautiful crystalline compounds of a metallic green glance, readily soluble in water, which dye yellowish-red to red. The solution in concentrated sulphuric acid is green, becoming blue, violet, and finally red on dilution with water. Eeduction gives rise to leuco-compounds, which are probably diamido-compounds of the as yet unknown sub- stance C6H4C6H4(B. 20, 2690, 3017, 3121, etc.). Mauveine, C27H25N4CI, the first aniline dye which was prepared on the technical scale (by PerTcin in 1856, from crude aniline, bichromate of potash and sulphuric acid), is possibly phenylated safranine, Magdala red, C30H21N4CI, is the safranine of the naphthalene series. Appendix. Dyes of unknown Constitution, The Indulines and Nigrosines are violet-blue to grey-blue dyes which result upon heating the amido-azo-benzenes with the aniline hydro- chlorides, and sulphurating the product so obtained. They are derived from Violaniline or azo-diphenyl blue, CigHisXs ' CeHg-N^N-C^H^.NH^ -^ C.Hg.NH^, HCl = CisHi^Ng + NH^Cl, which latter compound also results (in place of fuchsine) from the oxidation of chemically pure aniline, (cf. p. 351). Aniline black, (C30H27N5?), obtained by acting upon aniline with {e.g.) KCIO3 in the presence of copper or vanadium salts, is usually produced directly upon the fibre ; it is a dark green amorphous powder, insoluble in most menstrua. 504 XXXV. TERPENES AND CAMPHORS. XXXV. TERPENES AND CAMPHORS. The terpenes are hydrocarbons of the formula G^oH^g [or (C5H8)J, which are nearly related to cymene (p. 331). The camphors, e.g. common Camphor, C^oH^gO, contain oxygen in addition, but are closely allied to the terpenes. Both classes of compounds are widely distributed in nature. Ethereal oils. Many plants contain, especially in their blossoms and fruits, oily substances to which they owe their peculiar fragrance or odour, and which can be obtained from them e.g. by distillation with steam. These, which are termed ethereal oils, were formerly grouped together in a special class, but now they are recognized as being more or less heterogeneous ; thus oil of bitter almonds is benzoic aldehyde, and Ivoman oil of cumin is a mixture of cymene and cumic aldehyde, etc. Many of these ethereal oils contain terpenes, e.g. oil of thyme consists of thymene (a terpene) together with cymene and cumene ; in fact the terpenes are often their chief constituents, as in the case of turpentine, citron and orange oils, etc. Many oils deposit solid substances, the " stearoptenes," when exposed to cold, the liquid portions being termed "Elseoptenes." The camphor varieties resemble the ethereal oils in their occurrence and modes of preparation, but they are solid. A. Terpenes. The terpenes are nearly related to cymene, C^qH^^ ; thus oil of turpentine goes directly into cymene when heated with iodine. They yield terephthalic acid, CgH4(C02H)2, upon oxidation, and are therefore to be regarded as di-hydrides of cymene, C^QH^^.Hg (see p. 331). A peculiar reaction of the terpenes consists in their capacity for com- bining with hydrochloric acid to form either mono-hydrochlorides, CioHiyCl (in the case of the pinenes or camphenes), or di-hydrochlorides, CioHigClg ; the same applies to hydrobromic and hydriodic acids. They also unite with bromine, often to characteristic tetrabromides, CioH^gBr4, and also in part with water (see terpin hydrate), and with nitrogen trioxide. The combination with halogen hydride is readily effected in an acetic acid solution saturated with the gas, and that with bromine by using warm acetic ether as the diluent. When the solution of the halogen hydride addition product is heated with sodium acetate, the halogen acid is split off. THE TERPENES. 505 The terpenes polymerize readily and show great inclination to change into isomers under certain conditions. Their solution in acetic anhyd- ride gives a yellow, red, or blue colour reaction with concentrated sulphuric acid. The behaviour of the terpenes with regard to polarized light is very interesting. They are almost all optically active, and most of them exist both in dextro- and in Isevo-rotatory modifications. While no appreciable alteration (with the exception of the resulting optical inactivity) is apparent upon mixing equivalent amounts of dextro- and Isevo-pinenes or of dextro- and Itevo-camphenes, there results, oddly enough, when dextro- and Isevo-limonene are mixed together, a di- pentene which differs materially from these in (higher) boiling point, in melting point, and in the lesser solubility of its derivatives {e.g. tetra- bromide, see table) ; it was consequently formerly looked upon as an individual terpene, viz. , dipentene. The terpenes are widely distributed in the vegetable king- dom, especially in the coniferse (Pinus, Picea, Abies, etc.), in the varieties of Citrus, etc. The products which are isolated in the first instance from the individual plants, and which according to their source are designated terpene, citrene (from oil of citron), hesperidene (from oil of orange), thymene (from thyme), carvene (from oil of cumin), eucalyptene, olibene, etc., have for the most part the formula C^oHig and approximately equal boiling points (160-190°) ; they are not, however, chemical individuals but mixtures of isomeric com- pounds. The terpenes, which up to now have been prepared pure, differ from one another not only in boiling point but also in the fact that some of them yield liquid and others solid bromine addition products (in the latter case with 4 Br-atoms) of definite melting point ; further, in that some of them are only capable of combining with one but others with two mole- cules of hydrochloric acid to liquid or solid hydrochlorides ; lastly, in that only some of them yield crystalline compounds (nitrites) with NgOg (0. H^allach, A. 227, 277 3 230, 225 ; 239, 1 ; 246, 221, etc.). 506 XXXV. TERPENES AND CAMPHORS. Summary. M. Pt. B. Pt. Bromides, M. Pt. Hydrochlorides, M. Pt. Nitrites, M. Pt. 1. Pinene . Liq. 159-160° Liq. + HOI : 125° 2. Camphene . 49° 160-161° Liq. ,, : decomp. — 3. 3\ Dipentene . ±Limonene Liq. >) 180-182° 175° Br4 : 125° „ 104° I+2HC1 :50° — 4. Sylvestrene >> 1 /o-l /o „ 135 „ : 72 5. Terpinolene »> 185-190° „ 116° [ „ :50T 6. Terpinene . »» 180° 155° 7. Phellandrene »> about 170° 94° As is seen from the above table, dififerent isomers yield the same dipentene hydrochloride (M. Pt. 50°) on combination with 2HC1, which would indicate that they contain the same carbon chain (see p. 511). In addition to the "Terpenes proper," CioHjg, we have Hemiterpenes, CgHg (see Isoprene), which polymerize to terpenes (dipentene), and Poly- terpenes, (CsHs)!, e.^. Cedrene, Cubebene, C15H24 (B. Pt. 250-260°), Colophene, C20H32 (B. Pt. above 300°), and Caoutchouc, (CioHi6)x. 1. Pinene, C^oH^g, is the chief constituent of German and American oil of turpentine, oil of juniper, of eucalyptus, of sage, etc. It forms, together with sylvestrene and dipentene, Russian and Swedish turpentine oil. Oil of turpentine is obtained by distilling turpentine, the resin of pines, with steam, colophonium (fiddle resin) remain- ing behind. It is a colourless strongly refracting liquid of characteristic odour, almost insoluble in water but readily soluble in alcohol and ether. It dissolves resins and caoutchouc (being therefore used for the preparation of oil * Identical with dipentene dihydrochloride. PINENE; CAMPHENE; DIPENTENE. 507 paints, lakes, etc.), also sulphur, phosphorus, etc. It absorbs oxygen from the air with the formation of ozone and pro- duction of resin, minute quantities of formic acid, cymene, etc. being formed at the same time. Dilute nitric acid either gives rise to terephthalic acid in addition to fatty acids, or — under other conditions — to terpenylic acid, G^H^fi^ (which belongs to the fatty series), etc. Heating with iodine transforms it into cymene, the action being violent, and heating with hydriodic acid into the compounds C^oH^g and G-j^oH^o- Oil of turpentine shows physical differences, according to the source from which it is derived, the German, French and Venetian oils being Isevo- and the Australian dextro-rotatory. These differences depend upon the existence of Isevo- and dextro-pinenes, etc. (cf. the tartaric acids). B. Pt. 158-161°; Sp. Gr. 0-86-0*89. Pinene hydrochloride, CioH^^yCl (see table, p. 506) is a solid white crystalline mass with a camphor-like odour, whence its name of artificial camphor," insoluble in water but readily soluble in alcohol. If its 'hydrochloric acid is separated by weak alkali, e.g. by heating it with soap, camphene is obtained (see below). Further addition of HCl does not lead to a di-hydrochloride of pinene but to an isomer, dipentene-dihydrochloride. From this it may be concluded that pinene has only one double bond in the molecule, and the same applies to camphene. 2. Camphene, C^oH^g, of which there are two modifications, dextro- and laevo-, is a solid terpene. It is obtained by heating pinene mono-hydrochloride with alcoholic potash or with dry soap, and is more stable than pinene. It also results in an analogous manner from Bornyl chloride, CioHj^Cl (see Borneo camphor). It has an odour like that of oil of turpentine and camphor, and is oxidized to camphor by chromic acid mixture. With bromine it does not yield a tetrabromide but a mono-substitution product, and it combines with only one molecule of hydrochloric acid. 3. Dipentene, cine^ie, inactive Umonene, is found (e.g.) together with cineol in Oleum Cinae, and is prepared by heating pinene, camphene, sylvestrene or limonene to 250-270° for several hours, and also by the abstraction of 2 HCl from its di-hydrochloride (which is formed from various terpenes by 508 XXXV. TERPENES AND CAMPHORS. the addition of 2HC1). It is further produced from pinene under the influence of dilute alcoholic sulphuric acid, from terpin hydrate by the separation of water, by the polymeriza- tion of isoprene, and, together with the latter substance, on distilling caoutchouc. It has a pleasant odour like that of oil of citron, and is more stable than pinene or dextro-limonene, although it can still be inverted to terpinene by alcoholic sulphuric acid. Its tetra-bromide results from the combina- tion of the tetrabromides of dextro- and Isevo-limonene. Dipentene di-hydrochloride, CioH^gClg, crystallizes in rhombic tables, M. Pt. 50°, and is very readily soluble in hot alcohol. Its formation has already been given. Terpin hydrate, CjoHooOo + HgO, = CjoHiglOHja, is formed when the sohition of di-pentene di-hydrochloride in aqueous alcohol is allowed to stand, and also from pinene and water under the influence of certain acids. It crystallizes in large rhombic colourless crystals, M. Pt. 117°, which lose their water at lOO''. The compound thus formed, Terpin, CioHi8(OH)2 (needles, M. Pt. 105°), possesses the character of glycol and yields the above dichloride again with hydrochloric acid. By the separation of H2O it goes into Terpineol, CioHi7(OH), an unsaturated monatomic alcohol which is transformed by bromine into dipentene tetrabromide. Further elimination of HgO from terpineol (by boiling it with dilute acids) gives rise to dipentene, terpinene, or terpinolene as the principal product, according to the conditions of the experiment. 3a. Limonene, hesperidene^ citrene, or carvene. The oil of the orange rind consists almost entirely of dextro-limonene, which closely resembles pinene, but differs sharply from the latter in its tetrabromide (see table, p. 506). Dextro-limonene is likewise the chief constituent of carvene, oil of dill, oil of erigeron, etc. ; together with pinene it forms oil of citron. Lsevo-limonene is present together with Isevo-pinene in the oil of fir cones. The + and - tetrabromides are identical, except that their crystals are the mirror images of one another. Dextro-limonene is very easily rendered inactive. 4. Silvestrene, B. Pt. 173-175°, is the (dextro-rotatory) chief constituent of Swedish and Russian oil of turpentine. Its Di-hydrochloride is isomeric with dipentene di-hydrochloride and is dextro-rotatory. Sylves- trene is one of the most stable of the terpenes. It gives a magnificent blue colour reaction with acetic anhydride and concentrated sulphuric acid. 5. Terpinolene, which is very like dipentene, and : 6. Terpinene both result from the ' * isomeration " of pinene (see terpin hydrate). Terpinene and also : CAOUTCHOUC; CAMrHOR. 