The Hinsberg test is a method to identify primary, secondary and tertiary amines, named after its pioneer, Oscar Hinsberg. Here, amines are treated with benzenesulfonyl chloride, also known as the Hinsberg reagent, in the presence of an excess of aqueous base, followed by acidification. Based on the nature of the amines, differentchanges are observed.

Generally, a primary amine reacts with the Hinsberg reagent to produce an N-substituted benzenesulfonamide. The electron-withdrawing sulfonyl group makes the N–H proton acidic, enablingready deprotonation in a base to form awater-soluble salt. Further acidification of the clear solution results in the precipitation of anN-substituted benzenesulfonamide.

Secondary amines generate an insolubleN,N-disubstituted sulfonamideupon reaction with benzenesulfonyl chloride. Due to the lack of an N–H proton, the compound does not reactwith the base. Tertiary amines do not react with the Hinsberg reagent. However, upon acidification, tertiary amines are protonated and become water-soluble.