Basic Character of Amines : Aniline reacts with acid and from salts.
Structure and Basicity : Alkyl amines are more basic than ammonia. The alkyl group pushes the electrons towards nitrogen by +I effect. Thus line pair of electrons on nitrogen are more available for sharing with the proton of acid. Hence the basic nature of alkylamines increases with increase in number of alkyl groups. Thus in gaseous phase the basicity order of amines is in the order `3^(6)"amine"gt2^(0)"amine"gt1^(0)"amine"gt"ammonia"`.
In the aqueous phase the substituted ammonium cations get stabillised by +I effect and also by solvation with water molecules. Greater the size of the ion, lesser will be the solvation and less stabilised is the ion. The order of stability is.
Greater the stability of the ammonium cation, stronger is the basic nature of amine. The order of basicity of aliphatic amines is primary gt secondary gt tertiary. The - `CH_(3)` group creates less steric hindrance to hydrogen bonding than `C_(2)H_(5)` group. Thus the change of alkyl group changes the basic strength. The basic strength of methyl substituted and ethly substituted amines in aqueous soltuion is in the order.
`(C_(2)H_(5))_(2)NHgt(C_(2)H_(5))_(3)NgtC_(2)H_(5)-NH_(2)gtNH_(3)`
`(CH_(3))_(2)NHgtCH_(3)-NH_(2)gt(CH_(3))_(3)NgtNH_(3)`
Aromatic amines are less basic than ammonia. The lone pair of electrons on nitrogen is in conjugation with benzene ring.
