Give a chemical test to distinguish between ethylamine and aniline?

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Detailed Solution

Use the diazotization/azo dye test: aniline forms a stable diazonium salt at 0–5 °C and couples to give a colored azo dye, while ethylamine does not give a stable diazonium salt and no azo dye appears.

Test 1: Diazotization followed by coupling

Cool the amine solution to 0–5 °C; add NaNO₂ and dilute HCl (forms nitrous acid in situ).
Aniline: forms benzenediazonium chloride (stable in cold). On adding alkaline β-naphthol, a bright azo dye forms (orange/red).
Ethylamine: aliphatic diazonium salt is unstable and decomposes; no stable azo dye forms.

Test 2: Bromine water

Aniline: decolorizes bromine water and gives a white precipitate of 2,4,6-tribromoaniline.
Ethylamine: does not give this characteristic white precipitate under similar conditions.

Test	Ethylamine (C₂H₅NH₂)	Aniline (C₆H₅NH₂)
Diazotization + coupling	No stable diazonium; no azo dye	Stable diazonium at 0–5 °C; colored azo dye forms
Bromine water	No white ppt. like 2,4,6-tribromoaniline	White ppt. of 2,4,6-tribromoaniline; solution decolorizes