JEE Main · 2012 · 29 Apr 2012 · Offline · Aldehydes Ketones and Carboxylic Acids

In the given transformation, which of the following is the most appropriate reagent ?

(A) $NH_{2} NH_{2}, O (-) H$ ✓ Correct
(B) $Zn - Hg / HCl$
(C)Na ,Liq. $NH_{3}$
(D) $NaBH_{4}$

Answer: (A)

Solution

The task is to strip the ketone's

C = O

down to a

C H_{2}

while leaving the hydroxyl group intact. The Wolff--Kishner reduction, using

N H_{2} N H_{2}

with base, removes the carbonyl oxygen under alkaline conditions that the

- OH

tolerates. Clemmensen's

Zn - Hg/HCl

works in strong acid that the sensitive alcohol would not survive, sodium in liquid ammonia attacks the aromatic ring instead, and

NaB H_{4}

stops at the alcohol. The fitting reagent is therefore hydrazine with base.

JEE Main · 2012 · 29 Apr 2012 · Offline · Single correct option

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