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give a details account of HVZ reaction

give a details account of HVZ reaction

Grade:Upto college level

2 Answers

SAGAR SINGH - IIT DELHI
879 Points
11 years ago

Dear student,

When carboxylic acids react with chlorine or bromine  in the presence of red phosohorous, the alpha-hydrogen atoms are replaced by halogen atoms. It is called Hell-Volhard-Zelinsky(H.V.Z) reaction.
Ex:-
   acetic acid reacts with chlorine in presence of red phosphorus to form chloro acetic acid, dichloro acetic acid or trichloro acetic acid depending on the quantity of chlorine reacting.

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Sagar Singh

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AJAY LOGESH
16 Points
11 years ago

HVZ is a reaction used to prepare alpha-halo acids. The essential condition for this reaction is the presence of alpha hydrogen. Thus Formic acid does not undergo this reaction. The reagent used is Red phosphorous/X2   where X is a halogen. In the first step, -OH in acid group is replaced by X. On further reaction, alpha hydrogen is replaced by another X atom. On hydrolysis, the terminal X atom will be replaced by the -OH group. Thus the product obtained is alpha-halo acids.

RCH2COOH + Br2/P ----> RCH2COBr  + Br2/P ----> RCHBrCOBr + H2O ----> RCHBrCOOH ( alpha-halo acid)

 

 

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