Question

Which of the following halide shows highest reactivity towards $S_N1$ reaction?

• A. $C_6H_5CH_2Cl$
• B. $CH_3- CH_2Cl$
• C. $CH_3 - CH_2 - CH_2 - CH_2I$
• D. $C_6H_5Cl$

Answer 1

Answer: (A)

The rate of an $S _{ N } 1$ reaction is determined by the stability of the intermediate formed. In this case, the most stable intermediate formed would be for $C _{6} H _{5} CH _{2} Cl$ and the intermediate formed would be $C _{6} H _{5} CH _{2}{ }^{+}$. This intermediate is stabilised via resonance.