Understanding the inconsistency between mechanism and rate constants of acetylene ozonolysis

The reaction mechanism of acetylene with ozone was studied by using the complete active space self-consistent-field (CASSCF) and the CASPT2 methods. It was confirmed that the reaction follows the Criegee mechanism, yet a van de Waals complex was introduced in the mechanism. We found the master equation method is the key factor to accurately calculate the rate constants and Arrhenius parameters of this reaction, comparing to the results calculated by the traditional transition state method with steady-state assumption by Cremer which are about an order of magnitude smaller than the experimental data.