1,3cyclo.cdx


6

5

1 2

3

4
H

H

H

CH3
H

HH

CH3

HH

H H

5

6

1 2

3

4
H

H

H

CH3
H

HCH3

H

HH

H H

6 1
2

3

4

5

H H

CH3

H

H

H

CH3

H

H

H

H

H
6 1

2

3

4

5

H
CH3

H

H

H

H

CH3

H

H

H

H

H

trans-1,3 dimethylcyclohexane cis-1,3 dimethylcyclohexane

Lowest energy configuration of 
trans-1,2 dimethylcyclohexane.

Lowest energy configuration of 
cis-1,2 dimethylcyclohexane.

Newman Projection (looking down the 6,5 
and 2,3 C-C bonds) of trans isomer showing 
the diaxial interactions between hydrogens 
and methyl group.

H

H
H

H
H

CH3
H

H

H

H
H

H
H

CH3
H

H

CH3 H

H CH3H H

H H

Newman Projection (looking down the 6,5 
and 2,3 C-C bonds) of cis isomer showing 
the diaxial interactions between hydrogens 
and equitorial methyl groups.

Figure 3: Structural Formulas as Models.  The top row shows the two distinct structural formulas for 
1,3 dimethyl cyclohexane.  These formulas reveal only the information contained in the systematic 
names, which are reproduced below the corresponding formula.  The second and third rows contain 
structural formulas that bring out the steric differences between the lowest energy chair 
configurations of these distinct compounds.  The assignment of boiling points based on structural 
formulas used as names -- the first row -- was incorrect.  The correct assignment required recognizing 
and comparing the conformations available to these compounds as facilitated by the formulas in the 
second and third rows.