Question

Consider the reactions
(i) $(CH3)2CH - CH2Br \ce{->[{C_2H_5OH}]} (CH3)2CH - CH2OC2H5 + HBr $
(ii) $ (CH3)2CH - CH2Br \ce{->[{C_2H_2O^- }]} (CH3)2CH - CH2OC2H5 + Br^- $
The mechanisms of reactions (i) and (ii) are respectively

• A. $S _{ N } 1$ and $S _{ N } 2$
• B. $S _{ N } 1$ and $S _{ N } 1$
• C. $S _{ N } 2$ and $S _{ N } 2$
• D. $S _{ N } 2$ and $S _{ N } 1$

Answer 1

Answer: (A)

$C _{2} H _{5} OH$ being a weaker nucleophile, when used as a solvent in case of hindered $1^{\circ}$ halide, favours $S _{ N } 1$ mechanism while $C _{2} H _{5} O ^{-}$being a strong nucleophile in this reaction favours $S _{ N } 2$ mechanism.