The reaction of amines with mineral acids to form ammonium salts shows that these are basic in nature. Amines have an unshared pair of electrons on the nitrogen atoms due to which they behave as Lewis bases. The basicity of amines is related to their structure. The basic character of an amine depends upon the ease of formation of a cation by accepting a proton from the acid. The more stable the cation is relative to the amine, the more basic the amine.

The correct order of basicity of amines in gas phase

1° < 2° < 3°

It is known to you that amines are basic in nature as they have a lone pair of electrons on nitrogen. Therefore, they have a strong tendency to donate the lone pair of electrons to electron acceptors.

The basicity of amines depends on:

The electronic properties of the substituents (alkyl groups enhance the basicity, aryl groups diminish it) and also on the degree of solvation of the protonated amine, which includes steric hindrance by the groups on nitrogen.

In the gaseous phase, for R=Et, the order of basic strength is

Et₃N >  Et₂NH  > EtNH₂ > NH₃

but in a protic solvent like water, the order of basic strength is

Et₂NH > Et₃N > EtNH₂ > NH₃