Arrange the following compounds in decreasing order of their rate of hydrolysis via the S _ N 1 mechanism: I. II. III. IV.

Step-by-step solution

The rate of hydrolysis via the S _ N 1 mechanism depends on the stability of the intermediate carbocation formed after the departure of the bromide ion. The carbocations formed are benzyl cation (I) and its para-alkyl substituted derivatives (II, III, IV). All are stabilized by resonance with the benzene ring. The para-alkyl groups provide additional stabilization through hyperconjugation (+H) and inductive (+I) effects. For alkyl groups attached to a benzene ring, hyperconjugation dominates over the inductive effe