Question

Mention the catalyst and reaction condition in the given reaction

• A. $X_2$ /grey phosphorus, $H_{2}O$
• B. $X_2$ /red phosphorus, $H_{2}O$
• C. $X_2$ /white phosphorus, $H_{2}O$
• D. $X_2$ /blue phosphorus, $H_{2}O$

Answer 1

Answer: (B)

The given reaction is Hell-Volhard Zelinsky (H.V.Z.) reaction. In this reaction, carboxylic acids (except formic acid) react with chlorine or bromine in presence of small quantities of red phosphorus to give $\alpha$-chloro or $\alpha$-bromo acids.
$R-C{H}_2-COOH\underset{(ii)H_{2}O}{\overset{(i)X_2,\text{red}P}{\to }}$
$\underset{\alpha \text{- halo carboxylic acid}}{R-CH-\underset{\stackrel{|}{X}}{C}OOH}$ $[X=Cl,Br]$