II I INOI', STATE GEOLOGICAL SURVEY 
 
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 STATE OF ILLINOIS 
 
 ADLAI E. STEVENSON, Gtmtur 
 
 DEPARTMENT OF REGISTRATION AND EDUCATION 
 
 NOBLE J. PUFFER, Uinctor 
 
 DIVISION OF THE. 
 
 STATE GEOLOGICAL SURVEY 
 
 M. M. LEIGHTON, CUtf 
 
 CIRCULAR NO. 167 
 
 AROMATIC FLUORINE COMPOUNDS 
 
 1,2,4,5-TETRAFLUOROBENZENE AND RELATED COMPOUNDS 
 III. THE FLUOROMESITYLENES AND DERIVATIVES 
 IV. 1,2,3, 5-TETRAFLUOROBENZENE 
 V. 1,3,5-TRIFLUOROBENZENE 
 
 G. C. FINGER AND F. H. REED, ET AL. 
 
 lican Chemical Society, 
 73, 145-155, 1951 
 
 PRINTED BY THE AUTHORITY OF Till STATE OF ILLINOIS 
 
 URBAN A, ILLINOIS 
 
 ILLINOIS GEOLOGICAL 
 SURVEY LIBRARY 
 
 APR 6 .1951 
 
[Contribution from the Geochemical Section of the Illinois State Geological Survey] 
 
 Aromatic Fluorine Compounds. II. 1,2,4,5-Tetrafluorobenzene and Related 
 Compounds 12 
 
 By G. C. Finger, F. H. Reed, D. M. Burness, D. M. Fort and R. R. Blough 
 
 The synthesis of a complete series of fluorinated 
 benzenes would reveal the effect of progressive 
 fluorine substitution upon the physical and chemi- 
 cal properties of benzene and benzenoid structures. 
 A tetra- and pentafluorobenzene are needed to 
 complete such a series. In addition, a study of the 
 effect on properties of other substituents in the 
 polyfluorobenzenes would lead to generalizations 
 of theoretical and practical value. 
 
 1,2,4,5-Tetrafluorobenzene has been synthesized 
 and the properties of its intermediates were studied 
 in detail. For comparative purposes, a number of 
 chlorofluorobenzenes possessing the 1,2,4,5-struc- 
 ture are reported. Flash points and other physical 
 data accumulated thus far on the fluoro- and chloro- 
 fluorobenzenes are summarized. It was discovered 
 that 1,2,4,5-tetrafluorobenzene gave a quinone 
 rather than a nitro derivative under nitration con- 
 ditions. The anomalous behavior of 2-nitro-3,4,6- 
 trifluoroaniline under diazotization conditions was 
 studied. 
 
 F 
 
 0- 
 
 The nitration of 1,2,4-trifluorobenzene gave 2,4,5- 
 trifluoronitrobenzene (I) as expected by analogy 
 to the trichloro compound. A Schiemann re- 
 action on 4-nitro-2,5-difluoroaniline (III) produced 
 the same compound, and the position of the 
 nitro group was established by the identity of the 
 acetyl derivatives at II. Reduction gave 2,4,5- 
 trifluoroaniline (II) and a Schiemann conversion 
 
 (1) Presented in part before the Organic and Industrial and Engi- 
 neering Divisions at the 109th (April, 1946) and 116th (September, 
 1949) Meetings of the American Chemical Society, Atlantic City, N. J. 
 
 aterial in this paper is based on reports submitted to the OfEce of 
 Scientific Research and Development under Contract OEMsr-469 
 (1942-43), and the OfEce of Naval Research under Contract N6ori- 
 71; Task XIV (1946-50). The financial assistance of these agencies 
 | is gratefully acknowledged. 
 
 (2) Published with the permission of the Chief of the Illinois State 
 Geological Survey. 
 
 formed 1,2,4,5-tetrafluorobenzene (VII), and a 
 small amount of 2-chloro-l,4,5-trifluorobenzene 
 (VIII) as a by-product. 3 
 
 1,2,4,5-Tetrafluorobenzene resisted photochemi- 
 cal chlorination to a remarkable degree and the 
 only reaction product isolated was a trace of a 
 cyclohexane derivative, C6H 2 C1 6 F4 (X). In other 
 words, any chlorination that took place did not 
 involve hydrogen substitution, but chlorine addi- 
 tion across the double bonds to form a saturated 
 ring system. This is hardly comparable to the 
 tetrachlorobenzene analog. In contrast, 1,4-di- 
 fluoro- and 1,2,4-trifluorobenzene halogenated 
 normally, thus making available bromo and chloro 
 derivatives with a 1,2,4,5 structure. The 2-bromo 
 (XI) and 2,5-dibromo (XII) derivatives of 1,4- 
 difluorobenzene were obtained by bromination; 
 likewise, the 2-bromo (IX) derivative of 1,4,5- 
 trifluorobenzene. Sulfuryl chloride 4 chlorination 
 of 1,4-difluorobenzene gave such derivatives as 
 2-chloro- (XIII), 2,5-dichloro- (XIV) and a small 
 amount of 2,6-dichloro- (XV) and 2,3,5-tri- 
 chloro- 1,4-difluorobenzene (XVI). A trace of 
 F hexachlorobenzene was isolated. Apparently 
 the aluminum chloride catalyst caused substi- 
 tution of fluorine with chlorine in the forma- 
 tion of the hexachloro compound. 
 
 The behavior of 1,2,4,5-tetrafluorobenzene 
 with such acids as nitric, sulfuric and their 
 NH mixtures is unique and in sharp contrast to 
 the chlorine analog. Attempts to form a nitro 
 iNOs derivative were unsuccessful. The tetrafluoro 
 compound appeared to be inert to concen- 
 I trated or fuming nitric and sulfuric acids ; with 
 fuming nitric acid in a glass-sealed tube at 
 125° for four hours, a slight etching of the tube 
 was the only evidence of reaction. There was no 
 reaction with nitric-sulfuric acid mixtures if (1) 
 both components were concentrated, or (2) if one 
 component was fuming and the other concentrated. 
 A nitric-sulfuric acid mixture of fuming reagents 
 reacted with avidity, at times almost uncontrollable 
 even at 5° ; 2,5-difluoro-l,4-benzoquinone was iden- 
 tified in the decomposition products. This implies 
 a fluorine displacement-oxidation mechanism in- 
 volving a pair of fluorine atoms para to each other. 
 Since it was not feasible to obtain a nitro deriva- 
 tive of 1,2,4,5-tetrafluorobenzene by direct nitra- 
 
 (4) Cutter and B 
 
 l, J. Chem. Ed., 21, 443 (1944) 
 
146 
 
 G. C. Finger, F. H. Reed, D. M. Burness, D. M. Fort and R. R. Blough 
 
 Vol. 73 
 
 tion, the possibility of an alternate synthesis was 
 investigated. The proposed method involved the 
 formation of a 2-nitro derivative of 3,4,6-trifluoro- 
 aniline and a subsequent Schiemann reaction to 
 3-nitro-l,2,4,5-tetrafluorobenzene. Nitration of 
 the acetyl derivative of II gave a 50% yield of 
 2-nitro-3,4,6-trifluoroaniline (XVII). The Schie- 
 mann reaction, however, on the weakly basic 
 nitroamine was unsuccessful, due to failure to 
 obtain an insoluble diazonium fluoborate and the 
 multiplicity of anomalous reactions extent at the 
 diazo stage. 
 
 The perverseness of 2-nitro-3,4,6-trifluoroaniline 
 (XVI) to normal diazo reactions led to a study of 
 the anomalous reaction products of diazo tization. 
 Depending upon conditions, evidence was obtained 
 for the formation of two diazo oxides (XIX and 
 XX), nitrodifluorophenol (XXI), iodonitrodifluoro- 
 phenol (XXII), 2,3-dichloro-l,4,5-trifluorobenzene 
 (XXIII) 6 and dichlorodifluorophenol (XXIV). 
 The formation of these compounds revealed the 
 operation of several mechanisms at the diazo stage 
 such as (1) displacement of fluorine, ortho or para 
 to the diazo group, to form a diazo oxide or phenol, 
 (2) replacement of the nitro group with chlorine in 
 hydrochloric acid solutions, and (3) a combination 
 of these reactions. The ortho or para displace- 
 ment is supported by the isolation of two appar- 
 ently isomeric diazo oxides (XIX and XX). 
 Diazotization in hydrochloric acid gave one form 
 (XIX), whereas hydrofluoric gave the other (XX) 
 which, in contrast to the former, could be repeatedly 
 recrystallized from methanol to a definite melting 
 point. Both isomers were light orange in color, 
 exploded on heating or flame ignition, and impact 
 detonation gave a powerful concussion. No struc- 
 tural assignments were made to the diazo oxides 
 or the aforementioned phenols because of the un- 
 certainty of the position of the labilized fluorine 
 atom. 
 
 Counterparts of these separate mechanisms in 
 fluorine chemistry are found in Hodgson's 6 diazo 
 oxide from 3-nitro-4-fluoroaniline, and Schie- 
 mann 's 7 l-chloro-2-fluoronaphthalene from 1-nitro- 
 2-aminonaphthalene. In other words, the fluori- 
 nated nitroamine in question fulfils all the struc- 
 tural conditions necessary to demonstrate the 
 separate findings of Hodgson and Schiemann. 
 As a further test of these findings, 2-nitro-4- 
 chloro-3,6-difluoroaniline has been synthesized and 
 will be reported later. These findings are consist- 
 ent also with the discussion of Saunders 8 on similar 
 reactions with non-fluorine containing compounds. 
 
 Table I is a summary of some of the physical 
 properties of the fluoro- and chlorofluorobenzenes. 
 The boiling point of 1,2,4,5-tetrafluorobenzene is 
 not significantly different than the other fluoro- 
 benzenes, but its freezing point is close to that of 
 benzene. The flash point and surface tension 
 
 (5) A Sandmeyer reaction gave a 40% yield of this compound. 
 Frequent use of this reaction has been made in this Laboratory to con- 
 vert fluorinated ortho nitroamines to the corresponding fluorinated 
 ortho dichloro derivatives. 
 
 (6) Hodgson and Nixon, /. Chem. Soc, 2272 (1931). 
 
 (7) Schiemann and Ley, Bit., 69, 960 (1936). 
 
 (8) K. H. Saunders, "The Aromatic Diazo-Compounds and Their 
 Technical Applications," Edward Arnold & Co., London, 2nd ed., 
 1949. 
 
 data of the fluoro- and chlorofluorobenzenes are 
 significant in view of the increasing interest in 
 organic fluorine compounds. It is almost in- 
 conceivable that the flash point of tetrafluoro- 
 benzene is 4°; likewise, the low values for the other 
 fluorinated benzenes. The introduction of one 
 chlorine atom in the fluorinated benzenes elevated 
 the boiling and flash points to the vicinity of 
 chlorobenzene. Progressive fluorine substitution 
 in the benzene molecule caused a progressive de- 
 crease in surface tension. This is in contrast to an 
 increase characterized by chlorine or the other 
 halogens. The data also indicate that a decrease 
 in surface tension by fluorine is somewhat com- 
 pensated for by the introduction of chlorine into 
 the molecule. 
 
