Question

Mention the catalyst and reaction condition in the given reaction

• A. $ X_2 $ /grey phosphorus, $ H_2O $
• B. $ X_2 $ /red phosphorus, $ H_2O $
• C. $ X_2 $ /white phosphorus, $ H_2O $
• D. $ X_2 $ /blue phosphorus, $ H_2O $

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.
$R - CH_2 - COOH \xrightarrow[(ii) H_2O]{(i) X_2, \text{red} P}$
$ \underset{\alpha \text{- halo carboxylic acid}}{R - CH - \underset{\overset{|}{X}}{C}OOH }\,\,\,$ $[X = Cl, Br]$