Question

The correct order of leaving group ability in nucleophilic substitution reaction is

• A. $\ce{Br^{-} > Cl^{-} > CH3CO2^{-} > HO^{-} > H^{-} }$
• B. $\ce{H^{-} > HO^{-} > CH3CO2^{-} > CI^{-} > Br^{-} }$
• C. $\ce{Br^{-} > CH3CO_2^{-} > Cl^{-} > HO^{-} > H^{-}}$
• D. $\ce{CH3CO2^{-} > Br^{-} > Cl^{-} > HO^{-} > H^{-}}$

Answer 1

The Correct Option is A

The leaving group ability decreases as the basicity of the nucleophile increases. Since the basicity increases in the order: $ {Br^{-} < Cl^{-} < CH3COO^{-} < HO^{-} < H^{-} }$, therefore, their leaving group ability decreases in the reverse order, i.e., $ {Br^{-} > Cl^{-} > CH_3COO^{-} > HO^{-} > H^{-} }$. Thus, option (a) is correct.