Theoretical study on the generation of Criegee intermediates from the ozonolysis of trifluoropropene (CF3CHCH2)

Abstract

The O₃-initiated degradation mechanisms of trifluoropropene (CF₃CHCH₂) were studied using density functional theory (DFT). Three types of mechanisms were observed for the title reaction, namely, addition/elimination, H-abstraction and substitution. The computations showed that O₃ with a CC bond undergoes a 1,3-cycloaddition reaction to generate a primary ozone intermediate (POZ) with a relatively low free energy barrier, which then dissociates to generate an aldehyde group and carbonyl oxide, known as Criegee intermediates (CIs). Detailed analysis was conducted on the subsequent reactions of CIs. It is found that when a new type of CI-containing halogenated alkyl groups reacts with NO, NO₂, CH₂O, SO₂, H₂O and O₂, its reaction pathway is singularly analogous to that of the general CI. The degradation total rate coefficient and the estimated lifetime are in accordance with the experimental results. The current calculation results are of great significance for the atmospheric chemistry of the ozone oxidation of unsaturated halogenated compounds.