Structure–Activity Relationships for 1,3-Dipolar Cycloaddition Reactions of Criegee Intermediates with Carbonyls

Carbonyl oxides, or Criegee intermediates (CIs), are key species formed during the ozonolysis of alkenes and are an important atmospheric oxidant. However, direct measurements of CI gas-phase rate constants for many atmospherically relevant reactions are still unknown. Herein, we present various approaches for developing structure-activity relationships (SARs) to predict the reactivity of the simplest CI (formaldehyde oxide; CH₂OO) with a range of carbonyls that are significant primary emission components as well as secondary products of hydrocarbon oxidation in the atmosphere. Approaches include the application of Hammett analysis, frontier molecular orbital (FMO) theory, and global electrophilicity indices to develop SARs. By combining these parameters with available kinetic data, we establish substituent-based predictive models that extend to carbonyl species and CIs lacking measured rate constants that can enhance the predictive representation of CI chemistry in atmospheric models. Of the different approaches, Hammett constants yield the best correlations overall, however, low-cost quantum chemical calculations of orbital energies offer a practical alternative for systems lacking experimental substituent parameters. Finally, we extend this framework to explore the influence of substitution on the CI and the corresponding cycloaddition kinetics.