An aryl group is a group derived from an aromatic ring, such as the phenyl group obtained from benzene, attached to the rest of the molecule through a ring carbon. It matters because, like the vinyl group, a leaving group bonded directly to an aromatic sp²-carbon is held very firmly: aryl halides resist nucleophilic substitution. This contrasts with an alkyl halide, whose sp³ carbon undergoes substitution readily.

芳基是由芳香环衍生的基团,如由苯得到的苯基,通过一个环碳连接到分子的其余部分。它之所以重要,是因为与乙烯基类似,直接连在芳香 sp² 碳上的离去基团结合得非常牢固:芳基卤化物不易发生亲核取代。这与卤代烷形成对照,后者的 sp³ 碳很容易发生取代反应。