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MolSynapse / Question bank / Aldehydes, Ketones and Carboxylic Acids / Oxidation and reduction of carbonyls (Clemmensen, Wolff-Kishner, Tollens, Fehling)

JEE Advanced levelSingle correct optionDifficulty 3 of 3co152

Ethyl 4-oxopentanoate, $CH X_{3} COCH X_{2} CH X_{2} COOC X_{2} H X_{5}$ , is to be converted to ethyl pentanoate, with the ester group remaining intact. The most suitable reagent set is

A $Zn - Hg$ , conc. $HCl$
B $N X_{2} H X_{4}$ , $KOH$ , ethylene glycol, heated to $180^{\circ} C$
C $NaBH X_{4}$ , then $H X_{3} O X^{+}$
D $LiAlH X_{4}$ , then $H X_{3} O X^{+}$

Answer: A

The ketone must be deoxygenated to

CH X_{2}

without touching the ester. Clemmensen conditions achieve this. Hot

KOH

in the Wolff-Kishner method would hydrolyse the ester,

NaBH X_{4}

gives an alcohol, and

LiAlH X_{4}

would reduce the ester as well.

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