Question

$C{H}_3-COOH\to C{H}_{3}COCl$ Here the reagent is __________.

• A. $C{l}_2$
• B. $\text{Red}P+C{l}_2$
• C. $CHC{l}_3$
• D. $PC{l}_5$

Answer 1

The correct option is D $PC{l}_5$

A carboxylic acid converted to acid chloride by reaction with phosphorus pentachloride $\left(PC{l}_5\right)$. Thus acetic acid on reaction with phosphorous pentachloride produces acetyl chloride.
Hell-Volhard-Zelinsky reaction involves the replacement of an $\alpha$-hydrogen atom from from the alkyl group of a monocarboxylic acid by a halogen atom in presence of red phosphorous.
Acetic acid do not react with $CHC{l}_3$ and $C{l}_2.$
$C{H}_{3}COOH+PC{l}_5\to C{H}_{3}COCl+POC{l}_3+HCl\text{Acetic acid}\text{Acetyl chloride}$