For every disubstituted cyclohexane, we can draw a Haworth projection and two chair conformations. This is true for all disubstituted cyclohexanes, including cis-1,3-dimethylcyclohexane and trans-1,3-dimethylcyclohexane.

True or False?

True.

Explanation:

Both Haworth and chair conformations can be used to represent disubstituted cyclohexanes. However, the energies for each chair conformation are different, thus one conformation will be more favored than the other.

For the 1,3-cyclohexanes, the most stable conformation of the cis isomer has both methyl groups in equatorial positions. Any conformation of the trans isomer puts a methyl group in an axial position. Therefore, the trans isomer has more energy than the cis isomer. We need to remember, though, that cis and trans isomers can’t be interconverted and there is no equilibrium between these.