A primary aliphatic amine on reaction with nitrous acid in cold (273 K) and there after raising temperature of reaction mixture to room temperature (298 K), gives a/an

Solution

Chemistry ma’am · 4 steps

An alkyl diazonium ion has no ring to steady it, so it loses N₂ and water makes an alcohol.

1. Diazotisation first. In the cold, nitrous acid (made from NaNO₂ and HCl) converts RNH₂ into the alkyl diazonium ion R-N₂⁺.
2. No stability. An aryl diazonium ion is stabilised by resonance with the benzene ring, so it lasts below 278 K. An alkyl group gives no such resonance. So R-N₂⁺ breaks down even in the cold, and it decomposes completely as the mixture warms to 298 K.
3. Water attacks. The ion loses N₂ gas, an excellent leaving group, and leaves behind a carbocation R⁺. Water from the aqueous medium attacks this carbocation, which gives the alcohol ROH.

   RNH₂ + HNO₂ → ROH + N₂ ↑ + H₂O

4. So. The product is an alcohol, option (b). The quantitative release of N₂ gas is also the test for a primary aliphatic amine.

The idea to keep. Only aryl diazonium salts survive, because resonance with the ring holds them together. Aliphatic ones give off N₂ straight away and turn into alcohols, so look for the brisk effervescence.

Answer from the NTA final answer key. Solution by PrepWiser.