Reaction between peracetic acid and carbonyl oxide: Quantitative kinetics and insight into implications in the atmosphere

Peracetic acid (PAA, CH₃C(O)OOH) is one of the most abundant organic peroxyacid in the atmosphere. PAA is often assumed to be removed by hydroxyl radical in the gas phase of troposphere, but its reaction rate is quite low. Here, we investigated the new reaction between PAA and carbonyl oxide (CH₂OO) by using quantum chemical methods, reaction kinetics in combination with atmospheric modeling. We first performed W3X-L calculations close to CCSDT(Q)/CBS accuracy with the reaction systems containing eight carbon and oxygen atoms. The present findings show that the post-CCSD(T) contribution is about 0.50 kcal/mol, which is important for obtaining quantitative relative enthalpy of activation at 0 K. We find that the recrossing effect reduces the rate constant by an order of magnitude for the mechanism of the hydrogen-shift coupled carbon-oxygen addition at low temperature. The calculated results reveal that the anharmonicity increases the rate constants of CH₂OO + CH₃C(O)OOH by a factor of 6.27 at 298 K. The present findings uncover that the PAA + CH₂OO reaction is a dominant pathway for PAA sinks in the gas phase of troposphere at the lower nighttime OH concentrations at 298 K, since the rate of PAA + CH₂OO is even an order of magnitude higher than the rate of the PAA + OH reaction. Moreover, atmospheric modeling simulations unveil that CH₂OO can make certain contribution to the reduction of PAA in the Amazon.