 
 Table I 
 
 
 Physical Properties 
 
 of Some 
 
 Fluorinated Benzenes 
 
 Compound 
 
 »«£■ 
 
 Flash Surface 
 
 point, tension 
 
 B. p., °C. dynes/ 
 
 °C. (open cup) cm., 20° 
 
 C 6 H 6 
 
 5.5"- 6 
 
 80* -\\ b - c 28. 9' 
 
 C 6 H S F 
 
 -41. 9* 
 
 84. 8 d -15 27.71' 
 
 C 6 H 4 F 2 -1,4 
 
 -13' 
 
 88. 5' - 5.5 27.05* 
 
 C,H 8 F,-1,2,4 -35" ' 88° - 5 26.2 
 
 C 6 H S F«-1,2,4,5 4 88 4 24.9 
 
 CeHiCl 6 -45 132 32' 33.2 
 
 C 6 H 4 (F)(C1)-1,4 -27" 130" 32 31.3 
 
 C^,(F) 2 (C1)-1,4,2 -24.6 127 31 29.9 
 
 ° Melting point. 6 Data taken from Lange, "Handbook 
 of Chemistry," Handbook Publishers, Inc., Sandusky, 
 Ohio. c Closed cup. d Timmermans and Hennaut-Ro- 
 land, J. chim. phys., 32, 501 (1935). ■ Desreux, Bull. soc. 
 chim. Belg., 44, 249 (1935). 'Schiemann and Pillarsky, 
 Ber., 62, 3035 (1929). "Schiemann, J. prakt. Chem., 40, 
 97 (1934). 
 
 Experimental 9- 1 : 
 
 2,4,5-Trifluoronitrobenzene (I). — To a mixture of 200 g. 
 of coned, nitric and 736 g. of coned, sulfuric acids, 264 g. of 
 1,2,4-trifluorobenzene 12 was added with stirring. The re- 4 
 action temperature was maintained at 20 ° and the time was : 
 three hours. Steam distillation of the crude material gave ' 
 a yield of 307 g. or 87% of practically pure nitro compound. 
 Pure 2,4,5-trifluoronitrobenzene has a mild nitrobenzene' 
 odor, but is somewhat lachrymatory, f. p. ca. —11°, b. p.* 
 93.5° (20mm.) or 192° (atm.), m m d 1.49384. 
 
 Anal. Calcd. for C 6 H 2 F,N0 2 : C, 40.69; H, 1.14; N,' 
 7.91. Found: C, 40.73; H, 1.15; N, 8.19. 
 
 The same nitro compound was obtained by a Schiemann: 
 reaction on 4-nitro-2,5-difluoroaniline (III), thus proving' 
 its structure. 
 
 2,4,5-Trifluoroaniline (II). — This compound was ob-: j 
 tained in a 90% yield by an iron reduction of I. Steam dis-' 
 tillation gave a colorless oil which solidified to a white solid 
 on cooling. Recrystallization from high boiling petroleum 
 ether gave white needles, m. p. 58.5-60°. 
 
 Anal. Calcd. for C 6 H 4 F S N: C, 48.99; H, 2.74; N, 
 9.52. Found: C, 48.90; H, 2.95; N, 9.45. 
 
 The acetyl derivative was recrystallized from aqueous 
 ethanol as white microcrystals, m. p. 129-130°. A mixed: 
 melting point of the acetyl derivatives of the amines derived 
 from the two routes proved them to be identical. 
 
 Anal. Calcd. for C 8 H 6 F 3 NO: C, 50.80; H, 3.20; N 
 7.41. Found: C, 50.80; H.3.28; N, 7.46. 
 
 (9) Analyses by H. S. Clark, microanalyst for the Survey. 
 
 (10) Melting and boiling points are uncorrected. Freezing point 
 were determined with a toluene thermometer. 
 
 (11) The assistance of Messrs. J. L Finnerty, E. W. Maynert, 
 Oesterling, H. G. Schneider, A. M. Weiner and O. F. Williams is , 
 fully acknowledged. 
 
 (12) Schiemann, J. prakt. Chem., 140, 97 (1934): 
 
Jan., 1951 
 
 1,2,4,5-Tetrafluorobenzene and Related Compounds 
 
 147 
 
 4-Nitro-2,5-difluoroaniline (III). — To a solution of 116 
 g. of 2,5-difluoroacetanilide 13 in 500 cc. of coned, sulfuric 
 acid and 50 cc. of acetic acid, a mixture of 57.5 cc. of coned, 
 nitric and 75 cc. of coned, sulfuric acids was added in 75 min- 
 utes, and the temperature maintained below 10°. The 
 crude nitroacetylamino compound, obtained in a quantita- 
 tive yield, was hydrolyzed in 150 cc. of coned, sulfuric acid 
 by heating for ten minutes on a steam-bath. A yield of 105 
 g. or 89% of crude nitroamine was obtained. Recrystalli- 
 zation from ethanol gave pure 4-nitro-2,5-difluoroaniline 
 as golden needles, m. p. 153-153.5°. The mother liquor 
 was reserved for the isolation of an isomer (IV) . 
 
 Anal. Calcd. for C 6 H<F 2 N 2 2 : C, 41.40; H, 2.32; N, 
 16.10. Found: C, 41.63; H, 2.14; N, 16.31. 
 
 Recrystallization of the acetyl derivative from ethanol 
 gave cream-colored crystals, m. p. 189-189.5°. 
 
 Anal. Calcd. for C 8 H 6 F 2 N 2 0,: N, 12.96. Found: 
 N, 12.77. 
 
 6-Nitro-2,S-difluoroaniline (IV). — This compound, an 
 isomer of III, was isolated in a very small amount from the 
 mother liquor obtained in the purification of III. A com- 
 bination of sublimation and recrystallization from ethanol 
 gave pure 2-nitro-3,6-difluoroaniline as orange needles, 
 m. p. 80-80.5°. 
 
 Anal. Calcd. for C 6 H<F 2 N 2 2 : C, 41.40; H, 2.32; N, 
 16.10. Found: C, 41.57; H, 2.38; N, 16.10. 
 
 Sublimation gave the acetyl compound as a white solid, 
 m. p. 160-161°. 
 
 Anal. Calcd. for C 8 H,F 2 N 2 3 : N, 12.96. Found: N, 
 12.90. 
 
 The structure of this nitroamine was proven by reduction 
 to the diamine (V) and the subsequent formation of a quin- 
 oxaline. 
 
 3,6-Difluoro-l,2-phenylenediamine (V). — The diamine 
 was prepared from IV by the usual stannous chloride reduc- 
 tion. It was quite soluble in water and was extracted with 
 ether. Vacuum sublimation gave the pure diamine as fine 
 white needles, m. p. 80.8-81.1°. 
 
 Anal. Calcd. for C 6 H 6 F 2 N 2 : C, 50.00; H, 4.20; N, 
 19.45. Found: C, 50.15; H, 4.22; N, 19.60. 
 
 The 2,3-diphenyl-5,8-difluoroquinoxaline derivative was 
 prepared by condensation of the diamine with benzil. Re- 
 crystallization from ethanol gave fine white crystals, m. p. 
 191-191.5°. 
 
 Anal. Calcd. for C 20 H 12 F 2 N 2 : C, 75.45; H, 3.80; N, 
 8.80. Found: C, 75.55; H, 3.80; N, 8.75. 
 
 2,5-Difluoro-l,4-phenylenediamine (VI). — This diamine 
 was prepared from III by the same procedure described for 
 V. Vacuum sublimation gave white crystals, m. p. 129- 
 129.6°. 
 
 Anal. Calcd. for C 6 H 6 F 2 N 2 : C, 50.00; H, 4.20; N, 
 19.45. Found: C, 49.91; H.4.28; N, 19.52. 
 
 The diacetate derivative upon recrystallization from acetic 
 acid gave white microneedles, m. p. 304.5-305.5°. 
 
 Anal. Calcd. for Ci H 10 F 2 N 2 O 2 : N, 12.28. Found: N, 
 12.00. 
 
 1,2,4,5-Tetrafluorobenzene (VII).— A well -stirred mix- 
 ture of 294 g. of 2,4,5-trifluoroaniline and 1100 cc. of com- 
 mercial hydrochloric acid (18° Be.) was heated until com- 
 plete solution was obtained and then rapidly cooled to —5° 
 to precipitate the amine hydrochloride. The resulting mix- 
 ture was diazotized by the submerged addition of a solution 
 )f 140 g. of sodium nitrite in 210 cc. of water, and the tem- 
 perature not allowed to go above 0°. After completion of 
 he diazotization , a solution of 660 g. of sodium fluoborate 
 n 940 cc. of water was added rapidly. The heavy slurry 
 vas stirred for 30 minutes, cooled to —15°, filtered and the 
 ight yellow fluoborate salt was dried. The yield of dry 
 alt was over theory. After thermal decomposition by the 
 isual procedure, 14 the crude reaction product was made al- 
 :aline with sodium carbonate solution and steam distilled, 
 distillation through a packed column gave a fraction boiling 
 t 89-90.5°, yield 113-137 g. or 38-46% based on the amine. 
 *ure 1,2,4,5-tetrafluorobenzene has a faint sweet odor. 
 . p. ca. 4°, b. p. 88°, <f 20 4 1.4256, w 20 d 1.4074. 
 
 (13) Swarts, Bull, classe sci., Acad. roy. Belg., 241 (1913); 186 
 .914). 
 
 (14) Finger and Reed, This Journal, 66, 1972 (1944). 
 
 Anal. Calcd. for C«H S F 4 : C, 48.01; H, 1.34. Found: 
 C, 47.93; H, 1.42. 
 
 2-Chloro-l,4,5-trifluorobenzene (VIII).— This compound 
 was obtained in a 60% yield from 2,4,5-trifluoroaniline by a 
 Sandmeyer reaction or as a by-product from the tetrafluoro- 
 benzene synthesis, f. p. ca. -24.5°, b. p. 124-125°. 
 
 Anal. Calcd. for C 6 H 2 C1F,: C, 43.27; H, 1.21. Found: 
 C, 43.65; H, 1.19. 
 
 2-Bromo-l,4,5-trifluorobenzene (IX). — Bromination of 
 1,2,4-trifluorobenzene with iron as a catalyst gave a 76% 
 yield of 2-bromo-l,4,5-trifluorobenzene, f. p. ca. —19°, 
 b. p. 144°, d*\ 1.8022, « 20 d 1.4862, y*« 25.6 dynes/cm. 
 
 Anal. Calcd. for C 6 H 2 BrF 3 : C, 34.15; H, 0.95; Br, 
 37.88. Found: C, 34.07; H, 0.95; Br, 37.87. 
 
 1,2,3,4,5,6 - Hexachloro - 1,2,4,5 - tetrafluorocyclohexane 
 (X) . — A small amount of high-boiling material was the only 
 evidence of the effect of exhaustive chlorination on 1,2,4,5- 
 tetrafluorobenzene. A combination of vacuum distillation, 
 recrystallization from ethanol, and sublimation gave a very 
 small amount of white crystals, m. p. 79-80°, as the only 
 isolable product. According to the analytical data, the 
 white solid is a hexachlorotetrafluorocyclohexane. 
 
 Anal. Calcd. for C 6 H 2 C1 6 F 4 : C, 19.85; H, 0.55; CI, 
 58.64. Found: C, 19.84; H.0.70; CI, 58.38. 
 
 Halogenation of />-Difluorobenzene. — Bromination of p- 
 difluorobenzene with bromine in the presence of iron gave 
 the mono and dibromo derivatives with the latter being in 
 largest amount. Both derivatives were removed from the 
 reaction mixture by steam distillation, and then separated 
 by vacuum distillation. 
 
