Answer: the charge is delocalised into the ring.
- A they have a higher molar mass
- B the charge is delocalised into the ring
- C the aromatic ring is electron-poor
- D aliphatic salts are always ionic
Correct answer: B. the charge is delocalised into the ring
Explanation: Resonance spreads the positive charge from the -N<sub>2</sub><sup>+</sup> group into the aromatic ring, stabilising the salt at low temperature.
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.