| Abstract
| - Reliable estimates of high-pressure-limit reaction rates as a function of temperature are essential for thedevelopment of reaction sets that can be used to model complex chemical processes. As these reaction ratesdepend primarily on the thermodynamic properties of the reactants and the corresponding transition state,this work attempts to predict these properties within the framework of group additivity. Using ab initiocalculations at the CBS-Q level, with additional HF/6-31G(d‘) potential energy surfaces (PES) to define thehindrance potential for internal rotations, we calculate heats of formation (ΔfH298), entropies (S298), and heatcapacity values (Cp(T)) of species involved in prototypical H abstraction reactions. From these, we derivenew group additivity values (GAV) for transition-state-specific moieties. The new GAV allow rapid calculationof reaction rates for entire reaction families with good accuracy. This work presents a detailed description ofthe methodology and has its focus on H abstraction from alkanes by H and CH3. Subsequent papers willapply this methodology to derive GAV for other reaction families of interest in combustion processes.
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