Question

Which one of the following compounds can exist as cis-trans isomers?

• A. 2-Methylhex-2-ene
• B. 1,1-Dimethylcyclopropane
• C. 1,2-Dimethylcyclohexane
• D. Pent-1-ene

Hint:

For cis-trans isomerism to occur, the compound must have a double bond with two different groups attached to each of the carbons involved in the double bond.

Answer 1

The Correct Option is A

Cis-trans isomerism arises from differing groups on each carbon of a double bond, yielding non-superimposable mirror images. Analysis of each option: - Option (1) 2-Methylhex-2-ene: The double bond is between C2 and C3. C2 has a methyl group and a hydrogen atom. C3 has a methyl group and an ethyl group. Since each carbon of the double bond has two different substituents, cis-trans isomerism is possible. - Option (2) 1,1-Dimethylcyclopropane: Both methyl groups are attached to C1 of the cyclopropane ring. Due to the identical substituents on C1, cis-trans isomerism is not possible. - Option (3) 1,2-Dimethylcyclohexane: This molecule is a saturated hydrocarbon and lacks a double bond. Therefore, cis-trans isomerism is not applicable. - Option (4) Pent-1-ene: Although a double bond exists, C1 of the double bond is attached to two hydrogen atoms, and C2 is attached to a methyl group and an ethyl group. Since C1 has identical substituents, cis-trans isomerism is not possible. Consequently, 2-Methylhex-2-ene is the only compound among the options that exhibits cis-trans isomerism.