Question

The correct increasing order of reactivity for following molecules towards electrophilic aromatic substitution.

• A. I < IV < II < III
• B. I < IV < III < II
• C. I < III < II < IV
• D. I < III < IV < II

Answer 1

The correct option is B I < IV < III < II

Electrophilic substituion reactions (ESR) are favoured when an electron donating group is attached.
In (I) $-N{O}_2$ group shows $-R$ effect and hence it is least reactive towards ESR
In (II) $-OMe$ shows $+R$ effect and hence is the most reactive towards ESR
Between (III) and (IV)
(IV) is less reactive towards ESR because $-I>+R$ for $-Cl$
and hence makes less reactive towards ESR as compared to (III)
Correct order is
I < IV < III < II