Simple Marcus-Theory-Type Model for Hydrogen-Atom Transfer/Proton-Coupled Electron Transfer

Hydrogen-atom transfer reactions are the simplest class of proton-coupled electron transfer (PCET) processes. These reactions involve transfer of one electron and one proton from one reagent to another, in the same kinetic step, XH + Y -> X + HY. A predictive model for these reactions based on the Marcus cross relation is described. The model predicts rate constants within 1 or 2 orders of magnitude in most cases, over a very wide range of reactants and solvents. This remarkable result implies a surprising generality of the additivity postulate for the reaction intrinsic barriers and a smaller role for the quantum mechanical details of the proton and electron transfers.