The major product of the following reaction is: 4-oxo-4-phenylbutanenitrile C6H5-CO-CH2-CH2-CN is treated with (i) CH3MgBr (excess) and then (ii) H3O+.

NEET 2025 · ChemistryCarbonyl reductionPrevious Year Question

The major product of the following reaction is: 4-oxo-4-phenylbutanenitrile $C X_{6} H X_{5} - CO - CH X_{2} - CH X_{2} - CN$ is treated with (i) $CH X_{3} MgBr$ (excess) and then (ii) $H X_{3} O X^{+}$ .

Answer: (D) (D) $C X_{6} H X_{5} - C (CH X_{3}) (OH) - CH X_{2} - CH X_{2} - CN$ . \textbf{Answer:} (D) $C X_{6} H X_{5} - C (CH X_{3}) (OH) - CH X_{2} - CH X_{2} - CN$ \textbf{Solution:} The Grignard reagent $CH X_{3} MgBr$ adds to the more reactive ketone carbonyl.

A.(A) $C X_{6} H X_{5} - CH (OH) - CH X_{2} - C (CH X_{3}) X_{2} - OH$
B.(B) $C X_{6} H X_{5} - CO - CH X_{2} - CH X_{2} - CO - CH X_{3}$ (a diketone)
C.(C) $C X_{6} H X_{5} - C (CH X_{3}) (OH) - CH X_{2} - CN$
D.(D) $C X_{6} H X_{5} - C (CH X_{3}) (OH) - CH X_{2} - CH X_{2} - CN$ ✓

Correct Answer

(D) (D) $C X_{6} H X_{5} - C (CH X_{3}) (OH) - CH X_{2} - CH X_{2} - CN$

Solution & Explanation

\textbf{Answer:} (D) $C X_{6} H X_{5} - C (CH X_{3}) (OH) - CH X_{2} - CH X_{2} - CN$ \textbf{Solution:} The Grignard reagent $CH X_{3} MgBr$ adds to the more reactive ketone carbonyl. Nucleophilic addition of the methyl carbanion to the $C = O$ 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 $C X_{6} H X_{5} - C (CH X_{3}) (OH) - CH X_{2} - CH X_{2} - CN$ .

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The major product of the following reaction is: 4-oxo-4-phenylbutanenitrile CX6​HX5​−CO−CHX2​−CHX2​−CN is treated with (i) CHX3​MgBr (excess) and then (ii) HX3​OX+.

Solution & Explanation

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The major product of the following reaction is: 4-oxo-4-phenylbutanenitrile $C X_{6} H X_{5} - CO - CH X_{2} - CH X_{2} - CN$ is treated with (i) $CH X_{3} MgBr$ (excess) and then (ii) $H X_{3} O X^{+}$ .