Hofmann bromamide reaction template

N-bromination, migration of the alkyl group to nitrogen (isocyanate), hydration and decarboxylation turn acetamide into methylamine.

Mechanism step by step

A primary amide loses its carbonyl carbon to give an amine with one carbon fewer

1. Deprotonation – Hydroxide removes an N–H
2. N-Bromination – The amide anion attacks Br₂
3. Second deprotonation – The N–H of the N-bromoamide is acidic
4. Rearrangement – CH₃ moves to N as Br⁻ leaves: isocyanate
5. Hydroxide adds – Attack on the isocyanate carbon
6. Proton transfer – Carbamate anion
7. Decarboxylation – CO₂ is lost; water then protonates N

Key points

• The product amine has one carbon fewer than the amide.
• The migrating group keeps its configuration.
• Uses: aromatic amines (benzamide → aniline) and degrading carbon chains.
• Related: Curtius (acyl azide) and Lossen rearrangements via the same isocyanate.

Drawn with 86 atoms, 23 arrows, 9 shapes – every one editable in MolDraw.

Sources

• Hofmann, Ber. Dtsch. Chem. Ges. 1881, 14, 2725 Original paper
• Kürti & Czakó, Strategic Applications of Named Reactions in Organic Synthesis, Elsevier 2005 Textbook
• Smith, March's Advanced Organic Chemistry, 8th ed., Wiley 2020 Textbook