The correct order of the basic strength of methyl substituted amines in aqueous solution is

The basicity of amines in aqueous solution depends on the stability of the ammonium cation or conjugate acid formed by accepting a proton from water which in turn depends on the +I -effect of alkyl group, extent of hydrogen bonding and steric factor. All these factors are favourable for 2° amines. Therefore, 2° amines are the strongest bases. If the alkyl group is small i.e., CH3 then there is no steric hindrance to H-bonding. Thus, the stability due to hydrogen bonding predominates over the stability due to +I -effect of CH3 group and hence primary amine is a stronger base than 3° amine. Hence, overall decreasing basic strength for methylamines in aqueous solution is CH32NH>CH3NH2>CH33 N