Question

The compound which would undergo nucleophilic substitution fastest would be
$C{H}_{3}C{H}_{2}CON{H}_2$
$C{H}_{3}C{H}_{2}COOC{H}_3$
$C{H}_{3}C{H}_{2}COCl$

Answer 1

$Acylchloride>Anhydride>Ester$
In the acyl chloride, the Cl group is electronegative and electron-withdrawing in nature so it creates a positive charge on the carbon atom and a nucleophile can easily attack. The given reaction follows the withdrawl of the X group and Chlorine is the best leaving group among amide and ester.

The amide group is a very strong donating group and it increases the electron density around the carbon atom so nucleophile attack decreases.
Another factor for the reactivity is resonance stability provided by the C=O group and maximum the stability of this group least is the attack by a nucleophile. Amides exhibit two main resonance forms so that the amide bond between the carbonyl carbon and the nitrogen atom (-CO-NH-H) is a double bond character. Esters exhibit less resonance stabilization than amides so the formation of the tetrahedral intermediate is less favorable. Acid halides show the least resonance and they form tetrahedral intermediate easily so they are most reactive towards nucleophilic substitution.