This reaction is useful for the distinction of primary, secondary and tertiary amines.
(i) Primary amine (like ethyl amine) is treated with Hinsberg’s reagent (benzene sulphonyl chloride) forms N-alkyl benzene sulphonamide which dissolve in aqueous KOH solution to form a clear solution of potassium salt and upon acidification gives insoluble Nalkyl benzene sulphonamide.
(ii) Secondary amine like diethyl amine is treated with benzene sulphonyl chloride forms N, N-diethyl benzene which sulphonyl amide remains insoluble in aqueous KOH and does not dissolve in acid.
(iii) Tertiary amine like triethyl amine does not react with benzene sulphonyl chloride and remains insoluble in KOH, however it dissolves in dil. HCl to give a clear solution due to formation of ammonium salt
