Question

What is the action of following reagent on ethanoic acid?
$PC{l_3},$ Heat

Answer 1

Hint: Ethanoic acid $(C{H_3}COOH)$ is also known as acetic acid. It belongs to the group of carboxylic acids. Ethanoic acid is colourless having a strong odour like vinegar. It is a volatile organic compound having boiling point ${118^o}C$ .

Complete answer:
Phosphorus trichloride $\left( {PC{l_3}} \right)$ is a colourless fuming liquid (liquid at room temperature). It is a strong oxidizer and reacts with many organic compounds. It is toxic and reacts violently with water.
In the question it is given that ethanoic acid $\left( {C{H_3}COOH} \right)$reacts with Phosphorus trichloride $\left( {PC{l_3}} \right)$ in the presence of heat;
$3C{H_3}COOH + PC{l_3}\xrightarrow{\Delta }3C{H_3}COCl + {H_3}P{O_3}$
Ethanoic acid reacts with $PC{l_3}$ in the presence of heat to yield acetyl chloride and phosphorus acid. In this reaction three molecules of acetyl chloride are formed along with non-toxic by-products that can be easily removed by filtration. All three chlorine atoms of $PC{l_3}$ are used in the chlorination. We can say that phosphorus trichloride is a chlorinating agent that converts ethanoic acid into its corresponding acid chloride. It also converts alkyl alcohols into alkyl chlorides.
Thus, the products of this reaction are acetyl chloride and phosphorus acid.
Additional Information:
Phosphorus pentachloride also reacts with ethanoic acid to form acetyl chloride along with phosphorus oxychloride and steamy acid fumes of hydrogen chloride. Thionyl chloride $\left( {SOC{l_2}} \right)$ also reacts with acids to yield acyl chlorides.

Note:
We have seen that the action of $PC{l_3}$ and heat on ethanoic acid will form acetyl chloride and phosphorus acid. $PC{l_3}$ has a pungent and irritating odour, it can cause severe burns to skin, eyes and mucous membrane. It is very toxic and should be handled with care.