Chemical kinetics of the vinoxy radical + nitrogen dioxide: theoretical calculations and impacts on combustion model performance.

Existing studies have not reached a consensus on the kinetics of ĊH2CHO + NO2. The available rate parameters were extrapolated from limited experiments under low temperature and low pressure conditions, and their applicability has not been validated. A systematic theoretical investigation into ĊH2CHO + NO2 kinetics is carried out at the CCSD(T)/CBS//M06-2X/aug-cc-pVDZ level. Microcanonical variational transition state theory and RRKM/master equation calculations were employed to determine rate coefficients over a range of temperatures and pressures. The major pathway proceeds via radical-radical recombination: the unpaired electron on the terminal carbon of the vinoxy radical couples with the unpaired electron of NO2 to form a closed-shell O2NCH2CHO adduct through C-N bond formation, with chemical activation leading to NO release as a competing channel. Kinetic modeling shows that incorporating these results into established reaction mechanisms for predicting major species evolution causes distinct perturbations across different models. Further refinement is recommended for the NO2 self-reaction kinetics, the reactions of CHO and CH2O with NO2 and O2, as well as the reactions of CO and CH2O with ȮH, to improve model accuracy.