Question

Primary, secondary and teritary amines can be distinguished using Hinsberg’s reagent.

i) What is Hinsberg’s reagent?

ii) How will you distinguish primary, secondary and tertiary amines using Hinsberg’s reagent?

Answer 1

i) Benzene salphonyl chloride (C₆H₅SO₂Cl)
ii) a) The reaction of C₆H₅SO₂Cl with primary amine yields N-alkyl benzenesulphonamide which is soluble in alkali

The hydrogen attached to nitrogen in suiphonamide is strongly acidic due to the presence of strong electron withdrawing suiphonyl group. Hence, it is soluble in alkali.

b) Secondary amine read with benzene salphonyl chloride to form N, N-dialkylbenzene sulphonamide, which is insoluble in alkali. This is because it does not contain any hydrogen attached to nitrogen atom arid is not acidic.

c) Tertiary amines do not react with benzene salphonyl chloride, because they do not pos-sess any replacable hydrogen.