What is hell-volhard-zelinsky reaction mechanism?

The Hell-Volhard-Zelinsky reaction is a chemical reaction between a carboxylic acid and a halogen (usually chlorine or bromine) in the presence of a phosphorus halide (usually phosphorus tribromide) and a catalyst (usually a tertiary amine).

The mechanism of this reaction involves three main steps:

  1. Activation of the carboxylic acid: The phosphorus halide reacts with the carboxylic acid to form an activated intermediate, which makes the carbonyl group more susceptible to attack by the halogen.

  2. Halogenation of the carboxylic acid: The activated intermediate then reacts with the halogen to form an α-haloacid intermediate.

  3. Rearrangement: The α-haloacid intermediate is then rearranged via a catalytic process involving the tertiary amine catalyst to produce the final product, which is a α-haloacid with a bromine or chlorine atom attached to the alpha carbon.

The Hell-Volhard-Zelinsky reaction is widely used in organic chemistry for the synthesis of α-haloacids, which are important building blocks for many organic compounds.