Hinsberg reaction

What is Hinsberg reaction?

Although the preparation of arenesulfonamides was first reported by Gerhardt in 1853, it was Hinsberg who applied this reaction to the preparation of secondary amines in 1890 and further explored its potential uses.

The Hinsberg reaction, also known as the Hinsberg method, is named after the chemist who first developed it. This method involves the preparation of sulfonamides by treating primary or secondary amines with arenesulfonyl chloride, followed by the alkylation of resulting sulfonamides from primary amines, and ultimately, the hydrolysis of sulfonamides into primary or secondary amines.

Arenesulfonamides derived from primary amines possess an acidic hydrogen attached to the nitrogen atom. This property can be exploited to differentiate between primary, secondary, and tertiary amines based on their reaction with sulfonyl chloride and aqueous alkali. When treated with sulfonyl chloride and aqueous alkali, primary amines form an alkali-soluble sulfonamide, whereas secondary amines produce an alkali-insoluble sulfonamide. Tertiary amines, on the other hand, do not react with sulfonyl chloride under these conditions.

Hinsberg reaction
Hinsberg reaction

Arenesulfonyl chloride has found several applications in organic chemistry, including the protection of amino groups and the differentiation of amine types. However, it is important to note that in some cases, oversulfonation can occur, leading to the formation of disulfonylamides that are insoluble in alkali solutions. Additionally, certain monosulfonamides derived from primary amines may also exhibit low solubility in alkali solutions. Despite these limitations, arenesulfonyl chloride is still commonly used in the Hinsberg test to differentiate primary, secondary, and tertiary amines based on their solubility in alkali solution.