On the geometry of O–H⋯O hydrogen bonds

The asymmetry of hydrogen bonds arises from the repulsion between the O atoms forming the bonds. A bond-valence analysis of the repulsion leads to the conclusion that strong and weak hydrogen bonds are different in kind, the stronger ones (O-O less than 2.7 Å) involve strain and are linear while the weaker ones (O-O greater than 2.7 Å) have an extra degree of freedom and are generally bent. The strength of the hydrogen bond is determined by a …