Tentative study of the strong hydrogen bond dynamics. Part I. Geometric isotope effects

A qualitative interpretation is given to some dynamic effects of strong symmetric H bonds in terms of a new approximate potential energy surface model for the aha (ada) fragment. This surface is assumed to be common for different compounds containing the fragment aha (ada) with the same A atom. The proton potential is constructed from three parts joined together. The central part is the barrier separating two minima and the two side parts describe the proton repulsion from each A atom, the barrier width and height being dependent on the equilibrium A⋯A distance (Re). The proton (deuteron) energy terms are computed for three variants of such a potential energy surface using the adiabatic separation on the "fast" (proton, deuteron) and "slow" (A atoms) subsystems. This approximation enabled the geometric isotope effects to be computed for various compounds and Ichikawa's findings for these effects to be interpreted. © 1988.