Question

Which compound in the above pair undergoes faster $S_{N}1$ reaction?

Answer 1

In the $S{N}_1$ reaction, the big barrier is carbocation stability. Since, the first step of the $S{N}_1$ reaction is loss of a leaving group to give a carbocation, the rate of the reaction will be proportional to the stability of the carbocation. Carbocation stability increases with increasing substitution of the carbon ($tertiary>secondary>primary$) as well as with resonance.