Question

Benzyl chloride is reacted with different nucleophiles $(H{O}^{-},C{H}_{3}CO{O}^{-},Ph{O}^{-},C{H}_3{O}^{-}).$ Arrange them in the decreasing order of reactivity with Benzyl chloride.

• A. $C{H}_3{O}^{-}>H{O}^{-}>Ph{O}^{-}>C{H}_{3}CO{O}^{-}$
• B. $H{O}^{-}>C{H}_3{O}^{-}>Ph{O}^{-}>C{H}_{3}CO{O}^{-}$
• C. $H{O}^{-}>Ph{O}^{-}>C{H}_3{O}^{-}>C{H}_{3}CO{O}^{-}$
• D. $C{H}_{3}CO{O}^{-}>C{H}_3{O}^{-}>H{O}^{-}>Ph{O}^{-}$

Answer 1

The correct option is A $C{H}_3{O}^{-}>H{O}^{-}>Ph{O}^{-}>C{H}_{3}CO{O}^{-}$

For two charged nucleophiles with the ​same nucleophilic site but bonded to ​different groups, the one with a lower​
stability is a better nucleophile.

Here, $C{H}_{3}CO{O}^{-}$ is most stable as the negative charge is distributed among two oxygen atoms. In $Ph{O}^{-}$ the negative charge is in resonace with the phenyl ring, therefore, it is more stable than $H{O}^{-}$ and $C{H}_3{O}^{-}$. $H{O}^{-}$ is more stable than $C{H}_3{O}^{-}$ due to the $+I$ effect of $-C{H}_3$ group.

Hence, the correct order of nucleophilicity is:
$C{H}_3{O}^{-}>H{O}^{-}>Ph{O}^{-}>C{H}_{3}CO{O}^{-}$