Reaction: RCOOH + Br2/P → alpha-Br-RCOOH (alpha-brominated acid)

Mechanism: P converts RCOOH → RCOBr (acid bromide) → enolization of acid bromide (alpha-H more acidic in acid halide) → Br2 attacks alpha position → alpha-bromo acid bromide → hydrolysis → alpha-bromo acid

Key point: Only acids with alpha-H can undergo HVZ. The reaction goes through the acid HALIDE intermediate — the acyl halide enolizes more easily than the free acid.

Application: Alpha-bromo acids are useful intermediates for:

• SN2 with NH3 → alpha-amino acids
• SN2 with CN- → alpha-cyano acids → hydrolysis → malonic acid derivatives
• Elimination → alpha,beta-unsaturated acids