An unknown amine X is treated with nitrous acid ( NaNO ₂ and HCl ) at 0-5^ C . A clear solution is obtained without the evolution of nitrogen gas. However, when this solution is warmed to room temperature, brisk effervescence of a colorless gas is observed. The amine X is:

Step-by-step solution

The reaction of an amine with nitrous acid at 0-5^ C without the evolution of nitrogen gas indicates the formation of a stable diazonium salt. This is a characteristic property of primary aromatic amines. When the solution is warmed to room temperature, the arenediazonium salt becomes unstable and decomposes to form phenol, releasing nitrogen gas which causes brisk effervescence. Aniline is a primary aromatic amine and perfectly exhibits this behavior. Benzylamine and ethylamine are primary aliphatic amines (the am