509 7. Phellandrene, which occurs as dextro-phellandrene in water dropwort (Pliellandrium aquaticum) and as Isevo-phellandrene in eucalyptus oil, yield — in contradistinction to the above terpenes — compounds with nitrous acid. Phellandrene is among the most easily altered of the terpenes ; it is radically changed by contact with acids and readily converted into dipentene. 8. Caoutchouc, (CiQHig)^, is the hardened milky juice of the tropical euphorbiaceae, apocyneae, etc., especially Siphonia (ficus) elastica, which grows in Brazil, etc. It can be obtained pure, in the form of a white amorphous mass, by dissolving the crude material in chloroform and precipitating with alcohol. For its behaviour on distillation, see dipentene. It absorbs oxygen from the air and is converted into vulcanite on treat- ment with sulphur. Guttapercha (from Isonandra Gutta, which grows in India) is related to camphor. Homologues of the terpenes have also been prepared. For their constitution, see under camphor. B. Camphors. The most important variety of camphor is : 1. Common or Japan Camphor, CioH^gO, which is found in the camphor tree (Laurus Camphora) and can be obtained from the latter by distillation with steam. It forms colourless transparent and readily sublimable glancing prisms of chara- teristic odour; M. Pt. 175°, B. Pt. 204°, Sp. Gr. 0-985. It is dextro-rotatory in alcoholic solution, the amount of rotation varying with the source of the camphor. When distilled with phosphoric anhydride it goes into cymene, zinc chloride having the same effect, though in the latter case the reaction is less simple : Heated with iodine it yields carvacrol, i.e. oxy-cymene (p. 388), just as oil of turpentine yields cymene. Nitric acid oxidizes it to the dibasic Camphoric acid, C8Hj4(C02H)2 (which somewhat resembles phthalic acid), and then to Camphoronic acid, CyHi^Og, etc. Camphor 510 XXXV. TERPENES AND CAMPHORS. reacts with hydroxylamine to produce Camphor-oxime, CioH^g(NOH), and therefore in all likelihood contains a carbonyl group. The oxime can give up water and thus go into the Cyanide, CgHjg.CN, which yields Campholenlc acid, CgHjg.COgH, on saponification, and Camphyl- amine, CgHiglCHg.NHg), on reduction. For the constitution of camphor see B. 21, 1125. Camphor may be prepared artificially by oxidizing camphene (p. 507). Two Dichlorides, CjoHigCla, result upon treating camphor with phosphorus pentachloride. Chloro-, Bromo-, Nitro- and Amido- camphors are also known ; likewise [e.g.] Ethyl- camphor. Absynthol is an isomer of camphor, and Caryophyllin, CgoHg^Oa, a polymer. 2. Borneol or Borneo Camphor, CioH^gO, occurs in nature (in Dryobalanops Camphora), and is produced by the action of nascent hydrogen upon Japan camphor : CJio^ieO + H2 = CiqHiqO. It is very like the latter, but has at the same time an odour of pepper. It crystallizes in hexagonal plates, M. Pt. 198°, B. Pt. 212°. Oxidation converts it in the first instance into camphor. Borneol possesses the character of a secondary alcohol, yielding com- pound ethers, etc., and giving with PCI5 Bornyl chloride, C10H17CI (M. Pt. 148^), isomeric with pinene hydrochloride ; bornyl chloride goes into camphene when warmed with alkalies. Borneol comports itself as a saturated compound, but at the same time it forms unstable addition products with bromine and halogen hydride. Cineol, the chief constituent of 01. cinae, and which is frequently found accompanying the terpenes, is isomeric with borneol ; M. Pt. - 1°, B. Pt. 176°. It likewise yields an unstable HCl-compound and readily goes into dipentene. Its chemical behaviour seems to point to its being constituted similarly to ethylene oxide. Terpineol (from terpin hydrate, and present in certain ethereal oils), is also isomeric with borneol and is nearly related to dipentene ; it results, together with cineol, from terpin hydrate, as given at p. 508. 3. Mint-camphor, menthol, G-^^qH^qO, is the principal con- stituent of oil of peppermint (Mentha piperita). It is a monatomic alcohol and forms a crystalline mass; M. Pt. 42°, B. Pt. 213°. RESINS. 511 Comtitution of the terpenes and camphors. The close relation of the terpenes and camphors to cymene, and their convertibility into tere- phthalic acid show that they are derivatives of cymene ; they therefore contain a hydrogenized benzene nucleus in which the groups CH3 and C3H7 are in the para-position to one another. The terpenes appear to be dihydro-cymenes. The isomerism among them may depend upon the point at which a double (or diagonal ?) bond is dissolved, so that one and the same pinene di-hydrochloride (dichloro- hexa-hydro-cymene) may result from various isomerides upon the addition of 2HC1. (Cf. A. 230, 225). Pinene and camphene contain perhaps one double and one diagonal bond, terpineol a double bond (no diagonal one), dipentene, sylvestrene and terpinolene two double bonds in the benzene nucleus, and terpinene and phellandrene perhaps one such in the side chain (cf. Wallach, loc. cit. ; Goldschmidt, B. 18, 1733; Briihl, B. 21, 145, 457). Borneo camphor, CiqHisO, seems from its alcoholic character to be an oxy-tetrahydro-cymene (containing the group = CH.OH) ; and Japan camphor, CioHigO, to be the corresponding ketone with two atoms of hydrogen less, i.e. a keto-tetrahydro-cymene, its behaviour with hydroxylamine being in accordance with this view. Lastly, menthol is possibly an oxy-hexahydro-cymene. XXXVI. RESINS; GLUCOSIDES; VEGETABLE SUBSTANCES (of unknown constitution). A. Resins. Many organic compounds, the terpenes in particular, possess the property of becoming " resinified " by oxidation in the air or under the influence of chemical reagents, i.e. of being converted into substances very similar to the resins which occur in nature. These natural resins are solid, amorphous, and generally vitreous brittle masses of conchoidal fracture, insoluble in water and acids, but soluble in alcohol, ether and oil of turpentine. They are found naturally in abundance, partly also as balsams, i.e. dissolved in terpenes or ethereal oils, from which they can be separated by distilling with steam. The resins dissolve in alkalies to form compounds of the nature of soap (resin soaps), being again precipitated 512 XXXVI. RESINS; GLUCOSIDES; VEGETABLE SUBSTANCES. from the aqueous solutions of these on the addition of acids ; most resins must therefore consist of a mixture of somewhat complicated acids (the so-called resin-acids). Abietic acid (C^qH^qO^ ?) is an individual acid which has been isolated from colophonium (the residue from the distilla- tion of turpentine, see below) ; it crystallizes in small plates, M. Pt. 165°, and is soluble in hot alcohol. Pimaric acid, C20H3QO2, has been prepared {e.g,) from galipot resin (Pinus maritima) in a similar way; M. Pt. 148°. It closely resembles abietic acid, is crystalline and forms crystalline derivatives, and exists in two modifications, dextro- and laevo-pimaric acids. The resins show their relation to the aromatic compounds by being converted into hydrocarbons of the benzene or naphthalene series when distilled with zinc dust, and by the formation (e.g.)oi dioxy- and trioxy- benzenes when they are fused with potash. In addition to Colophonium, there may be mentioned among other resins Shellac (from East Indian Ficus varieties), and Amber, a fossil resin which contains succinic acid in addition to resin-acids and a volatile oil. The resins are largely used for the manufacture of lacs, varnishes, etc. B. Glucosides. (Cf. 0. Jacohsen^s "Die Glucoside," Breslau, Trewendt.) As glucosides are designated a series of vegetable substances which are so broken up by alkalies, acids, or ferments, that one of the products of this decomposition is a glucose, usually grape sugar. They are thus ethereal derivatives of the sugar varieties in question. Some of them have been mentioned already. Amygdalin, C20H27NO11 (p. 398), is found in bitter almonds, in the leaves of the cherry laurel, in the kernels of the peach, cherry and other amygdalaceae. It crystallizes in colourless prisms, M. Pt. 200°, is readily soluble in water, and breaks up GLUCOSIDES. 513 into oil of bitter almonds, dextrose and hydrocyanic acid under the influence of emulsin (p. 294), or when saponified. Among others there may be mentioned : Salicin, CigHigOy, found in varieties of SaHx, which breaks up into saligenin (o-oxy-benzyl alcohol) and dextrose ; Helicin, Ci^K^qO^ + HgO, which results from the action of N2O3 upon salicin and is decomposable into salicylic aldehyde and glucose, from which it can again be obtained synthetically ; Populin or benzoyl- saligenin, CioH2203 (in varieties of Populus), which can be prepared artificially from benzoyl chloride and salicin. Arbutin, Ci2Hig07, and Methyl-arbutin, CigHigOy, present in the leaves of the bear berry, etc. , break up into dextrose and hydroquinone or methyl-hydroquinone respectively. Hesperidin, C22H26O125 which is contained in unripe oranges, etc., can be decomposed into dextrose, iso-ferulic acid (isomeric with ferulic acid, p. 427), and phloroglucin. Phloridzin, C21H24O10 (fine prisms), found in the bark of fruit trees, can be split up into grape sugar and Phloretin, CigH^405, and this latter — in its turn — into phloretic acid and phloroglucin (p. 391). Aesculin, CigHigOQ (prisms), present in the bark of the horse chestnut, is decomposed by acids into grape sugar and Aesculetin (dioxy-cumarin, p. 428), Saponin, C32Hg40i8 (in the soapwort). Quercitrin, C36H38O20, found in Quercus tinctoria, chestnut blossoms, etc. ; yellow needles. Coniferin, C16H22O8 + 2H2O (in the cambium sap of the coniferae), breaks up into glucose and coniferyl alcohol, and serves for the pre- paration of vanillin, which results from it upon oxidation (p. 401). Myronic acid, C10H19O10NS2, is present as potassium salt, C10H18KO10NS2 (glancing needles), in black mustard seed. It is broken up into grape sugar, potassium bisulphate and allyl iso- thiocyanate by baryta water or by the ferment Myrosin, which likewise occurs in the mustard seed. Ruberythric acid ; see p. 474. For synthetized glucosides, see B. 18, 1960, 3481. O. Vegetable substances of unknown Constitution. Aloin, C17H18O7 (in the aloe plant), crystallizes in fine needles and is a powerful purgative ; it is a derivative of anthracene. (506) 2K 514 XXXVII. ALBUMINOUS SUBSTANCES; ANIMAL CHEMISTRY. Cantharidin, C10H12O4 (in Spanish fly), forms sublimable plates ; it blisters the skin. Picrotoxin, C30H34O13 (in the seeds of Cocculus indicus). Santonin, C15H18O3 (in worm seed), is derived from naphthalene (B. 16, 2686). Among natural dyes of unknown constitution we have : Brasilin, C16H14O5, the red dye of Brazil and Fernambuco woods. In the free state it crystallizes in colourless glancing needles. Curcumin, C14H14O4 ?, the yellow dye of the turmeric root, is turned brownish-red by alkalies, for which it forms a delicate test. Hsematoxylin, C16H14O6, is the colouring matter of logwood (Hsema- toxylon Campechianum). It forms yellowish prisms, which dissolve in alkalies with a violet-blue colour. Carminic acid, C17H18O10, the active principle of cochineal (Coccus Cacti), is a red amorphous mass which is split up by acids into a sugar (not glucose) and Carmine red, C11H12O7, the latter forming a purple-red mass with a green reflection; bromine converts carminic acid into a dibromo- derivative of a methylated and hydroxylated phthalic acid (B. 18, 3180). Harmin, C13H12N2O, and Harmalin, C13H14N2O, are the colouring matters of Peganum Harmala (B. 18, 400). Chlorophyll or Imf green, is the green colouring matter of plants, and contains iron in its molecule. Together with starch, wax, etc., it forms the chlorophyll granules of the cells, but, notwithstanding that it has been the subject of numerous investigations, its nature is not yet accurately known. Litmus is a blue dye obtained from Roccella tinctoria and other lichens ; it is related to orcein (p. 390), and is turned red by acids, the blue colour being restored by alkalies. Hence it is much used as an indicator in alkalimetry. XXXVII. ALBUMINOUS SUBSTANCES; ANIMAL CHEMISTRY. An extended description of the substances (other than those abeady mentioned) which are found in the animal organism and which are therefore of importance for physiological chemistry, will not be attempted here, since they are for the most part better known from a physiological than from a chemical point THE ALBUMENS. 