Benzenesulphonyl chloride or, C₆H₅SOCl is commonly known as Hinsberg’s reagent. Hinsberg’s reagent can be used to distinguish primary, secondary and tertiary amines.

Benzenesulphonyl chloride reacts with primary amine to yield a product that is soluble in alkali.

Benzenesulphonyl chloride reacts with secondary amine to yield a product that is insoluble in alkali whereas Benzenesulphonyl chloride does not react with the tertiary amine.