Azo coupling

In organic chemistry, an azo coupling is an reaction between a diazonium compound (R−N≡N⁺) and another aromatic compound that produces an azo compound (R−N=N−R’). In this electrophilic aromatic substitution reaction, the aryldiazonium cation is the electrophile, and the activated carbon (usually from an arene which is called coupling agent) acts as a nucleophile. The desired azo compound is synthesized from this para substitution reaction. In most cases, including the examples below, the diazonium compound is also aromatic.