 2-Bromo-l,4-difluorobenzene (XI). — This compound has 
 a mild bromobenzene odor, f. p. ca. —31.5°, b.p. 58-58.5° 
 (20 mm.), » 20 d 1.5086. 
 
 Anal. Calcd. for C 6 H 3 BrF 2 : C, 37.34; H, 1.56; Br 
 41.41. Found: C, 37.43; H, 1.62; Br, 41.06. 
 
 2,5-Dibromo-l,4-difluorobenzene (XII). — This is a crys- 
 talline solid, sublimes slowly on standing, and is recrystalliz- 
 able from ethanol, m. p. 64.5-65.5°, b. p. 96° (20 mm.). 
 
 Anal. Calcd. for C„H 2 Br 2 F 2 : C, 26.50; H, 0.74; Br, 
 58.78; F, 13.98. Found: C, 26.61; H, 0.74; Br, 58.91; 
 F, 13.48. 
 
 Chlorination of £-difluorobenzene was effected by the 
 sulfuryl chloride-sulfur monochloride method with alumi- 
 num chloride as a catalyst. 4 A moderate excess of reagent 
 gave the monochloro derivative, but this in turn chlorinated 
 readily to the 2,5-dichloro compound. Chlorination be- 
 yond the dichloro stage was much slower. A large excess of 
 chlorinating agent formed a complex mixture which gave a 
 60-70% yield of the 2,5-dichloro-l,4-difluorobenzene, a 
 small amount of what may be 2,6-dichloro-l,4-difluoro- 
 benzene, 15-20% of 2,3,5-trichloro-l,4-difluorobenzene, 
 and a trace of hexachlorobenzene. Separation of the com- 
 ponents was by steam and vacuum distillations, and re- 
 crystallizations. 
 
 2-Chloro-l,4-difluorobenzene (XIII). — In addition to the 
 direct chlorination, this compound was obtained as a by- 
 product from the synthesis of 1,2,4-trifluorobenzene or by 
 a Sandmeyer reaction on 2,5-difluoroaniline in a 60% yield, 
 f. p. ca. 24.6°, b. p. 128°, d M < 1.3561, « 2 °d 1.4772. 
 
 Anal. Calcd. for C 6 H 3 C1F 2 : C, 48.51; H, 2.04; CI, 
 23.87. Found: C, 48.46; H, 2.07; CI, 28.86. 
 
 2,5-Dichloro-l,4-difluorobenzene (XIV). — The reaction 
 product (177 g.) from exhaustive chlorination was divided 
 arbitrarily into three volatile fractions, and a small non- 
 volatile fraction by steam distillation. The order of volatile 
 fractions was (1) a condensate (87 g.) which solidified on 
 cooling, (2) an oil (86 g.) which remained a liquid at room 
 temperature, and (3) a white solid. The residue (1.2 g.) 
 and the last fraction (2.6 g.) was essentially hexachloro- 
 benzene. 
 
 The first volatile fraction was almost pure 2,5-dichloro-l,- 
 4-difluorobenzene. As a result of processing the second 
 fraction, an additional 25 g. of this dichloro derivative was 
 accumulated from this source. It was identified by a mixed 
 melting point with a known sample obtained from 4-nitro- 
 2,5-difluoroaniline (III). 
 
 The synthesis of this compound from III was accom- 
 plished in one step by the simultaneous replacement of a 
 nitro group with chlorine while a cuprous chloride Sand- 
 meyer reaction was operating on the amino group. Fre- 
 
148 
 
 G. C. Finger, F. H. Reed, D. M. Burness, D. M. Fort and R. R. Blough 
 
 Vol. 73 
 
 cment use of this reaction has been made with ortho-nitro- 
 
 tgesT a vacuum sublimation gave 3.2 g. of practically pure 
 Sloro compound as the most vo fertile ^^{l 1 4- 
 Recrystallization from ethanol gave J^chloro A 
 difluorobenzene as white crystals, m. p. 48-49 , b. p. b4 
 (20 mm.) or 164° (atm.). 
 
 Anal. Calcd. for C,H,C1,F, : C ,39 38 ; ; H , 1.10; CI, 
 38.75. Found: C, 39.44; H, 1.08; CI, 38 78 
 
 2 6 -Dichloro- 1,4 -difluorobenzene (XV) .-The second 
 voMile fraction described under XIV was processed by 
 fractional distillation into various cuts In general mate 
 rial boiling above 180° was reserved for the lsola ^" ot ^ 
 trtohloro derivative. Fractions boiling up to 180 were 
 orocessed by repeated distillations and freezing of fractions 
 KminaSth^ 2 ,5-di.hloro compound, The end result 
 was several grams of oil, f. p. 3.5 to -10 , b. p. bo-oo ^u 
 mm.), w 20 d 1.50750. n _, 
 
 Anal. Calcd. for CgW.: C, 39 38 H, 1.10; CI, 
 38.75. Found: C, 39.36; H, 1.17; CI, 38.63. 
 
 There is little doubt that this material essential ly is 2 b- 
 dichloro-l,4-difluorobenzene. A synthetic sample pre 
 oared recently by a Sandmeyer reaction on 3-chloro Z,0 
 dffluoroan'line y » had practically the same properties, f. p. 
 ca. -1.5 to 2.5°, b. p. 165°, « 2 °d 1.50405. 
 
 Anal. Calcd. for C 6 H 2 C1 2 F 2 :C, 39.38; H, 1.10. Found: 
 C, 39.40; H, 1.06. 
 
 2 ,3 ,5-Trichloro-l ,4-difluorobenzene (XVI) -The trac- 
 tion boiling above 180° as indicated under XV and the 
 hSer cuts" obtained from the isolation of the^-dichloro 
 compound were combined. This composite sample was re - 
 Sled to give about 30 g. of a middle fraction, b. p 180- 
 207° Repeated fractional distillation and freezing ; of the 
 fractions removed the hexachlorobenzene as a solid and 
 with the elimination of the lower boiling fractions an en- 
 riched trichloro fraction, b. p. 190-205°, was obtained Re- 
 distillation of the enriched fraction gave about 25 g. of fairly 
 pSe material. Approximately 20 g ofpure2,3 5- tnchloro- 
 1,4-difluorobenzene was finally isolated, f. p. ca. -\lf to 
 -12° b p 94-95° (20 mm.) or 200° (atm.), »»d 1.5340. 
 
 Anal Calcd for C 6 HC1 3 F 2 : C, 33.14; H, 0.46; CI, 
 48 92 Found C, 33.43; H, 0.56; CI, 48.94. 
 
 Quinone Formation.— All attempts to prepare a nitro de- 
 rivative of 1,2,4,5-tetrafmorobenzene (VII) by nitration 
 failed. The unusual stability of this compound to n.tr.c- 
 sulfuric acid mixtures was discussed previously, and for the 
 sake of brevity the isolation of the quinone intermediate 
 
 Wi To b a d :enSrred mixture of 30 g. of l^.Metrafljgo- 
 benzene (VII) and 13.9 g. of fuming sulfuric acid (30% 
 S0 3 ), 20 cc. of fuming nitric acid (1.49-1.5) was added 
 dropwise and the reaction temperature maintained at 25- 
 30° The mixture became orange -red in color, a yellow 
 solid formed, and a slow evolution of hydrogen fluoride was 
 observed. After pouring the reaction mixture over ice 
 the yellow solid was removed by filtration, washed with 
 water, dried, yield 8-10 g. It was purified by "crystalliza- 
 tion from carbon disulfide or by sublimation, m.p 171.5 
 172° A mixed melting point with a known sample of 2,5- 
 difluoro-l,4-benzoquinone 16 proved its identity. 
 
 2-Nitro-3,4,6-trifluoroaniline (XVII) .-To a solution of 
 500 g of 2,4,5-trifluoroacetanilide in 445 cc. of glacial acetic 
 and 1550 cc. of concentrated sulfuric acids, a mixture of 200 
 ec of fuming nitric acid (1.49-1.5) in 55 cc °f acetic and 
 195 cc. of coned, sulfuric acids was added slowly, and the 
 temperature maintained at 20°. Stirring was continued 
 for 30 minutes after addition, and some hydrogen fluoride 
 evolution was observed during the nitration. After re- 
 moval of the precipitate by filtration, the aqueous filtrate 
 was extracted with ether for maximum recovery. The .en- 
 tire crude product (425 g.) was hydrolyzed with 300 cc of 
 coned hydrochloric acid in 2700 cc. of water by refluxmg for 
 two nours. Steam distillation gave 267 g. (53%) of mtro- 
 amine, sufficiently pure for subsequent reactions. Vacuum 
 
 (15) Finger, Reed and Finnerty, unpublished results. 
 
 (16) Finger, Finnerty and Schneider, Abstracts of llfith A. C. S. 
 Meeting, September, 1949, Atlantic City, N. J., p. 17K. 
 
 sublimation gave pure 2-nitro-3,4,6-trifluoroaniline as a 
 bright orange solid, m.p. 57.3-57.8 . 
 
 Anal. Calcd. for C,H 3 F,N 2 2 : C ,37 .52; H, 1.57; N, 
 14 59 Found: C, 37.78; H, 1.44; N, 14.51. 
 
 The acetyl derivative was purified by recrystalhzation 
 from carbon tetrachloride and by vacuum sublimation, 
 m.p. 124.5-124.8°. 
 
 Anal. Calcd. for C 8 H 6 F 3 N 2 O s : N, 11.97. Found: 
 
 3 4 6-Trifluoro-l ,2-phenylenediamine (XVIII) .—This di- 
 amine was prepared in an 82% yield by an iron reduction 
 from the preceding nitroamine. Vacuum sublimation gave 
 white needles, m.p. 74.6-75.2°. 
 
 Anal Calcd. for C 6 H 6 F 3 N 2 : C, 44.45; H, 3.11; N, 
 17 28 Found- C, 44.65; H, 2.95; N, 17.06. 
 
 The quinoxaline derivative was prepared by the usual 
 reactfo^with benzil in a 75% yield, and purified ^ passage 
 through an aluminum oxide chromatograph 111 addition to 
 ecrystalhzation from ethanol. The pure 2,3-dipheny - 
 5 'ff|-trifluoroquinoxaline was obtained as white needles, 
 m p. 169.5-170°. 
 
 Anal Calcd. for C 2 oH u F 3 N a : N.8.33: Found: N,8.26. 
 Diazotization of 2-Nitro-3 ,4 6-trifluoroaniUne.-A variety 
 of products was obtained by diazotization of 2-nitro-3,4,b- 
 t riflToroaniline, depending upon the acid media and re 
 asrents used. Since a fluorine atom in the 4- or 6-position 
 couW be replaced, the structures of the diazo oxides or the 
 nhenolic compounds were not determined. In general the 
 pnenolic compounds were converted to a benzoyl derivative 
 in order to obtain a satisfactory analysis. 
 
 Siazo Oxides (XIX and XX) -Two apparently different 
 diazo oxides of the same chemical composition were obtained 
 one was derived from diazotization in hydrochloric acid 
 (XIX) and the other from hydrofluoric acid (XX). It is 
 conceivable that one represents a fluorine replacement at the 
 • 4 -position and the other at the 6-position. . . 
 
