Will (CH3)2COO Survive in Humid Conditions?

Abstract

AbstractCriegee intermediates (CIs) are thought to be important oxidizing agents in the atmosphere; whereas in high humidity conditions, some CIs are quenched by water vapor, while some are immune from it. CIs’ reactivity toward water vapor is strongly dependent on the substituents of the CIs. It was reported previously that syn‐substituted CIs are less reactive toward water vapor than anti‐substituted ones, and this characteristic allows syn‐substituted CIs to survive in high humidity and react with other atmospheric trace gases, for example, SOx, NOx. In this paper, we calculated the rate coefficients of (CH3)2COO+(H2O)n,n=1,2 and compared them with those of syn‐CH3CHOO+(H2O)n,n=1,2 reported in our previous work. We discussed the substituent effect of CIs and the competition between SO2 and water vapor reaction at atmospheric conditions. In addition, we also discussed the tunneling correction with four different methods on these water mediated hydrogen transfer reactions. We calculated the rate coefficients with anharmonic correction for the partition function, with energetic values from our ratio extrapolation strategy, and with tunneling correction by small curvature approximation. At 298K the calculated bimolecular rate coefficients of (CH3)2COO+(H2O)2 and (CH3)2COO+H2O are 7.4×10−15 and 2.3×10−18 cm3sec−1, which are slow enough that (CH3)2COO can survive in high humidity condition, allowing it to possibly play an important role to oxidize SO2.