Explain the basicity of aliphatic amines.

(N/A) The basicity of amines is related to their structure. The basic character of an amine depends upon the ease of formation of the cation by accepting a proton from the acid. The more stable the cation is relative to the amine,the more basic the amine is.
Alkanamines versus ammonia: Let us consider the reaction of an alkanamine and ammonia with a proton to compare their basicity:
$R-NH_2 + H^+ \rightleftharpoons R-NH_3^+$
$NH_3 + H^+ \rightleftharpoons NH_4^+$
Due to the electron-releasing nature of the alkyl group $(R)$,it pushes electrons towards nitrogen and thus makes the unshared electron pair more available for sharing with the proton of the acid.
Moreover,the substituted ammonium ion formed from the amine gets stabilized due to the dispersal of the positive charge by the $+I$ effect of the alkyl group.
Hence,alkylamines are stronger bases than ammonia.
$(b)$ Comparison of $1^{\circ}, 2^{\circ}, 3^{\circ}$ alkylamines: The basic nature of aliphatic amines should increase with an increase in the number of alkyl groups. This trend is followed in the gaseous phase.
The order of basicity of amines in the gaseous phase follows the expected order: Tertiary amine $>$ Secondary amine $>$ Primary amine $>$ Ammonia $(3^{\circ} > 2^{\circ} > 1^{\circ} > NH_3)$.