title: Modeling the influence of resonance stabilization on the kinetics of hydrogen abstractions.
abstract: Resonance stabilization of the transition state is one of the key factors in modeling the kinetics of hydrogen abstraction reactions between hydrocarbons. A group additive model is developed which allows the prediction of rate coefficients for bimolecular hydrogen abstraction reactions over a broad range of hydrocarbons and hydrocarbon radicals between 300 and 1300 K. Group additive values for 50 groups are determined from rate coefficients determined using the high level CBS-QB3 ab initio method, corrected for tunneling and the hindered internal rotation around the transitional bond. Resonance and hyperconjugative stabilization of the transition state is accounted for by introducing 4 corrections based on the structure of the reactive moiety of the transition state. The corrections, fitted to a set of 28 reactions, are temperature-independent and reduce the mean absolute deviation on E(a) to 0.7 kJ mol(-1) and to 0.05 for log A. Tunneling contributions are accounted for by using a fourth order polynomial in the activation energy. Final validation for 19 reactions yields a mean factor of deviation between group additive prediction and ab initio calculation of 2.4 at 300 K and 1.8 at 1000 K. In comparison with 6 experimental rate coefficients (600-719 K), the mean factor of deviation is less than 3.
authors.affiliation: Laboratorium voor Chemische Technologie, Universiteit Gent, Krijgslaan 281 S5, B-9000 Gent, Belgium.
authors.forename: Maarten K
authors.initials: MK
authors.lastname: Sabbe
authors.forename: Aäron G
authors.initials: AG
authors.lastname: Vandeputte
authors.forename: Marie-Françoise
authors.initials: MF
authors.lastname: Reyniers
authors.forename: Michel
authors.initials: M
authors.lastname: Waroquier
authors.forename: Guy B
authors.initials: GB
authors.lastname: Marin