Question

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

Aniline and N-methylaniline

Answer 1

Aniline and N-methylaniline can be distinguished using the Carbylamine test. Primary amines, on heating with chloroform and ethanolic potassium hydroxide, form foul-smelling isocyanides or carbylamines. Aniline, being an aromatic primary amine, gives a positive carbylamine test. However, N-methylaniline, being a secondary amine, does not.

\[\ce{\underset{(Primary amine)}{\underset{Aniline}{C6H5NH2}} + CHCl3 + 3KOH ->[\Delta] \underset{(foul smell)}{\underset{Benzyl isocyanide}{C6H5NC}} + 3KCl + 3H2O}\]

\[\ce{\underset{(Secondary amine)}{\underset{N-methylaniline}{C6H5NHCH3}} + CHCl3 + 3KOH ->[\Delta] No reaction}\]