 The hydrochloric acid diazotization involved 5 , g. o : the 
 nitroamine, 10 cc. of coned, hydrochloric acid and 3 g. of 
 sodStoitVin 5 cc. of water. The bright orange-colored 
 precMtate was removed by filtration; the titrate gave 
 no nrecinitate with sodium fluoborate solution, thus negat- 
 &TSSSS reaction. After drying the P/eciPitate 
 it m P lt P d near 80°. and burned explosively in a flame, one 
 
 ing a Schiemann reaction. Aiiei uijus «-. ^—^;" 
 it melted near 80°, and burned explosively in a flame l 
 ecrystalhzation from methanol gave orange colored crystals 
 (XIX) which darkened upon heating but not melting up 
 to 350 °, and exploding violently on impact. 
 
 Anal Calcd for C 6 HF 2 N 3 3 : C, 35.83; H, 0.50; N; 
 20 90 Found- C, 35.95; H, 0.55; N, 20.71. 
 
 The hydrofluoric acid diazotization was similar to the 
 above except 48% aqueous acid was used, and the reaction 
 was performed in a rubber beaker. Due to the presence o 
 msoluble salts, the dried orange precipitate was extractea 
 with ether in a Soxhlet, and evaporation of the ether ex 
 Tract gave a crude red product. Repeated recrystallizatioD 
 from methanol gave a bright orange powder (XX), J 
 119.3-120° (dec), with the same characteristics as the pre, 
 ceding compound. 
 
 Anal Calcd for C 6 HF 2 N 3 3 : C, 35.83; H, 0.50; N 
 20 90 Found: C, 35.75; H,0.43; N, 20.80. 
 
 Nitrodifluorophenol (XXI) .-Diazotization of the mtro, 
 amine (25 g.) in coned, sulfuric acid and application of M 
 Cophosphorous deamination method gave a small amoun 
 (one gram) of a steam distillable solid. Recrystallizatio 
 of the solid from chloroform and vacuum sublimation gav 
 vellow crystals , m.p. 105-105.5°. A benzoyl derivatw 
 Ss preyed by the" Schotten-Baumann reaction ; recrys 
 tallization from ethanol gave white plates, m.p. »8-»y . 
 
 Anal. Calcd. for C 13 H 7 F 2 N0 4 : C 55^2; H, 2.53; N 
 5 02. Found: C, 56.31; H.2.27; N, 5.01. 
 
 Iodonitrodifluorophenol (XXII) -This compound W a 
 obtained in very small amount by diazotization of the nitro 
 amfneln sulfuric acid followed by treatment with potass u 
 tod de A Schotten-Baumann reaction gave the benzo> 
 derivative, recrystallizable from ethanol to cream-colore 
 needles, m.p. 135-136°. 
 
 Anal. Calcd. for CuH.FgNO*: C 38 54; H, 1.49 
 N 3 46 Found: C, 39.14; H, 1.46; N, 3.12. 
 
 2,3-Dichloro-l,4,5-trifluorobenzene (XXIII) .-A susper 
 sion of 25 g. of powdered nitroamine in 50 cc. of coned, hj 
 
Jan., 1951 
 
 The Fluoromesitylenes and Derivatives 
 
 drochloric acid was diazotized at —5° with the slow addi- 
 tion of 15 g. of powdered sodium nitrite. The resulting 
 mixture was poured into a solution of 25 g. of cuprous 
 chloride in 100 cc. of coned, hydrochloric acid. Steam dis- 
 tillation removed the dichloro compound as an oil, and the 
 aqueous layer was reserved for the isolation of the dichloro- 
 difluorophenol. The crude product, yield 10.6 g. or 40%, 
 on distillation gave pure 2,3-dichloro-l,4,5-trifluoroben- 
 zene.f.p. ca. -3 to -4°, b.p. 153°, w ! °d 1.48866. 
 
 Anal. Calcd. for C 6 HC1 2 F 3 : C, 35.85; H, 0.50; CI, 
 35.28. Found: C, 35.92; H, 0.57; CI, 34.90. 
 
 The cloudy supernatant liquid from steam distillation on 
 chilling gave a few drops of oil, with a phenolic odor (XXIV) , 
 which was converted to a benzoyl derivative. Recrystal- 
 lization from ethanol and a subsequent vacuum sublimation 
 gave the derivative as a white powder, m.p. 84.5-85°. 
 
 Anal. Calcd. for C 13 H 6 C1 2 F S 2 : C, 51.51; H, 2.00; 
 CI, 23.40. Found: C, 51.48; H, 1.74; CI, 23.40. 
 
 Flash Points and Surface Tension. — The flash points 
 were determined by the Pensky-Martens closed tester. 17 
 
 Surface tension was determined by H. S. Clark using the 
 micro-capillary tube method. 18 
 
 (17) "1949 Book of A. S. T. M. Standards," A. S T. M. Designation: 
 :ty for Testing Materials, Philadelphia, Pa. 
 ind Pearl, This Journal, 57, 1520 (1935). 
 
 Summary 
 
 The synthesis and properties of 1,2,4,5-tetra- 
 fluorobenzene and a group of bromofluoro and 
 chlorofluorobenzenes with a predominating 1,2,4,5- 
 structure are described. Flash point and surface 
 tension data for the fluorinated benzenes and the 
 influence of chlorine substitution upon these 
 values were studied. 
 
 Under nitration conditions, 1,2,4,5-tetrafluoro- 
 beuzene will not form a nitro derivative, but will 
 undergo a preferential 1,4-fluorine displacement- 
 oxidation mechanism to give 2,5-difluoro-l,4- 
 benzoquinone. 
 
 Diazotization reactions on 2-nitro-3,4,6-tri- 
 fluoroaniline reveal that the nitro group or a 
 fluoriue atom in the 4- or 6-position may become 
 labilized, under certain conditions, and undergo 
 replacement. 
 
 Urbana, Illinois 
 
 Received June 9, 1950 
 
 [Contribution from the Geochemical Section of the Illinois State Geological Survey ] 
 
 Aromatic Fluorine Compounds. III. The Fluoromesitylenes and Derivatives 1 
 By G. C. Finger, F. H. Reed, E. W. Maynert and A. M. Weiner 
 
 As part of a study in this Laboratory on aromatic 
 fluorides, 2,4-difluoro- and 2,4,6-trifluoromesitylene, 
 and various fluorinated mesitylene derivatives 
 were synthesized. Monofluoromesitylene was syn- 
 thesized by Tohl 2 as early as 1892. Of special 
 [note is the synthesis of 2,4,6-trichloro-l,3.5-tri- 
 fluorobenzene. 
 
 Dinitromesitylene was prepared in quantitative 
 yields by the nitration of mesitylene in anhydrous 
 hydrofluoric acid by the Frederiha»en process. 3 
 This method has much in its favor over the Fittig" 1 
 fed fuming nitric acid procedure. A sodium 
 Dolysulfide reduction of the dinitro compound gave 
 litromesidine (I), and by means of a diazotization- 
 Schiemann transformation 2-fluoro-4-nitromesityl- 
 fene (II) was obtained. An iron reduction of II 
 jave fluoromesidine (III), and a Schiemann re- 
 iction on the amine gave a 80-90% yield of 2,4- 
 lifluoromesitylene (IV). 
 
 A 90% yield of 2,4-difluoro-6-nitromesitylene (V) 
 vas obtained by the above hydrogen fluoride 
 titration process on IV. Difluoromesidine (VI), 
 prepared by an iron reduction of V, was converted 
 p an 86% yield to 2,4,6-trifluoromesitylene (VII) 
 ! iy a Schiemann reaction. The yields of difluoro- 
 liesitylene and trifluoromesitylene from their 
 
 I (1) Presented in part before the Organic Division at the 109th 
 leeting of the American Chemical Society, Atlantic City, N J., April 
 346. The material in this paper is based, primarily, on reports sub- 
 mitted to the Office of Scientific Research and Development under 
 ontract OEMsr-469( 1942-43) and on data obtained after the ex- 
 iration of the contract. Published with the permission of the Chief of 
 le Illinois State Geological Survey. 
 
 (2) Tohl, Ber., 25, 1525 (1892). 
 
 (3) (a) Fredenhagen, German Patent 529,538 (Aug. 2, 1930); C. A., 
 i>, 5175 (1931). (b) "Newer Methods of Preparative Organic Chemis- 
 y," Interscience Publishers, Inc., New York, N. Y., 1948, pp. 340- 
 
 (4) Fittig, Ann., 141, 133 (1867). 
 
 h,n/\ 
 
 CH, 
 
 l Ny CH 3 
 
 N0 2 
 
 CH 3 
 
 'CH 3 
 NOj 
 
 ICH 3 
 NH 2 
 
 chXJc 
 
 VI 
 
 VII 
 
 respective amines are among the highest recorded 
 for a Schiemann reaction. 5 
 
 The chlorination of trifluoromesitylene readily 
 gave a "hexachloro" derivative, probably 2,4,6- 
 tris-(dichloromethyl)-l,3,5-trifluorobenzene, and 
 this was converted slowly at a higher tempera- 
 ture to 2,4,6-tris-(trichloromethyl)-l,3,5-trifluoro- 
 benzene. The latter was complicated by chlorin- 
 olysis which gave rise to 2,4,6-trichloro-l,3,5- 
 trifluorobenzene and carbon tetrachloride. Similar 
 results had been reported for mesitylene and the 
 ehloromesitylenes. 6 ' 7 Trifluoromesitylene with its 
 chlorinated derivatives, and trichlorotrifluoroben- 
 
 (5) "Organic Reactions," John Wiley and Sons, Inc., New York, 
 N. Y., 1949, Vol. V, Ch. 4, pp. 217-222. 
 
 (6) I. G. Farbenind. A.-G, French Patent 798,727 (May 25, 1936), 
 C. A , SO, 7121 (1936). 
 
 (7) McBee and Leech, Ind. Eng. Chem., 39, 393 (1947). 
 
G. C. Finger, F. H. Reed, E. W. Maynert and A. M. Weiner 
 
 Vol. 73 
 
 150 
 
 zene possess the characteristic structure of sym- 
 metrical trifluorobenzene. 
 
 Mesitylene with trifluoroacetic anhydride under- 
 goei SeFnedel-Crafts acylation reaction to form 
 the trifluoroaceto derivative. Various aceto i deriv- 
 atives of difluoromesitylene were prepared and 
 oresumably, the same reactions could be applied to 
 Cofluoro y mesitylene. Sodium hypobrom^e con- 
 verted the acetodifluoromesitylene to the tri- 
 bromoaceto derivative which was degraded to 
 eS-Soro-/3-isodurylic acid. Attempts to produce 
 the same acid by the hydrolysis of 2-cyano-4 6- 
 SfluorSnesTtylenl failed because of the stability 
 of the amide intermediate. tr ; fll1 nro- 
 
 The boiling points of mono-, di- and trifluoro 
 mesitylene, 167/ 169 and 169° .respectively are 
 slightly higher than mesitylene, b. p. 164 . ine 
 trifluoro compound is a solid, m. p. 68° in contrast 
 to mesitylene and the other fluoromesrtylenes which 
 are liquids; it is quite volatile, sublimes slowly on 
 standing, and exhibits thixotropic properties. 
 Experimental 8,9 
 
 that the reaction temperature was held below 5 . btrmng 
 was continued for 15-30 minutes. The dinitromesity ene 
 pTecipitated^ a yellow solid, and the final reason mixture 
 
 * AteJ2S£& reaction mixture over 5 kg. of crushed 
 ice "?h porous stirring, the dinitromesitylene was re- 
 moved and washed with water on a Buchne, -funnel and 
 dried Yield was 805-840 g. or 94-98%, m. p. 84-8i) 
 (Ffttig reported 86°). This product was sufficiently pure 
 for the sodium polysulfide reduction to nitromesidine. 
 for the g^poiy _ 6nitromesityleiie (y) Difduoromesi- 
 
 tvlene (0 77 mole) was nitrated in liquid anhydrous hydro- 
 fluoric acid (50 moles) by the addition of sodium nitrite 
 m R mole) according to the above procedure except that 
 £ti"al cooling J was" not necessary. Yield of crude mtro 
 compound was 90-92%, m. p. 53 . 
 
