Write Hinsberg's test to distinguish between `1^(@), 2^(@) and 3^(@)` amines.

Explanation

Hinsberg.s test is one of the tests to distinguish between `1^@, 2^@` and `3^@` amine with benzenesulphonyl chloride in presence of an excess of aqueous KOH solution. The three type of amine can be distinguished on the basis of following observations.
(i) A primary amine gives a water soluble salt which on acidification gives an insoluble N-alkylbenzene sulphonamide.

The Hinsberg test, which can distinguish primary, secondary, and tertiary amines, is based upon sulfonamide formation. In the Hinsberg test, an amine is reacted with benzene sulfonyl chloride. If a product forms, the amine is either a primary or secondary amine, because tertiary amines do not form stable sulfonamides. If the sulfonamide that forms dissolves in aqueous sodium hydroxide solution, it is a primary amine. If the sulfonamide is insoluble in aqueous sodium hydroxide, it is a secondary amine. The sulfonamide of a primary amine is soluble in an aqueous base because it still possesses an acidic hydrogen on the nitrogen, which can be lost to form a sodium salt. (ii) A tertiary amine does not react with Hinsberg reagent. Therefore, it remains insoluble in the alkaline solution but dissolve on adicification to give a clear solution.