Theoretical study on the hydrogen bonding and solvation of ammonium and pyridinium ions

Abstract

Hydrogen bond energies (Δ E 1,0 ) for methyl-substituted ammonium and para-substituted pyridinium ions to one water molecule were calculated by an ab initio MO using a 3-21G basis set; for the ammonium ions also a 6-31G * basis set was used. The energies calculated with the 6-31G * basis set, being in good agreement with experimental values, were compared with the proton affinities of the bases and the aqueous solvation energies of the protonated bases. The data on the aqueous solvation energy of the Me 3 NH + ion deviate from those of other ammonium ions, indicating that the poor hydration of the Me 3 NH + ion is due to not only the hydrogen bond energies but also to the inability of forming a successive strong hydrogen bond.