11: The Nature of the Hydrogen Bond, from a Theoretical Perspective Check Access

The original concept of the H-bond has undergone a good deal of generalization over the years to include a wide range of proton donor atoms and electron-donor sources. The means by which theoreticians study and understand the fundamental aspects of H-bonds are discussed, including various techniques that focus upon energetics, electrostatic potentials, charge transfer, electron density patterns, and spectroscopic features. In order to provide concrete examples of these methods, the chapter focuses on H-bonds in which C serves as proton-donor atom, a type of interaction which was not hitherto considered as an H-bond. The discussion ranges from very small systems to those with biological relevance. The sensitivity of H-bond strength to stretching and bending is critically examined as are the effects of placing a charge on one or both of the subunits.