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

Explanation

Hinsberg test is one of the best tests to distinguish between `1^(@), 2^(@) and 3^(@)` amines. This test involves shaking the given amine with benzensulphonyl chloride (Hinsberg reagent) in the presence of an excess of aqueous KOH solution. The three types of amines can be distinguished on the basis of following observations.
(i) A primary amine gives a clear solution which on acidification gives an insoluble N-alkyl benzene sulphonamide.

(ii) A secondary amine gives an insoluble N, N-dialkylbenzenesulphonamide which remains unaffected on addition of acid.

(iii) A tertiary amine does not react with Hinsberg reagent. Therefore, it remains insoluble in the alkaline solution but dissolve on acidification to give a clear solution.