Which of the following compounds would undergo `S_(N)1` reaction faster and why?

Explanation

`S_(N)1` reactions occur through carbocation intermediates. Obviously more stable the carbocation, more reactive the alkyl halide. Since carbocation obtained from compound (B) by loss of `Cl^(-)` ion is stabilized by resonance while that obtained from compound (A) is not stabilized by resonance, therefore, compound (B) reacts faster than compound (A).