An empirical potential for the O-H ⋯ O hydrogen bond: Part 2. Comparison with observed hydrogen bond geometries

The room temperature distribution of O-H ? O hydrogen bond geometries has been predicted by a Monte Carlo calculation, with an empirical potential energy function for the hydrogen bond. The results are compared with a recent survey of hydrogen bonds in carbohydrate crystal structures. The calculated and observed distributions of the O-H ? O angle have mean values of 165.5° and 167.1° respectively. Both the theoretical and experimental results suggest that short O ? H hydrogen bonds tend to be more linear than long O ? H bonds. The distribution of hydrogen bonding within the lone pair plane of the acceptor oxygen atom is predicted to be broader than the distribution perpendicular to this plane, in agreement with the experimental data. The empirical hydrogen bond function, in conjunction with the molecular mechanics program MMI, has also been used to predict the geometries of inter-residue hydrogen bonds in five disaccharides. The O ? H distances and O-H ? O angles are reproduced with r.m.s. deviations of 0.06 Å and 9° respectively.