Illustrated Glossary of Organic Chemistry

Electrophilic aromatic substitution (EAS): A substitution reaction in which an atom or group bonded to an aromatic ring is replaced by some other atom or group. Hydrogen is most commonly replaced attachment. The reaction mechanism involves attack of the aromatic ring by an electrophile.

Selected Electrophilic Aromatic Substitution Reactions


Bromination with Br₂ and FeBr₃, a Lewis acid catalyst.


Chlorination with Cl₂ and AlCl₃, a Lewis acid catalyst. The methoxy group is an ortho/para director.


Iodination with I₂ and HgO. Like other alkyl groups, the tert-butyl group is an ortho/para director.


Nitration with aqueous nitric acid and aqueous sulfuric acid. The methyl group is an ortho/para director, and the nitro group is a meta director.


Sulfonation of naphthalene with sulfur trioxide and sulfuric acid gives a sulfonic acid.


Friedel-Crafts alkylation of benzene with tert-butyl chloride and AlCl₃ or with isobutylene and sulfuric acid gives tert-butyl benzene.


Friedel-Crafts acylation of furan with acetyl chloride and AlCl₃, a Lewis acid catalyst.


Diazo coupling of N,N-dimethylaniline and phenyl diazonium chloride gives butter yellow, an diazo compound.