Out of chlorobenzene and benzyl chloride which one gets easily hydrolysed by aqueous NaOH and why

Benzyl chloride because in chlorobenzene due to partial double bond character which is a result of resonance, makes hydrolysis difficult.

Chlorine is directly attached to benzene ring in phenyl chloride. It gives rise to its more stability as it is resonance stabilized. Chlorine has 3 lone pairs in conugation with pi bond along with +M (mesomeric effect) due to which partial double bond character develops thereby decreasing its reactivity, also chlorobenzene can undergo resonance easily by the participation of lone electron pairs. Cl is A Deactivating group. Also phenyl is electron withdrawing group and chlorine is very electronegative. So carbon chlorine bond in chlorobenzene is very strong. Chlorine is not a good leaving group here so nucleophilic substitution is not easy in case of chlorobenzene. Now coming to the case of benzyl chloride. Benzyl chloride can undergo SN1 reaction mechanism easily to form benzyl carbocation. Benzyl carbocation is very stable because of resonance. It is the most stable carbocation. Whereas, Phenyl carbocation is the most unstable. Though the intermediate is more stable benzyl chloride has a tendency to be converted into benzyl carbocation always, in addition to it Cl is attached 1° Carbon atom in benzyl chloride. Chlorobenzene (or any aryl halide) is less reactive than Benzyl chloride (or any alkyl halide) because in case of aryl halides, the halogen is directly attached to sp2 hybridised carbon atom. Due to resonance, carbon-halogen bond acquire partial double bond character and the cleavage of C=X bond becomes difficult Therefore, Benzyl chloride is more easily hydrolysed by aqueous NaOH than that of chlorobenzene.