Answer: 3° > 2° > 1° > NH3.
- A 3° > 2° > 1° > NH3
- B 1° > 2° > 3°
- C NH3 > all amines
- D All equal
Correct answer: A. 3° > 2° > 1° > NH3
Explanation: In the gas phase, more alkyl groups increase electron density on N, so 3° > 2° > 1° > NH3.
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.