Answer: 4-Methylbenzenesulfonanilide (soluble in NaOH).
- A 4-Methylbenzenesulfonanilide (soluble in NaOH)
- B An insoluble sulfonamide precipitate that resists dissolution in NaOH
- C An azo dye formed via electrophilic coupling at the ring
- D A diazonium salt stable only below 5°C
Correct answer: A. 4-Methylbenzenesulfonanilide (soluble in NaOH)
Explanation: Primary amine gives monosubstituted sulfonamide with one N-H still present, making it soluble in NaOH.
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.