Computational study on the mechanism and kinetics of NO3-initiated atmosphere oxidation of vinyl acetate

It is known the NO3 radical contributes to the oxidation of volatile organic compounds in the atmosphere in the night, leading to the formation of carbonyl compounds and organic nitrates. The mechanistic and kinetic properties of NO3-initiated oxidative degradation of vinyl acetate (VAC), a typical unsaturated ester, have been studied using density functional method. According to the computational results, two types of primary reactions were identified: NO3-addition and H-abstraction. The NO3-addition reaction especially the C-beta-addition pathway dominates the entrance channel of NO3 into VAC while the H-abstraction reaction is negligible. Further reactions of the two adducts were discussed in the presence of O-2/NOx. The rate constants were estimated by using the MultiWell software. The overall rate constant of NO3-initiated oxidation of VAC was about 7.30 x 10(-15) cm(3) molecule(-1) s(-1) at 298.15 K and atmospheric pressure, in good agreement with the experimental value of (7.30 +/- 1.8) x 10(-13) cm(3) molecule(-1) s(-1). The atmospheric lifetime of VAC reacting with NO3 radicals (5.0 x 10(8) molecule cm(-3)) is about 76.1 h under atmospheric conditions.