Question

In HVZ reaction substitution takes place at:
A.Carbon atom of \[ - COOH\]group
B.\[\alpha - \] Carbon atom
C.Both A and B
D.None of the above

Answer 1

Hint: Here we must know that Here in this reaction it halogenated carboxylic acids at the carbon atom. We should know that the carbon next to the carbonyl carbon is called the \[\alpha - \] Carbon atom.

Complete step by step answer:
Firstly we should know the full form of the reaction which is abbreviated as HVZ reaction so it stands for hell-volhard-zelinsky halogenation reaction.
Here in this reaction it halogenated carboxylic acids at the carbon atom. We should must know that the carbon next to the carbonyl carbon is called the \[\alpha - \] Carbon atom.we can further say that here the bromide ion gets replaced by the \[\alpha - \] Carbon atom and this can be further shown by the following equation:
\[R - C{H_2} - COOH + B{r_2}\xrightarrow[{ - {H_3}P{O_4}}]{{P\left( {CATALYST} \right)}}R - CH\left( {Br} \right) - COOH + HBr\]
Here we must note that unlike other halogenation reactions this reaction takes place in the absence of a halogen carrier.
This reaction basically gets initiated when the bromine is added to the acidic group and further a catalyst is added to it which will further lead to the substitution of the one bromine into the chain and further leads to the release of the hydrogen bromide.
Hence from this we conclude that the substitution takes place at the carbon next to the carbonyl carbon is called the \[\alpha - \] Carbon atom.we can further say that here the bromide ion gets replaced by the \[\alpha - \] Carbon atom.
Therefore, option (B) is correct.

Note:
We can see the best example of this reaction in our day to day lives as it is used in the production or we can say used in the preparation of the alanine.