Answer: 3° < 2° < 1°.
- A 3° < 2° < 1°
- B 1° < 2° < 3°
- C All equal
- D 3° > 1° > 2°
Correct answer: A. 3° < 2° < 1°
Explanation: More alkyl groups on N increase steric hindrance, making tertiary amines least reactive toward acylation (3° do not acylate easily).
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.