Dynamics of molecular hydrogen exchange in hydrogen-bonded systems

The kinetics of hydrogen exchange in molecular systems with H-bonds studied by kinetic IR spectroscopy and low-temperature NMR spectroscopy methods is critically reviewed. The experimental rate constants and activation energies obtained so far for molecules capable of forming H-bonds as both proton donors and proton acceptors are collected and analyzed from the point of view of the influence of H-bond formation ability of the molecules-partners. The evidence available testifies to a molecular mechanism of the H-exchange reactions in inert solvents and in the gas phase via the formation of cyclic, mostly bimolecular, intermediates. The different mechanisms of the molecular H-exchange process in inert media are discussed and the possible paths of experimental elucidation of reaction mechanism are offered.