Answer: -NH 2.
- A -NH<sub>2</sub>
- B -OH
- C -COOH
- D -CHO
Correct answer: A. -NH<sub>2</sub>
Explanation: Amines contain the amino (-NH<sub>2</sub>) functional group derived from ammonia.
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.