ANION-ANION REPULSION, COORDINATION-NUMBER, AND THE ASYMMETRY OF HYDROGEN-BONDS

By examining which coordination numbers are not known for a large vari ety of cations, it is found that the closest approach of two O atoms, R(min), is given by, R(min) = 220 - 34.ln(s') pm, where s' is the proj ection onto the O-O vector of the valence of the bonds formed to a com mon cation. This equation is then used to show that the asymmetry of O -H...O hydrogen bonds is a consequence of the repulsion between the do nor and acceptor O atoms. The model leads to a natural division of hyd rogen bonds into three classes: strong, normal, and weak, and it gives good predictions for the geometries of each.