Explain the halogenation of benzene with the example of chlorination.

(D) Benzene reacts with chlorine in the presence of a Lewis acid catalyst like anhydrous $FeCl_3$ or $AlCl_3$ to form chlorobenzene. This is an electrophilic aromatic substitution reaction.
Reaction: $C_6H_6 + Cl_2 \xrightarrow{FeCl_3} C_6H_5Cl + HCl$
Mechanism:
$1.$ Generation of electrophile: The Lewis acid reacts with the halogen to produce the electrophile $Cl^{+}$.
$Cl-Cl + FeCl_3 \rightarrow Cl^{+} + [FeCl_4]^{-}$
$2.$ The electrophile $Cl^{+}$ attacks the benzene ring to form a sigma complex (carbocation).
$3.$ Loss of a proton from the sigma complex to $[FeCl_4]^{-}$ restores the aromaticity,yielding chlorobenzene and $HCl$.