An Extended Computational Study of Criegee Intermediate-Alcohol Reactions

Abstract

High-level ab initio calculations (DF-LCCSD(T)-F12a//B3LYP/aug-cc-pVTZ) are performed on a range of stabilized Criegee intermediate (sCI)-alcohol reactions, computing reaction coordinate energies, leading to the formation of α-alkoxyalkyl hydroperoxides (AAAHs). These potential energy surfaces are used to model bimolecular reaction kinetics over a range of temperatures. The calculations performed in this work reproduce the complicated temperature-dependent reaction rates of CH 2 OO and (CH 3 ) 2 COO with methanol, which have previously been experimentally determined. This methodology is then extended to compute reaction rates of 22 different Criegee intermediates with methanol, including several intermediates derived from isoprene ozonolysis. In some cases, sCI-alcohol reaction rates approach those of sCI-(H 2 O) 2 . This suggests that in regions with elevated alcohol concentrations, such as urban Brazil, these reactions may generate significant quantities of AAAHs and may begin to compete with sCI reactions with other trace tropospheric pollutants such as SO 2 . This work also demonstrates the ability of alcohols to catalyze the 1,4-H transfer unimolecular decomposition of α-methyl substituted sCIs. ©