Answer: Lone pair is delocalised into benzene ring.
- A Lone pair is delocalised into benzene ring
- B Its higher molecular weight reduces the lone pair's basicity
- C Steric hindrance from the ring blocks proton approach to nitrogen
- D The aromatic ring raises the electronegativity of the attached nitrogen
Correct answer: A. Lone pair is delocalised into benzene ring
Explanation: In aniline, the N lone pair is delocalised into the aromatic ring, reducing its availability for protonation.
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.