Question

Among the following the strongest nucleophile is

• A. $C_2 H_5 SH$
• B. $CH_3 COO^-$
• C. $CH_3 NH_2$
• D. $NC CH_2^-$

Answer 1

Answer: (A)

$C_2 H_5 SH$

Answer 2

Nucleophile is a species which has high electron density on it and it attack on the site of less electron density. More the electron density on a species better nucleophile it is. Nucleophiles may be neutral (but with an atom with lone pairs of electron) or it can be negatively charged. $C _{2} H _{5} SH$ is the weakest acid so it readily lose a proton to form strong conjugate base $C _{2} H _{5} S ^{-}$which is a strong nucleophile ( $+I$ effect of $C _{2} H _{5}$ group).