Explain the reaction of amines with arylsulphonyl chlorides.

(N/A) Benzenesulphonyl chloride $(C_{6}H_{5}SO_{2}Cl)$,also known as Hinsberg's reagent,reacts with primary and secondary amines to form sulphonamides.
$(i)$ The reaction of benzenesulphonyl chloride with a primary amine $(R-NH_{2})$ yields $N$-alkylbenzenesulphonamide. The hydrogen atom attached to the nitrogen in the resulting sulphonamide is strongly acidic due to the presence of the strong electron-withdrawing sulphonyl group. Hence,it is soluble in alkali.
$(ii)$ In the reaction with a secondary amine $(R_{2}NH)$,an $N,N$-dialkylbenzenesulphonamide is formed. Since this product does not contain any hydrogen atom attached to the nitrogen atom,it is not acidic and is therefore insoluble in alkali.
$(iii)$ Tertiary amines $(R_{3}N)$ do not react with benzenesulphonyl chloride. This difference in reactivity is used to distinguish between primary,secondary,and tertiary amines and to separate them from a mixture. Note: $p$-toluenesulphonyl chloride is often used in place of benzenesulphonyl chloride.