Greater is the stability of the substituted ammonium cation, stronger should be the corre sponding amine as a base. Thus, the order of basicity of aliphatic amines should be: primary ¿ secondary ¿ tertiary, which is opposite to the inductive effect-based order. Secondly, when the alkyl group is small, like the-CH3 group, there is no steric hindrance to H-bonding. In case the alkyl group is bigger than the-CH3 group, there will be steric hindrance to H-bonding. Therefore, the change of nature of the alkyl group, e.g., from-CH3 to-C2H5 results in a change of the order of basic strength. Thus, there is a subtle interplay of the inductive effect, solvation effect, and steric hindrance of the alkyl group which decides the basic strength of alkyl amines in the aqueous medium.
