Question

Which of the following steps is not involved in the general mechanism of an electrophillic substitution of benzene?

• A. Generation of an electrophile
• B. Formation of arenium ion as intermediate.
• C. Addition of proton on benzene ring to give carbocation.
• D. Removal of proton from $s{p}^3$ carbon atom to restore aromatic character.

Answer 1

The correct option is C Addition of proton on benzene ring to give carbocation.

Electrophilic Substitution Reaction Mechanism:
$S_E$ of benzene takes place in 3 steps:
1. Generation of an electrophile.
2. Formation of an arenium ion (intermediate).
3. Removal of proton (H+) from the arenium ion.

Electrophiles for Different Electrophilic Substitutions:
$\text{Halogenation}:X^{+}:C{l}^{+},B{r}^{+},I^{+}\text{Nitration}:N{O}_2^{+}\text{Sulphonation}:S{O}_3\text{Friedel-Crafts reaction}:R^{+},RC{O}^{+}$
Formation of Carbocation Intermediate:
Attack on the electrophile results in the formation of arenium ion.
Here E is an electrophile.



Removal of Proton: