Question

The decreasing order of reactivities of the following compounds towards electrophilic substitution is:

• A. $I>II>III>IV$
• B. $II>I>III>IV$
• C. $IV>I>II>III$
• D. $III>I>II>IV$

Answer 1

The correct option is D $III>I>II>IV$

The presence of $-R,-I,-H$ groups decrease the reactivity of benzene towards aromatic electrophilic substitution reaction.
$-C{F}_3$ group is a strong $-I$ group and it decreases the reactivity of benzene towards electrophilic aromatic substitution reaction.

The presence of $+R,+I,+H$ groups increase the reactivity of the benzene towards aromatic electrophilic substitution reaction.
$-C{H}_3$ shows hyperconjugation and is $+I$ group whereas $-OC{H}_3$ is $+R$ group.

$+R$ effect dominates over $+H$ effect, hence the order will be: $III>I>II>IV$