Question

What is the role of pyridine in the acylation of amines?

Answer 1

Hint : in the given question we should know about the chemical reaction of the acylation of amines. When the acyl group is added to a molecule, that type of chemical reaction is called an acylation reaction. Amines are the organic compounds which contain a nitrogen atom with a lone pair of electrons. Acylation of amines is the reaction of amines with the acetyl chloride.

Complete Step By Step Answer:
Acylation of amines is the reaction between the amines ( $- N{H_2}$ group) and the acetyl group ( $C{H_3}CO -$ ) that comes from either acetyl halide or acetic anhydride. This reaction takes place in the presence of pyridine ( ${C_5}{H_5}N$ ) which acts as a strong base during the reaction. During substitution reaction of acylation of ( $- N{H_2}$ ) group with acetyl group followed by hydrolysis of substituted amide with substituted amine, the activating effect of $- N{H_2}$ group can be controlled. Pyridine is used to remove the side product formed in the acylation reaction i.e. $HCl$ from the reaction mixture. It acts as an acceptor for the acid byproduct formed in the reaction.
Pyridine also acts as a nucleophile for the carbonyl group due to its lone pair of electrons on nitrogen atoms which can be delocalized in its ring. It acts as a catalyst and is often used in the acylation reactions.
Structure of Pyridine-

Example- Chemical Reaction between primary amine and acetyl chloride

Note :
It needs to be remembered that pyridine is a basic heterocyclic organic compound that acts as a base as well as nucleophile. It has a lone pair of electrons on nitrogen atoms which get delocalized in the ring. Structure of pyridine and its molecular formula ( ${C_5}{H_5}N$ ) should be remembered. Pyridine is a water- miscible liquid with a distinctive and unpleasant fish like smell. It is a highly flammable and weakly alkaline liquid.