Inversion substitution reactions with participation of molecular oxygen: ZH3I + O2 → O2ZH3 + I (Z = C, Si). The potential energy surface and rate constants

A new class of reactions of molecular oxygen O-2 + ZH(3)I -> O(2)ZH(3) + I (Z = C, Si) proceeding by the mechanism of "inversion substitution" was investigated by quantum chemistry methods and the transition state theory (TST). The profiles of the potential energy surfaces (PES) along the reaction coordinate and the characteristics of transition states were calculated using the DFT approach with the B3LYP hybrid functional and the DZVP basis set. The characteristics of the transition states were then used for TST calculations of the rate constants for the direct and reverse "inversion substitution" reactions and their temperature dependences in the temperature interval 273-2000 K. The activation barriers to the substitution reactions under study were found to be substantially lower than the barriers to the abstraction reactions O-2 + ZH(3)I -> ZH(2)I + HO2 (by 16.3 kcal mol(-1) for Z = C and by 7.2 kcal mol(-1) for Z = Si). The results obtained show that the "inversion substitution" reactions dominate over the abstraction reactions in the interaction of molecular oxygen with carbon- and silicon-centered iodides as well as (probably) many other substrates.