A computational study of the radical-radical reaction of O(P-3) + C2H5 with comparisons to gas-phase kinetics and crossed-beam experiments

Abstract

We present density functional theory (DFT) and complete basis set (CBS) calculations of the prototypical radical-radical reaction of ground-state atomic oxygen [O(P-3)] with ethyl (C2H5) radicals. The respective reaction mechanisms and dynamics were investigated on the doublet potential energy surfaces using the DFT method and CBS model. In the title reaction, the barrierless addition of O(P-3) to C2H5 led to the formation of energy-rich intermediates that underwent subsequent isomerization and decomposition to yield various products. The products predicted to be found were: H2CO + CH3, CH3CHO + H, c-CH2OCH2 + H, (CH3COH)-C-1,3 + H, (HCOH)-H-1,3 + CH3, CH2CHOH + H, C2H3 + H2O, and CH2CH2 + OH. In particular, unlike previous kinetic results, proposed to proceed only through the direct H-atom abstraction process, two distinctive pathways to the formation of CH2CH2 + OH were predicted to be in competition: direct, barrierless H-atom abstraction mechanism versus addition process. The competition was consistent with the recent crossed-beam investigations, and their microscopic dynamic characteristics are discussed at the molecular level.