Explain HVZ reaction with example.

Explanation

Carboxylic acids having an `prop` hydrogen are halogenated at the `prop` position on treatement with chlorine or bromine in presnece of red phosphours to give `prop` halo-carboxylic acids. The reaction is known as Hell-Volharz-Zelinsky reaction.
`R-CH_(2)COOH overset((i)X_(2)("Red")P) underset((ii)H_(2)O) to underset(prop- "Halocarboxylic acid") underset(X) underset(|) (R-CH-COOH)`