Ab initio kinetics predictions for H-atom abstraction from diethoxymethane by hydrogen, methyl, and ethyl radicals and the subsequent unimolecular reactions

Abstract

Diethoxymethane (DEM) is a promising oxygenated fuel and fuel additive, which has similar positive combustion characteristics as dimethoxymethane. DEM contains C−C bonds and can form ethylene via β-scission, which potentially increases its sooting tendency. Since DEM is rarely studied, however, kinetic modeling attempts are forced to rely on rate constant analogies. Therefore, we employ high level CCSD(T)/aug-cc-pV(T+D)Z//B2PLYPD3BJ/6-311++(d,p) theory along with transition state theory to predict reaction rate constants for H-abstraction by H˙ and C˙H3 and the subsequent unimolecular reactions. We further prove that the DLPNO approximation to CCSD(T) leads to a deviation of less than 0.25 k/mol in barrier heights for the presently studied open-shell electronic structures and use it for the prediction of reaction rate constants for H-abstraction by C˙2H5 radicals. We find that H-abstraction by ethyl radicals might denote a significant pathway, which should not be neglected in kinetic modeling studies of DEM. It is also shown that reaction pathways leading to ethylene formation are of minor importance and give thereby a first insight into the fate of the C−C bonds. To the best of our knowledge, this study represents the first high-level ab-initio study of DEM, which makes the reaction kinetics and thermochemistry data provided by this study vital for future comprehensive kinetic modeling of DEM.