Answer: It is more sterically hindered for solvation by water despite three +I groups.
- A It is more sterically hindered for solvation by water despite three +I groups
- B It has a lower molecular weight than dimethylamine under typical conditions
- C Its nitrogen lone pair is delocalised into an aromatic ring according to standard textbooks
- D It exists mainly as a gas and cannot dissolve in water in general practice
Correct answer: A. It is more sterically hindered for solvation by water despite three +I groups
Explanation: In water, trimethylamine is less solvated than dimethylamine, so the latter is effectively more basic in aqueous solution.
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.