MCQ
Propionic acid with $Br_2/P$ yields a dibromo product. Its structure would be
  • A
    $\begin{array}{*{20}{c}}
      {Br\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,} \\ 
      {|\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,} \\ 
      {H - C - C{H_2}COOH} \\ 
      {|\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,} \\ 
      {Br\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,} 
    \end{array}$
  • B
    $CH_2(Br) - CH_2 - COBr$
  • $\begin{array}{*{20}{c}}
      {Br\,\,} \\ 
      {|\,\,\,\,\,} \\ 
      {C{H_3} - C - COOH} \\ 
      {|\,\,\,\,\,\,} \\ 
      {Br\,\,\,} 
    \end{array}$
  • D
    $CH_2(Br) - CH(Br) - COOH$

Answer

Correct option: C.
$\begin{array}{*{20}{c}}
  {Br\,\,} \\ 
  {|\,\,\,\,\,} \\ 
  {C{H_3} - C - COOH} \\ 
  {|\,\,\,\,\,\,} \\ 
  {Br\,\,\,} 
\end{array}$
c
Carbonylic acids reacts with $C l_{2}$ or $B r_{2}$ in presence of red $P$ to give exclusively $\alpha$ -chloro or $\alpha$ -bromo acids.

This reaction is called Hell-Volhard-Zelinsky $(HVZ)$ reduction. This reaction is example of $\alpha -H-$substitution.

$C{{H}_{3}}C{{H}_{2}}COOH\,\xrightarrow[-\,HBr]{B{{r}_{2}}/P}$ $\begin{matrix}
   \begin{matrix}
   Br  \\
   |  \\
\end{matrix}\,\,\,\,\,\,  \\
   C{{H}_{3}}-C-COOH  \\
   |\,\,\,\,\,\,\,  \\
   Br\,\,\,\,  \\
\end{matrix}$

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