515 of view. Only the albumens and albuminoids, both of which are classed as proteids, and some of the substances which are produced during metabolic processes, will be treated of. A. Albumens. The albumens make up the chief part of the organism, being present partly in the soluble and partly in the solid state; they are found in all the nutritive fluids of the body. In solution they are opalescent, optically ( - ) active, and do not diffuse through parchment paper, i,e, are colloids; but they are thrown down when the solution is warmed, or upon the addition of strong mineral acids, of many metallic salts [e.g, copper sulphate, basic lead acetate and mercuric chloride], of alcohol, tannic acid, acetic acid together with a little potassium ferrocyanide, etc. When boiled : (a) with nitric acid, they are coloured yellow (the xantho-protei'n reaction) ; (b) with a solu- tion of mercuric nitrate containing N2O3 (Millon^s reagent), red; (c) with caustic soda solution and a very little cupric sulphate, violet. The albumens combine both with acids and alkalies to acid- and alkali-albuminates (see below). The different albumens vary only slightly among themselves in percentage composition ; they contain : C = 52.7 to 54.5 p.c; H = 6.9 to 7.3 p.c; N = 15.4: to 16.5 p.c; 0 = 20.9 to 23.5 p.c; and S = 0.8 to 2.0 p.c. Since they have not yet been obtained pure, it is impossible to give a formula for them, even for the crystalline albumen which occurs in hemp, castor oil, and pumpkin seeds (see B. 15, 953). The fact that albumen contains sulphur is worthy of note, though the mode in which it is combined in the molecule is unknown ; warming with a dilute alkaline solution is sufficient to eliminate it partially, e.g. when white of egg is boiled with an alkaline solution of lead oxide, sulphide of lead is separated (the test for sulphur in albumen). Constitution. The way in which albumen is split up by acids 516 XXXVII. ALBUMINOUS SUBSTANCES; ANIMAL CHEMISTRY. (especially in presence of stannous chloride), or by baryta water, gives some indication of its constitution. Here, in addition to ammonia and carbonic acid, amido-acids are the principal products, and these belong not only to the fatty series [e.g, glycocoll, leucine, aspartic acid, glutamic acid and ^qeucein," (C4H7N02)^ (B. 19, Eef. 30)], but also to the aromatic {e.g, phenyl-amido-propionic acid and tyrosine). Loew's hypothesis that albumen is essentially a condensation product of aspartic aldehyde, C4H7NO2, ^. c. of leucein, is worthy of mention. The putrefaction of albumen gives rise not only to amido- acids but also to other aromatic and fatty acids {e.g. butyric acid), indole, skatole and cresol ; further, to the alkaloid-like Ptomaines (the poisonous alkaloids produced in dead bodies), of which neurine and pentamethylene-diamine (or **Cadaverin," B. 19, 2585) have been isolated. Albuminous matters undergo change when acted upon by the juices of the stomach at a temperature of 30-40°, pepsin converting them in the first instance into Anti- and Hemi-albumoses, both of which then go into peptone ; trypsin likewise gives rise to the two above album- oses, but then transforms the anti-compound into peptone and the hemi- compound into leucine, tyrosine and asparagine (the pancreatic diges- tion ; for details, see Kuh7ie, B. 17, Ref. 79). The peptones are readily soluble in water, and they are neither coagulated upon heating nor by most of the reagents which coagulate albumen. Classification of the albumens, 1. Those which are soluble in water, but become insoluble, i.e, coagulate, when the solution is heated to 70-75°; to this class belong the Albumens, e.g, egg albumen, serum albumen, vegetable albumen, etc. 2. Those insoluble in water and which curdle at once when outside the organism; this class includes the Fibrins, e.g, blood fibrin, vege- table fibrin, etc. 3. Those insoluble in water and in a solution of sodium chloride, but readily soluble in dilute hydrochloric acid and in alkaline carbonate ; they are neither precipitated on boiling, nor on neutralizing the dilute solution in presence of potassium phosphate. These are the Albumin- ates, which include the caseins, e.g. milk casein and vegetable casein THE ALBUMINOIDS. 517 (legumin), and also alkali-albuminate, which results on dissolving albumen in alkali. 4. Those insoluble in water but soluble in a dilute solution of com- mon salt or sulphate of magnesia, and which coagulate on heating their solution or which are precipitated on saturating it with MgS04 at 30°. These are the Globulins, e.g. fibrinogene and fibrinoplastic substance (which combine with one another to fibrin), globulin (in the crystalline lens of the eye), myosin (muscle albumen) and vitellin. 5. Those which are insoluble in water and sodium chloride solution, but readily soluble in dilute acids and alkalies or alkaline carbonates, and which are precipitated on neutralizing the solution but not by heat : Syntonin (acid-albumen). 6. Hemi-albumoses and Peptones (see above). B. Albuminoids. The albuminoids are to be regarded as the nearest deriva- tives of the albumens, being closely related to these ; they are mostly organized, and are important constituents of the tissue. Some of them are converted into glue when boiled with water, and hence are termed glue-yielding substances. They give bone oil " (p. 480) on destructive distillation. To this group belong : 1. Glutin or Bone glue, known as gelatine in the pure state, which is characterized by its solution solidifying to a jelly on cooling ; it is obtained by boiling bone cartilage, connective tissue, stages horn, calves' feet, etc. (the so-called " collogenes ") with water. 2. Chondrin or CartUage glue, which closely resembles the above, results from cartilage proper (which is termed a " chondrogene "). Neither of these, unlike the albumens, are precipitated from the aqueous solution by nitric acid or potassium ferrocyanide. Tannic acid throws down gelatine from solution, and unites with the glue- yielding substances of the organism to form compounds insoluble in water (the tanning of hide ; leather). Chondrin is precipitated from its solution by many salts which do not throw down glutin, e.g. by alum. Bone glue yields glycocoU and leucine when boiled with acids, and chondrin yields leucine. Gelatine is for the most part transformed into the ether of an 518 XXXVII. ALBUMINOUS SUBSTANCES; ANIMAL CHEMISTRY. amido-acid by an alcoholic solution of hydrochloric acid, possibly the compound : CH(NH2)=C(OH)-C02.C2H5, Amido-oxy-acrylic ether, so that it is permissible to surmise that gelatine is a condensation product of amido-acrolein, CH(NH2)=Cfl— CHO, possessing as it does the same percentage composition as the latter (Curtius and Buchner, 10, 850 ; cf. also B. 19, Ref. 697). 3. Mucin or Mucus, found in slime secretions, is free from sulphur. 4. Keratin or horn substance goes to build up the epidermis, nails, hair, etc. ; it contains sulphur. 5. Elastin is the chief constituent of the elastic ligaments of the organism. It does not contain sulphur, and yields leucine with sulphuric acid. 6. The unorganized ferments diastase, ptyalin, pepsin, trypsin, etc., already mentioned at p. 294, also belong to this group. 7. Chitin, the principal constituent of the cuticular covering of the articulata, e.g. of the shell of the crab, differs from horn substance in being insoluble in alkalies ; it yields glucosamine (p. 289) when boiled with acids. 0. Compounds of a higher order than Albumen. 1. Colouring matters. Haemoglobin, the chief constituent of the red blood corpuscles, probably possesses a still more complicated composition than albumen, since it gives albumen and heematin (the colouring matter of blood) when broken up. Haemoglobin combines very readily with oxygen, e.g. in the lungs, to Oxy-haemoglobin, which yields up its oxygen again, not only in the organism but also in a vacuum and when exposed to the action of re ducing agents. With carbon monoxide it combines to the compound, Carbon monoxide- haemoglobin. All three compounds can be obtained crystal- lized in the cold, and they possess characteristic absorption- spectra. Hsematin (G^^^^^eO^V}^ a dark brown powder containing 8 p.c. of iron, results even from the spontaneous decomposition of haemoglobin. Its hydrochloride, HsBmin (C32H3oN4Fe03, HCl ?), is obtained in the form of characteristic microscopic, reddish-brown crystals by the action of glacial NUCLEIN; LECITHIN. 519 acetic acid and some common salt upon oxy-hsemoglobin ; this is a delicate test for the presence of blood. 2. Nuclein is an important constituent of the cell nucleus, e,g. of pus cells, of nucleated blood corpuscles, of yeast cells, etc. It forms a white mass insoluble in water or dilute mineral acids but readily soluble in alkalies. It contains phosphoric acid in ethereal combination, and breaks up when boiled with water or dilute acids into albumen, hypoxanthine and the acid just named. Some varieties of nuclein are free from sulphur while others contain it, the latter yielding tyrosine when decom- posed. Nuclein appears to be formed synthetically when albumen is coagulated by meta-phosphoric acid. D. Substances produced during Metabolic processes. 1. Acids of the, bile. Bile contains the sodium salts of Glyco- cholic acid, C26H43NO6, and Taurocholic acid, C26H45NSO7, both of which are decomposed by alkalies into Cholic acid, C24H40O5, = C2iH32(OH)(C02H)(CH2.0H)2, on the one hand, and giycocoll and taurine respectively on the other. 2. The bile also contains various colouring matters : Bilirubin, Biliverdin, Bilifuscin, etc. These apparently bear some simple relation to the colouring matter of blood, the formula of bilirubin being C32H36N4O6 (see B. 17, 2265). 3. The Cholesterins, C26H43(OH), of which numerous varieties are now known, are present in blood, bile, nerve substance, vegetable fats, etc. They are monatomic alcohols. 4» Cerebrin, C17H33NO3, is an important ingredient of the medullary substance of the nerve. Lecithin, C42H84NO9P, is a characteristic constituent of nerve sub- stance, brain, yolk of egg, etc. It forms a waxy mass capable of crystallization, which dissolves in alcohol and ether, and swells up to an opalescent liquid with water. It breaks up on saponification into choline, glycerine-phosphoric acid, stearic and palmitic acids, and is therefore to be regarded as glycerine in which the three hydroxyl hydrogens have been replaced by the palmitic, stearic and phosphoric acid residues, the last of which still remains in ethereal combination with choline. INDEX. A a = asymmetric, 313. Abietic acid, 512. Absynthol, 510. Acenaphthene, 468. Acetals, 132, 136. Acetaldehyde, 135. Acetamide, 183. Acetamido-chloride, 183. Acetamidine, 185. Acetanilide, 341, 357. Acetenyl-benzene, 332. Acetic acid, 8, 156. Acetic anhydride, 179. Acetic ether, 175. Acetic fermentation, 156. Acetimido-chloride, 183. Acetimido-hydrate, 185. Acetimido-thio-ethyl, 185. Acetimido-thio-hydrate, 184. Acetins, 202. Aceto-acetic acid, 224. Aceto-acetic aldehyde, 222, 321. Aceto-acetic anilide, 493. Aceto-acetic ether, 224. Aceto-acetic ether synthesis, 160, 407. Aceto-malonic ether, 227. Aceto-nitrile, 108. Aceto-phenone, 332, 399. Aceto-phenone-acetone, 400. Aceto-propionic acid, 223. Aceto-succinic ether, 227. Aceto-thiamide, 184. Acetol, 221. Acetone, 143. Acetone alcohol, 221. Acetone-amines, 141. Acetone cyanhydrin, 193. Acetone-dicarboxylic acid, 224, 390. Acetone phenyl'hydrazine, 436. Acetonic acid, 217. Acetonyl-acetone, 221, 299. Acetoxime, 142, 144. Acet-toluide, 358. Aceturic acid, 213» Acetyl, 153. Acetyl-acetone, 221. Acetyl-amido-benzoic acid, 494. Acetyl bromide, 178. Acetyl-carbinol, 221. Acetyl chloride, 177. Acetyl-diphenylamme, 347. Acetyl-indole, 436. Acetyl-naphthols, 466. Acetyl peroxide, 179. Acetyl -phenol, 382, 383. Acetyl-sulphanilic acid, 353. Acetyl-thio-urea, 277. Acetyl-toluidines, 358. Acetyl-urea, 273. Acetylene, 56, 320. Acetylene-dicarboxylic acid, 238. Acetylene series, 53. Acid-albuminates, 515, 517. " Acid decomposition," 225. Acid derivatives, 173. Acid fuchsine, 453. Acid green, 453. Acid violet, 453. Acids, aromatic, 401 et seq., 428. Acids, fatty, 146 et seq. Aconitic acid, 246. Acridine, 355, 478, 498. Acridine-carboxylic acid, 499. Acridinic acid, 497. Acridyl aldehyde, 499. Acrolein, 137. Acrolein-ammonia, 138. Acrolein-aniline, 492. Acroses, 289. Acrylic acid, 164, 165. Adenine, 284. Adipic acid, 228. * iEsculin, 513. iEsculetin, 428. Affinities, free, 16, 49. Alanine, 216. Albuminates, 516. Albumens, 515. Albumenoids, 517. Alcohol, 79. Alcohol, constitution of, 17. 