Question

What is the decreasing order of reactivity among the following compounds towards aromatic electrophilic substitution? I. Chlorobenzene
II. Benzene
III. Anilinium chloride
IV. Toluene.

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

Answer 1

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

Reactivity towards electrophilic substitution reaction increases with electron density on benzene ring. Among the given options, toluene has maximum electron density due to $C{H}_3$ group on benzene ring which acts as electron donating by hyperconjugation and $+I$ effect. $Cl$ and $N{H}_3^{+}$ groups present on benzene ring acts as deactivating group and hence decreases electron density on benzene ring. $N{H}_3^{+}$ is more deactivating than $Cl$. So, the correct option is (b).