# How many stereoisomers does cis-1/3-Dimethylcyclohexane have?

## How many stereoisomers does cis-1/3-Dimethylcyclohexane have?

three stereoisomers
As a result, only three stereoisomers of 1,3-dimethylcyclohexane are observed: cis-1,3-dimethylcyclohexane, which is a meso compound, and a pair of trans-1,3-dimethylcyclohexane enantiomers. The relative configuration of the cis isomer is (1R*,3S*) while the relative configuration of the trans isomer is (1R*,3R*).

What is the most stable conformation of cis-1/3-Dimethylcyclohexane?

diequatorial conformer
Because large groups prefer to be equatorial, the most stable conformer for cis-1,3-dimethylcyclohexane is the diequatorial conformer, shown here. The diaxial conformer would be higher in energy.

What is the order of stability of 1/3-Dimethylcyclohexane?

For trans-1,3-dimethylcyclohexane both conformations have one methyl axial and one methyl group equatorial. Each conformer has one methyl group creating a 1,3-diaxial interaction so both are of equal stability.

### What is a 1/3-Diaxial interaction?

1,3-Diaxial interactions are steric interactions between an axial substituent located on carbon atom 1 of a cyclohexane ring and the hydrogen atoms (or other substituents) located on carbon atoms 3 and 5.

Are there any stereoisomers of 1, 3 dimethylcyclohexane?

As a result, only three stereoisomers of 1,3-dimethylcyclohexane are observed: cis -1,3-dimethylcyclohexane, which is a meso compound, and a pair of trans -1,3-dimethylcyclohexane enantiomers. Tab.2 The relative configuration of the cis isomer is (1 R*, 3 S*) while the relative configuration of the trans isomer is (1 R*, 3 R*).

What are the conformations of CIS and trans stereoisomers?

A similar conformational analysis can be made for the cis and trans stereoisomers of 1,3-dimethylcyclohexane. For cis -1,3-dimethylcyclohexane one chair conformation has both methyl groups in axial positions creating 1,3-diaxial interactions.

#### Which is more stable cis or trans 1, 3, 4 dimethylcyclohexane?

The trans-1,3-dimethylcyclohexane isomer , on the other hand, has one methyl axial in both ring-flip conformers, so that it is less stable than the cis isomer by 1.8 kcal/mol. Both trans-1,4-dimethylcyclohexane and cis-1,3-dimethylcyclohexane have essentially the same energy, since neither one of them has any strain at all.

Why do CIS 1, 4 disubstitued cyclohexanes have two chair conformations?

Based on the table above, cis -1,4-disubstitued cyclohexanes should have two chair conformations each with one substituent axial and one equatorial. Based on this, we can surmise that the energy difference of the two chair conformations will be based on the difference in the 1,3-diaxial interactions created by the methyl and chloro substituents.