NEET 2025 · ChemistryCarbonyl reductionPrevious Year Question
The major product of the following reaction is: 4-oxo-4-phenylbutanenitrile \ce{C6H5-CO-CH2-CH2-CN} is treated with (i) \ce{CH3MgBr} (excess) and then (ii) \ce{H3O+}.
- A.(A) \ce{C6H5-CH(OH)-CH2-C(CH3)2-OH}
- B.(B) \ce{C6H5-CO-CH2-CH2-CO-CH3} (a diketone)
- C.(C) \ce{C6H5-C(CH3)(OH)-CH2-CN}
- D.(D) \ce{C6H5-C(CH3)(OH)-CH2-CH2-CN}✓
Correct Answer
(D) (D) \ce{C6H5-C(CH3)(OH)-CH2-CH2-CN}
Solution & Explanation
\textbf{Answer:} (D) \ce{C6H5-C(CH3)(OH)-CH2-CH2-CN} \textbf{Solution:} The Grignard reagent \ce{CH3MgBr} adds to the more reactive ketone carbonyl. Nucleophilic addition of the methyl carbanion to the \ce{C=O} carbon, followed by acidic work-up, converts the ketone into a tertiary alcohol bearing a new methyl group on the benzylic carbon. The nitrile group is retained, giving \ce{C6H5-C(CH3)(OH)-CH2-CH2-CN}.
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