Theoretical study of the reaction mechanism and kinetics of the OH + trimethyl orthoformate ((CH3O)3CH) + O2 reaction

Publication date: 1 July 2019Source: Computational and Theoretical Chemistry, Volume 1159Author(s): Benni Du, Weichao ZhangAbstractThe profiles of potential energy surface (PES) of Trimethyl orthoformate (TMOF) with OH radicals under atmospheric conditions have been studied by performing M06-2X-GD3/6-311++G(d,p) approach for geometry optimization and ab initio method QCISD (T)/6-311++G(d,p) for energy calculations. The reaction of the OH radicals with TMOF in the presence of O2 is found to form mainly OH radicals, 2,2-dimethoxy-1,3-dioxetane, dimethyl carbonate [(CH3O)2CO] and HC(O)H. Regeneration of OH radicals for the TMOF + OH + O2 reaction is verified in the present calculations, which is consistent with the experimental observations. Based on the PES of the TMOF + OH reaction, temperature-dependent rate coefficients and branching ratios at 298–1500 K are determined using the conventional transition state theory. At 298 K, the calculated individual rate coefficients for H-abstraction from the CH site and the CH3O site of TMOF are 3.90 × 10−12 and 1.58 × 10−12 cm3 molecule−1 s−1, respectively. It is found that ∼71% of the TMOF + OH reaction takes place through the CH site H-abstraction and ∼29% of the TMOF + OH reaction belongs to the CH3O site H-abstraction. The overall rate coefficient displays opposite temperature dependencies at low and high temperatures, viz., negative at low temperatures and positive at high tempe...

Source: Computational and Theoretical Chemistry - May 25, 2019 Category: Chemistry Source Type: research