The major product of the following reaction is \[ \mathrm{R}-\mathrm{C} \equiv \mathrm{~N} \xrightarrow[(2) \mathrm{H}_{2} \mathrm{O}]{(1) \mathrm{AlH}(\mathrm{i}-\mathrm{Bu})_{2}} ? \]

(D) $\mathrm{RCH}_{2} \mathrm{NH}_{2}$

JEE Main · 2019 · 09 Jan 2019 · Shift 1 · Aldehydes Ketones and Carboxylic Acids

The major product of the following reaction is

R - C \equiv N (1) AlH (i - Bu)_{2} (2) H_{2} O ?

(A)RCOOH
(B) $RCONH_{2}$
(C)RCHO✓ Correct
(D) $RCH_{2} NH_{2}$

Answer: (C)

Solution

DIBAL-H is a bulky reagent that delivers only one hydride, so the reduction stops partway. With a nitrile it adds once to give a metalated imine, and the mild aqueous work-up then hydrolyses that imine to an aldehyde rather than pushing on to the amine or the acid. The product is therefore

RCHO

JEE Main · 2019 · 09 Jan 2019 · Shift 1 · Single correct option

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