JEE Main 2024 · 31 January · morning · Single correct · +4 / −1
Given below are two statements:
Statement I: IUPAC name of HO-CH₂-(CH₂)₃-CH₂-COCH₃ is 7-hydroxyheptan-2-one.
Statement II: 2-oxoheptan-7-ol is the correct IUPAC name for above compound. In the light of the above statements, choose the most appropriate answer from the options given below:
- (a) Statement I is incorrect but Statement II is correct.
- (b) Statement I is correct but Statement II is incorrect.
- (c) Both Statement I and Statement II are correct.
- (d) Both Statement I and Statement II are incorrect.
Answer and solution
Answer (b) Statement I is correct but Statement II is incorrect.
Solution
Chemistry ma’am · 5 steps
The ketone outranks the alcohol, so it takes the suffix '-one' and the OH becomes a 'hydroxy' prefix.
- Count the chain. HO-CH₂ (1) + (CH₂)₃ (3) + CH₂ (1) + C=O (1) + CH₃ (1) gives a straight chain of 7 carbons, so the parent is heptane.
- Pick the principal group. In IUPAC priority, a ketone ranks above an alcohol. So the ketone is named as the suffix -one, and the -OH is named as the prefix hydroxy.
- Number the chain. Start from the end nearer the C=O: CH₃ is C1 and the carbonyl carbon is C2. Counting on, the CH₂OH carbon is C7. The name is 7-hydroxyheptan-2-one, so Statement I is correct.
- Check Statement II. '2-oxoheptan-7-ol' treats the alcohol as the principal group and the ketone as an 'oxo' prefix. That reverses the priority order, and it also gives the principal group the high locant 7 instead of the lowest possible one.
- So. Statement I is correct and Statement II is incorrect, which is option (b).
The idea to keep. Decide the principal group first, using the priority order (acid > ester > aldehyde > ketone > alcohol > amine). It alone gets the suffix and the lowest locant. Every other group becomes a prefix.
Answer from the NTA final answer key. Solution by PrepWiser.