Answer: Trimethylphenylammonium hydroxide.
- A Trimethylphenylammonium hydroxide
- B N,N-Dimethylaniline left after only partial exhaustive methylation
- C N-Methylaniline formed after a single methylation step
- D Phenol formed via hydrolytic displacement of the amino group
Correct answer: A. Trimethylphenylammonium hydroxide
Explanation: Exhaustive methylation gives the quaternary ammonium hydroxide (trimethylphenylammonium hydroxide).
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.