Q.54. - Organic Chemistry

Question

Question: Draw the two possible chair conformations for cis-1,3-dimethylcyclohexane. Which conformation, if either, is more stable?

Step-by-Step Solution

Answer

Answer

The two possible chair conformations are as follows:

 and 

The more stable conformation is that in which the methyl groups are at equatorial positions.

Step 1: Cis and trans configuration in the chair conformation

The cis conformation is obtained when two locations have axial (it may be up or down) substitution or equatorial substitution. Trans conformation is in contrast to cis.

 

The stable chair conformation is that in which the bulky groups are at equatorial positions.   

Step 2: Explanation

The cis-1,3-dimethylcyclohexane can be shown by substituting the two-methyl group at the axial position or two methyl groups at equatorial positions.

Least stable conformation

Most stable conformation

 

Here, ax represents axial and eq represents equatorial.

 

The more stable conformation of cis-1,3-dimethylcyclohexane is the one in which two methyl groups are at equatorial positions. In this conformation, there is minimum electron cloud distortion.