Question

The order of reactivity of the compounds $C_6{H}_{5}C{H}_{2}Br,C_6{H}_{5}CH\left(C_6{H}_5\right)Br,C_6{H}_{5}CH\left(C{H}_3\right)Br$ and $C_6{H}_{5}C\left(C{H}_3\right)\left(C_6{H}_5\right)Br\text{ in }{S}_N^2$ reaction is

• A. $C_6{H}_5-\underset{\stackrel{|}{C_6{H}_5}}{\stackrel{\underset{|}{C{H}_3}}{C}}-Br<C_6{H}_5-\underset{\stackrel{|}{C_6{H}_5}}{\stackrel{\underset{|}{H}}{C}}-Br<C_6{H}_5-\underset{\stackrel{|}{C}{H}_3}{\stackrel{\underset{|}{H}}{C}}-Br<C_6{H}_5-\underset{\stackrel{|}{H}}{\stackrel{\underset{|}{H}}{C}}-Br$
• B. $C_6{H}_5-\underset{\stackrel{|}{H}}{\stackrel{\underset{|}{H}}{C}}-Br<C_6{H}_5-\underset{\stackrel{|}{C{H}_3}}{\stackrel{\underset{|}{H}}{C}}-Br<C_6{H}_5-\underset{\stackrel{|}{C_6{H}_5}}{\stackrel{\underset{|}{H}}{C}}-Br<C_6{H}_5-\underset{\stackrel{|}{C_6{H}_5}}{\stackrel{\underset{|}{C{H}_3}}{C}}-Br$
• C. $C_6{H}_5-\underset{\stackrel{|}{C{H}_3}}{\stackrel{\underset{|}{H}}{C}}-Br<C_6{H}_5-\underset{\stackrel{|}{H}}{\stackrel{\underset{|}{H}}{C}}-Br<C_6{H}_5-\underset{\stackrel{|}{C_6{H}_5}}{\stackrel{\underset{|}{H}}{C}}-Br<C_6{H}_5-\underset{\stackrel{|}{C_6{H}_5}}{\stackrel{\underset{|}{C{H}_3}}{C}}-Br$
• D. $C_6{H}_5-\underset{\stackrel{|}{C_6{H}_5}}{\stackrel{\underset{|}{H}}{C}}-Br<C_6{H}_5-\underset{\stackrel{|}{H}}{\stackrel{\underset{|}{H}}{C}}-Br<C_6{H}_5-\underset{\stackrel{|}{C{H}_3}}{\stackrel{\underset{|}{H}}{C}}-Br<C_6{H}_5-\underset{\stackrel{|}{C_6{H}_5}}{\stackrel{\underset{|}{C{H}_3}}{C}}-Br$

Answer 1

Answer: (A)

Lesser the steric hindrance, easier and higher the rate of reaction towards $S{N}^2$