Question

What is electrophilic substitution of benzene?

Answer 1

Electrophilic substitution reaction of benzene:

• Benzene is a $\mathrm{\pi }$ electron rich system and is also resonance stabilized.
• It undergoes electrophilic substitution reactions to give monosubstituted benzene.
• Electrophilic substitution reactions are carried out in presence of a catalyst which helps in the formation of electrophiles which are electron-deficient species.

Mechanism

• Electrophile is produced as a result of Lewis acid's presence.
• An arenium ion, also known as a positively charged cyclohexadienyl cation, was created by the electrophile-generated attacks on the benzene ring.
• The aromaticity is eventually restored when the arenium ion transfers its proton from the $s{p}^3$ hybridized carbon to a Lewis base.

Examples of electrophilic substitution reaction of benzene

• Nitration: When benzene reacts with nitric acid $\left({\mathrm{HNO}}_3\right)$ in presence of Sulfuric acid $\left({\mathrm{H}}_2{\mathrm{SO}}_4\right)$, it results in the formation of nitrobenzene.
• In this reaction, Sulfuric acid acts as a catalyst that helps in the formation of electrophile $\left({\mathrm{NO}}_2^{+}\right)$.

Chemical reaction for nitration of benzene: