Question

The decreasing order of reactivity towards electrophilic substitution of the following compounds is

• A. $1>3>4>2$
• B. $4>1>3>2$
• C. $4>1>2>3$
• D. $1>4>3>2$

Answer 1

Answer: (C)

Due to $+I$ effect of $-C{H}_3$ group (4) has higher electron density than benzene (1).
Due to strong $-I$ effect of $-Cl$ group and strong $-I$ and $-M$ effects of $-N{O}_2$ group, both (2) and (3) have lower electron density than benzene (1).
As $-I$ effect of $-Cl$ group is weaker than that of $-N{O}_2$, (3) has much lower electron density than (2).
Thus the overall reactivity order towards electrophilic substitution is
$4>1>2>3$