NaNO2in aq.H2SO4
(CH3CO)2Oand pyridine
C6H5SO2Clin aq.NaOH
CH3(excess) followed byAgOH
Benzene sulphonyl chloride (C6H5SO2Cl) is used in Hinsberg's test of amines to form sulfonamides. A primary amine forms a precipitate of N-alkyl benzene sulphonamide with Hinsberg reagent. This precipitate is soluble in alkali. The reaction involves the replacement of a hydrogen atom on the amine by the benzenesulfonyl group. The resulting sulfonamide is initially insoluble in the aqueous alkaline solution but becomes soluble upon addition of excess base due to the formation of a negatively charged salt. Secondary amines also react with Hinsberg's reagent to produce a sulfonamide that is insoluble in alkali (no further reaction is possible). Tertiary amines do not react with Hinsberg's reagent.