Question

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

Ethylamine and aniline

Answer 1

Ethylamine is a primary aliphatic amine, while aniline is a primary aromatic amine. They can be differentiated by azo dye test.

Azo dye test: In this, aromatic primary amine reacts with HNO₂ (NaNO₂ + dil. HCl) at 273 – 278 K and then reacts with alkaline solution of 2-naphthol (β-naphthol) to give a deep yellow, orange or red colored dye.

Aliphatic primary amines under the above conditions rapidly release nitrogen gas with the formation of primary alcohols, i.e., the solution remains transparent.

\[\ce{\underset{Ethylamine}{C2H5NH2} + HONO ->[273 - 278 K] \underset{ethyl alcohol}{C2H5OH} + H2O + N2 ^}\]