Question

Give one chemical test to distinguish between the following pair of compounds.

Methylamine and dimethylamine

Answer 1

Methylamine and dimethylamine can be distinguished by the carbylamine test.

Carbylamine test: Aliphatic and aromatic primary amines on heating with chloroform and ethanolic potassium hydroxide form foul-smelling isocyanides or carbylamines. Methylamine (being an aliphatic primary amine) gives a positive carbylamine test, but dimethylamine does not.

\[\ce{\underset{Methylamine (1^\circ)}{CH3 - NH2} + CHCl3 + 3KOH ->[\Delta] \underset{(foul smell)}{\underset{Methyl isocyanide}{CH3 - NC}} + 3KCl + 3H2O}\]

\[\ce{\underset{Dimethylamine}{(CH3CH2)2NH} ->[CHCl3/KOH (alc.)][Heat] No reaction}\]