$\mathrm{R}-\mathrm{CN} \xrightarrow[\text { (ii) } \mathrm{H}_{2} \mathrm{O}]{\text { (i) } \text { DIBAL-H }} \mathrm{R}-\mathrm{Y}$ Consider the above reaction and identify " Y "

(B) $-\mathrm{CH}_{2} \mathrm{NH}_{2}$

JEE Main · 2021 · 27 Jul 2021 · Shift 2 · Aldehydes Ketones and Carboxylic Acids

R - CN (i) DIBAL-H (ii) H_{2} O R - Y

Consider the above reaction and identify " Y "

(A)-COOH
(B) $- CH_{2} NH_{2}$
(C)-CHO✓ Correct
(D) $- CONH_{3}$

Answer: (C)

Solution

DIBAL-H (diisobutylaluminium hydride) is a selective reducing agent. When a nitrile (

R - CN

) is treated with DIBAL-H followed by hydrolysis with water, it is reduced to an aldehyde (

R - CHO

). Complete reduction to a primary amine would require stronger conditions (e.g.,

LiAlH_{4}

). Therefore, Y is -CHO.

JEE Main · 2021 · 27 Jul 2021 · Shift 2 · Single correct option

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