Hinsberg reaction

The Hinsberg separation is named after the German chemist Oscar Hinsberg. The separation is a method in organic chemistry in order to separate primary, secondary, and tertiary amines, or organic in qualitative analysis to identify them.

The reaction of an amine mixture with benzenesulfonyl chloride (or - more rarely - p- toluenesulfonyl chloride ) in the presence of sodium hydroxide leads to the formation of the corresponding sulfonamides ( sulfa drugs ). The amines react as follows:

• Primary amines form sulfonamides of formula R -SO 2 NHR, in which the bound on the nitrogen hydrogen is acidic. These sulfonamides are therefore acids and form after reaction with sodium hydroxide in water -soluble sodium salts.

• Secondary amines are very difficult fissile sulfonamides of formula R- SO2 - NR2. These products do not contain acidic hydrogen atom and thus can not be deprotonated by sodium hydroxide solution and are therefore insoluble in water.

• Tertiary amines do not react with the sulfonyl chloride.

The different behavior of the amines thus allows their separation or distinction.