Kinetics of CH₂OO Reactions with Fluorinated Compounds: Temperature-Dependent Study of CF₃CH=CHCF₃ and Upper Limit Determination for SF₆

Criegee intermediates are highly reactive zwitterionic species formed from alkene-ozone reactions that play important roles in atmospheric oxidation chemistry. This study investigates the kinetics of formaldehyde oxide (CH₂OO) reactions with (E)-1,1,1,4,4,4-hexafluoro-2-butene (CF₃CH=CHCF₃) and sulfur hexafluoride (SF₆) using time-resolved laser-induced fluorescence detection of OH radicals. For the CH₂OO + CF₃CH=CHCF₃ reaction, we measured rate coefficients from 280-323 K at 5-10 Torr, finding values ranging from (1.4 ± 0.3) × 10^-14 to (3.0 ± 0.5) × 10^-14 cm³ molecule^-1 s^-1. The reaction shows positive temperature dependence with an activation energy of (2.7 ± 0.4) kcal mol^-1. Compared to non-fluorinated alkenes, the fluorinated compound reacts approximately 33 times faster, demonstrating the significant enhancement effect of trifluoromethyl groups. For CH₂OO + SF₆, no measurable reaction was observed up to SF₆concentrations of 6.5 × 10¹⁷ cm^-3, yielding an upper limit rate coefficient of 7 × 10^-18 cm³ molecule^-1 s^-1. These results expand the kinetic database for Criegee intermediates reactions with fluorinated compounds and provide insights into atmospheric oxidation pathways involving these species.