Benzenesulphonyl chloride reacts with primary amines to form sulphonamides, such as N-ethylbenzenesulphonyl amide. The sulphonyl group imparts acidity to the hydrogen attached to nitrogen, making it soluble in alkali.

Aromatic amines react with nitrous acid at low temperatures to form diazonium salts, a crucial class of compounds employed in the synthesis of various aromatic compounds. Secondary and tertiary amines exhibit different reactions with nitrous acid.

Primary aliphatic amines, when treated with nitrous acid, form unstable aliphatic diazonium salts that quantitatively release nitrogen gas and alcohols. The quantitative evolution of nitrogen is used for the estimation of amino acids and proteins.

Aliphatic and aromatic primary amines undergo the carbylamine reaction, producing foul-smelling isocyanides, when heated with chloroform and ethanolic potassium hydroxide. This reaction, known as the carbylamine reaction or isocyanide test, is utilized as a test for primary amines.