The substitution reactions RH+O2→RO2+H:: transition sdtate theory calculations based on the ab initio and DFT potential energy surface

The new class of substitution reactions with oxygen molecule as an agent has been studied by combination of quantum chemistry calculation and transition state theory (TST). The 'inversion substitution' processes RH + O-2 RO2 + H (R = CH3 and SiH3) have been investiaated. The energy for the stationary points (reagents, products and transition states) on the reaction coordinate has been calculated by G2M(CC,MP2) method and rate constants have been calculated within TST approach. The results show that in methane case the reaction considered (CH4 + O-2 --> 4CH(3)O(2) + H) does not compete with generally accepted mechanism (CH4 + O-2 --> CH3 + HO2), but it does at elevated temperature in silane case. (C) 2004 Published by Elsevier B.V.