An Extended Computational Study of Criegee Intermediate-Alcohol Reactions

Area of Science:

• Atmospheric Chemistry
• Computational Chemistry
• Chemical Kinetics

Background:

• Stabilized Criegee intermediates (sCIs) are key species in atmospheric oxidation processes.
• Understanding sCI reaction kinetics is crucial for atmospheric modeling.
• The role of alcohols in sCI reactions and their product formation requires further investigation.

Purpose of the Study:

• To computationally investigate the reaction kinetics of various sCIs with alcohols.
• To model the formation of α-alkoxyalkyl hydroperoxides (AAAHs).
• To assess the atmospheric significance of sCI-alcohol reactions, especially in high-alcohol concentration regions.

Main Methods:

• High-level ab initio calculations (DF-LCCSD(T)-F12a//B3LYP/aug-cc-pVTZ) were employed.
• Potential energy surfaces were computed for sCI-alcohol reaction coordinates.
• Bimolecular reaction kinetics were modeled across a range of temperatures.

Main Results:

• Calculations accurately reproduced experimentally determined temperature-dependent reaction rates for CH2OO and (CH3)2COO with methanol.
• Reaction rates were computed for 22 different sCIs with methanol, including isoprene-derived intermediates.
• sCI-alcohol reaction rates were found to approach sCI-(H2O)2 rates in some cases.

Conclusions:

• sCI-alcohol reactions can form significant amounts of AAAHs in alcohol-rich environments.
• These reactions may compete with sCI reactions involving other atmospheric pollutants like SO2.
• Alcohols can catalyze the unimolecular decomposition of α-methyl substituted sCIs via 1,4-H transfer.