Question

Correct arrangement of the following nucleophiles in the order of their nucleophilic strength is

• A. $C_6{H}_5{O}^{-}<C{H}_3{O}^{-}<C{H}_{3}CO{O}^{-}$
• B. $C{H}_3{O}^{-}<C{H}_{3}CO{O}^{-}<C_6{H}_5{O}^{-}$
• C. $C_6{H}_5{O}^{-}<C{H}_{3}CO{O}^{-}<C{H}_3{O}^{-}$
• D. $C{H}_{3}CO{O}^{-}<C_6{H}_5{O}^{-}<C{H}_3{O}^{-}$

Answer 1

The correct option is D $C{H}_{3}CO{O}^{-}<C_6{H}_5{O}^{-}<C{H}_3{O}^{-}$

Given nucleophiles have same nucleophilic sites but bonded to different groups. The one with lower stability is a better nucleophile.

In $C{H}_{3}CO{O}^{-}$ and $C_6{H}_5{O}^{-}$, the negative charge charge on $O^{-}$ is delocalised and makes them more stable. Hence, they are less nucleophilic than $C{H}_3{O}^{-}$.

Comparing $C{H}_{3}CO{O}^{-}$ and $C_6{H}_5{O}^{-}$, $C{H}_{3}CO{O}^{-}$ is more stabilised because it forms two equivalent resonating structure. Thus, it is the least nucleophilic.

Hence, the order of their nucleophilic strength is
$C{H}_{3}CO{O}^{-}<C_6{H}_5{O}^{-}<C{H}_3{O}^{-}$