Question

Complete the following reaction:

\[\begin{array}{cc}
\ce{CH3}\phantom{..............}\\
|\phantom{..............}\phantom{...}\\
\ce{CH3-CH-COOH->[(i) Br2/Red P4][(ii) H2O]}\\
\phantom{.......}\
\end{array}\]

Answer 1

Carboxylic acid having α-hydrogen are halogenated at α-position on treatment with Br₂ in presence of red phosphorous to give α -halocarboxylic acids. This is Hell-Volhard-Zelinsky reaction.

\[\begin{array}{cc}
\ce{CH3}\phantom{..........................}\ce{CH3}\\
|\phantom{..............................}|\phantom{...}\\
\ce{CH3-CH-COOH->[(i) Br2/Red P4][(ii) H2O]CH3-C-COOH}\\
\phantom{............................}|\\
\phantom{.............................}\ce{Br}
\end{array}\]