The Friedel-Crafts reaction encompasses two key types of reactions: alkylation and acylation.

Alkylation involves the introduction of an alkyl group into an aromatic ring, whereas acylation entails the addition of an acyl group (denoted as $RCO^-$) to the aromatic ring. In both processes, a Lewis acid catalyst—commonly aluminum chloride—is employed to activate the electrophile and facilitate the reaction.

In the alkylation process, the alkyl group is usually derived from a primary or secondary alkyl halide. This halide interacts with the Lewis acid catalyst to produce a carbocation. Subsequently, the carbocation reacts with the aromatic ring, leading to the formation of a new carbon-carbon bond and the incorporation of the alkyl group into the ring.

In contrast, during acylation, the acyl group is typically sourced from a carboxylic acid derivative, such as an acid chloride or an anhydride. Similar to alkylation, the Lewis acid catalyst activates the electrophile, which then reacts with the aromatic ring, resulting in the formation of a new carbon-carbon bond and the addition of the acyl group to the ring.

In summary, the primary distinction between alkylation and acylation in the Friedel-Crafts reaction lies in the type of substituent added to the aromatic ring: alkylation introduces an alkyl group, while acylation introduces an acyl group.