Question

Give the chemical tests to distinguish between the following pairs of compounds:

(a) Ethylamine and Aniline

(b) Aniline and Benzylamine

Answer 1

(a) Ethylamine and aniline:

By Azo dye test: It involves the reaction of any aromatic primary amine with HNO₂ (NaNO₂ + dil. HCI) at 273-278 K followed by treatment with an alkaline solution of 2-naph- thol when a brilliant yellow, orange or red coloured dye is obtained.

(b) Aniline and Benzylamine:

By Nitrous acid test: Benzylamine reacts with HNO₂ to form a diazonium salt which being unstable even at low temperature, decom poses with evolution of N₂ gas.

Aniline on the other hand, reacts with HNO₂ to form benzene diazonium chloride which is stable at 273¬278 K and hence does not decompose to-evolve N₂ gas.