Addition complex formation s. direct abstraction in the OH+C2H4 reaction

Abstract

The potential energy surface of the C₂H₅O system was studied by high level ab initio methods. Unimolecular rate constants have been computed using a simple transition state theory approach. The good agreement between predicted and experimental high pressure limiting rate constants supported the reliability of the proposed procedure. The direct bimolecular H-atom abstraction from ethylene by OH is unimportant and the reaction proceeds ia the intermediate adduct. We predict high pressure bimolecular rate constants above 600 K for the following reactions under the condition that the pre-equilibrium is established:

We also predict that the addition of H-atoms to acetaldehyde proceeds without an appreciable barrier and that redissociation is efficient above 400 K and a thermal equilibrium will be established. We found the barrier for addition of CH₃ to formaldehyde to be 12 kJ mol⁻¹ lower than the currently accepted barrier for the competing hydrogen abstraction reaction leading to CH₄+CHO.