It is the conversion of an amide (R–CONH₂) into a primary amine (R–NH₂) with one carbon less using Br₂ + KOH/NaOH.

---

Overall Reaction

$$RCONH_2 + Br_2 + 4KOH \rightarrow RNH_2 + K_2CO_3 + 2KBr + 2H_2O$$

Key point: Chain length decreases by one carbon

---

Stepwise Mechanism

Step 1: Formation of N-bromoamide

Amide reacts with bromine in basic medium:$$RCONH_2 + Br_2 + OH^- \rightarrow RCONHBr + H_2O$$

---

Step 2: Deprotonation

$$RCONHBr + OH^- \rightarrow RCONBr^- + H_2O$$

Step 3: Rearrangement (Key Step )

• Alkyl group (R) migrates from carbonyl carbon → nitrogen
• Br⁻ leaves

Forms isocyanate (R–N=C=O)$$RCONBr^- \rightarrow R–N=C=O + Br^-$$

Step 4: Hydrolysis of Isocyanate

$$R–N=C=O + H_2O \rightarrow RNHCOOH$$

Step 5: Decarboxylation

• $$RNHCOOH \rightarrow RNH_2 + CO_2$$

Final Product

✔ Primary amine (R–NH₂)
✔ CO₂ released

Important Features

• ✔ One carbon less than starting amide
• ✔ Always gives 1° amine
• ✔ Rearrangement step is key (migration)

Quick Trick“CONH₂ → NH₂ (minus one carbon)”

Exam Points

• Migration order:

$$3^\circ > 2^\circ > 1^\circ > CH_3$$

• Works only for primary amides
• Intermediate: Isocyanate (very important)