Question

Arrange the following compounds in order of their reactivity towards $S_{N}2$ reaction.
(i) $C{H}_3(C{H}_2{)}_{3}C{H}_{2}Br$
(ii) $(C{H}_3{)}_{2}CHC{H}_{2}C{H}_{2}Br$

• A. $(i)>(ii)>(iii)>(iv)(b)$
• B. $(ii)>(iii)>(iv)>(i)$
• C. $(iii)>(i)>(ii)>(iv)$
• D. $(iv)>(ii)>(i)>(iii)$

Answer 1

Answer: (A)

The $S_{N}2$ reaction is prone to steric inhibition. Th order of reactivity of alkyl halide is $1^{\circ }>2^{\circ }>3^{\circ }.$
The $S_{N}2$ reaction follows a particular order as the crowding around $C-X$ bond increases the steric inhibition increases. The order of reactivity of the halides are $R-I>R-Br>R$ $-Cl>R-F$