 Anal. Calcd. for C.H.O.NF,: C 53 73; H, 4.51; N, 
 6 96 Found: C, 53.93; H.4.49; N, 7.10. 
 
 A "mixed" acid nitration with coned, nitric and sulfuric 
 adds g^ve the same nitro compound but in a slightly lower 
 yield. Steam distillation gave a fairly pure product 
 
 2-Fluoro-4-nitromesitylene (II) .-A mixture of 400 g. 
 of crude, powdered nitromesidine"- and 1150 cc. of coned, 
 hydrochloric acid was heated to form the amine hydro- 
 chloride, and then chilled rapidly to 0°. A solution of 190 
 g of sodium nitrite in 350 cc. of water was added slowly 
 while the reaction temperature was maintained at -5 to 
 0° The clear diazonium chloride solution after skimming 
 off' any tar-like material floating on the surface, was cooled 
 to -10°, and a solution of 360 g. of sodium fluoborate in 
 430 cc of water was added to form the insoluble diazonium 
 Suoborate. In general, a yield of 95% was obtained 
 
 The fluoborate salt was decomposed by careful heating in a 
 large round-bottom flask equipped with a large bore, air re- 
 
 (8) The authors are indebted to Mr. H. S. Clark, microanalyst of the 
 Survey, for the analyses given in this investigation. Acknowledgment 
 is made also of the assistance of Messrs. D. M. Burness, D. M. Fort, 
 T L. Finnerty and R. E. Oesterling. 
 
 (9) All melting and boiling points are uncorrected, and freezing 
 ooints were determined with a toluene thermometer. 
 
 (10) Morgan and Davies. J. Chem. Soc. 123. 231 (1923). 
 
 flux condenser, and allowing the exit gases to escape in a 
 ho^d After gas evolution had ceased, an ether extraction 
 Amoved the ^de product from the black, solid residue. 
 ¥S Ither extmct, after the usual water and 5% sodium 
 nydroxide solution washings drying and evaporatior^gav^ 
 a crude yield ranging from 210-270 g. or 53-67% based on 
 the^nesfdine. Vacuum distillation gave pure 2-fluoro-4- 
 nTtromesitylene as a pale yellow, crystalline solid, m. p. 
 43-44°, b. p. 97-99° (10 mm.). 
 
 Ana. Calcd. for C 9 H 10 O,NF: C 59.00; H, 5.50; N, 
 7 64 Found: C, 58.73; H, 5.52; N, 7.63. 
 
 " 2-Fluoro-4-aminomesitylene (III) .—This amine was pre- 
 oared from the preceding nitro compound by the usual iron 
 reduction" in an 88% yield. Steam distillation gave a prod- 
 uct sufficiently pure for the subsequent reactions. Recrys- 
 tallization from low boiling petrole um ., et ^ r ^P^ 6 ^ 
 fluoro-4-aminomesitylene as a white solid, m. p. 38.5-39.5 . 
 
 Anal. Calcd. for C 9 H 12 NF: C 70.56; H.7.90; N, 9.15. 
 Found: C, 70.68; H, 7.75; N, 9.21. 
 
 Recrystallization of the acetyl derivative from aqueous 
 ethanol gave white needles, m. p. 181-18^ . 
 
 Anal. Calcd. for C u HuONF: N, 7.18. Found: N, 
 
 '24-Difluoromesitylene (IV).— This compound was pre- 
 pared from 2-fluoro-4-aminomesitylene (III) by the usual 
 nrocedure " The yield of diazonium fluoborate salt was 
 85300%, and the crude yield of difluoromesitylene was| 
 80-90% based on the amine. ■ 
 
 Pure 2,4-difluoromesitylene is a co }°g&M u %l}: ? ' M 
 -18 5° b p 69.5° (20 mm.) or 168-169 (atm.), a 4 
 1 183, « 2 »d 1.4682, •y 20 30.94 dynes/cm. 
 
 'Anal. Calcd. for C 9 H 10 F 2 : C 69.21; H, 6.46. Found:! 
 C, 69.36; H, 6.20. 
 
 2,4-Difluoro-6-aminomesitylene (Vl).-Crude 2,4-di- 
 fluoro-6-nitromesitylene (V) was reduced to the am me 
 with iron filings as described previously. The crude amine 
 waTremoved from the reaction mixture by steam distillation, 
 yield 183%. Recrystallization from aqueous ethanol gavel 
 white, granular crystals, m. p. 51-51.5 . | 
 
 Anal Calcd. for C 9 H U NF 2 : C, 63.13; H, 6.48. Found; 
 C, 63.31; H,6.28. 
 
 The acetyl derivative upon recrystallization from ethano, 
 gave white needles, m. p. 185-186°. 
 
 Anal. Calcd. for C u H„ONF,: C, 61.96; H, 6.14 
 Found: C, 62.21; H, 6.07. 
 
 2 4 6-Trifluoromesitylene (VII) .—Approximately 349 g, 
 (2 04 'moles) of powdered crude difluoromesidine was di 
 ges?ed?n tic cc. of hot coned, hydrochloric add to form tM 
 Snine hydrochloride, and then chilled rapidly to witl 
 stirring. To the thick pasty mass, a solution of 17C I g. c 
 sodiuni nitrite in 230 cc. of water was added slowly and th 
 empe^atuVe not allowed to rise above 0° The J««JJ 
 chloride solution with its precipitate of sodium chloride wa 
 cooled to -10°, and a solution of 560 g. of sodium fluoborat, 
 in 675 cc. of water was added. A heavy white magma of th 
 diazonium fluoborate was obtained. The fluoborate sa 
 was removed by filtration and dried m cool ail - (below 20 
 A cool drying temperature was necessary as the damp sa 
 had a tendency to liquefy at 25-30° until the moisture W 
 tent had been reduced below a certain limit. Yield of d* 
 salt was 533 g. or 97% ; other experiments gave a yield ran^j 
 
 ^'fluoborate salt was decomposed thermally by 1 
 continuous heating in a large flask equipped with a refit 
 condenser. Air was passed through ^condenser jacke 
 but periodically some steam was used to melt down t . 
 solid condensate and thereby avoid condenser pluggm, 
 Vacuum distillation of the crude product gave a colorle 
 main fraction, b. p. 91-94° (65 mm.), which solidified upc 
 Sg Purification may be effected al so ^"gato 
 The yield data based on amine was (1) crude, 308 g. 
 86% and (2) distilled, 278 g. or 78%. Pure 2,4,6-t. 
 fln^omesitvlene, m. p. 68°, b. p. 169°, is a white solid, qui 
 vXtT "ulLes slowly on standing to long slender cry 
 tals, and it exhibits thixotropic properties in that the cry 
 tals appear to partially melt on mechanical working. 
 
 Arml. Calcd. for C.H.F.: C 62.03; H, 5.14. Foun 
 C, 61.84; H, 5.16. 
 
 (11) Finger and Reed. This Journal, 66, 1973 (1944). 
 
Jan., 1951 
 
 The Fluoromesitylenes and Derivatives 
 
 151 
 
 Chlorination of 2,4,6-Trifluoromesitylene. — The chlorina- 
 tion apparatus and procedure was similar to that described 
 by McBee, et al. 11 No yield data were obtained due to the 
 complexity of the reaction products and the difficulties en- 
 countered in isolating pure components. 
 
 Trifluoromesitylene was dissolved in a large excess of 
 carbon tetrachloride and chlorinated below the boiling point 
 of the solvent. The chlorination was strongly exothermic 
 and rapid up to a "hexachloro" stage, whereupon it became 
 very slow and the solvent was removed by distillation. 
 This sluggish condition prevailed even at the higher tem- 
 peratures (<200°). At the elevated temperatures, chlo- 
 rinolysis of the methyl groups also took place since carbon 
 tetrachloride in an appreciable amount and 2,4,6-trichloro- 
 1,3,5-trifluorobenzene were found in the complex mixture 
 of products. The yield of 2,4,6-tris-(trichloromethyl)- 
 1,3,5-trifluorobenzene was rather low and it is quite con- 
 ceivable that the chlorinolysis reaction was largely re- 
 sponsible for it. Fractional distillations and recrystalliza- 
 tions were used in isolating the various products. 
 
 The "hexachloro" compound was dissolved in petroleum 
 ether and chromatographed through an aluminum oxide 
 column with benzene as an eluant. A final recrystallization 
 from ethanol gave white needles, m. p. 116-116.5°. It is 
 quite likely that this compound is 2,4,6-tris-(dichloro- 
 methyl ) -1 ,3 ,5-trifluorobenzene . 
 
 Anal. Calcd. for C,H,C1 6 F 8 : C, 28.38; H, 0.79. 
 Found: C, 28.49; H, 0.79. 
 
 2,4,6-Tris-(trichloromethyl)-l,3,5-trifluorobenzene upon 
 recrystallization from ethanol gave white needles, m. p. 
 126-126°. 
 
 Anal. Calcd. for C,C1 9 F,: C, 22.32; CI, 65.90. Found 
 C, 22.36; CI, 66.03. 
 
 2,4,6-Trichloro-l,3,5-trifluorobenzene is a white solid 
 m. p. 62-63°, b. p. 79.5° (12 mm.). 
 
 < Anal. Calcd. for C,C1 3 F,: C, 30.61. Found: C, 30.34. 
 30.45. 
 
 Aceto Derivatives: Trifluoroacetomesitylene. — Trifluoro- 
 acetic anhydride reacts with mesitylene in carbon disulfide 
 with anhydrous aluminum chloride as a catalyst. A 16% 
 yield of impure trifluoroacetomesitylene was obtained, b. p, 
 95-96.5° (25 mm.) , and it was identified by nitration in red 
 liming nitric acid to a dinitro derivative, m. p. 82.5' 
 [ethanol) . 
 
 Anal. Calcd. for C u H 9 F 3 5 N 2 : C, 43.14; H, 2.96 
 ?ound: C, 43.26; H, 3.04. 
 
 Acetodifluoromesitylene .— Difluoromesitylene was 
 rerted to the aceto derivative by the usual Friedel-Crafts 
 eaction with acetic anhydride, 85% yield. Pure acetodi- 
 luoromesitylene distils as a colorless product m. p. 23-24°, 
 i{ p. 120° (20 mm.) or 202-205° (atm.). 
 \ Anal. Calcd. for C n H l2 OF 2 : C, 66.65; H, 6.10. 
 ound: C, 66.65; H, 5.98. 
 
 Tribromoacetodifluoromesitylene. — -The Hofmann hypo- 
 romite reaction 13 on acetodifluoromesitylene gave an 88% 
 ield of the tribromoaceto derivative. Recrystallization 
 ; om ethanol gave long, white needles of pure tribromoaceto - 
 {fluoromesitylene, m. p. 81.5°. 
 
 1 Anal. Calcd. for C u H 9 Br 3 F 2 0: C, 30.38; H, 2.09. 
 found: C, 30.35; H, 2.10. 
 
 Trichloroacetodifluoromesitylene. — This compound was 
 
 Jtained in a 74% yield from acetodifluoromesitylene by 
 
 le Hofmann hypochlorite reaction. 13 The pure compound 
 
 a heavy viscous oil, f. p. ca. —20.5°, b. p. 123° (5 mm.). 
 
