Q.

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