Class 12 NEET Chemistry Haloalkanes and Haloarenes

I < II < IV < III
The order of reactivity is dependent on the stability of the intermediate carbocation formed by cleavage of C—X bond. The 3° carbocation (formed from III) will be more stable than its 2° counter part (formed from IV) which in turn will be more stable than the arcnium ion (formed from I). Also, the aryl halide has a double bond character in the C—X bond which makes the cleavage more difficult. However, inspite of all the stated factors, II will be more reactive than I due to the presence of the electron withdrawing −NO2 group. C—X bond becomes weak and undergoes nucleophilic substitution reaction