522 INDEX. Alcohol-acids, 206, 402, 403. Alcohol of crystallization, 78. Alcohols, aromatic, 395. Alcohols, fatty, 70. Aldehyde, 135. Aldehyde-acids, 205, 212, 222. Aldehyde-alcohols, 220, 286. Aldehyde "condensations," 133. Aldehydes, aromatic, 398. Aldehydes, fatty, 128. Aldehydes, the fuchsine test for, 135, 452. Aldehydine, 350, 482, 487. Aldine, 491. Aldines, 143. Aldol, 134, 220, 492. Aldol " condensations," 134, 408. Aldoximes, 134, 406. Alizarin, 472, 474. Alizarin black, 467. Alizarin blue, 475. Alizarin orange, 475. Alkali-albuminate, 517. Alkali blue, 453. Alkaloids, 481, 499. Alkaloids from dead bodies, 516. Alkarsin, 124. Alkeins, 196. Alkines, 196. Alkyl, 37. Alkyl-hydro-anthracenes, 472. Alkyl-hydro-anthranols, 472. Alkyl-malonic acids, 230. Alkylenes, 46. AUantoin, 280, 283. Allan turic acid, 280. AUene, 55, 57. AUophanic acid, 273. Alloxan, 280, 282. Alloxanic acid, 280, 282. Alloxantin, 280, 282. Allyl-acetic acid, 166. AUyl alcohol, 87. AUyl-aniline, 494. Allyl bromide, 60, 70. Allyl chloride, 60, 70. Allyl cyanide, 108. Allyl ether, 92. Allyl iodide, 60, 70. Allyl " mustard oil," 262. AUyl-pyridine, ^7. Allyl sulphide, 97. Allyl thiocyanate, 262. Allylene, 55, 57, 320. Aloin, 513. Alpha-compounds (see individually). Aluminium chloride, action of, 324. Aluminium methide, 128. Amalic acid, 283. Aniber, 512. "Amidating," 842. ' Amides of the fatty series, 180. Amidines, 185. Amido-acetic acid, 212. Amido-acetone, 143. Amido-acids, 208, 212. Amido-acrdlein, 518. Amido-azo-benzene, 368, 370. Amido-azo-benzene-sulphonic acid, 371. Amido-azo-compounds, 363, 365, 368. Amido-azo-naphthalene, 465. Amido-azo-phenylene, 350. Amido-azo-toluenes, 371. Amido-benzaldehyde, 399, 493. Amido-benzene, 340, 350. Amido-benzene-sulphonic acids, 375. Amido-benzoic acids, 308, 358, 402, 414. Amido-benzoyl-formic acid, 424. Amido-butyric acids, 217. Amido-camphor, 510. Amido-caproic acid, 217. Amido-chlorides, 183. Amido-cinnamic acids, 418, 492. Amido-cinnamic aldehyde, 492. Amido -derivatives, aromatic, 340. Amido-dimethyl-aniline, 341, 354, 356. Amido-diphenyl, 438. Amido-diphenylamine, 341, 355. Amido-durene, 359. Amido-ethyl-benzenes, 359. Amido-ethyl-sulphonic acid, 197. Amido-hydrocinnamic acid, 417. Amido-isobutyl-benzene, 343, 359. Amido-ketones, 143. Amido-mesitylene, 359. Amido-naphthols, 446. Amido-oxy-acrylic ether, 518. Amido-phenols, 382, 386. Amido-phenyl-acetic acids, 416. Amido-phenyl-methyl-quinoline, 497. Amido-phthalic acid, 429. Amido -propionic acid, 216. Amido-propyl-benzene, 359. Amido-pseudo-cumene, 359. Amido-quinolines, 480, 496. Amido-succinic acid, 239, 240. Amido-tetramethyl-benzenes, 359. Amido-thiazol, 302. Amido-thiophene, 297, 301. Amido-thio-phenols, 386. Amido-trimethyl-benzenes, 359. Amido-valeric acids, 217. Amido-xylenes, 359. Amimides, 185. Amines, aromatic, 340. Amines, fatty, 110. Aminic acids, 212. Amm elide, 265. Ammeline, 265. Ammonium bases, 110, 115, Ammonium cyanide, 254. INDEX. 523 Amygdalin, 252, 398, 612. Amyl alcohols, 85. Arayl-bcnzenc, 323. Amyl bromide, 66. Amyl chloride, 60, 66. Amyl iodide, 66. Amyl nitrite, 100. Amylenes, 46. Amyloid, 293. Amylum, 293. Analysis, qualitative, 2. Analysis, quantitative, 4. Analysis, elementary, 4. Angelic acid, 164, 166. Anhydrides of the fatty acids, 178. Anhydro-bases, 349, 386. Anilides, 345, 357. Aniline, 341, 350. Aniline black, 351, 503. Aniline blue, 453. Aniline red (see Fuchsine). Aniline violet (see Methyl violet). Aniline yellow, 869. Animal chemistry, 514. Anisic acid, 410, 421. Anisic alcohol, 400, 401. Anisic aldehyde, 400, 401. Anisidine, 382, 386. Anisidine-sulphonic acid, 382. Anisol, 382. Anthracene, 469. Anthracene-carboxylic acids, 473. Anthracene hydrides, 471. Anthracene-sulphonic acids, 472. Anthrachrysone, 472. Anthraflavic acid, 472, 474. Anthra-hydroquinone, 472, 473. Anthramine, 472, 473. Anthranil, 414. Anthranilic acid, 414. Anthranol, 472, 473. Anthra-purpurin, 472, 475. Anthra-quinoline, 497. Anthraquinone, 470, 472, 473. Anthraquinone-sulphonic acids, 472, 474. Anthrarufin, 472. Anthrol, 472, 473. Anti-albumoses, 516. Antimony ethide, 126. Antimony methide, 126. Antipyrine, 302. Apo-quinine, 500. Aposorbic acid, 243. Arabic acid, 294. Arabin, 294. Arabinose, 220. Arachinic acid, 147. Arbutin, 513. Aromatic compounds, V. Meyer's defini- tion of, 806. Aromatic compounds, 303. Aromatic hydrocarbons, 323. Aromatic hydrocarbons, isomers and con- stitution, 325. Arsenic compounds, 122. Arsines, 122. Arsonium compounds, 122. Aseptol, 387. Asparagine, 239. Aspartic acid, 239. Aspartic aldehyde, 516. Asphalt, 46. Asymmetric carbon atoms, 31, 32. Atoms, law of even numbers of, 22. Atro-lactinic acid, 424. Atropic acid, 403, 410, 418. Atropine, 490. Auramine, 445. Aurantia, 355. Aurin, 454. Avogadro and Ampere* s theory, 10. Azimido-benzene, 350. Azines, 501. Azo-benzene, 351, 368. Azo-blue, 441. Azo-dyes, 869. Azo-dyes of the naphthalene series, 370, 465. Azo-compounds, aromatic, 860, 366, 368. Azo-diphenyl blue, 503. Azo-naphthalene, 465. Azo-phenols, 386. Azo-phenyl-ethyl, 368. Azo-phenylene, 501. Azo-toluenes, 368. Azoxy -benzene, 367. Azoxy-compounds, 366. B Barbituric acid, 279, 282. Bassorin, 295. Beer, 81. Behenic acid, 147. Behenolic acid, 168. Belladonnine, 490. Benzal chloride, 332, 336, 398. Benzaldehyde, 305, 359. Benzaldehyde-phenyl-hydrazone, 399. Benzaldoxime, 399, 406. Benzal violet, 449. Benzamide, 401, 413. Benzamide-silver, 414. Benzanilide, 413. Benzene, 303, 328. Benzene, constitution of, 311, 816. Benzene, formation, 320. Benzene, properties and behaviour, 326. 524 INDEX. Benzene-azo-dimethyl-aniline, see Di- methyl-amido-azo-benzene. Benzene derivatives, 303. Benzene derivatives, formation, 820. Benzene derivatives, isomeric relations, 307, 310, 315. Benzene-dicarboxylic acids, 428. Benzene-disulphonic acids, 375. Benzene disulphoxide, 384. Benzene hexabromide, 328. Benzene hexachloride, 312, 328. Benzene hexahydride, 327, 328. Benzene hydrocarbons, 323. Benzene of crystallization, 447. Benzene sulphonamide, 374. Benzene-sulphinic acid, 375. Benzene-sulphinic ethers, 375. Benzene-sulphonic chloride, 374. Benzene-sulphonic acid, 305, 306, 373. Benzene thio-hydrate, see Phenyl thio- hydrate. Benzene-tricarboxylic acids, 402, 430. Benzene trichloride, 332, 336. Benzene-trisulphonic acid, 305, 375. Benzhydrol, 442, 444. Benzhydrol-benzoic acids, 442, 445. Benzidam, 350. Benzidine, 367, 438, 439. Benzile, 458. Benzilic acid, 442, 445. Benzoic acid, 305, 307, 410, 412. Benzoic anhydride, 401, 413. Benzoic ethers, 401, 413. Benzoin, 458. Benzo-nitrile, 305, 363, 374, 402, 415. Benzophenone, 442, 444. Benzo-purpurin, 441. Benzoyl-acetic acid, 410, 424. Benzoyl-acetone, 400. Benzoyl-benzoic acids, 442, 445, 470. Benzoyl-carbinol, 401. Benzoyl chloride, 401, 413. Benzoyl cyanide, 413. Benzoyl-ecgonine, 501. Benzoyl-formic acid, 410, 424. Benzoyl-glycocoll, see hippuric acid. Benzoyl-sulphone-imide, 415. Benzyl-aceto-acetic ether, 407. Benzyl alcohol, 305, 336, 395, 397. Benzyl-benzoic acids, 442, 445. Benzyl-benzene, see Diphenyl-methane. Benzyl chloride, 318, 332, 335. Benzyl cyanide, 415. Benzyl mercaptan, 397. Benzylamine, 359, 397. Benzylidene-aniline, 345. Berberine, 488. Berberonic acid, 488. Berlin blue, 256. Betain, 213, Biebrich scarlet, 370, 372. Bile, 519. Bilifuscin, 519. Bilirubin, 519. Bismarck brown, 360, 371. Bitter almond oil, 305, 398. Bitter-almond-oil green, 448. Biuret, 273. Blood colouring matter, 518. Blood fibrin, 516. Boiling point, laws regulating, 26. Bone glue, 517. Bone oil, 480. " Bordeaux" (dyes), 372. Borneol, 510. Borneo camphor, 510. Bornyl chloride, 510. Boron compounds, 125. Brain, 519. Brandy, 81. Brazil wood, 514. Brasilin, 514. Brassylic acid, 228. Brilliant green, 449. Brom-aceto-acetic ether, 321. Bromo-acetophenone, 400. Bromo-acetyl bromide, 177. Bromo-acetylene, 70. Bromanil, 394. Bromanilic acid, 394. Bromo-anilines, 352. Bromo-anthraquinones, 474. Bromo-benzene, 307, 332, 335. Bromo-benzoic acids, 308. Bromo-benzyl bromide, 469, 476. Bromo -camphor, 510. Bromo-ethyl-benzene, 332. Bromo-ethylene, 70. Bromoform, 69. Bromo-isatin, 433. Bromo-naphthalene, 463. Bromo-nitro-benzenes, 318, 339, 405. Bromo-phenols, 384. Bromo-styrenes, 336. Bromo-succinic acids, 235. Bromo-toluenes, 335. Brucine, 500. Butanes, 41. Butine, 57. Butyric acid, 159, 160. Butyric ether, 175. Butyric fermentation, 159. Butyl-acridine, 498. Butyl alcohols, 84. Butyl-benzenes, 323, 331. Butyl bromides, 66. Butyl chlorides, 66. Butyl iodides, 66. Butyl-phenol, 380, 380. Butylene diamine, 195. INDEX. 525 Butylencs, 46, 51, 62. Butyrone, 144. Butyro-nitrile, 108. Butyryl chloride, 177. C Cacodyl, 125. Cacodyl compounds, 122, 124, 125. Cacodylic acid, 125. Cacodylic oxide, 124. Cadaverin, 516. Caffeic acid, 427. Caffeine, 284. Caffetannic acid, 426. Cairolin, 496. Campechy wood, 514. Camphene, 507. Campholene cyanide, 510. Campholenic acid, 510. Camphor, 509. Camphoric acid, 509. Camphoronic acid, 509. Camphor-oxime, 510. Camphylamine, 510. Cane sugar, 291. Cane sugar group, 289. Cantharidin, 514. Caoutschin, 57. Caoutchouc, 506, 509. Capric acid, 161. Caprilic acid, 161. Caproic acid, 161. Caramel, 291. Carbamic acid, 270. Carbamic chloride, 270. Carbamic compounds, 274. Carbamic ethers, 270. Carbamide, 270. Carbamines, 109. Carbanihde, 341, 358. Carbazole, 438, 440. Carbimide, 250, 269. Carbinol, 77. Carbo-cinchomeronic acid, 488. Carbo-di-imide, 264. Carbohydrates, 285. Carbohydrates, reaction with a-naphthol and sulphuric acid, 285. Carbo-hydrocinnamic acid, 465. Carbo-pyrrolic acid, see Pyrrol-carboxylic acid. Carbostyril, 418, 492, 496. Carbolic acid, 381. Carbon bisulphide, 275. Carbon oxychloride, 268. Carbon tetra-iodide, 69. Carbonic acid, derivatives of, 266. Carbonyl compounds, 274. Carbonyl di-urea, 274. Carboxyl group, 152. Carboxylic acids, aromatic, 325, 401, etc. Carboxylic acids, fatty, 146. Carbyl sulphate, 197. Carmine, 284. Carmine red, 514. Carminic acid, 514. Cartilage glue, 517. Carvacrol, 377, 388, 509. Carvene, 505, 508. Carvol, 388. Caryophyllin, 510. Caseins, 516. Catechu-tannic acid, 426. Cedrene, 506. Cedriret, 440. Celluloid, 293. Cellulose, 292. Cerebrin, 519. Ceresine, 46. Cerotene, 46, 52. Cerotic acid, 162, 163. Ceryl alcohol, 86. Ceryl cerotate, 175. Cetyl alcohol, 86. Cetyl bromide, 66. Cetyl iodide, 66. Chain isomerism, 93. Chelidonic acid, 491. Chitin, 518. Chloral, 137. Chloral alcoliolate, 137. Chloral hydrate, 68, 137. Chloranil, 351, 394. Chloranilic acid, 394. Chlorhydrins, 192, 200. Chlorinated alcohols, 83. Chloro-acetamide, 183. Chloro-acetene, 136. Chloro-acetic acids, 168, 172, 211. Chloro-acetic ethers, 175. Chloro-aceto-acetic ether, 227. Chloro-acetyl chloride, 178. Chloro-acetylene, 70. Chloro- acrylic acids, 169. Chloro-aniline, 352. Chloro-anthracenes, 472. Chloro-benzene, 305, 332, 335, 363. Chloro-benzoic acid, 402, 414. Chloro-benzyl chloride, 333. Chloro-bromo-benzenes, 335. Chloro-camphor, 510. Chloro-carbonic acid, 268. Chloro-carbonic ether, 269, 406. Chloro-derivatives of benzene, 332. Chloro-diphenyl, 438, 439. Chloro-ethyl-sulphonic acid, 197. Chloroform, 68, 407. Chloro-iodo-benzenes, 336, 526 INDEX. Chloro-isatln, 433. Chloro-malonic ether, 234. Chloro-naphthalenes, 463. Chloro-nitro-benzenes, 318, 339. Chloro -phenols, 382, 384. Chloro-phenyl-acetic acid, 408. Chloro-phthalic acids, 429. Chlorophyll, 514. Chloro-picrin, 103. Chloro-propionic acids, 168, 169, 172. Chloro-pyridine, 480, 482. Chloro-quinoline, 480. Chloro-quinone, 393. Chloro-toluenes, 318, 332, 335. Chloro-xylenes, 332. Cholesterin, 519. Cholestrophane, 282. Cholic acid, 519. Choline, 194, 196. Chondrin, 