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

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 the given compounds with `HBr // HCl` is a nucleophilic substitution reaction it follows `S_N1` mechanism depends upon the stability of carbocation presence of electron withdrawing group decreases the stability of carbocation. In compound (II) and (III) EWG is present at para position. Since, - N02 group is a stronger EWG than - Cl. So, `NO_2-C_6H_5-overset+CH_2` carbocation will be less stable than `Cl-C_6H_5-overset+CH_2` carbocation
Thus, the order of stability of carbocation is

Therefore, compound (II) is least reactive and correct option is (c).