Alkyl Halides and Aryl Halides
13.0 Halogenation
13.0 Halogenation
In the presence of ferric chloride or anhydrous aluminum chloride (catalysts), aryl halides can react with halogens (in this case chlorine) to form $1,4$-dichloro-benzene as the major product and $1,2$-dichlorobenzene as the minor product.
Mechanism:
Step 1: Generation of Chloronium ion (electrophile)
Step 2: Attack of chloronium ion and the formation of carbocation
Step 3: Loss of a proton, formation of $1,2$-Dichlorobenze and $1,4$-Dichlorobenzene (if $X$ is Chlorine) and regeneration of the catalyst.