517. Chondrogene, 517. Chromogenes, 24, 356. Chrysaniline, 499. Chrysazin, 472. Chrysazol, 472. Chrysene, 477. Chrysoidin, 350, 369. Chrysoi'dine, 371. Chrysoidines, 370. Chrysoin, 871. Cincho-lepidine, 497. Cinchomeronic acid, 488. Cinchona alkaloids, 500. Cinchoninic acid, 497. Cinchonidine, 500. Cinchonine, 482, 500. Cinene, 507. Cineol, 510. Cinnamenyl compounds, 418. Cinnamic acid, 403, 408, 410, 417. Cinnamic alcohol, 397. Cinnamic aldehyde, 399. Cinnamon, oil of, 399. Cinnamyl compounds, 418. Cinnoline compounds, 498. Circular polarization, 30, 31. Citraconic acid, 236. Citrazinic acid, 247, 482. Citrene, 505, 508. Citric acid, 246. Citron, oil of, 504, 508. Classification of Organic compounds, 23. Closed chains and rings, 47, 198, 295, 311. Cloves, oil of, 390. Coagulation, 516. Cocaine, 501. Cocceryl alcohol, 192. Coccerylic acid, 218. Codeine, 499. Ccerulein, 457. ^ Coerulin, 457. Ccerulignone, 440. Collidine, 481, 482, 487. CoUidine-dicarboxylic ether, 482, 484. Collodion, 293. Collogenes, 517. Colophene, 506. Colophonium, 506, 512. " Condensation," 134, 459, 494. Condensation of ketones, etc., 226. Condensed benzene nuclei, 459 et seq. Colouring matters, natural, 614. Combustion, organic, 4. Combustion, heat of, 30. ''Congo" (dye), 440. Coniceins, 489. Coniferin, 401, 513. Coniferyl alcohol, 401. Conic acid, 218. Conine, 489. Constitution of organic compounds, 16 et seq. Conydrine, 489. Conylene, 57. Conyrine, 486. Copper-zinc couple, 40. Coridine, 481. Cotarnine, 500. Cotton dyes, 440, 457. Creatine, 278. Creatinine, 278. Creosol, 390. Cresol, 377, 387. Cresol ethyl ether, 862. Cresorcin, 390. Cresyl-sulphuric acid, 388. Crocein scarlet, 370. Croconic acid, 296. Crotonic acids, 164, 165. Crotonic aldehyde, 134. Crotonylene, 57, 320. Cryptidine, 497. Crystal violet, 453. Crystalline, 350. Cubebene, 506. Cumalic acid, 239, 491. Cumaric acids, 410, 427. Cumarin, 409, 427. Cumene, 323, 330. Cumenols, 377. Cumic acid, 330, 410, 417. Cumic alcohol, 396. Cumic aldehj^'de, 399. Cumidine, 341, 359. Cumin, oil of, 388, 504. Cuminol, 399. Cupric ferrocyanide, 255. Curcumin, 514. Cyamelide, 258. Cyan-acetic acid, 172. INDEX. 527 Cyanamlde, 264. Cyan-etholine, 259. Cyanic acid, 257. Cyanic ether, 258. Cyanines, 496. Cyanmethine, 108. Cyano-benzene, 402. Cyano-carbonic ether, 223. Cyano-diphenyl, 438. Cyano-fatty acids, 171. Cyano-naphthalenes, 465. Cyano-pyridine, 486. Cyano-quinoline, 496. Cyanogen, 248, 249. Cyanogen bromide, 257. Cyanogen chloride, 257. Cyanogen compounds, 248, 250. Cyanogen iodide, 257. Cyanogen sulphide, 262. Cyanol, 350. Cyanuramide, 265. Cyanuric acid, 259. Cyanuric chloride, 257. Cymene, 323, 325, 331. Cymidine, 359. Cymogene, 44. Cystine, 224, Cyste'in, 224. D Dambose, 289, Daphnetin, 428. Daphnin, 428. Decane, 44. Decomposition of hydrocarbons, 45. Decomposition of optically active com- pounds by ferments, 31. Decyl alcohols, 86. Desmotropism, 266, 430. Desoxalic acid, 247. Desoxy-benzoin, 458. Developer, photographic, 391. Dextrine, 294. Dextro- tartaric acid, 240. Dextrose, 286, 288. Diacetamide, 180. Diacetin, 202. Diaceto-acetic ether, 227. Diaceto-succinic ether, 227. Diacetyl, 221, 322. Diacetylene, 58. Diacetylene-dicarboxylic acid, 68, 238. Diacetylene-monocarboxylic acid, 168. Di-allyl, 57. Dialuric acid, 279, 282. Diamide, 117. Diamido-azo-benzene, 369, 371. Diamido-benzenes, 314. Diamido-benzoic acids, 314, 414. Diamido-benzophenone, 444. Diamido-diphenyl, 439. Diamido-diphenylamine, 341, 356. Diamido-phcnols, 386. Diamido-plienyl-acridine, 355. Diamido-stilbene, 457. Diamido-triphenyl-methane, 449. Diamines, 193. Diamines, aromatic, 349, 359. Diastase, 294. Diazo-acetic ether, 213. Diazo-amido-benzene, 366. Diazo-amido-compounds, 364, 365. Diazo-amido-naphthalene, 465. Diazo-amido-toluene, 371. Diazo-benzene, 361, 364. Diazo-benzene imide, 364. Diazo-benzene nitrate, 364. Diazo-benzene perbromide, 364. Diazo-benzene-potassium oxide, 364. Diazo-benzene-potassium sulphite, 372. Diazo-benzene-silver oxide, 364. Diazo-benzene-sulphonic acid, 375. Diazo-benzoic acids, 414. Diazo-cinnamic acids, 418. Diazo-compounds, aromatic, 346, 360. Diazo-compounds, fatty, 118. Diazo-ethane-sulphonic acid, 118. Diazo-ethoxane, 103. Diazo-phenols, 386. Diazotising, 361. Dibenzoyl-acetic acid, 459. Dibenzoyl-methane, 459. Dibenzyl, 437, 457. Dibromo-anthracenes, 472. Dibromo-acrolein, 138. Dibromo-benzenes, 314, 332, 335. Dibromo-indigo, 432. Dibromo-propionic acids, 170. Dibromo-pyridine, 500. Dibromo-succinic acid, 235, 243. Dibromo-w-xylene, 331. Dicetyl-ether, 92. Dicetyl-malonic acid, 228. Dichloro-acetic acid, 172. Dichloro-aceto-acetic ether, 227. Dichloro-acetone, 247. Dichloro-aldehyde, 137. Dichloro-anthraquinone, 474. Dichloro-benzenes, 305, 332, 335. Dichloro-diphenyl, 438. Dichloro-indigo, 432. Dichloro-tetroxy-benzene, 392. Dichloro-toluenes, 332, 333. Dicyan-diamide, 250, 264. Dicyano-benzenes, 375. Dicyano-diphenyl, 438. Diethyl, see Normal Butane. Diethylamine, 117. 528 INDEX. Diethyl-aniline, 341. Diethyl-benzenes, 323. Diethyl disulphide, 95. Diethyl ether, 91. Diethyl-glycol, 192. Diethyl-hydrazine, 118. Diethyl-hydrazine, urea derivatives of, 118. Diethyl-indigo, 432. Diethyl ketone, 144. Diethyl-phosphinic acid, 121. Diethyl sulphide, 94. Diethyl sulphone, 96. Diethyl sulphoxide, 90. Diethyl-toluidine, 436. Diethyl-urea, 270. Diethylene-diamine, 195. Digallic acid, see Tannin. DiglycoUamic acid, 212. Dihydro-collidine-dicarboxylic ether, 482. Dihydro-methyl-pyridine, 485, Dihydro-phthalic acid, 428. Dihydro-pyridine, 488. Dihydro-quinoline, 496. Di-iodo-benzenes, 332. Di-isocyanic acid, 260. Diketo-butane, 221. Diketo-hexane, 221. Diketones, 221, 222, 400. Dill, oil of, 508. Dimethyl-acetamide, 180. Dimethyl-aceto-acetic ether, 226. Dimethyl-alloxan, 282. Dimethyl-amido-azo-benzene, 363, 371. Dimethyl-amido-azobenzene-sulphonic acid, 371, Dimethylamine, 116. Dimethyl-aniline, 341, 354. Dimethyl-anthracenes, 472, 475. Dimethyl-arsine compounds, 122, 124. Dimethyl-benzenes, see Xylene. Dimethyl-benzoic acids, 416. Dimethyl-conine, 489. Dimethyl ether, 92. Dimethyl-ethyl-benzenes, 323. Dimethyl-furfurane, 297, 300. Dimethyl ketone, 141, 143. Dimethyl-malonic acid, 234. Dimethyl-naphthalenes, 467. Dimethyl-naphthylamines, 465. Dimethyl-nitrosamine, 115. Dimethyl-oxamic ether, 113, 233. Dimethyl-parabanic acid, 282. Dimethyl-phenylene green, 356. Dimethyl -phosphine, 120. Dimethyl-phosphinic acid, 120. Dimethyl-piperidine, 489. Dimethyl-pyridine, 480, 487. Dimethyl-pyridine-carboxylic ether, 483. Dimethyl-pyrrol, 297, Dimethyl-quinolines, 480. Dimethyl sulphide, 93. Dimethyl-thiazol, 302. Dimethyl-thiophene, 297. Dimethyl-toluidine, 359. Dimethyl-uric acid, 283. Dinaphthols, 466. Dinaphthyl, 468. Dinicotinic acid, 488. Dinitranilines, 353. Dinitro-benzenes, 305, 337, 338. Dinitro-cresol, 388. Dinitro-diphenyl, 438, 439. Dinitro-diphenyl-diacetylene, 459. Dinitro-diphenylamines, 355. Dinitro-ethane, 103. Dinitro-naphthol, 466. Dinitro-naphthol-sulphonic acid, 466. Dinitro-phenols, 305, 338, 385. Dinitro-toluenes, 316, 337, 338. '* Dioses," 290. Dioxindole, 434. Dioxy-acids, 165, 204. Dioxy-anthracenes, 472, 473. Dioxy-anthraquinones, 472. Dioxy-azobenzene-sulphonic acid, 371. Dioxy-benzenes, 375, 388, Dioxy-benzoic acids, 425. Dioxy-benzophenone, 445. Dioxy-cinnamic acids, 427. Dioxy-diphenylamine, 357. Dioxy-diphenyl-phthalide, 455. Dioxy-diquinoyl, 395. Dioxy-naphthalenes, 467. Dioxy-quinone, 395. Dioxy-tartaric acid, 243, 244, 322. Dioxy-terephthalic acid, 429. Dioxy-xylenes, 390. Dipentene, 506, 507. Dipentene dihydrochloride, 508. Dipentene tetrabromide, 508. Diphenols, 438, 440. Diphenyl, 438. Diphenyl-acetic acid, 442, 445. Diphenyl-acetylene, 457. Diphenyl-benzene, 438, 441. Diphenyl-bromo-ethane, 444. Diphenyl-carbinol, see Benzhydrol. Diphenyl-carboxylic acid, 438. Diphenyl-diacetylene, 459. Diphenyl-dicarboxylic acid, 438, 441. Diphenyl-ethane, 442, 445, 457. Diphenyl-ethylene, 457. Diphenyl-glycollic acid, 445. Diphenyl group, 438 . Di phenyl-hydrazine, 373. Diphenyl ketone, 444. Diphenyl-methane, 437, 442, 444. Diphenyl-nitrosamine, 355 Diphenyl oxide, 382, INDEX. 529 Diphenyl-phthalide, 455. Diphenyl-succinic acid, 458. Diphenyl-tolyl-methane, 446, 447. Diphenyl-thio-nrea, 358. Diphenyl-urea, 351, 358. Diphenylamine, 341, 355. Diphenylamine blue, 355, 453. Diphenylene ketone, 442. Diphenylene-methane, 446. Diphenylene oxide, 438, 440. Diphenyline, 438, 440. Diphenylol, 438. Dipicolinic acid, 488. Dipiperidyl, 490. Dipropargyl, 58. Dipyridine, 480, 485. Dipyridyl, 480, 485. Diquinoline, 480, 496. Diquinolyline, 480, 496. Disazo- compounds, 370. Distillation, fractional, 27, 81. Disulphanilic acid, 375. Dithio-acids, 179. Dithio-carbamic acid, 276. Dithio-dicyanic acid, 263. Dithio-urethane, 276. Ditolylamine, 359. Ditolyls, 438. Dodecane, 34. Double bond, 49, 50. Dulcite, 204. Durene, 323, 331. Durenols, 377. Dyes, 376, 514, etc. Dynamite, 202. E Ecgonine, 501. Egg albumen, 516. Egg, white of, 515. Elseoptenes, 504. Elaidic.acid, 167. Elastin, 518. Elayl, see ethylene. Electrolysis, 39, 49. Empirical formulae, 7. Emulsin, 294, 398. Eosins, 455. Epichlorhydrin, 201. Erigeron, oil of, 508. Erucic acid, 167. Erythrin, 203, 425. Erythrite, 203. Erythritic acid, 219. Erythro-oxy-anthraquinone, 472, 474. Erythrosin, 456. Etard reaction, the, 398. Ethal, 86. (506) Ethane, 16, 40. Ethane-tricarboxylic acid, 245. Ethenyl-amidine, 185, 349. Ethenyl-amidoxime, 187. Ethenyl-diphenyl-amidine, 185. Ethenyl-triethyl ether, 199. Ethereal oils, 504. Ether-acids, 98. Ethers, simple, 88. Ethers, compound, 70, 97, 173. Ethers of the fatty acids, 173. Ethidene chloride, 68. Ethionic acid, 197. Ethyl-acetamide, 180, 181. Ethyl-aceto-acetic ether, 226. Ethyl-acetamido chloride, 183. Ethyl-acetimido chloride, 183. Ethyl alcohol, 79. Ethyl-amine, 117. Ethyl-aniline, 341. Ethyl-benzene, 318, 323, 329. Ethyl-benzhydroxamic acid, 187. Ethyl-benzoic acids, 416. Ethyl bromide, 64. Ethyl-camphor, 510. Ethyl-carbamine, 110. Ethyl-carbonic acid, 268. Ethyl-cetyl ether, 92. Ethyl chloride, 64. Ethyl cyanamide, 264. Ethyl cyanide, 108. Ethyl-dithiocarbamic acid compounds, 276. Ethyl-glycollic acid, 211. Ethyl-giycoUic acid, derivatives of, 211. Ethyl-hydrazine, 118. Ethyl hydride, 40. Ethyl hydrosulphide, 93 et seq. Ethyl-indoxyl, 435. Ethyl iodide, 65. Ethyl isocyanide, 110. Ethyl isothiocyanate, 263. Ethyl-lactic acid, 216. Ethyl-malonic ethers, 234. Ethyl-methyl-pyridine, 486. Ethyl nitrate, 99. Ethyl nitrite, 100. Ethyl-nitrogen chloride, 117. Ethyl-nitrolic acid, 102. Ethyl-oxalic acid, 232. Ethyl-oxalyl chloride, 232. Ethyl-oxanthranol, 472. Ethyl-phenol, 380, 388. Ethyl-phosphines, 120, 121. Ethyl-piperidine, 489. Ethyl-pyridine, 486. Ethyl-salicylic acid, 421. Ethyl sulphide, 93. Ethyl-sulphinic acid, 105. Ethyl-sulphonic acid, 105. 2L 530 INDEX. Ethyl-sulphonic chloride, 105. Ethyl-sulphonic ether, 106. Ethyl-sulphuric acid, 104. Ethyl-sulphurous acid, 105. Ethyl-toluenes, 330. Ethyl-urea, 272. Ethylene, 46, 50. Ethylene bromide, 67. Ethylene chloride, 61, 67. Ethylene cyanhydrin, 193, 207. Ethylene cyanide, 192. Ethylene diamine, 188, 195. Ethylene-disulphonic acid, 106. Ethylene glycol, 191. Ethylene hydramine, 194. Ethylene-imine, 194. Ethylene iodide, 67. Ethylene-lactic acid, 216. Ethylene oxide, 193. Ethylidene chloride, 61, 68. Ethylidene cyanhydrin, 133, 193, 207. Ethylidene-diphenyl diamine, 345. Ethylidene-disulphonic acid, 106. Ethylidene glycol, 131, 191. Ethylidene-lactic acid, 214. Ethylidene -succinic acid, 235. Eugenol, 390. Eupion, 46. Eupittone, 454. Eurhodines, 502. F Fast yellow, 369. Fast red, 466. Fats, 162. Fatty acid series, 146. Fehling's solution, 241. Fermentation, 80. Ferments, 293. Fernambuco wood, 514. Ferulic acid, 427. Fibrins, 516. Fibrogene, 517. Fibrino -plastic substance, Fiddle resin, 500. Fittig reaction, the, 324. Flavaniline, 497. Flavean hydride, 252. Flavol, 472. Flavo-purpurin, 472, 475. Fluo-benzene, 335. Fluoranthene, 477. Fluorene, 442, 446. Fluorenyl alcohol, 442. Fluorescein, 456. Fluorescin, 456. Formamide, 183. Formic acid, 154. Formic aldehyde, 135. Formic ether, 175. Formose, 286. Formulae, rational, 19. Formulae, constitutional, 16. Formyl, 153. Formyl. acetic acid, 222. Formyl-acetic ether, 321. Formyl-diphenylamine, 498. Formyl-trisulphonic acid, 198. Fruit ethers, 175. Fruit sugar, 288. Fuchsine, 351, 451. Fumaric acid, 236, 237. Furfurane, 297, 299. Furfurane alcohol, 297, 300. Furfurane compounds, 300. Furfurol, 297, 300. Fusel oil, 80. G Galactose, 288. Galipot resin, 512. Gallein, 456. Galline, 456. Gallic acid, 391, 411, 425. Gallofiavin, 475. Gallo-tannic acid, 426. Garlic, oil of, 97. Garnet brown (dye), 386. Gasoline, 44. Gelatine, 517. Globulins, 517. Gluconic acid, 219. Glucosamines 287, 289. Glucoses, 285, 286. Glucosides, 426, 512. Glue, 517. Glutamic acid, 240. Glutaric acid, 235. Glutazine, 486. Glutin, 517. Glyceramic acid, see Serine. Glyceric acid, 219. Glyceric aldehyde, 220. Glycerides, 162, 163, 202. Glycerine, 199. Glycerine nitrate, 201. Glycerine-phosphoric acid, 200. Glycerine-sulphuric acid, 200. Glyceryl chloride, 69. Glycide alcohol, 201. Glycide compounds, 201. Glycocholic acid, 212, 519. Glycocoll, 211, 212. Glycocoll-amide, 211. Glycocyamine, 278. Glycocyamidine, 278, INDEX. 