 \Anal. Calcd. for C n H 9 Cl,F 2 0: C, 43.81; H, 3.01. 
 
 umd: C, 43.91; H, 2.95. 
 
 eso-Di£Luoro-/3-isodurylic Acid. — Ten grams of the tri- 
 bromoacetodifluoromesitylene was hydrolyzed with diffi- 
 culty to the /3-isodurylic acid derivative by the Fuson and 
 Walker 13 method. Recrystallization from benzene and 
 sublimation gave the pure acid as white needles, m. p. 156- 
 157°. 
 
 Anal. Calcd. for C 10 H 10 F 2 O 2 : C, 60.00; H, 5.04. 
 Found: C, 60.25; H, 4.81. 
 
 e5o-Difluoro-/3-isodurylamide. — A small sample of di- 
 fluoromesidine was diazotized in hydrochloric acid and a 
 Sandmeyer cuprous cyanide reaction gave the crude nitrile 
 as a solid. The nitrile after recrystallization from ethanol 
 and sublimation gave white needles, m. p. 67.5-68°, but an 
 analysis indicated that it was slightly impure. 
 
 Hydrolysis of the impure nitrile by warming in concen- 
 trated sulfuric acid gave the isodurylamide derivative. 
 Attempts to convert the amide to the acid failed even with 
 a nitrosyl sulfuric acid mixture. Recrystallization from 
 ethanol followed by sublimation gave the pure amide as a 
 white powdery material, m. p. 196-197°. 
 
 Anal. Calcd. for C 10 H„F 2 NO: C, 60.29; H, 5.57; N, 
 7.02. Found: C, 60.37; H, 5.61; N, 7.39. 
 
 Miscellaneous Derivatives 
 
 4,6- Dinitro - 2 - fluoromesitylene . — This compound was 
 prepared by the nitration of fluoromesitylene or 4-nitro-2- 
 fluoromesitylene in red, fuming nitric acid. Recrystalli- 
 zation from aqueous ethanol gave white needles, m. p. 95- 
 96.5°. 
 
 Anal. Calcd. for C 9 H 9 0<N 2 F: C, 47.37; H, 3.97; N, 
 12.27. Found: C, 47.40; H.3.96; N, 12.23. 
 
 4-Amino-6-nitro-2 -fluoromesitylene. — A sodium poly- 
 sulfide reduction on the preceding dinitro compound gave a 
 quantitative yield of 4-amino-6-nitro-2-fluoromesitylene. 
 An aqueous ethanol recrystallization gave yellow crystals, 
 m. p. 72°. The acetyl derivative was obtained as almost 
 colorless needles, m. p. 204.5-206°. 
 
 Anal. Calcd. for C H H 13 3 N 2 F: C, 54.99; H, 5.45; N, 
 11.66. Found: C, 54.88; H, 5.42; N, 11.69. 
 
 4,6-Diamino-2-fluoromesitylene. — Reduction of the pre- 
 ceding dinitro- or nitroaminofluoromesitylene gave the 
 corresponding diamine. Recrystallization from high boil- 
 ing petroleum ether gave long, white needles, m. p. 134-135 °. 
 
 Anal. Calcd. for C 9 H 13 N 2 F: C, 64.14; H, 7.78. Found: 
 C, 64.50; H.7.61. 
 
 2-Chloro-4-fluoromesitylene. — This compound was ob- 
 tained in a very small amount as a by-product in the syn- 
 thesis of 2,4-difluoromesitylene. It is a colorless liquid, 
 f. p. -8°, b. p. 203-204°, « 2 °d 1.51046. 
 
 Anal. Calcd. for C 9 H 10 C1F: C, 62.61; H, 5.84. Found: 
 C, 62.61; H, 5.82. 
 
 Summary 
 
 Nitration of mesitylene and difluoromesitylene 
 in anhydrous hydrofluoric acid gave near quantita- 
 tive yields of dinitromesitylene and 2,4-difluoro-6- 
 nitromesitylene, respectively. Difluoro- and tri- 
 fluoromesitylene were synthesized by the Schie- 
 mann reaction in record yields reported for this 
 type of reaction. Various intermediates and 
 derivatives are reported for the fluoromesitylenes. 
 
 Among the products of exhaustive chlorination of 
 trifluoromesitylene, 2,4, 6-tris- (trichloromethyl) - 1 , - 
 3,5-trifluorobenzene and 2,4,6-trichloro-l,3,5-tri- 
 fluorobenzene were identified. 
 
 Urbana, III. 
 
 Received June 9, 1950 
 
G. C. Finger, F. H. Reed and R. E. Oesterling 
 
 [Contribution from the Geochemical Section of the Illinois State Geological Survey ] 
 
 Aromatic Fluorine Compounds. IV. 1,2,3,5-Tetrafluorobenzene 1 
 
 By G. C. Finger, F. H. Reed and R. E. Oesterling 
 
 As a result of the availability of 3-nitro-4-amino- 
 1,2,5-trifluorobenzene 2 in this Laboratory, the 
 synthesis of 1,2,3,5-tetrafluorobenzene has been 
 accomplished, and a study made of some of its 
 properties and derivatives. 
 
 The first step in the synthesis involved the de- 
 amination of 3-nitro-4-amino-l,2,5-trifluorobenzene 
 (I) to 3-nitro-l,2,5-trifluorobenzene (II). Since 
 I is a weakly basic amine, it was diazotized by 
 
 the nitrosylsulfuric phosphoric acid procedure. 3,4 
 Reduction of the diazonium salt by the usual 
 hypophosphorous acid method 6 was unsuccessful 
 until it was discovered that cuprous oxide cat- 
 alyzed the reaction to give a 60-70% yield of 3- 
 nitro-l,2,5-trifluorobenzene. The catalyst not only 
 changed failure to success, but also effected the 
 reduction in minutes rather than hours as is usually 
 the case. The reductive power of the hypophos- 
 phorous acid-cuprous oxide combination was re- 
 flected also in the formation of some 3-amino- 
 1,2,5-trifluorobenzene (III) as a secondary reduc- 
 tion product. This catalyst was used effectively 
 in another instance which will appear in a later 
 publication. In spite of the general application 
 of cuprous oxide in ethanol deaminations, it is 
 only recently that this catalyst had been used in 
 the hypophosphorous acid method by Kornblum 
 and co-workers. 6 
 
 An iron reduction of II readily gave a 90% 
 yield of 3-amino-l,2,5-trifluorobenzene (III), and a 
 subsequent diazotization-Schiemann transforma- 
 tion gave a 40% yield of 1,2,3,5-tetrafluorobenzene 
 (IV). 
 
 1,2,3,5-Tetrafluorobenzene in contrast to the 
 1,2,4,5-isomer 2 boils lower, 83° versus 87°, and can 
 be converted readily to a nitro derivative, 4-nitro- 
 1,2,3,5-tetrafluorobenzene. An iron reduction of 
 the nitro compound gave 4-amino-l,2,3,5-tetra- 
 fluorobenzene. 
 
 (1) Presented before the Organic Division at the 117th Meeting of 
 the American Chemical Society, Philadelphia, Pa., April, 1950. The 
 authors wish to acknowledge the financial assistance of the Office of 
 Naval Research provided by cooperative research contract N6ori-71; 
 Task XIV. Published with the permission of the Chief of the Illinois 
 State Geological Survey. 
 
 (2) Finger, Reed, Burness, Fort and Blough, This Journal, 73, 
 145 (1951). 
 
 (3) Schoutissen, ibid., 66, 4531 (1933). 
 
 (4) C. Weygand, "Organic Preparations," Interscience Publishers, 
 Inc., New York, N. Y., 1945, Ch. 2, p. 110. 
 
 (5) "Organic Reactions," John Wiley and Sons, Inc., New York, 
 N. Y., 1944, Vol. II, Ch. 7, p. 277. 
 
 (6) Kornblum and Cooper, Abstracts of the 116th Meeting, Ameri- 
 can Chemical Society. Atlantic City, N. J., Sept. 1949, p. 50M 
 
 Experimental 7 - 8 
 
 3-Nitro-l,2,5-trifluorobenzene (II). — Approximately 96 
 g. of 3-nitro-4-amino-l,2,5-trifluorobenzene 2 was dissolved 
 in 250 cc. of coned, sulfuric acid with stirring. The clear 
 orange solution was allowed to stand 2-3 hours to come to 
 room temperature. A prolonged time interval appears to 
 be necessary to complete the formation of the amine hy- 
 drosulfate, otherwise diazotization will be quite unsatis- 
 factory. Nitrosylsulfuric acid solution was prepared by 
 adding 40 g. of sodium nitrite to 200 g. of coned, sulfuric acid 
 (precooled to 0°) with stirring, and then cooled to 20°. 
 The amine salt was diazotized at 0° with vigorous stirring 
 by adding the nitrosylsulfuric acid followed by the dropwise 
 addition of 450 cc. of sirupy phosphoric acid (85%). Stir- 
 ring was continued for thirty minutes at 0-10°. 
 
 To the diazonium solution, a slurry of 71 g. of cuprous 
 oxide, 169 g. of sodium hypophosphite and 200 cc. of water 
 was added at such a rate as to control the foaming due to 
 nitrogen evolution, In order to minimize the formation 
 of amine (III) from the nitro (II) compound by a secondary 
 reaction, the exothermic reaction was kept below 50°. 
 After completion of the reaction, within five minutes after 
 the slurry had been added, the reaction mixture was diluted 
 with an equal volume of water and immediately steam dis- 
 tilled. The crude nitro distillate, contaminated with amine, 
 gave a yield of 55-61 g. or 62-67%. An ether extraction 
 of the aqueous distillate increased the yield by 10-15%. 
 Vacuum distillation gave pure 3-nitro-l,2,5-trifluoroben- 
 zene.f.p.cc. -20°,b.p. 187° (micro cap.), « 2 °d 1.4873. 
 
 Anal. Calcd. for C 6 H 2 2 NF 3 : C, 40.69; H, 1.14; N, 
 7.91. Found: C, 40.71; H, 1.38; N, 8.10. 
 
 3-Amino-l,2,5-trifluorobenzene (III). — This compound 
 was prepared by the usual reduction with iron filings iD 
 ammonium chloride solution (0.78 N)* and the amine was 
 removed by steam distillation! Vacuum distillation gave 
 a yield of 95-100 g. or 89-92% of pure 3-amino-l,2,5-tri- 
 fluorobenzene as a colorless liquid, b.p. 76° (20 mm.), , 
 « m d 1.4899. 
 
 Anal. Calcd. for C,H 4 NF 3 : C, 48.99; H, 2.74; N, 
 9.52. Found: C, 49.08; H,2.49; N, 9.69. 
 
 The acetyl derivative was recrystallized from ether as : 
 white granular crystals, m.p. 120-121°. 
 
 Anal. Calcd. for C 8 H 6 ONF 3 : N, 7.41. Found: N, < 
 7.69. 
 
 1,2,3,5-Tetrafluorobenzene (IV).— To 20 cc. of coned.? 
 hydrochloric acid in 10 cc. of water, 14.7 g. of 3-amino-l,2,5- 
 trifluorobenzene was added slowly with rapid stirring, and 
 the amine hydrochloride was formed as a very insoluble salt. 
 
