A theoretical analysis of the reaction between ethyl and molecular oxygen

Using a combination of electronic-structure theory, variational transition-state theory and solutions to the time-dependent master equation, we have studied the kinetics of the reaction between ethyl and molecular oxygen theoretically over wide ranges of temperature and pressure. The agreement between theory and experiment is quite good. By comparing the theoretical and experimental results describing the kinetic behavior, we have been able to deduce a value for the C2H5-O-2 bond energy of similar to 34 kcal/mol and a value for the exit-channel transition-state energy of - 4.3 kcal/mol (measured from reactants). These numbers compare favorably with our electronic-structure theory predictions of 33.9 kcal/mol and -3.0 kcal/mole, respectively. The master-equation solutions show three distinct temperature regimes for the reaction, discussed extensively in this paper. Above T approximate to 700 K, the reaction can be written as an elementary step. C2H5 + O-2 <----> C2H4 + HO2, with the rate coefficient k(T) = 3.19 x 10(-17) T-1.02 exp(2035/RT) cm(3) (molecules s) independent of pressure, even though the intermediate collision complex may suffer a large number of collisions.