Concept:The compound contains a cyclopentane ring with a hydroxyl group, so it is named as a cyclopentanol. The carbon bearing the
−OH group must be given the lowest possible locant, which is 1.
Explanation:Number the cyclopentane ring starting from the carbon attached to the
−OH group.
From the structure, the ethyl group (
C2​H5​) is present at carbon 2, and the methyl group (
CH3​) is present at carbon 3.
This numbering gives the locant set
(2,3), which is lower than the alternative set
(4,5) obtained by numbering in the opposite direction.
According to IUPAC rules, substituents are arranged alphabetically in the name.
Since ethyl comes before methyl alphabetically, the ethyl group is named first.
Therefore, the correct IUPAC name is 2-ethyl-3-methylcyclopentanol.
Option C is incorrect because it places methyl before ethyl, violating alphabetical order.
Options B and D are incorrect because they do not match the correct numbering or position of substituents.
Answer:Option A: 2-Ethyl-3-methylcyclopentanol
