Question

Draw both cis- and trans-1,4-dimethylcyclohexane in their more stable chair conformations.

(a) How many stereoisomers are there of cis-1,4-dimethylcyclohexane, and how many of trans-1,4-dimethylcyclohexane?

---

(b) Are any of the structures chiral?

---

(c) What are the stereochemical relationships among the various stereoisomers of 1,4-dimethylcyclohexane?

Answer 1

The possible chair conformations of cis chair conformation of 1,4-dimethylcyclohexane are,

The possible chair conformations of trans chair conformation of 1,4-dimethylcyclohexane are,

Thus, the cis and trans forms of 1,4-dimethylcyclohexane in their more stable forms are shown below:

(a)

Stereoisomer of cis-1,4-dimethylcyclohexane is,

Stereoisomer of trans-1,4-dimethylcyclohexane is,

Thus, one stereoisomer for cis-1,4-dimethylcyclohexane, and one stereoisomer for trans-1,4-dimethylcyclohexane are there.

(b)

In the above isomers, there are no chiral compounds. This is because cis-1,4-dimethylcyclohexane has a plane of symmetry whereas trans-1,4-dimethylcyclohexane has a center of symmetry. This is can be explained as follows:

So, there are no chiral compounds.

(c)

cis and trans isomers are always diastereomers, they are stereoisomers that do not mirror images of one another. Therefore, the stereoisomers of 1,4-diemethylcyclohexane are diastereomers.

The question answer is above .