(N/A) The mechanism of electrophilic substitution in benzene occurs in two main steps:
Step $1$: Generation of the $\sigma$-complex (arenium ion).
In this step,the electrophile $(E^+)$ attacks the benzene ring,leading to the destruction of the stable $\pi$-electron cloud. This forms a carbocation intermediate known as the $\sigma$-complex or arenium ion. Since this step involves the loss of aromaticity and requires significant energy,it is the slow,rate-determining step. One carbon atom in the $\sigma$-complex becomes $sp^3$ hybridized,making the intermediate non-aromatic. The positive charge is delocalized over the ring through resonance,as shown by structures $A$,$B$,and $C$,with $D$ representing the resonance hybrid.
Step $2$: Loss of a proton to restore aromaticity.
In this fast step,the $\sigma$-complex loses a proton $(H^+)$ from the $sp^3$ hybridized carbon to a base. This restores the aromaticity of the ring,resulting in the final substituted benzene product.