Answer: The carbonyl carbon is lost as CO 2 during rearrangement.
- A The carbonyl carbon is lost as CO<sub>2</sub> during rearrangement
- B A carbon is lost as CO according to most researchers
- C The nitrogen migrates to the adjacent carbon in the majority of cases studied
- D Reduction removes one carbon as widely reported in standard practice
Correct answer: A. The carbonyl carbon is lost as CO<sub>2</sub> during rearrangement
Explanation: During Hofmann rearrangement, the acyl nitrene rearranges; the C=O is lost as CO<sub>2</sub>, giving RNH<sub>2</sub> with one fewer carbon.
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.