What is meant by a coupling reaction? Explain with
suitable examples.

Explanation

Diazonium salts react with certain aromatic compounds
having an electron-rich group `(e.g.-OH,-NH_(2), etc.)` to form azo
compounds. This reaction is an electrophilic substitution and are called
coupling reaction. Azo compounds are brightly coloured and are used
as dyes and indicators. Coupling reaction is an electrophilic
substitution reaction, Benzene diazonium chloride reacts with alkaline
solution of phenol to give p-hydroxy azo benzene (orange dye).
Benzene diazonium chloride reacts with aniline in mild alkaline
medium to give p-aminobenzene (yellow dye).