Reduced Mechanism for the Phenyl O2 System

The ThermKin code described in chapter 2 is used to determine the elementary reaction rate coefficients and express the rate coefficients in several Arrhenius forms. It utilizes canonical transition state theory to determine the rate parameters. Thermodynamic properties of reactants and transition states are required and can be obtained from either literature sources or computational calculations. ThermKin requires the thermodynamic property to be in the NASA polynomial format. ThermKin determines the forward rate constants, k(T), based on the canonical transition state theory (CTST). 

In this study, thermodynamic properties of intermediates, transition states and products important to the formation and destruction of the aromatic ring in the phenyl radical + O2 reaction system were calculated. 

Enthalpy, entropy and heat capacities are determined by using DFT and ab initio methods (G3 and G3MP2B3). Our calculated values were compared to the vinyl + O2 calculation data of Mebel et al., to the phenyl + O2 calculation data of Hadad et al. and to recent data for phenyl + O2 by Tokmakov et al. Group additivity calculations were performed as well to test our group additivity values. 

We show that the vinyl radical is a good model for phenyl, for which high level calculations on the smaller vinyl system can be used to calibrate ab initio and Density Functional Calculations of the phenyl system. 

High pressure limit kinetic parameters are obtained from the calculation resulting from the Canonical Transition State Theory. Quantum RRK analysis is utilized to obtain k(E) and master equation analysis is used to evaluate fall-off in this bimolecular, chemically activated reaction system. The Phenyl + O2 association results in a chemically activated phenyl-peroxy 

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