 In order to avoid undesirable side reactions and a low 
 yield, diazotization and diazonium fluoborate precipitation 
 were effected concurrently. To a solution of 20 cc. of coned, 
 hydrochloric acid in 10 cc. of water, there were added, si- 
 multaneously but separately, three reactants, (1) the 
 amine hydrochloride slurry, (2) 7.6 g. of sodium nitrite in 
 10 cc. of water, and (3) 40 g. of sodium fluoborate in 60 cc. 
 of water. The additions required 30 minutes, and the re- 
 action temperature was maintained at 0°. Stirring was 
 continued for one hour at 0-10°. The diazonium fluoborate 
 was removed by filtration at — 10°, dried and a yield of 22 g. 
 or 89% was obtained. Thermal decomposition of the salt 
 and a subsequent steam distillation gave the crude tetra- 
 fluorobenzene, yield 6.5 g. or 43% based on the amine. 
 1,2,3,5-Tetrafluorobenzene is a colorless liquid with a faint 
 sweet odor, f.p. ca. -48°, b.p. 83°, d 2 \ 1.393, » 20 d 1.40381, 
 7 20 23.99. 
 
 Anal. Calcd. for C 6 H 2 F«: C, 48.01; H, 1.35; F, 50.64. 
 Found: C, 48.21; H, 1.43; F, 50.43. 
 
 (7) Analyses by Mr. H. S. Clark, microanalyst for the Illinois Geo 
 logical Survey. 
 
 (8) All melting and boiling points are uncorrected, and freezing 
 points were determined with a toluene thermometer. 
 
 (9) Finger and Reed. This Journal, 66, 1972 (1944). 
 
Jan., 1951 
 
 1 ,3,5-Trifluorobenzene 
 
 3-Chloro-l,2,5-trifluorobenzene. — This compound was 
 obtained as a by-product from IV. It is a colorless liquid, 
 b.p. 121 ° (micro cap.) , w 20 d 1.4550. 
 
 Anal. Calcd. for C 6 H 2 C1Fj: C, 43.27; H, 1.21. Found: 
 C, 43.57; H, 1.24. 
 
 4-Nitro-l,2,3,5-tetrafluorobenzene. — To a mixture of 25 
 g. of 1,2,3,5-tetrafluorobenzene and 30 cc. of coned, sulfuric 
 acid, a solution of 12 cc. of coned, nitric acid in 10 cc. of 
 coned, sulfuric acid was added at 0-10°, followed by stirring, 
 for two hours at 10°. The yield of crude steam distilled 
 nitro compound was 23 g. or 72%. Vacuum distilatlion 
 gave pure 4-nitro-l,2,3,5-tetrafluorobenzene, b.p. 78.5° 
 (20mm.),w 20 Dl.46507,f.p.ca. -5°. 
 
 Anal. Calcd. for CsHOjNF,: C, 36.94; H, 0.52; N, 
 7.18. Found: C, 37.17; H.0.65; N, 7.24. 
 
 4-Amino-l,2,3,5-tetrafluorobenzene. — This amine was 
 obtained from the preceding nitro compound by the usual 
 
 iron reduction 9 in an 86% crude yield. It is a steam dis- 
 tillable liquid, b.p. 65° (20 mm.), m 2 °d 1.46228. 
 
 Anal. Calcd. for C 6 H,NF,: C, 43.65; H, 1.83; N, 
 8.49. Found: C, 43.65; H, 1.79; N, 8.35. 
 
 The acetyl derivative was obtained as white, granular 
 crystals from ethanol, m.p. 140-141°. 
 
 Anal. Calcd. for C 8 H 6 ONF 4 : N.6.76. Found: N, 6.78. 
 
 Summary 
 
 The preparation of 1,2,3,5-tetrafluorobenzene 
 and some of its intermediates is described. 
 
 Cuprous oxide as a catalyst was used to ad- 
 vantage in the hypophosphorous acid deamination 
 method. 
 
 Urbana, Illinois 
 
 June 9, 1950 
 
 [Contribution from the Geochemical Section of the Illinois State Geological Survey] 
 
 Aromatic Fluorine Compounds. V. 1,3,5-Trifluorobenzene 1 
 
 By G. C. Finger, F. H. Reed and J. L. Finnerty 
 
 Among the polyfluorobenzenes there has been 
 considerable speculation as to the probable phys- 
 ical and chemical properties of symmetrical tri- 
 fluorobenzene. This compound has now been 
 synthesized and some of its properties and deriva- 
 tives have been studied. 
 
 The nitration of the acetyl derivative of 4- 
 amino-l,3-difluorobenzene (I) gave 4-amino-5-nitro- 
 1,3-difluorobenzene (II). Reduction of the nitro- 
 amine to the diamine, followed by the formation 
 of 2,3-diphenyl-5,7-difluoroquinoxaline proved the 
 adjacency of the nitro and amine groups. A modi- 
 fied hypophosphorous acid deamination procedure 2 
 gave an average yield of 50% of 5-nitro-l,3- 
 difluorobenzene (III), and a subsequent iron 
 reduction gave 5-amino-l,3-difluorobenzene (IV). 
 
 IV 
 
 V 
 
 A diazotization-Schiemann transformation on the 
 imine gave a 60% yield of 1,3,5-trifluorobenzene 
 ■ 
 
 The boiling point of 1,3,5-trifluorobenzene is 
 i 7 5.5°, thus making it the only fluorinated benzene 
 soiling lower than benzene, 80°. It is odorless, 
 vhereas its isomer 1,2,4-trifluorobenzene, and the 
 text higher homolog, 1,2,4,5-tetrafluorobenzene 
 lave a faint, sweet odor. 
 
 (1) Presented before the Organic Division at the 117th Meeting of 
 le American Chemical Society, Philadelphia. Pennsylvania, April 
 950. The authors wish to acknowledge the financial assistance of the 
 ffice of Naval Research provided by cooperative research Contract 
 
 ['6ori-71; Task XIV. Published with the permission of the Chief of 
 le Illinois State Geological Survey. 
 
 (2) Finger, Reed and OesterUng, TBrs Journal, 73, 152 (1951). 
 
 Chlorination and bromination gave the mono, 
 di and trihalo derivatives. The trichloro deriva- 
 tive was identical with 2,4,6-trichloro-l,3,5-tri- 
 fluorobenzene obtained by the chlorinolysis of 
 trifluoromesitylene. 3 
 
 Symmetrical trifluorobenzene was readily ni- 
 trated to 2-nitro- 1,3,5-trifluorobenzene, and an iron 
 reduction gave the corresponding 2-amino-l,3,5- 
 trifluorobenzene. The amine reacted readily with 
 hydrochloric or sulfuric acids to form the amine 
 salts. The hydrosulfate salt was surprisingly 
 soluble. 
 
 Nitration of the acetyl derivative of IV gave 4- 
 nitro-5-amino-l,3-difluorobenzene; the nitro group 
 entered an ortho position to the amino rather 
 than the expected para. The structure of the 
 nitroamine was proven by deamination to the 
 known 4-nitro- 1 ,3-difluorobenzene . 
 
 Experimental 45 
 
 4 -Amino -5 -nitro -1 ,3-difluorobenzene (II). — In a mixture 
 of 400 cc. of coned, sulfuric acid and 140 cc. of acetic acid, 
 340 g. of 4-acetylamino-l,3-difluorobenzene 6 ' 7 was dis- 
 solved with stirring. After cooling to 20°, a mixture con- 
 taining equal volumes (140 cc. each) of coned, nitric and 
 sulfuric acids was added in fifteen minutes, and the tem- 
 perature allowed to rise to 40°. Stirring was continued for 
 90 minutes at 40-50°. The reaction mixture was poured 
 over ice, and the crude nitroacetylamino compound after 
 drying weighed 400 g. The crude product was hydrolyzed 
 to the nitroamine in 350 cc. of coned, sulfuric acid by heat- 
 ing for two hours on a steam -bath, and then poured over 
 ice. The yield of dry crude product was 228 g. or 65%. 
 The nitroamine is steam distillable, but the purest product 
 was obtained by recrystallization from ethanol followed by 
 sublimation. No tangible evidence was obtained for the 
 existence of other nitroamine isomers. Pure 4-amino-5- 
 nitro-l,3-difluorobenzene is a yellow solid, m.p. 85.5-86.5°. 
 
 Anal. Calcd. for C 6 H<0 2 N 2 F 2 : C, 41.39; H, 2.31; N, 
 16.08. Found: C, 41.48; H.2.14; N, 15.91. 
 
 The acetyl derivative was recrystallized as cream colored 
 
 (3) Finger, Reed, Maynert and Weiner, ibid., 73, 149 (1951) 
 
 (4) Analyses, densities and surface tension measurements by H. S. 
 Clark, microanalyst for the Illinois Geological Survey. 
 
 (5) Melting and boiling points are uncorrected, and the freezing 
 
 (6) Swarts, Rec. trav. chim., 35, 154 (1916). 
 
 (7) Schiemann, J. prakt. Chtm . 140, 97 (1934). 
 
G. C. Finger, F. E. Reed and J. L. Finnerty 
 
 needles from an ethanol-chloroform mixture, m.p. 142- 
 143°. 
 
 Anal. Calcd. for C 8 H 6 3 N 2 F 2 : N, 12.96. Found: N, 
 12.66. 
 
 4,5-Diamino-l,3-difluorobenzene. — Four grams of the 
 preceding nitroamine (II) was reduced to the diamine by- 
 addition with stirring to 24 g. of stannous chloride in 30 cc. 
 of coned, hydrochloric acid. The reaction mixture after 
 being made alkaline with sodium hydroxide solution, was 
 extracted with ether, and evaporation of the ether extract 
 gave the crude diamine. Recrystallization from an n- 
 pentane-ether mixture followed by sublimation gave the 
 4,5-diamino-l,3-difluorobenzene as white crystals, m.p. 
 48.5-49.5°. 
 
 One gram of the diamine was condensed with 1.4 g. of 
 benzil in 70 cc. of water by heating and stirring for one hour. 
 The insoluble crude product was purified by recrystalliza- 
 tions from ethanol and methanol and also sublimations to 
 give pure 2,3-diphenyl-5,7-difluoroquinoxaline as a white 
 solid, m.p. 137-138°. 
 
 Anal. Calcd. for C 20 H 12 N 2 F 2 : C, 75.46; H, 3.80; N, 
 8.80. Found: C, 75.56; H,3.73; N, 8.87. 
 
 5-Nitro-l,3-difluorobenzene (III). — The 4-amino-5-nitro- 
 1,3-difluorobenzene was diazotized by the nitrosylsulfuric- 
 phosphoric acid procedure 8 ' 8 for weakly basic amines. The 
 final deamination step with hypophosphorous acid 10 was 
 successful only when cuprous oxide was used as a catalyst. 
 
 A solution of 67 g. of pure 4-amino-5-nitro-l,3-difluoro- 
 benzene (II) in 150 cc. of coned, sulfuric acid was stirred for 
 three hours to form the amine salt. Nit rosylsulf uric acid 
 was prepared by dissolving 28 g. of sodium nitrite in 150 cc. 
 of coned, sulfuric acid (precooled to 0°) with stirring, and 
 the mixture cooled to 20°. To the amine hydrosulfate at 
 0°, the nitrosylsulfuric acid was added and the reaction 
 temperature allowed to rise to 10°. In order to complete 
 the diazotization , 300 cc. of 85% phosphoric acid was 
 added slowly in two hours while the temperature was main- 
 tained at 10-15°. 
 
