Explain hell-vollhard-zelinski reaction. also illustrate its synthetic importance.
Answers
Hell-Volhard-Zelinsky Reaction
Treatment with bromine and a catalytic amount of phosphorus leads to the selective α-bromination of carboxylic acids.
Mechanism of the Hell-Volhard-Zelinsky Reaction
Phosphorus reacts with bromine to give phosphorus tribromide, and in the first step this converts the carboxylic acid into an acyl bromide.
An acyl bromide can readily exist in the enol form, and this tautomer is rapidly brominated at the α-carbon. The monobrominated compound is much less nucleophilic, so the reaction stops at this stage. This acyl intermediate compound can undergo bromide exchange with unreacted carboxylic acid via the anhydride, which allows the catalytic cycle to continue until the conversion is complete.
Hell-Volhard-Zelinski reaction is a chemical reaction of organic compounds.
Organic Reaction:
It involves procedures that modify the halogen and alpha hydrogen contained carboxylic acid into an alpha halo carboxylic acid in the presence of water. Phosphorus plays the catalyst role in the reaction.
The halide anion is formed along with P-O bonding when phosphorous trihalide reacts with carbonyl oxygen.
It reacts again with carbonyl and gives rise to actyl chloride, which on further reaction with halogen results in the formation of alpha halo carboxylic acid.
Uses:
Synthetic manufacturing of organic compounds that are more complex in structure are formed by adding halogens.