Investigation of Potential Energy Surfaces of Reaction Systems Containing Ethylene, Hydrogen, and Oxygen Atoms by Quantum Chemical Calculations.

In order to study the potential energy surfaces (PESs) of systems containing ethylene, hydrogen, and oxygen atoms, quantum chemical calculations are carried out using the hybrid B3LYP method of the density functional theory (DFT) and the composite CBS-QB3 method. An enthalpy diagram reflecting the PES of this reaction system is constructed. It is shown that the addition of a hydrogen atom to ethylene with the formation of an ethyl radical occurs through the formation of a van der Waals complex. The diagram of enthalpies of monomolecular reactions of decomposition and isomerization of the ethoxyl radical is presented in detail, and a conclusion is made about the probability of their occurrence. The global PES minimum of the system describing the sequential addition of hydrogen and oxygen atoms to ethylene is the hydroxyethyl radical. Intermediates CHCH₂OH and CH₂OCH₂ are localized on the PES of the C₂H₄ + O system and possible pathways for their further transformation are analyzed. The data obtained make it possible to estimate the ranking of individual elementary reactions in the processes of combustion and oxidation of hydrocarbons and the probabilities of various directions for the transformation of chemical species in the studied systems. [ABSTRACT FROM AUTHOR]