Toluene undergoes electrophilic substitution when treated with halogens in the presence of \(FeCl_{3}\), a Lewis acid catalyst. The methyl group on toluene activates the ortho and para positions for substitution due to its electron-donating effect. The reaction mechanism involves:
Generation of an electrophile \((e.g., Cl^{+}) by FeCl_{3}\)
Electrophile attack at the activated positions.
Stabilization of the intermediate carbocation and subsequent restoration of aromaticity.
This reaction is characteristic of aromatic compounds.