Detailed kinetic modeling of dimethoxymethane. Part I: Ab initio thermochemistry and kinetics predictions for key reactions

Despite the great interest in oxygenated methyl ethers as diesel fuel additives and as fuels themselves, the influence of their methylenedioxy group(s) (O–CH₂–O) has never been quantified using ab initio methods. In this study we elucidate the kinetics and thermochemistry of dimethoxymethane using high-level ab initio (CCSD(T)/aug-cc-pV(D+T)Z//B2PLYPD3BJ/6-311++g(d,p)) and statistical mechanics methods. We model torsional modes as hindered rotors which has a large influence on the description of the thermal behavior. Rate constants for hydrogen abstraction by Ḣ and ĊH₃ are computed and show that abstraction from the methylenedioxy group is favored over abstraction from the terminal methyl groups. β-scission and isomerization of the radicals are computed using master equations. The effect of rovibrationally excited radicals from preceding hydrogen abstraction reactions on subsequent hot β-scission is computed and has large influence on the decomposition of the formed dimethylether radical. The quantification of the effect of the dominant methylenedioxy group using ab initio methods can guide modeling of oxygenated methyl ethers that contain that group several times.