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

I. a < b < c

 

II. b < a < c

 

III. b < c < a

 

IV. c < b < a 

This is a multiple choice answer as classified in NCERT Exemplar

(III) b < c < a 

The reaction will proceed by SN¹ mechanism to form the carbocation intermediate, more the stability of carbocation more will be the reactivity of the given compound with HBr/HC1.

-NO₂ group is an electron withdrawing group and d