The Hinsberg reaction is a chemical test for the detection of amines. A reagent containing an aqueous solution of sodium hydroxide and benzenesulfonyl chloride is added to a substrate. A primary amine will form a soluble sulfonamide salt, which precipitates after the addition of dilute hydrochloric acid. A secondary amine, in the same reaction, will directly form an insoluble sulfonamide. A tertiary amine will not react with benzenesulfonyl chloride, but will remain insoluble. After adding dilute acid, the insoluble amine will become a soluble ammonium salt. In this way, the reaction can distinguish between the three types of amine.
Hinsberg's reaction was first described by Oscar Hinsberg in 1890.
http://www.quimicaorganica.org/foro/117-cuestiones-varias/1402-prueba-de-hinsberg-para-aminas.html
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