Question

Consider the reactions
(i) $(C{H}_3{)}_{2}CH-C{H}_{2}Br\stackrel{C_2{H}_{5}OH}{\to }(C{H}_3{)}_{2}CH-C{H}_{2}O{C}_2{H}_5+HBr$
(ii) $(C{H}_3{)}_{2}CH-C{H}_{2}Br\stackrel{C_2{H}_5{O}^{-}}{\to }(C{H}_3{)}_{2}CH-C{H}_{2}O{C}_2{H}_5+B{r}^{-}$
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)

$S_{N}1$ and $S_{N}2$

$C_2{H}_{5}OH$ being a weaker nucleopbile, 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.