The reaction mechanisms of vinyl acetate with OH radicals in the atmosphere have been studied using the density functional theory method. The geometry parameters and frequencies of all of the stationary points are calculated at the MPWB1K level with the 6-31G(d,p) basis sets. The single-point energy calculations are carried out at the MPWB1K/6-311+G(3df,2pd) level. The detailed profiles of the potential energy surfaces for the reactions are constructed. Two OH addition and three H abstraction reaction pathways are considered for the reaction of vinyl acetate with OH radicals. The theoretical study shows that the most energetically favorable isomer is that of OH addition to the terminal carbon positions (C1 atom). The α-ester rearrangement, which is characteristic of ester oxidation processes, is confirmed to be thermodynamically and kinetically favorable. The main products of the OH-initiated atmospheric oxidation of vinyl acetate are formaldehyde, formic acetic anhydride, and acetic acid.

The mechanism for OH radical initiated atmospheric photoxidation reaction of ethyl acetate was carried out by using the density functional theory method. Geometries have been optimized at the B3LYP level with a standard 6-31G(d,p) basis set. The single-point energy calculations have been performed at the MP2/6-31G(d), MP2/6-311++G(d,p), and CCSD(T)/6-31G(d) levels, respectively. All of the possible degradation channels involved in the oxidation of ethyl acetate by OH radicals have been presented and discussed. Among the five possible hydrogen abstraction pathways of the reaction of ethyl acetate with OH radicals, the hydrogen abstractions from the C1-H3 and C2-H5 bonds are the dominant reaction pathways due to the low potential barriers and strong exothermicity. The ␤-ester rearrangement of IM6 is energetically favorable but is not expected to be important. The ␣-ester rearrangement reaction and O 2 direct abstraction from IM17 are the more favorable pathways and are strongly competitive. In addition, the ␣-ester rearrangement reaction is confirmed to be a one-step process. Acetic acid, formic acetic anhydride, acetoxyacetaldehyde, and acetic anhydride are the main products for the reaction of ethyl acetate with OH radicals.

The chlorine-initiated reaction mechanism of ethyl formate in the atmosphere was investigated using the density functional theory method. The geometry parameters and frequencies of all of the stationary points were calculated at the B3LYP/ 6-31G(d,p) level. The single-point energy calculations were carried out at different levels, including MP2/6-31G(d), MP2/6-311++G(d,p), and CCSD(T)/6-31G(d). A detailed oxidation mechanism is provided and discussed. Present results show that α-ester rearrangement reaction and the O2 direct abstraction from IM6 (HC(O)OCH(O)CH3) are the more favorable pathway and are competitive. The 1,4-H shift isomerization of IM6 proved to be feasible under general atmospheric conditions. The decomposition of IM18 (CH3CH2OC(O)O) is favorable both thermodynamically and kinetically. Canonical variational transition theory with small-curvature tunneling correction was employed to predict the rate constants. The overall rate constant of ethyl formate at 298 K is 8.63 × 10−12 cm3 molecule−1 s−1. The Arrhenius equations of rate constants at the temperature range of 200–380 K were fitted.