Cis-Trans Isomers in Organic Chemistry

Which of the following compounds form cis-trans isomers?

a. 2,3-dimethylpentane

b. 2,2-dimethylpentane

c. 2,2-dimethylcyclopentane

d. 1-ethyl-2-methylcyclopentane

Final answer: The compound that forms cis-trans isomers is d. 1-ethyl-2-methylcyclopentane.

Answer:

Isomers are molecules with the same chemical formula but different arrangement of atoms. Cis-trans isomers, also known as geometric isomers, occur when two functional groups are positioned differently around a rigid bond.

In the case of 1-ethyl-2-methylcyclopentane, it has a double bond between two carbon atoms. The methyl and ethyl groups can be arranged on the same side of the double bond (cis) or on opposite sides (trans), resulting in two different isomers.

In contrast, the compounds 2,3-dimethylpentane and 2,2-dimethylpentane do not have any functional groups that can create cis-trans isomers. Similarly, 2,2-dimethylcyclopentane does not have a double bond to allow for cis-trans isomerism. Therefore, the compound that forms cis-trans isomers is 1-ethyl-2-methylcyclopentane, which is the correct option.