Mark the correct increasing order of reactivity of the following compounds with HBr/HCI.

Options

A. `(I) lt (II) lt (III)`
B. `(II) lt (I) lt (III)`
C. `(II) lt (III) lt (I)`
D. `(III) lt (II) lt (I)`

Answer

C

Explanation

Reaction of HBr/HCl with benzyl alcohols involves the formation of an intermediate carbocation, in a slow rate determining step. Obviously, more stable the carbocation, more reactive is the alcohol. Since the electron-withdrawing groups such as `NO_(2),Cl`, etc. decrease the stability of the carbocation and `-NO_(2)` group is a stronger electron-withdrawing group than Cl, therefore, stability of carbocations follows the order

Hence, the reactivity of benzyl alcohols follows the order : `II lt III lt I`