Hydrogen bonding considerations in silica gels.

Hydrogen bonding is expected to play an important part in the structural aspects of silica gels. All simple and a number of the more complex hydrogen-bonding configurations involving the proton donors F-H and O-H interacting with the proton acceptor lone electron pairs on F and O are tabulated. This includes solvent-solvent interactions, solvent molecules hydrogen-bonded to silicon- attached species, and a variety of silicon-silicon bridges involving hydrogen bonds. Ab initio calculations were performed for a number of model structures. Using these as well as literature values in addition to steric considerations, it is possible to assign estimated hydrogen- bonding energy values to various configurations and locate those expected to be dominant. It is found that the presence of fluoride is not expected to change the hydrogen bonding significantly.