Advices For Studying Organic Chemistry

Enantiomers

(+)- and (−)-trans-1,3-Dimethylcyclohexane

CH 3

H 3 C CH 3

CH 3

CH 3

H 3 C CH 3

CH 3

Mirrorplane

3. 1,2-Dimethylcyclohexanes: three isolable stereoisomers
   
   
   1. 1,2-Dimethylcyclohexane has two stereocenters ⇒ 4 stereoisomers are possible.
   
   
   2. trans-1,2-Dimethylcyclohexane has no plane of symmetry ⇒ exists as a pair of
      enantiomers.
   
   
   
   

H

CH 3

CH 3

H 3 C

H 3 C

H

H

H

(a) (b)

Figure 5.20 trans-1,2-Dimethylcyclohexane has no plane of symmetry and exists as
a pair of enantiomers (a and b). [Notice that we have written the most
stable conformations for (a) and (b). A ring flip of either (a) or (b)
would cause both methyl groups to become axial.]
3) cis-1,2-Dimethylcyclohexane:

CH 3

CH 3

CH 3

H 3 C

H

H

(c)

H

H

(d)