531 Glycogen, 294. GlycoUamide, 211. Glycol bromhydrins, 192. Glycol chlorhydrins, 188, 192. Glycol, ethers of, 192. Glycol mercaptan, etc., 193. Glycollic acetate, 188, 192. Glycollic acid, 170, 210. Glycollic aldehyde, 220. Glycollic anhydride, 212. Glycollic chloride, 211. Glycollic ether, 211. Glycolide, 212. Glycols, 187. Glycuronic acid, 244. Glyoxal, 221. Gly oxalic acid, 222. Glyoxaline, 221. Granulose, 293, Grape sugar, 288. Griess reaction, the, 363. Guaiacol, 389. Guanidine, 277. Guanine, 281, 284. Gums, 294. Gum benzoin, 412. Gum lac, 512. Gun cotton, 293. Guttapercha, 509. H Hsematin, 618. Hsematoxylin, 514. Hsemin, 518. Haemoglobin, 518. Halogen derivatives of the aromatic series, 332. Halogen derivatives of the fatty series, 58. Harmin, 514. Harmalin, 514. Heat of formation, 30. Helianthin, 360, 371. Helicin, 513. Hemellithene, 323, 330. Hemi-albumoses, 516. Hemi-mellitic acid, 305, 430. Hemipinic acid, 430. Hemiterpenes, 506. Heptanes, 44. Heptyl alcohols, 86. Heptylene, 46. Hesperidin, 513. Hesperidene, 505, 508. Hexabromo-benzene, 321, 335. Hexachloro-benzenc, 332, 335. Hexachloro-ethane, 60. Hexa-decane, 34. Hexadecyl alcohol, 86. Hex-ethyl-benzene, 323. Hexahydro-bcnzene, 312, 322. Hexahydro-dipyridyl, 490. Hexahydro-pyridinc, 479. Hexahydro-tercphthalic acid, 312, 429. Hexamethyl-benzene, 320, 323, 331. Hexa-methylene, 52, 312. Hexamethyl-triamido-triphenyl-methane 452. Hexamethyl-rosaniline, 452, 453. Hexanitro-diphenylamine, 355. Hexoxy-anthraquinone, 474. Hexoxy-benzene, 322, 377, 392. Hexoxy-diphenyl, 440. Hexagon formula, 312. Hexanes, 44. Hexine, 57. Hexyl alcohols, 86. Hexyl chloride, 66. Hexyl iodide, 321. Hexylene, 46. Hippuric acid, 212, 414. Homatropine, 490. Homoconic acid, 218. Homo-pyrocatechin, 377, 390. Homologous series, 20. Homology, 20. Honey stone, 431. Horn substance, 518. Hydantoic acid, 273. Hydantoin, 273. Hydracrylic acid, 216. Hydramines, 194. Hydratropic acid, 410, 417. Hydrazides, 135. Hydrazine, 117. Hydrazines, aromatic, 362, 372. Hydrazines, fatty, 117. Hydrazo-benzene, 367. Hydrazo-compounds, 119, 367. Hydrazones, 135, 143, 287, 373. Hydrindic acid, 423. Hydro-acridine, 479. Hydro-anthranol, 472, 473. Hydro-benzamide, 398. Hydro-benzoin, 458. Hydro-benzoin acetic ether, 458. Hydrocarbons, aromatic, 323. Hydrocarbons, fatty, 34. Hydro-carbostyril, 417, 492. Hydrocinnamic acid, 408, 410, 417. Hydro-coerulignone, 441. Hydro-collidine-dicarboxylic ether, 482, 484. Hydrocumaric acid, 408, 410. Hydrocyanic acid, 252. Hydro-ferricyanic acid, 256. Hydro-ferrocyanic acid, 255. Hydro-mellitic acid, 431, 532 INDEX. Hydro-muconic acid, 236. Hydronaphthalene-tetracarboxylic ether, 461. Hydro-naphthoquinones, 467. Hydro-paracumaric acid, 408, 410. Hydro-phenazine, 360, 502. Hydroquinone, 389. Hydroquinone-dicarboxylic acid, 429. Hydroquinone-tetracarboxylic acid, 430. Hydrosulphides, 93. Hydroxamic acids, 187. Hyoscine, 490. Hyoscyamine, 490. Hypogseic acid, 164. Hypoxanthine, 284. Hypochlorous ether, 103. I Imesatin, 433. Imides, 111, 231. Imido-carbamic compounds, 274, 277. Imido-carbonic acid, 269. Tmido-carbonic compounds, 274. Imido-carbonic ether, 269. Imido-chlorides, 183. Imido-ethers, 184. Imido-thio-ethers, 184. Imines, 194, 300. Indamines, 356. Indene, 468. Indican, 431. Indicator, 371. Indigo, 399, 431. Indigo-brown, 431. Indigo-gelatine, 431. Indigo-purpurin, 432. Indigo-red, 431. Indigo-sulphonic acids, 432. Indigo-white, 432. Indin, 432. Indirubin, 432. Indole, 433, 436. Indonaphthene, 468. Indophenin, 301. Indophenols, 356. Indoxyl, 433, 435. Indoxyl-sulphuric acid, 435. Indoxylic acid, 435. Indoxylic ether, 435. Indulines, 503. Inosite, 289. Inulin, 294. lodo-benzene, 332, 363. lodo-propiolic acid, 169. lodo-propionic acids, 170, 172. Iodoform, 69. Iodoform reaction, the, 83. lodol, 300. Iridoline, 497. Isatic acid, 424. Isatin, 424, 433. Isatin chloride, 434, Isatoic acid, 434. Isatoxime, 434. Isethionic acid, 197. Iso-anthraflavic acid, 472. Isbbutyric acid, 160. . Isobutyl alcohol, 85. Iso-cinchomeronic acid, 488. Iso-citric acid, 247. Iso-crotonic acid, 166. Isocyanic ethers, 258. Isocyanides, 109, 405. Isocyanuric ethers, 269. Iso-cymenes, 331. Iso-cymidine, 359. Iso-dipyridyl, 490. Iso-durene, 323. Iso-ferulic acid, 513. Iso-hydrobenzoin, 458. Iso-melamine, 265. Isomerism, 12, 16, 41, 92, 208. Isomerism in the cyanogen group, 265. Isomerism of the benzene derivatives, 307, 318. Isomerism of position, 93, 317. Iso-nicotine, 490. Iso-nicotinic acid, 487. Iso-nitrile reaction, the, 114. Iso-nitriles, 109. Iso-nitroso-acetone, 143, Iso-nitroso-ketones, 143. Iso-nitroso-methyl-acetone, 221. Iso-nitroso-naphthols, 467. Iso-paraflSns, 43. Isophthalic acid, 429. Isoprene, 57, 608. Isopropyl alcohol, 84. tsopropyl-benzene, 323, 330. tsopropyl-benzoic acid, 417. Isopropyl chloride, 65. Isopropyl iodide, 65. Isopropyl-piperidine, 489. [so-propyl-pyridine, 486. [so-purpuric acid, 386. [so-saccharic acid, 219, 244. [so-succinic acid, 235. [so-tropine, 490. [so-xylene, 329. [suret, 187. [taconic acid, 236. J Japan camphor, 509. Juglone, 467. Juniper, oil of, 506. INT)EX. 533 K Keratrin, 518. Ketines, 491. Keto-compounds, 140. Keto-dihydro-pyridine, 486. Keto-propionic acid, 223. Keto-tetrahydro-cymene, 511. Ketone-acids, aromatic, 402. Ketone-acids, fatty, 222. Ketone-acids, decomposition of, 225. Ketone-aldehydes, 143, 222. Ketone-alcohols, 205, 221, 286, 400. Ketones, aromatic, 399. Ketones, fatty, 128, 138. Ketones, mixed, 139. Kino-tannic acid, 426. L. Lactames, 416. Lactic acids, 214 to 216. Lactic acids, derivatives of, 216. Lactic fermentation, 214. Lactide, 215, 216. Lactimes, 416. Lactones, 218. Lactose, 288. Lactyl chloride, 178, 216. Lactyl-urea, 273. Lsevo-conine, 489. Lsevo-tartaric acid, 242. Lsevulose, 286, 288. Lakes, 474. Laurie acid, 161. Laurone, 144. Lauth's violet, 356. Lead acetates, 158. Lead, sugar of, 158. Lead tetra-methide, 128. Leather, 517. Lecithin, 519. Legumin, 517. Lekene, 46. Lepargylic acid, 228. Lepidine, 497. Leucaniline, 450. Leucaurin, 454. Leucic acid, 217. Leucine, 217. Leuco-bases, 448. Leuco-compounds, 448. Leuco-malachite green, 354, 449. Leuco-rosolic acid, 454. Leuco-thionine, 356. Leuconic acid, 296. Levulinic acid, 227. Lichen acids, 425. Lichenin, 294. " Life force," 1. Liebermann reaction, the, 354, 380. Light blue, 453. Light green, 453. Lignoceric acid, 147. Ligroin, 44. Limonene, 508. Linking, double, 49, 403. Linking, triple, 55. Linoleic acid, 167. Litmus, 390, 514. Logwood, 514. Lupetidines, 489. Lutidines, 480, 481, 487. Lutidinic acid, 488. M m = meta, see Meta-compounds. Madder root, 474. Magdala red, 503. Malachite green, 449. Malamic acid, 239. Malamide, 239. Maleic acid, 236, 237. Malic acid, 238. Malonic acid, 233. Malonic aldehyde-acid, 409. Malonic ether, 233. Malonic ether synthesis, 234, 407. " Malonyl," 229. Malonyl-urea, 282. Maltose, 291. Mandelic acid, 402, 408, 428. Mannide, 204. Mannitan, 204. Mannite, 203. Mannitic acid, 219. Mannose, 204, 289. Margaric acid, 163. Marsh gas, 39. Martins' yellow, 466. Mauveine, 503. Meconic acid, 491. Meconine, 500. Meconinic acid, 430. Melamine, 265. Melene, 46, 52. Melilotic acid, see o-Cumaric acid. Melissic acid, 147, 163. Melissic alcohol, 86. Melitose, 292. Mellitene, 331. Mellitic acid, 322, 402, 431. Mellophanic acid, 430. Melting point, rules regulating, 28. Mendius' reaction, the, 113, 182. Menthol, 510. Mercaptals, 132. 534 INDEX. Mercaptan, 93 et seq. Mercurialin, 116. Mercuric cyanide, 254. Mercury diphenyl, 339. Mercury ethide, 127. Mercury-ethyl hydroxide, 128. Mercury, fulminate of, 108. Mercury methide, 127. Mercury-methyl chloride, 128. Mesaconic acid, 236. Mesidine, 343, 359. Mesityl oxide, 142, 144. Mesitylene, 142, 320, 330. Mesitylene, constitution of, 315. Mesitylene hexahydride, 330. Mesitylenic acid, 416. Meso-paraffins, 43. Mesorcin, 377, 390. Meso-tartaric acid, 242. Mesoxalic acid, 244. Metacyl chloride, 144. Meta-compounds, see individually. Metaldehyde, 136. Metallic cyanides, 254 et seq. Metamerism, 93, 319. Metanil yellow, 375. Metanilic acid, 375. Meta-styrene, 332. Methacrylic acid, 166. Methane, 39. Methane-di- and tri-carboxylic acids, 233, 245. Methane di- and tri-sulphonio acids, 106. Methane series, 34. Methyl-amido-phenol, 386. Methenyl-amido-thiophenol, 386. Methenyl-amidoxime, 187. Methionic acid, 196. Methoxy-pyridine, 486. Methoxy-quinoline. 496. Methyl-acetanilide, 341. Methyl-aceto-acetic ether, 226. Methyl-acridine, 498. Methyl alcohol, 78. Methyl aldehyde, 135. Methyl-alloxan, 282. Methyl-amine, 116. Methyl-amyl ether, 90. Methyl-aniline, 341, 353. Methyl-anthracenes, 472, 475. Methyl-anthraquinone, 475. Methyl-arsenic compounds, 122 et seq. Methyl-benzene, see Toluene. Methyl bromide, 64. Methyl-carbostyril, 493. Methyl-carbamine, 110. Methyl chloride, 64. Methyl-chloroform, 69. Methyl-conine, 489. Methyl-cumarin, 408. Methyl-cyanamide, 260. Methyl cyanide, 108. Methyl-diphenylamine, 347, 355. Methyl ether, 17, 92. Methyl-ethyl-acetic acid, 161. Methyl-ethyl-aceto-acetic ether, 226. Methyl-ethylamine, 114. Methyl-ethyl-benzenes, 323, 330. Methyl-ethyl-benzoic acids, 412. Methyl-ethyl-carbin-carbinol, 86. Methyl-ethyl-carbinol, 84. Methyl-ethyl ether, 89. Methyl-ethyl ketone, 138, 320. Methyl-ethyl sulphide, 95. Methyl-furfurane, 297, 300. Methyl green, 453. Methyl-hydantoin, 273. Methyl-hydroquinone, 513. Methyl hydrosulphide, 93 et seq. Methyl-imesatin, 434. Methyl-indole, 437. Methyl iodide, 64. Methyl-isatin, 434. Methyl-isatic acid, 484. Methyl isocyanide, 110. Methyl iso-thiacetanilide, 185. Methyl isothiocyanate, 263. Methyl-ketole, 436. Methyl-morphine, 499. Methyl-naphthalenes, 467. Methyl-naphthylamines, 465. Methyl nitrate, 99. Methyl nitrite, 100. Methyl-nonyl ketone, 144. Methyl orange, 371. Methyl-oxamic ether, 113. Methyl-oxy-quinoline, 493. Methyl-parabanic acid, 282. Methyl-phosphine, 121. Methyl-phenazine, 502. Methyl-piperidines, 489. Methyl-propyl-benzenes, 331. Methyl-pseudo-isatin, 434. Methyl-pyridines, 480, 486- Methyl-pyridone, 486. Methyl-pyrogallol, 377. Methyl-pyrrol, 297. Methyl-quinoline, 480, 492, 496. Methyl sulphide, 93 et seq. Methyl-sulphonic acid, 105. Methyl-sulphuric acid, 104. Methyl-thio-carbimide, 275. Methyl-thiophenes, 297, 299. Methyl-toluidines, 342, 359. Methyl-uracyl, 273. Methyl-urea, 272. Methyl-uric acid, 283. Methyl violets, 354, 452. Methylal, 136. "Methylene," 46, 60. INDEX. 