Diazonium salts are electrophilic in nature and can be attacked by activated benzenes (phenol, aniline). This reaction is known as azo coupling and generates products of industrial interest called azo dyes.

 

Step 1 . Formation of the diazonium salt

 

Stage 2 . Attack of activated benzenes on the nitrogen of the salt.

 

Azo dyes are used in the food industry, in the textile industry and also as pH indicators.