Advices For Studying Organic Chemistry

CH 3 CH 3

CH 3 CH 3

H 3 C

CH 3

H 3 C CH^3

cis-1,4-Dimethylcyclohexane

Symmetry plane

Top view

Chair view

trans-1,4-Dimethylcyclohexane

Diastereomers

(stereoisomers but not mirror images)

Symmetry plane

H

H

H H

Figure 5.17 The cis and trans forms of 1,4-dimethylcyclohexane are diastereomers
of each other. Both compounds are achiral.

2. 1,3-Dimethylcyclohexanes: three isolable stereoisomers
   
   
   1. 1,3-Dimethylcyclohexane has two stereocenters ⇒ 4 stereoisomers are possible.
   
   
   2. cis-1,3-Dimethylcyclohexane has a plane of symmetry and is achiral.
   
   
   
   

H

H 3 C CH 3

CH 3

CH 3

Symmetry plane

H

Figure 5.18 cis-1,3-Dimethylcyclohexane has a plane of symmetry and is therefore
achiral.

3) trans-1,3-Dimethylcyclohexane does not have a plane of symmetry and exists as