Question

The reagent that gives an acid chloride on treatment with carboxylic acid is?
A.$$PC{l}_5$$
B.$PC{l}_3$
C.$SOC{l}_2$
D.$(COCl{)}_2$

Answer 1

Hint: In organic chemistry acid chloride are the compounds with functional group $-COCl$ and overall these organic compounds are represented by $RCOCl$ where $R$ is side chain. These are also known as acyl chloride and these are the reactive derivatives of carboxylic acid.

Complete step by step answer:
We will check whether these reagents produce acid chloride or not by reacting with carboxylic acid by their reactions. The reactions are as follows:
Reaction of carboxylic acid with $$PC{l}_5$$:
$$RCOOH+PC{l}_5\to RCOCl+POC{l}_3+HCl$$
We can see that in this reaction $RCOCl$ is produced as a product which is acid chloride.
 Reaction of carboxylic acid with $PC{l}_3$:
$$RCOOH+PC{l}_3\to RCOCl+H_{3}P{O}_3$$
In this reaction $RCOCl$ (acid chloride) is produced.
Reaction of carboxylic acid with $SOC{l}_2$:
$$RCOOH+SOC{l}_2\to RCOCl+S{O}_2+HCl$$
$RCOCl$ is produced in this reaction as a product.
Reaction of carboxylic acid with $(COCl{)}_2$:
$$RCOOH+(COCl{)}_2\to RCOCl+C{O}_2+CO$$
$RCOCl$ (acid chloride) is produced in this reaction as a product.
Hence we can see that all the given reagents give acid chloride on treatment with carboxylic acid.
So all options are correct (A), (B), (C) and (D).
Note:
During the reaction of carboxylic and sulphonyl chloride the hydroxyl group of the carboxylic acid is converted to a chlorosulfite intermediate making it a better leaving group.