Answer: N 2 gas evolution.
- A N<sub>2</sub> gas evolution
- B Yellow oily liquid
- C No reaction
- D Orange precipitate
Correct answer: A. N<sub>2</sub> gas evolution
Explanation: Primary aliphatic amines react with HNO<sub>2</sub> to form unstable diazonium salts that immediately release N<sub>2</sub>.
In aniline, the nitrogen's lone pair is pulled into the benzene ring through resonance, leaving less electron density available to accept a proton - which is why aniline is a much weaker base than methylamine, where the lone pair is fully available.
Concept context
Nitrogen-containing organic compounds. Covers classification (primary, secondary, tertiary), basicity comparison, preparation methods, and reactions including diazotization and coupling, key for understanding dyes and pharmaceuticals.