What are Amines?
Amines are organic compounds and functional groups which contain a nitrogen atom with a lone pair of electrons. They are the derivatives of ammonia wherein one or more hydrogen atom can be replaced by substituent groups such as alkyl or aryl. These are classified on the basis of the presence of replaceable hydrogen atoms. When one of the three hydrogen atoms are replaced by an alkyl or aryl group, the amine is primary. In case of replacing two out of three hydrogen atoms we get secondary amines and when all the three hydrogen atoms are replaced, tertiary amines are formed. Cyclic amines are secondary or tertiary amines forming a cyclic structure.
Chemical properties of amines
The difference in electronegativity of hydrogen and nitrogen atom and the presence of a lone pair of electrons on nitrogen atom makes the amine reactive. The number of hydrogen atoms attached to nitrogen determines the course of action for the amine. This is the reason why primary, secondary and tertiary amines undergo different reactions. Amines behave like nucleophiles due to the presence of unshared electrons. Following are the reactions of amines:
Basicity of amines:
Being basic in nature, they react with acids to form salts.
Amine salts on reaction with bases like NaOH regenerate the parent amine.
Amine salts are water-soluble but insoluble in organic solvents such as alcohol and ether. This reaction is the basis for the separation of amines from non-basic organic compounds which are insoluble in water. The reaction between amines and mineral acids forms ammonium salts which clearly depicts the basic nature of amines.
Aliphatic and aromatic, primary and secondary amines react with acid chlorides, anhydrides and esters by the process of nucleophilic substitution reaction. This is known as acylation. These are the end products of acylation. The reactions are carried out in the presence of a stronger base as compared to amines for example pyridine in order to remove the HCl formed during the reaction and therefore shift the equilibrium to the right-hand side of the reaction.
This article covers the basic details of acylation reaction of amines. For any further query on topics like classification and nomenclature of amines install, Byju’s the learning app.