See image — IUPAC and Nomenclature Chemistry Question

💡 Solution & Explanation

Step 1: Identify the structure. The compound is: CH2(Cl) — C(CH3) = CH — CH2OH. This is a four-carbon chain with a chlorine on one terminal carbon, a methyl branch on the adjacent carbon, a double bond between C2 and C3, and a hydroxyl group on the other terminal carbon. Step 2: Choose the principal characteristic group. The hydroxyl group (-OH) is the principal characteristic group (alcohol), so it gets the lowest possible locant. Number the chain starting from the CH2OH end. Step 3: Number the carbon chain. Numbering from the CH2OH end: - C1: CH2OH (hydroxyl group) - C2: CH= (part of double bond) - C3: C(CH3)= (part of double bond, bears methyl substituent) - C4: CH2Cl (bears chlorine substituent) Step 4: Assign locants. - -OH at C1 → suffix: but-...-1-ol - Double bond between C2 and C3 → but-2-en-1-ol - Methyl group at C3 → 3-methyl - Chloro group at C4 → 4-chloro Step 5: Assemble the name. Alphabetical order of prefixes: chloro before methyl. Name: 4-Chloro-3-methylbut-2-en-1-ol. Step 6: Evaluate other options. - (b) 1-Chloro-2-methylbut-2-en-4-ol: numbering from the Cl end gives OH at C4, but OH should receive lowest locant, so this numbering is incorrect. - (c) 4-Chloro-1-hydroxy-3-methylbut-2-ene: 'hydroxy' is used as a prefix only when a higher-priority group is present; here -OH is the principal group and must appear as a suffix (-ol), not as a prefix. - (d) 1-Chloro-4-hydroxy-2-methylbut-2-ene: same error as (c) with incorrect numbering. Therefore, the correct answer is A.