Reaction Kinetics of CH 2 OO and syn -CH 3 CHOO Criegee Intermediates with Acetaldehyde.

Criegee intermediates exert a crucial influence on atmospheric chemistry, functioning as powerful oxidants that facilitate the degradation of pollutants, and understanding their reaction kinetics is essential for accurate atmospheric modeling. In this study, the kinetics of CH 2 OO and syn -CH 3 CHOO reactions with acetaldehyde (CH 3 CHO) were investigated using a flash photolysis reaction tube coupled with the OH laser-induced fluorescence (LIF) method. The experimental results indicate that the reaction of syn -CH 3 CHOO with CH 3 CHO is independent of pressure in the range of 5-50 Torr when using Ar as the bath gas. However, the rate coefficient for the reaction between CH 2 OO and CH 3 CHO at 5.5 Torr was found to be lower compared to the near-constant values observed between 10 and 100 Torr. Furthermore, the reaction of syn -CH 3 CHOO with CH 3 CHO demonstrated positive temperature dependence from 283 to 330 K, with a rate coefficient of (2.11 ± 0.45) × 10 -13 cm 3 molecule -1 s -1 at 298 K. The activation energy and pre-exponential factor derived from the Arrhenius plot for this reaction were determined to be 2.32 ± 0.49 kcal mol -1 and (1.66 ± 0.61) × 10 -11 cm 3 molecule -1 s -1 , respectively. In comparison, the reaction of CH 2 OO with CH 3 CHO exhibited negative temperature dependence, with a rate coefficient of (2.16 ± 0.39) × 10 -12 cm 3 molecule -1 s -1 at 100 Torr and 298 K and an activation energy and a pre-exponential factor of -1.73 ± 0.31 kcal mol -1 and (1.15 ± 0.21) × 10 -13 cm 3 molecule -1 s -1 , respectively, over the temperature range of 280-333 K.