535 Methylene bromide, 66. Methylene bhie, 356, 360. Methylene chloride, 66. Methylene glycol, 191. Methylene iodide, 66. Methylenitan, 286. Mint camphor, 510. Milk sugar, 291. Milton's reagent, 515. Molecular rearrangements, 166, 309. Molecular refraction equivalent, 30. Molecular weight, determination of, 8. Molecular volume, 25. Mono-compounds, see individually. Monocliloro-acetone, 144. Monochloro -aldehyde, 137. Mono-ethylin, 200. Monoformin, 154, 202. Mordants, 475. Morintannic acid, 426. Morphine, 499. Moss starch, 294. Mucic acid, 243, 244. Mucilage, 295, 518. Mucin, 518. Murexide, 283. Muscle albumen, 517. Mustard oils, 262. Mustard oil reaction, the, 114. Myosin, 517. Myricyl alcohol, 72, 86. Myristic acid, 161. Myristone, 144. Myronic acid, 513. Myrosin, 513. N Naphtha, see Petroleum ether. Naphthalene, 428, 460. Naphthalene, constitution of, 463. Naphthalene-dicarboxylic acids, 468. Naphthalene dichloride, 462. Naphthalene hydrides, 462. Naphthalene-sulphonic acids, 465. Naphthalene tetrachloride, 462. Naphthalene yellow, 466. Naphthalic acid, 468. Naphthazarin, 467. Naphthazine, 502. Naphthenes, 45, 53, 327. Naphthidine, 465. Naphthionic acid, 465. Naphtho-acridine, 498. Naphtho-anthracene, 477. Naphthoic acids, 468. Naphthol-acetyl ethers, 466. Naphthol dyes, 466. Naphthol-sulphonic acids, 466. Naphthol yellow, 466. Naphthols, 356, 401, 466. Naphtho-quinolines, 492, 497. Naphtho-quinones, 467. Naphthylamines, 464, 465. Naphthylamine-sulphonic acids, 465. Naphthylene- diamines, 465. Narceine, 499. Narcotine, 499. Neo-paraffins, 43. Nerve substance, 519. Neurine, 196. Neutralization, heat of, 29. Neutral red, 502. Nicotidine, 490. Nicotine, 490. Nicotinic acid, 487. Nigrosines, 503. Nitracetanilides, 349, 352. Nitranilines, 318, 338, 341, 352. Nitranilic acid, 394. Nitric acid, constitution, 102. Nitric ether, 99. Nitriles, aromatic, 405. Nitriles, fatty, 107. Nitriles, fatty, constitution of, 110. Nitro-acetic acid, 172. Nitro-aceto-nitrile, 108. Nitro-alizarin, 475. Nitro-amido-phenols, 386. Nitro-benzaldehydes, 358, 399. Nitro-benzene, 305, 338. Nitro-benzene-sulphonic acids, 375. Nitro-benzoic acids, 402, 414. Nitro-benzoyl-formic acid, 424. Nitro -bitter-almond-oil green, 449. Nitro-bromo-benzoic acids, 418. Nitro-camphor, 510. Nitro-chloro-benzene, 339. Nitro-cinnamic acids, 418. Nitro-cinnamic dibromide, 417. Nitro-cumene, 339. Nitro-derivatives, aromatic, 336, 337. Nitro-derivatives, fatty, 99, 100. Nitro-diamido-triphenyl-methane, 449. Nitro-dibromo-benzenes, 314. Nitro-dibromo-ethane, 102. Nitro-dimethyl-aniline, 354. Nitro-diphenyl, 438. Nitro-erythrite, 203. Nitro-ethane, 100. Nitro-glycerine, 201. Nitro-isatin, 433. Nitro-malachite green, 449. Nitro-mesitylene, 337, 839. Nitro-methane, 100 et seq. Nitro-naphthalenes, 461, 464. Nitro-oxybenzoic acids, 308. Nitro-phenols, 318, 338, 382, 385. Nitro-phenols, salts of, 386 ► ' 536 INDEX. Nitro-phenyl-acetylene, 332, 419, 459. Nitro-phenyl-lacto-methyl ketone, 432. Nitro-phenyl-propiolic acid, 419. Nitro-phthalic acids, 429. Nitro-propionic acid, 172. Nitro-pseudo-cumeiie, 339. Nitro-quinolines, 496. Nitro-thiophene, 301. Nitro-toluenes, 316, 337, 338. Nitro-toluidines, 359. Nitro-xylenes, 314, 337, 339. Nitrogen bases of the alcoholic radicles, 110. Nitrolic acids, 102. Nitrosamines, 115, 347. Nitroso-aniline, 353. Nitroso-benzene, 339, 368. Nitroso-compounds, see also Isonitroso- compounds. Nitroso-dimethyl-aniline, 341, 350, 354, 384. Nitroso-diphenylamine, 341, 355. Nitroso-indole, 436. Nitroso-indoxyl, 435. Nitroso-methyl-aniline, 347, 354. Nitroso-phenol, 384, 393. Nitroso -reaction, the, 354. Nitrous ether, 100. Nomenclature of the alcohols, 77. Nomenclature of the hydrocarbons, 42. Nonanes, 44. Nonylene, 46. Nonylic acid, 163. Nuclein, 519. O o=ortho, see Ortho -compounds. Oak -tannic acid, 426. Octanes, 44. Octo-nitrile, 82. Octyl alcohols, 86. Octyl-amine, 182. Octyl-benzene, 323. Octylenes, 46. Octylic acid, see Caprylic acid. CEnanthol, 137. Oil of the Dutch chemists, 48. " Oil-forming gas," 50. Oils, fatty, 162. Oleic acid, 166. Olefines, 46. Olein, 162, 202. Olibene, 505. Opianic acid, 430. Opium alkaloids, 499. Optically active compounds, their pre- paration by means of ferments, 31. Orange II. and III., S)0, 371. Orange, oil of, 504. Orange peel, oil of, 508. Orcein, 390. Orchil, 390. Orcin, 377, 390. Orcinol, 390. Organo-metallic compounds, 126. Orsellinic acid, 390, 425. Ortho-acetic acid, derivatives of, 225. Ortho-acetic ether, 199. Ortho-acids, derivatives of, 175. Ortho-compounds, 309, 315. Ortho-formic ether, 149. Ortho-leucaniline, 449. Osazones, 287, 373. Oxal-ethyline, 221. Oxalic acid, 154, 231. Oxalic ether, 112, 232. Oxaluric acid, 279, 281. " Oxalyl," 229. Oxalyl-urea, 281. Oxamethane, 233. Oxamic acid, 233. Oxamide, 232. Oxanthranol, 472, 473. Oximes, 142. Oximide, 233. Oxindole, 434. Oxy-acetic acid, 206, 210. Oxy-acids, aromatic, 403. Oxy-acids, fatty, 206. Oxy-alcohols, aromatic, 400. Oxy-aldehydes, aromatic, 400, 407. Oxy-alkyl bases, 196. Oxy-anthracenes, 472. Oxy-anthraquinones, 472, 474. Oxy-azo-benzene, 368, 371. Oxy-azo-compounds, 368 et seq. Oxy-benzaldehydes, 400, 401. Oxy-benzoic acids, 307, 309, 380, 402, 420. Oxy-benzyl alcohols, 400, 401. Oxy-butyric aldehyde, 134, 220 Oxy-butyric acid, 206, 217. Oxy-caproic acids, 206, 217 Oxy-cinnamic acids, 427. Oxy-citric acid, 247. Oxy-diphenylamines, 387. " Oxy-ethyl," 194. Oxy-ethyl-methyl-tetrahydro-pyridine, 490. Oxy-ethyl-sulphonic acid, 197. Oxy-ethylamine bases, 187, 193 et seq. Oxy-fatty acids, 206. Oxy-haemoglobin, 518. Oxy-hydroquinone, 377, 392. Oxy-isobutyric acid, 206, 217. Oxy-lepidine, 493. Oxy-malonic acid, 238. Oxy-methyl-benzoic acid, 423. Oxy-naphthoquinones, 467. INDEX. 537 Oxy-nicotinic acid, 491. Oxy-phenyl-acetic acid, 408, 422. Oxy-phthalic acids, 314, 429. Oxy-pyridines, 480, 486. Oxy-quinolines, 480, 496. Oxy-stearic acid, 218. Oxy-stearic acid, sulphuric ether of, 218. Oxy-succinic acid, 238. Oxy-tetrahydro-cymene, 511. Oxy-thio-naphthene, 437. Oxy-toluic acids, 410. Oxy-tropine, 490. Oxy-valeric acids, 206, 217. Ozokerite, 46. P 2)=para, see Para-compounds. Palmitic acid, 162, 163. Palmitic ethers, 175. Palmitin, 162, 202. Palmitolic acid, 168. Palmitone, 144. Palmito-nitrile, 108. Palmityl chloride, 177. Papaverine, 499. Para-anthracene, 471. Para-aldehyde, 136. Para-compounds, see individually. Para-cumaric acid, 427. Para-fuchsine, 450. Para-lactic acid, 216. Para-leucaniline, 450. Para-rosaniline, 450. Para-xylic acid, 416. Parafl&n, 45. Paraffins, 35. Parabanic acid, 279, 281. Parchment paper, 293. Parvoline, 481. Pelargonic acid, 163. Penta-chlor-aniline, 352. Penta-chloro-benzene, 332. Penta-decane, 34. Penta-decylic acid, 147. Penta-methyl-amid o-benzene, 359 . Penta-methyl-benzene, 323. Penta-methyl-phenol, 377, 388. Penta-methylene derivatives, 295, 296. Penta-methylene-diamine, 195, 482, 516. Pen ta-m ethyl ene-imine, 482. Penta-triacontane, 34. Pentanes, 44, 485. Pen-thiophene, 301. Pepsin, 294, 516. Peptones, 516. Perbromo-acetone, 144, 822. Per-acid salts, 157. Perchloric ether, 103. Perchloro-ethane, 69. Perchloro-cther, 92. Perchloro-ethylene, 60, 70. Perkin reaction, the, 408. Persulphocyanic acid, 261. Peru balsam, 397, 413. Petroleum, 45, 53, 320. Petroleum ether, 44. Peppermint, oil of, 510. Phaseo-mannite, 289. Phellandrene, 506, 509. Phenacyl bromide, 400. Phenanthrene, 475, 476. Phenanthrene-hydroquinone, 476. Phenanthrene-quinone, 477. Phenanthrol, 476. Phenazine, 501. Phenetol, 382. Phenol, 305, 307, 362, 374, 381. Phenol blue, 356. Phenol-calcium, 381. Phenol carbonate, 383. Phenol-carbonic acid, salts of, 383, 421. Phenol-disulphonic acid, 387. Phenol, ethers of, 382. Phenol methyl ether, see Anisol. Phenol-phthalein, 456. Phenol-phthaline, 456. Phenol-potassium, 381. Phenol-sulphonic acids, 309, 382, 387. Phenol-sulphuric acid, 382. Phenol-trisulphonic acid, 387. Phenolic acids, 402. Phenols, 376, 388, 391, 392. Pheno-safranine, 503. Phenose, 392. "Phenyl," 327. Phenyl-acetaldehyde, 399. Phenyl-acetic acid, 403, 415. Phenyl-acetylene, 332. Phenyl-acridine, 498. Phenyl-acrylic acid, 403. Phenyl-alanine, 417. Phenyl alcohol, 381. Phenyl-amido-acetic acid, 416. Phenyl-amido-crotonic ether, 493. Phenyl-amido-propionic acids, 417. Phenyl-amine, 340, 350. Phenyl-anthracene, 472. Phenyl-anthranol, 472, 473. Phenyl-bromo-acetic acid, 445. Phenyl-butylene dibromide, 415, 460. Phenyl-butyric acids, 412. Phenyl-carbinol, 396. Phenyl-chloracetic acid, 416. Phenyl-cinnamic acid, 458. Phenyl cyanate, 341, 358. Phenyl cyanide, see Benzonitrile. Phenyl-dibromo-propionic acid, 418. Phenyl disulphide, 384. 538 INDEX. Phenyl-ditolyl-methane, 446. Phenyl ether, 382. Phenyl-ethyl alcohols, 396. Phenyl-ethyl-amine, 341. Phenyl-ethyl-hydrazine, 372. Phenyl-ethyl-sulphone, 375. Phenyl-glucosazone, 288. Phenyl-glycerine, 396. Phenyl-glyoxylic acid, 424. Phenyl-guanidines, 358. Phenyl-hydrazine, 372. Phenyl-hydrazine-potassium sulphite, 372. Phenyl-hydrazine-sulphonic acid, 373. Phenyl hydrosulphide, 382. Phenyl-imido-butyric acid, 358. Phenyl-isocrotonic acid, 418. Phenyl isothiocyanate, 341, 358. Phenyl-lactic acid, 424. Phenyl-methyl-carbinol, 397. Phenyl-methyl ketone, 399. Phenyl-methyl-pyrazolone, 302. Phenyl-methyl-pyrrol, 400. Phenyl-naphthalene, 468. Phenyl-naphthylamines, 465. Phenyl-oxanthranol, 472. Phenyl-oxypropionic acids, 424. Phenyl-propiohc acid, 332, 403, 419. Phenyl-propionic acids, 408, 417. Phenyl-propyl alcohol, 396. Phenyl-pyridines, 480, 487. Phenyl-quinolines, 480, 497. Phenyl salicylate, 421. Phenyl-salicylic acid, 421. Phenyl sulphide, 374, 384. Phenyl sulphone, 384. Phenyl-sulphuric acid, 383. Phenyl-thio-ureas, 341, 358. Phenyl-tolyl-amine, 359. Phenyl-tolyl-carbinols, 442. Phenyl-tolyl ketones, 445. Phenyl-tolyl-methanes, 445. Phenyl-tolyls, 438. Phenylene blue, 356. Phenylene brown, 371. Phenylene diamines, 305, 341, 349, 359. Phenylene-ethenyl-amidine, 349. Phloretic acid, 513. Phloretin, 391, 513. Phloridzin, 513. Phloroglucin, 321, 377, 391. Phloroglucin tricarboxylic ether, 321. Phloroglucin trimethyl ether, 391. Phoroglucin-trioxime, 391. Phloxin, 456. Phorone, 142, 144. Phosgene, 268. Phosphin, 499. Phosphines, 119, 121. Phosphlnic acids, 120, 121. Phosphoric ethers, 120, 121. Photographic developer, 391. Phthaleins, 455. Phthalic acids, 305, 314, 405, 428, 429. Phthalic anhydride, 429. Phthalide, 424. Phthalideins, 472, 473. Phthalidines, 472, 473. Phthalines, 455. Phthalo-nitriles, 375. Phthalo-phenone, 455. Phthalyl alcohol, 396. Phthalyl chloride, 429. Physical properties of organic compounds, 24, 217, 237. Physical isomerism, 217. Picolines 480, 482, 485. Picolinic acid, 487. Picramide, 353. Picric acid, 382, 385. Picrotoxin, 514. Picryl chloride, 339, 385. Pimaric acid, 512. Pimelic acid, 228. Pinacoline, 144. Pinacone, 190, 191. Pinene, 506. Pinene hydrochloride, 507. Pipecolein, 488. Pipecolines, 489. Piperic acid, 427. Piperideins, 488. Piperidine, 480, 488. Piperidine, constitution of, 483. Piperine, 488. Piperonylic acid, 425. Piperylene, 57, 489. Pirylene, 58. Pittacall, 454. Pivalic acid, 161. Plaister, 163. Poly-ethylene glycols, 193. Poly-terpenes, 506. Polymerism, 13. " Ponceaux " (dyes), 372. Populin, 513. Position, determination of, in aromatic bi-derivatives, 315. Position-isomerism, 93, 317. Potassium carboxide, 322, 392. Potassium cyanate, 258. Potassium cyanide, 254. Potassium-diazo-ethane sulphonate, 118. Potassium ethide, 126. Potassium-ethyl-hydrazine sulphite, 118. Potassium ferricyanide, 255. Potassium ferrocyanide, 255. Potassium methide, 126. Prehnldine, 859. Prehnitene, 323. INDEX. 539 Prehnitic acid, 430. Primary, secondary and tertiary com- pounds, 62, 73, 209. Prism formula, 317. Propane, 41. Propane-tricarboxylic acid, 245. Propane-trisulphonic acid, 106. Propargylic acid, 167. Propargylic alcohol, 88. Propiolic acid, 167. Propione, 144. Propionic acid, 159. Propio-nitrile, 108. Propionyl-carboxylic acid, 224. Propionyl chloride, 177. Propyl-alcohols, 83. Propyl aldehyde-phenyl-hydrazine, 436. Propyl-amine, 113, 114. Propyl-benzenes, 318, 323, 330. Propyl-benzoic acids, 410, 417. Propyl bromides, 65. Propyl chlorides, 65. Propyl iodides, 65, 66. Propyl-phenols, 388. Propyl-pseudo-nitrol, 102. Propyl-piperidines, 489. Propyl-pyridines, 486. Propylene, 51, 61. Propylene bromides, 68. Propylene chlorides, 68. Propylene glycols, 191. Protein substances, 516. Protocatechuic acid, 410, 425. Protocatechuic aldehyde, 400, 401. Prussian blue, 256. Prussic acid, 252. Pseudo-butylene, 51. Pseudo-cumene, 323, 330. Pseudo-cumidine, 341, 359. Pseudo-forms, 265, 391. Pseudo-indoxyl, 435. Pseudo-leucaniline, 449. Pseudo-nitrols, 102. Pseudo-tropine, 490. Ptomaines, 516. Purpuric acid, 283. Purpurin, 472, 475. Purpuro-xanthine, 472. Pyrazine, 491. Pyrazols, 302. Pyrene, 477. Pyridine, 478, 485. Pyridine-carboxylic acids, 480, 487. Pyridine-methyl iodide, 485. Pyridine-sulphonic acids, 480, 486. Pyridone, 486. Pyrocatechin, 322, 377, 388. Pyro-cinchonic acid, 236. Pyro-meconic acid, 491. Pyro-mellitic acid, 430. Pyro-mucic acid, 298, 300. Pyro-racemic acid, 223. Pyro-racemic aldehyde, 222. Pyro-tartaric acids, 235. Pyro-terebic acid, 166. Pyrocoll, 301. Pyrogallol, 305, 377, 391. Pyrogallol-carboxylic acid, 426. Pyrogallol dimethyl ether, 391. Pyroxyline, 293. Pyrrol, 297, 300. Pyrrol-carboxylic acids, 297, 301. Pyrrol group, 297. Pyrrol-potassium, 300, 482. Pyrrolidine, 300. Pyrroline, 300. Pyrrolylene, 57. Q Quercite, 392. Quercitrin, 513. Quick vinegar process, 156. Quinaldine, 480, 492, 496. Quinaldine-carboxylic acids, 480. Quinazine, 498. Quinazole compounds, 498. Quinhydrone, 390, 393. Quinic acid, 389, 411, 426. Quinine, 500. Quinine alkaloids, 500. Quininic acid, 497. Quinizarin, 472, 474. Quinoline, 351, 478, 495. Quinoline-benzo-carboxylic acids, 497. Quinoline-carboxylic acids, 480, 497. Quinoline group, 491. Quinoline-sulphonic acids, 480, 496. Quinoline yellow, 496. Quinolinic acid, 488. Quinone, 350, 351, 384, 392. Quinone-carboxylic acid, 425. Quinone chlorimide, 357, 386, 395. Quinone dichlorimide, 395. Quinone-dioxime, 394. Quinone-oxime, 393. Quinone phenol-imide, 357. Quinone tetrahydride, 394, 430. Quinone-tetrahydro-carboxylic acid, 425, 430. Quinoxaline, 350, 498. R Racemates, 242. Racemic acid, 242. Radicles, 14, 22. Radicles, mixed, 88. 