Which one of the pairs undergoes hydrolysis by aqueous KOH readily and Why?
(i) `C_(6)H_(5)CH_(2)Cl`.

Explanation

Both the halides undergo alkaline bydrolysis by `S_(N)1` mechanism because the carbocation obtained on their ionisation are stabilised by resonance. Water is a polar solvent , it aslo creates an appropriate environment for their easy ionisation. Higher the stability of teh carbocation, higher is the `S_(N)1` reactivity of thee halide. The carbocation `(C_(6)H_(5)overset(o+)(C)HC_(6)H_(5))` obtained from `C_(6)H_(5)CHClC_(6)H_(5)` is stabilised by resonance involving two phenyl groups while the carbocation `(C_(6)H_(5)overset(o+)(C)H_(2))` obtained from `C_(6)H_(5)CH_(2)Cl` is stabilised by resonance involving only phenyl group. Hence, the carbocation `C_(6)H_(5)overset(o+)(C)HC_(6)H_(5)` is relatively more stable than the carbocation `C_(6)H_(5)overset(o+)(C)H_(2)`. Thus, hydrolysis of `C_(6)H_(5)CHClC_(6)H_(5)` by aqueous KOH is much faster than that of `C_(6)H_(5)CH_(2)Cl`.
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