Ozonolysis chemistry is receiving renewed attention as a means to break down long chain biomass molecules into more useful renewable chemical intermediates. However, ozonolysis reaction pathways and mechanisms are not yet fully understood. We have performed density functional theory (DFT) calculations to explore the possibility of the unconventional mechanistic pathways for the ozonolysis reaction. The fate of the ozonolysis reaction in the presence of diatomic (e.g., O2) and triatomic (e.g., O3, NO2) species is examined in a quantum mechanical fashion. The computations suggest that the reaction might be intercepted at the Criegee intermediate (CI) stage leading to a change in the final product distribution. The O3 attack on CI results in the aldehyde formation and the release of O2. This unprecedented reaction is accompanied by a modest activation barrier. The reaction with NO2 also leads to the formation of aldehyde with a similar activation barrier. The anti form of CI is found to be more reactive towards these reactions than its syn form. If extra O3 is present in the reaction mixture, it can further oxidize the aldehyde into the carboxylic acid. This CI reaction has direct implications for atmospheric chemistry because it is believed that formic acid (HCOOH) in the troposphere is formed via ozonolysis. The calculated moderate activation barriers imply that O3 or NO2 may help either in the formation of HCOOH or in enhancing its atmospheric concentration. The possibility of secondary ozonide (SOZ) reacting with O3 has also been explored. The mechanistic insight gained via our computations can be used for both understanding and designing ozonolysis reactions.

DFT modeling suggests unconventional mechanistic pathways for ozonolysis: Direct relevance to industry and atmosphere

246th National Meeting (2013)

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