Thermochemical Kinetic Analysis of Tunneling and the Incorporation of Tunneling Contributions in Thermochemical Kinetics

We partition the phenomenological enthalpy and entropy of activation for five hydrogen atom transfer reactions, H + H₂ → H₂+ H, D + H₂→ HD + H, H + D₂→ HD + D, O(³P) + H₂→ OH + H, and OH + H₂→ H₂O + H into substantial and nonsubstantial contributions. The latter, which are not considered explicitly in previous thermochemical kinetic models, are very significant. The present analysis could serve as the start of a semiempirical data base for the inclusion of variational and tunneling effects in future thermochemical kinetic models.