 To the rapidly stirred diazonium solution at 0°, a slurry 
 of 250 g. of sodium hypophosphite, 35 g. of cuprous oxide 
 and 150 cc. of water was added slowly and the exothermic 
 reaction kept below 35°. Nitrogen evolution was practi- 
 cally complete after 80% of the slurry had been added. The 
 reaction mixture, after dilution with an equal volume of 
 water and transference to a large flask (12-1.) was cautiously 
 steam distilled. A large flask is essential as the hypophos- 
 phorous acid, near the end of the steam distillation, reduces 
 the copper salts by an almost uncontrollable exotherma 
 reaction causing the entire mixture to superheat and foam 
 suddenly. The yield of pure 5-nitro-l,3-difluorobenzene 
 was 37 g. or 60%, f.p. ca. 17.5°, b.p. 78-79° (20 mm.) or 
 176-177° (atm.). 
 
 Anal. Calcd. for C 6 H 3 2 NF 2 : C, 45.30; H, 1.90; N 
 8.80. Found: C, 45.50; H, 1.70; N, 8.92. 
 
 5-Amino-l,3-difluorobenzene (IV). — To a stirred, re- 
 fluxing mixture of 140 g. of iron filings in 200 cc. of ammo- 
 nium chloride solution (0.78 N) , 100 g. of 5-nitro-l,3-di- 
 fluorobenzene was added slowly. The reduction was com- 
 plete in two hours. Removal of the amine by steam dis- 
 tillation gave a yield of 75 g. or 92%. Vacuum distillation 
 gave the pure amine as a white solid, m.p. 39-40°, b.p. 
 81-82° (20 mm.). 
 
 Anal. Calcd. for C 6 H S NF 2 : C, 55.82; H, 3.90; N, 
 10.84. Found: C, 55.89; H.4.03; N, 11.11. 
 
 The acetyl derivative was obtained as a white solid by 
 successive recrystallizations from ethanol and benzene fol- 
 lowed by sublimation, m.p. 129-129.5°. 
 
 Anal. Calcd. for C 8 H 7 ONF 2 : C, 56.14; H, 4.13; N, 
 8.18. Found: C, 55.93; H,4.09; N.8.40. 
 
 4-Nitro-5-amino-l,3-difluorobenzene. — To a solution of 
 7 g. of the acetyl derivative of IV in 20 cc. of coned, sulfuric 
 and 10 cc. of acetic acids, a mixture of coned, nitric-sul- 
 furic acids (3.5 cc. of each acid) was added, and the reac- 
 tion temperature maintained at 30-40°. Stirring was con- 
 tinued for 90 minutes after addition. After isolation of the 
 
 (8) Schoutissen, This Journal, 55, 4531 (1933). 
 
 (9) C. Weygand, "Organic Preparations," Interscience Publishers, 
 Inc., New York, N. Y., 1945, Ch. 2, p. 110. 
 
 (10) "Organic Reactions," John Wiley and Sons, Inc., New York, 
 N. Y., 1944, Ch. 7, p. 277. 
 
 crude reaction product, it was hydrolyzed to the nitroamine 
 by warming with 10 cc. of coned, sulfuric acid. Recrys- 
 tallization from ethanol and m-fluorobenzotrifluoride, 11 and 
 a final sublimation gave pure 4-nitro-5-amino-l,3-difluoro- 
 benzene as orange crystals, m.p. 107-108°. No evidence 
 was found for the formation of other isomers, although this 
 compound is isomeric with II. 
 
 Anal. Calcd. for C 6 H 4 N 2 2 F 2 : C, 41.39; H, 2.31; N, 
 16.08. Found: C, 41.46; H, 2.12; N, 16.17. 
 
 Recrystallization of the acetyl derivative from w-fluoro- 
 benzotrifluoride gave white needles, m.p. 137-138°. 
 
 The structure of the nitroamine was established by de- 
 amination to 4-nitro-l,3-difluorobenzene 6 using the special 
 procedure applied to II. 
 
 1,3,5-Trifluorobenzene (V).— To 200 cc. of coned, hy- 
 drochloric acid with rapid stirring, 75 g. of melted 5-amino- 
 1,3-difluorobenzene was added slowly, and the amine hydro- 
 chloride paste was diluted with 80 cc. of water. Diazotiza- 
 tion was effected at 0° by the addition of 42 g. of sodium 
 nitrite as a 40% solution. To the clear diazonium solution, 
 160 g. of sodium fluoborate was added as a 40% solution, 
 and the white diazonium fluoborate precipitate was filtered 
 at -10°. The yield of dried fluoborate salt was 132 g. or 
 98%. The salt was thermally decomposed 12 by continuous 
 heating, and steam distillation of the crude product gave a 
 yield of 44 g. or 62.8% of trifluorobenzene based on the 
 amine. A further treatment with cold coned, sulfuric acid 
 followed by distillation through a packed 5-ft. vacuum- 
 jacketed column gave pure 1,3,5-trifluorobenzene as a 
 colorless, odorless liquid, f.p. ca. —5.5°, b.p. 75.5°, d 20 t 
 1.277, « 2 °d 1.41403, 7 20 27.16 dynes/cm. 
 
 Anal. Calcd. for C 6 H 3 F 3 : C, 54.56; H, 2.29; F, 43.15. 
 Found: C, 54.59; H.2.19; F, 42.90. 
 
 l-Chloro-3,5-difluorobenzene. — This compound was ob- 
 tained as a by-product from the synthesis of V. The pure 
 compound is a colorless liquid, b.p. 118.5°, » 20 d 1.4683. 
 
 Anal. Calcd. for C 6 H 3 C1F 2 : C, 48.51; H,2.03. Found: 
 C, 48.59; H.2.16. 
 
 Chlorination of 1,3,5-Trifluorobenzene. — A sample of 
 1,3,5-trifluorobenzene was chlorinated for six hours by 
 bubbling chlorine through it in the presence of an iron cata- 
 yst. The chief product was 2-chloro-l,3,5-trifluoroben- 
 zene, f.p. ca. -2 to -3°, b.p. 124°, d 2 °< 1.463, « 2 °d 1.45505, 
 7 20 28.59 dynes/cm. 
 
 Anal. Calcd. for C 6 H 2 C1F 3 : C, 43.27; H, 1.21. Found: 
 C, 43.52; H, 1.26. 
 
 Chlorination by the sulfuryl chloride-sulfur monochloride 
 method 13 in the presence of aluminum chloride gave chiefly 
 the dichloro compound along with a small amount of the tri- 
 chloro derivative. The reaction product was steam dis- 
 tilled, and purified by fractional distillation. Pure 2,4- j 
 dichloro-1 ,3 ,5-trifiuorobenzene is a colorless liquid, f.p. 
 ca. -10 to -11°, b.p. 161.5-162°, d M , 1.599, w 2 °d 1.48637, : 
 •y 20 30.41 dynes/cm. 
 
 Anal. Calcd. for C 6 HC1 2 F 3 : C, 35.85; H, 0.50; F, 
 28.36. Found: C, 35.91; H, 0.70; F, 28.41. 
 
 The trichloro derivative was isolated as a white solid by 
 freezing the preceding high boiling fraction. Vacuum sub- 
 limation gave pure 2,4,6-trichloro-l,3,5-trifluorobenzene, 
 m.p. 60-62°. A mixed melting point with a pure sample.' 
 (m.p. 62-63°) obtained by the chlorinolysis of trifluorome- 
 sitylene 3 showed no depression. 
 
 Bromination of 1,3,5-Trifluorobenzene. — Liquid bromine 
 was added drop wise to 1,3,5-trifluorobenzene in the pres- 
 ence of iron with stirring at room temperature. A molar 
 ratio of reactants gave the monobromo compound as the 
 chief product and a small amount of the dibromo derivative. 
 After steam distillation, the reaction mixture was fraction- 
 ally distilled. 2-Bromo-l,3,5-trifluorobenzene is a colorless 
 liquid with an unpleasant odor, f.p. ca. 3.5°, b.p. 140.5°, 
 k 2 °d 1.48385. 
 
 Anal. Calcd. for C 6 H 2 BrF 3 : C, 34.15; H, 0.96. Found: 
 C, 34.16; H.0.96. 
 
 2,4-Dibromo-l,3,5-trifluorobenzene was obtained from 
 the higher boiling fraction in the preceding experiment. 
 
 (11) This compound has been found to be an excellent recrystalliza- 
 tion solvent for many polyfluoronitroamines and their derivatives. 
 
 (12) Finger and Reed, This Journal, 66, 1972 (1944). 
 
 (13) Cutter and Brown, J. Chem. Ed., 21, 443 (1944). 
 
Jan 1951 
 
 1,3,5-Trifluorobenzene 
 
 155 
 
 The data on the pure compound are i 
 
 5-29°, b.p. 
 
 Anal. Calcd. for C 6 HBr 2 F 3 : C, 24.86; H, 0.35; F, 
 19.66. Found: C.25.02; H.0.40, F, 19.44. 
 
 A large excess of bromine along with heating converted 
 the monobromo compound to the tribromo derivative. 
 Alternate vacuum sublimation and recrystallization from 
 ethanol gave pure 2,4,6-tribromo-l,3,5-trifluorobenzene, 
 m.p. 98-98.5°. 
 
 Anal. Calcd. for CeBraF,: C, 19.54. Found: C, 19.55. 
 
 2-Nitro-l,3,S-trifluorobenzene. — To a well-stirred mix- 
 ture of 36 g. of 1,3,5-trifluorobenzene in 50 cc. of coned, 
 sulfuric acid, a nitrating solution of 19 cc. of coned, nitric 
 and 17 cc. of coned, sulfuric acids was added at such a rate 
 that the temperature was controlled at 50°. At the end, 
 the temperature was raised to 70° for sixty minutes. The 
 reaction mixture was poured over ice, and the yield of crude 
 nitro compound was 41 g. or 85%. Pure 2-nitro-l,3,5- 
 trifluorobenzene is a heavy, pale yellow liquid, f.p. ca. 
 3.5°, b.p. 81° (20 mm.) or 172° (atm.), « 2 °d 1.47833. 
 
 Anal. Calcd. for CsH 2 2 NF 3 : C, 40.69; H, 1.14; N, 
 7.91. Found: C, 40.76; H, 1.16; N, 8.17. 
 
 2-Amino-l,3,5-trifluorobenzene. — This amine was pre- 
 pared from the preceding nitro compound by the same gen- 
 eral method as indicated for IV. A 90% yield of crude amine 
 was obtained. Vacuum distillation gave pure 2-amino- 
 1,3,5-trifluorobenzene as a white solid, m.p. 33-34°, b.p. 
 57° (22 mm.). 
 
 Anal. Calcd. for C 6 H 4 NF 3 : C, 48.99; H, 2.74; N, 
 9.52. Found: C, 48.99; H.2.69; N, 9.58. 
 
 The amine forms a very soluble hydrochloride and hy- 
 drosulfate in contrast to most other fluorinated anilines. 
 
 The acetyl derivative was sublimed after preliminary 
 recrystallizations from ethanol and benzene, m.p. 152-153°. 
 
 Anal. Calcd. for C 8 H 6 ONF 3 : C, 50.80; H, 3.20; N, 
 7.41. Found: C, 50.70; H, 3.11; N, 7.58. 
 
 Summary 
 
 The synthesis and properties of 1,3,5-trifluoro- 
 benzene, its intermediates and some of its deriva- 
 tives have been described. 
 
 Urbana, Illinois 
 
 Received June 9, 1950