Question

The rate of the reaction will be fastest when Z is :

• A. $Cl$
• B. $OCOC{H}_3$
• C. $O{C}_2{H}_5$
• D. $N{H}_2$

Answer 1

Answer: (A)

$Cl$

For the reaction to be faster the $Z$ should be weak nucleophile and better leaving group. Weaker base are good leaving groups.

In the given options, $C{l}^{-}$ is the weakest conjugate base of strong acid $HCl$ and thus will be removed by nucleophile at the fastest rate.

$C{H}_{3}CO{O}^{-},C_2{H}_5{O}^{-}andN{H}_2^{-}$ are strong conjugate base of weak acids and therefore have weak leaving tendency.