JEE Main · 2004 · 24 Apr 2004 · Offline · Aldehydes Ketones and Carboxylic Acids

Rate of the reaction

is fastest when Z is

(A)Cl✓ Correct
(B) $OCOCH_{3}$
(C) $OC_{2} H_{5}$
(D) $NH_{2}$

Answer: (A)

Solution

This is nucleophilic acyl substitution, and its speed turns on how good a leaving group Z makes, which in turn follows how weak a base Z is. Chloride is the weakest base of the four and so the best leaving group, making the reaction fastest when Z is

Cl

. The order of leaving ability runs

Cl > OCOCH X_{3} > OC X_{2} H X_{5} > NH X_{2}

, with the strongly basic

NH X_{2}

the poorest.

JEE Main · 2004 · 24 Apr 2004 · Offline · Single correct option

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