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 CH2OO and (CH3)2COO 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-(H2O)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 SO2. This work also demonstrates the ability of alcohols to catalyze the 1,4-H transfer unimolecular decomposition of α-methyl substituted sCIs.
Highlights
Criegee intermediates are produced through several different reactions mechanisms including the UV photolysis of iodoalkanes in the presence of oxygen, reaction between oxygen and dimethyl sulfoxide radicals, and the 1,3-cycloaddition of ozone to alkenes (Scheme 1).[2−4]
There has been a significant body of work investigating bimolecular reaction mechanisms and rates of stabilized Criegee intermediates with trace atmospheric constituents, focusing on the fate of tropospheric sCIs and the role of these reactions in influencing the tropospheric HOx budget, and in the formation of atmospheric aerosols
The sCIs investigated in this study are chosen for two purposes
Summary
Criegee Intermediates (CIs), known as carbonyl oxides, are atmospheric intermediates that are a significant nonphotolytic source of tropospheric hydroxyl (OH) radicals, often considered as atmospheric “detergents”.1. Scheme 1 (shown above) is a prevalent loss mechanism for tropospheric alkenes, and it is the most significant source of tropospheric Criegee intermediates. Alkene ozonolysis produces carbonyl oxides with significant internal energy (e.g., 2,3dimethylbutane ozonolysis produces an excess energy of 200− 250 kJ mol−1).[5] This internal energy leads to 37%−50% of the total tropospheric yield of carbonyl oxides, undergoing rapid unimolecular decomposition.[5−15] The remaining fraction are collisionally stabilized and eventually lost through bimolecular reactions, UV photolysis, or slower thermal decomposition.[5,6,12,14,15] There has been a significant body of work investigating bimolecular reaction mechanisms and rates of stabilized Criegee intermediates (sCIs) with trace atmospheric constituents, focusing on the fate of tropospheric sCIs and the role of these reactions in influencing the tropospheric HOx budget, and in the formation of atmospheric aerosols
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