540 INDEX. Raffinose, 292. Rapinic acid, 218. Rational formulae, 19. Red prussiate of potash, 255. "Reduced" ring, 317. Refraction equivalent, 30. Resin acids, 512. Resin soaps, 511. Resinification," 511. Resins, 511. Resorcin, 377, 389. Resorcin-phthalein, 389, 456. Retene, 477. , Rhigolene, 44. Rhodanic acid, 261. Rhodizonic acid, 395. Ricinoleic acid, 167, 218. " Ricinoleic-sulphuric " acid, 475. Ring linking, 52, 198, 295, 311. Rocellic acid, 228. Roman oil of cumin, 504. Rosaniline, 450. Rosaniline blue, 453. Rose de Bengale, 456. Rosolic acid, 454. Rubean hydride, 252. Ruberythric acid, 474, 513. Rufigallic acid, 472. Rufiopin, 472. Rufol, 472. S s=symmetrical, 318. Saccharic acid, 204, 243, 244, 291. Saccharimetry, 291. Saccharine, 219. "Saccharine " (from coal tar), 415. Saccharose, 291. Safranines, 351, 503. Sage, oil of, 506. Salicin, 513. Salicylic acid, 305, 411, 420. Salicylic aldehyde, 400, 401. Salicylic methyl ether, 78, 421. Saligenin, 400, 401. Salol, 421. Santonin, 514. Saponification, 95, 98. Saponin, 513. Sarcine, 284. Sarco-lactic acid, 216. Sarcosine, 213. Saturated hydrocarbons, 34. Scarlet, Biebrich, 372. Sebacic acid, 228. Secondary alcohols, 73 et seq. Secondary compounds, 62, 73, 209. Secondary ring, 317, 391. Seignette salt, 241. Selenium compounds, 97. Serine, 219. Serum albumen, 516. Shellac, 512. Side chain isomerism, 318. " Side chains," 318, 325. Silicium tetramethyl, 126. Silver cyanide, 254. Silver fulminate, 109. Sinapine, 501. Sincaline, 196. Skatole, 436. Skraup synthesis, the, 492. Soaps, 163. Sodio-aceto-acetic ether, 226. Sodio-malonic ether, 233, 321. Sodium acetanilide, 357. Sodium ethide, 126. Sodium ethylate, 83. Sodium methide, 126. Sodium nitro-prusside, 256. Solanine bases, 501. Sorbic acid, 168. Sorbin, 289. Sorbite, 204. Sparteine, 501. Specific gravity, 23. Specific rotatory power, 32. Spermaceti, 86, 162. Sprit blue, 453. Starch, 293. Stearic acid, 162, 163. Stearin, 162, 202. Stearin candles, 162. Stearolic acid, 168. Stearone, 144. Stearoptenes, 504. Stilbene, 457. Stilbene dibromide, 457. Stilbene-dicarboxylic acid, 458. Storax, 331, 397. Structural formulae, see Constitution. Strychnine, 500. Stycerine, 396. Styphnic acid, 389. Styracin, 397. Styrene, 331. Styrone, 397. Suberic acid, 228. " Substantive dyes," 440. Substitution, laws governing, 317. Substitution, backward, 37. Succinamic acid, 235. Succinamide, 235. Succinic acid, 234. Succinic anhydride, 235. Succinic ether, 321. Succinimide, 235. Succino-succinic acid, 430. INDEX. 541 Succino-succinic ether, 321, 430. " Succinyl," 229. Succinyl chloride, 235. Sugars, the, 221. Sugars, synthesis of, 285. Sulphanilic acid, 305, 375. Sulphides, 93. Sulphine bases, 96, 97. Sulphinic acids, aromatic, 374. Sulphinic acids, fatty, 105. Sulpho-acetic acid, 172. Sulpho-benzide, 374. Sulpho-benzoic acids, 402, 415. Sulpho-benzoic imide, 415. Sulphonic acids, aromatic, 325, 373. Sulphonic acids, fatty, 105. Sulphones, 96. Sulphur, valency of, 96. Sulphuric acid, constitution of, 106. Sulphuric ethers, 103, 104. Sulphurous ethers, 104. Sylvane, 300. Sylvestrene, 506, 508. Sylvestrene dihydrochloride, 608. Syntonin, 517. T Tallow, 162. Tannic acids, 426. Tannin, 411, 426. Tanning, 426. Tar, 319. Tartar, 241. Tartar emetic, 241. Tartaric acid, 240. Tartrazine, 245. Tartronic acid, 238. Taurine, 197. Taurocholic acid, 519. Tautomerism, 266. Tellurium compounds, 97. Teraconic acid, 236. Teracrylic acid, 166. Terebic acid, 240. Terephthalic acid, 429. Terephthalic aldehyde, 399. Terpene hydrochlorides, see Pinene. Terpenes, 504. Terpenylic acid, 507. Terpin hydrate, 508. Terpinene, 508. Terpineol, 508. Tertiary alcohols, 73 et seq. Tertiary compounds, 62, 73, 209. Tertiary hydrogen atoms, 423. Tertiary ring, 317. Tetra-acetylene-dicarboxylic acid, 238. Tetra-amido-benzene, 349. Tetra-bromo-ethane, 469. Tetra-bromo-di-iodo-eosin, 456. Tetra-bromo-dinitro-benzene, 337. Tetra-bromo-fluoresccin, 456. Tetra-bromo-methane, 69. Tetra-bromo-quinone, 394. Tetra-chloro-aniHne, 352. Tetra-chloro-benzenes, 332. Tetra-chloro-indigo, 432. Tetra-chloro-methane, 69, 407. Tetra-chloro-quinone, 394. Tetra-decane, 34. Tetra-ethyl-tetrazone, 118. Tetra-hydro-naphthylamincs, 464, 465. Tetra-hydro-phthalic acids, 312, 429. Tetra-hydro-pyridine, 488, 490. Tetra-hydro-quinoline, 480, 496. Tetra-iodo-pyrrol, 300. Tetra-methyl-amido-benzenes, 359. Tetra-methyl-ammonium compounds, 117. Tetra-methyl-arsenic compounds, 122. Tetra-methyl-benzenes, 323. Tetra-methyl-diamido-benzophenone, 354, 444, 445. Tetra-methyl-diamido-diphenylamine, 341, 356. Tetra-methyl-diamido-triphenyl-carbinol, 449. Tetra-methyl-diamido-triphenyl-methane 449. Tetra-methyl-methane, 44. Tetra-methyl-quinoline, 497. Tetra-methyl-rosaniline, 453. Tetra-methylene, 52. Tetra-methylene-diamine, 195. Tetra-methylene-imine, 300. Tetra-nitro -methane, 103. Tetra-nitro-naphthalene, 464. Tetra-oxy-anthraquinone, 472. Tetra-oxy -benzene, 392. Tetra-oxy-benzoic acids, 426. Tetra-oxy-quinone, 395. Tetra-phenyl-ethane, 459. Tetra-phenyl-ethylene, 459. Tetrazo-diphenyl chloride, 440. Tetrazones, 118, 373. Tetr,olic acid, 168. Thebame, 499. Theine, 284. Theobromine, 284. Theobromic acid, 162. Thiacetamide, 184. Thiacet-anilide, 184, 357. Thiacetic acid, 179. Thiacetic ether, 180. Thiacetone, 142. Thiamides, 184. Thiazols, 302. Thiazoline, 302. 542 INDEX. Thio-acids, 179. Thio-alcohols, 93, 95. Thio-aldehydes, 134. Thio-anhydrides, 179. Thio-aniline, 351. Thio-carbamic compounds, 274 et seq. Thio-carbamide, 261, 276. Thio-carbanilide, 358. Thio-carbonic compounds, 93. Thio-carbonyl chloride, 275. Thio-compounds, 93. Thio-cyanates, 261, 262. Thio- cyanic acid, 261. Thio-cyanic ether, 262. Thio-cyanuric acid, 263. Thio-diglycollic chloride, 193. Thio-diphenylaraine, 355. Thio-diphenylamine dyes, 350, 356. Thio-ethers, 93, 96. Thio-gly collie acid, 211. Thio-hydantoin, 277. Thio-ketones, 142. Thio-naphthene, 437. Thio-phenols, 382, 383. Thio-phosgene, 275. Thio-urea, 276. Thionine, 356, 360. Thiophene, 297 , 301. Thiophene-carboxylic acids, 297, 299. Thiophene group, 301. Thiophthene, 468. Thyme, oil of, 388, 504. Thymene, 505. Thymol, 377, 388. Thymo-hydroquinone, 890. Thymo-quinone, 394. Tiglic acid, 166. Tin, alkyl compounds of, 128, Tolane, 458. Tolidine, 441. Tolu, balsam of, 397, 412. Tolu-hydroquinone, 390. Tolu-quinoline, 495. Tolu-quinone, 394. Tolu-safranine, 503. Toluene, 305, 323, 328. Toluene, formation of, 324. Toluene hydrides, 329. Toluene-sulphonic acids, 376. Toluic acids, 405, 410, 415. Toluic aldehydes, 399. Toluidines, 341, 358. Toluylene blue, 502. Toluylene-diamines, 341, 360. Toluylene red, 360, 502. Tolyl alcohols, 396. Tolyl-aniline, 498. Tolylene glycol, 396. Transformations, molecular, 166, 309, 330, 365, Tri-acetamide, 180. Tri-acetyl-benzene, 321. Tri-acetin, 198, 202. Tri-amido-azobenzene, 371. Tri-amido-benzenes, 341. Tri-amido-diphenyl-tolyl-carbinol, 450. Tri-amido-diphenyl-tolyl-methane, 450. Tri-amido-phenol, 386. Tri-amido-triphenyl-carbinol, 450. Tri-amido-triphenyl-methane, 450. Tri-amines, aromatic, 349. Tri-azo-compounds, 370. Tri-benzoyl-methane, 459. Tri-bromo-benzene, 314, 335. Tri-bromo-phenol, 384. Tricarballylic acid, 245. Tri-chloro-acetal, 137. Tri-chloro-acetamide, 183. Tri-chloro-acetic acid, 172. Tri-chloro-acetic ether, 175. Tri-chloro-aceto-acrylic acid, 322. Tri-chloro-aldehyde, 137. Tri-chloro-aniline, 351, 352. Tri-chloro-benzenes, 332, 335. Tri-chloro-phenomalic acid, 322. Tri-chlorhydrin, 69, 70. • Tri-cyanogen, 256, 257. Tri-decane, 34. Tri-ethyl-alkine, 196. Tri-ethylamine, 117. Tri-ethyl-benzene, 320, 323. Tri-ethyl-phosphine, 121. Tri-ethyl-phosphine oxide, 121. Tri-ethylin, 200. Tri-glycoUamic acid, 212. Tri-keto-hexamethylene, 391. Tri-mellitic acid, 430. Trimesic acid, 222, 430. Trimesic ether, 321. Tri-methylamine, 116. Tri-methyl-arsine, 122, 124. Tri-methyl-arsine dichloride, 122. Tri-methyl-arsine oxide, 122. Tri-methyl-benzenes, 305, 323, 330. Tri-methyl-benzoic acids, 412. Tri-methyl-methane, 41. Tri-methyl-oxy ethyl-ammonium hy drox - ide, 196. Tri-methyl-phenyl-ammonium com- pounds, 348, 354. Tri-methyl-phosphine, 121. Tri-methyl-pyridines, 480. Tri-methyl-quinolines, 480. Tri-methylene, 52. Tri-methylene bromide, 68. Tri-methylene-carboxylic acids, 295. Tri-methylene compounds, 295. Tri-methylene diamine, 195. Tri-nitraniline, 353. Tri-nitro-benzene, 337. INDEX. 643 Tri-nltro-chloro benzenes, 832, 335. Tri-nitro-naphthalene, 464. Tri-nitro-phenol, see Picric acid. Tri-nitro-triphenyl-carbinol, 447. Tri-nitro-triphenyl-methane, 447. "Trioses," 290. Tri-oxy-anthraquinone, 472. Tri-oxy-benzenes, 377. Tri-oxy-benzoic acids, 425. Tri-oxy-cinnamic acids, 428. Tri-oxy-methylene, 135. Tri-oxy-pyridine, 483, 486. Tri-oxy-triphenyl-methane, 454. Tri -phenyl-amine, 341, 355. Tri-phenyl-benzene, 438, 441. Tri-phenyl-carbinol, 447, Tri-phenyl-carbinol-o-carboxylic acid, 455. Tri-phenyl-guanidine, 358. Tri-phenyl-methane, 446, 447. Tri-phenyl-methane bromide, 447. Tri-phenyl-methane-o-carboxylic acid, 455. Tri-phenyl-rosaniline, 453. Tri-phenyl-rosaniline-sulphonic acid, 453. Triple bond, 55. Tri-quinoyl, 395. Tri-thio-carbonic acid, 275. Tropaolines, 370, 371. Tropeines, 490. Tropic acid, 411, 424. Tropidine, 489. Tropilidene, 58, 490. Tropine, 490. Trypsin, 254, 516. Turkey red, 475. Turmeric, 514. Turnbull's blue, 256. Turpentine, 504, 506. Turpentine, oil of, 504, 506. Types, theory of, 13, 14. ''Typical" hydrogen, 73, 153. Tyrosine, 411, 422. U Umbellic acid, 427. Umbelliferone, 427. Undecane, 34. Undecolic acid, 168. Undecylenic acid, 166. Undecylic acid, 163. Urea, 1, 270. Urea, salts, etc., of, 272. Urea, alkyl derivatives of, 272. Ureide-acids, 279. Ureides, 272, 273, 279. Urethane, 270. Uric acid, 281, 283. Uric acid group, 279. Urine-indican, 435. V 1? = vicinal, 313. Valency, theory of, 13. Valency of sulphur, 96. Valeric acids, 160, 161. Valero-nitrile, 108. Valerylene, 53, 57. Vanillic acid, 411, 425. Vanillic alcohol, 400, 401. Vanillin, 400, 401. Vapour density, determination of, 11. Vaseline, 46. Vegetable albumen, 516. Vegetable fibrin, 516. Vegetable substances of unknown con- stitution, 513. Veratrine, 501. Veratrol, 389. Vesuvin, 369. Victoria green, 449. Victoria orange, 388. Vinasse, 79. Vinyl-amine, 117. Vinyl bromide, 60. Vinyl chloride, 60. Vinyl compounds, 70, 87, 92. Vinyl sulphide, 97. Violaniline, 351, 503. Vitellin, 517. Vulcanite, 509. Vulpic acid, 459. W Water blue, 453. "Wax varieties, 162. Williamson's blue, 256. Wine, 81. Wine, spirits of, 80. Wintergreen, oil of, 78, 420. Wood spirit, 78. X Xanthamide, 276. Xanthic acid, 276. Xanthine, 281, 284. Xantho-protein reaction, 515. Xantho-purpurin, 472, 544 INDEX. Xylene-carboxylic acids, 416. Xylene hydrides, 329. Xylene -sulphonic acids, 376. Xylenes, 305, 314, 318, 323, 329. Xylenols, 377, 388. Xylic acids, 410, 416. Xylidines, 341, 359. Xylo-quinone, 394. Xylorcin, 377, 390. Xylyl chlorides, 332. Xylylene bromides, 832, 460. Xylylene-diamines, 360. Y Yeast, 80, 294. Yellow prussiate of potash, 255. Z Zinc ethide, 127. Zinc methide, 127. Zinc-methyl iodide, 127.