To determine the adequate quantum chemistry method for the reaction exploration, we evaluated the performance of a broad range of methods, focusing on the first step of the ozonolysis reaction. This 1,3-dipolar cycloaddition of ozone to the double bond of the olefin leads to an ozonide intermediate. Figure shows the mechanism of the ozonolysis, known as the Criegee mechanism, for the two olefins, ethene and tetramethylethene, studied in this work. We used as reference the data reported by Wheeler et al. on the 1,3-dipolar cycloaddition reactions, which consisted of the molecular structures of ozone, ethene, and the TS, as well as the corresponding activation energy (14.2 kJ•mol -1 ). Moreover, Figure depicts the expected products for the aqueous ozonolysis of ethene (formaldehyde and αhydroxymethylhydroperoxide) and tetramethylethene (acetone and hydrogen peroxide). The final products of the ozonolysis and their yields reported in Dowideit and Von Sonntag 37 are used in the final section of the work to validate the outcome of the CRN exploration in kinetic simulations.