Temperature‐dependent kinetics of the simplest Criegee intermediate reaction with dimethyl sulfoxide

Criegee intermediates are thought to play roles in atmospheric chemistry, including OH radical formation, oxidation of SO 2 , NO 2 , etc. CH 2 OO is the simplest Criegee intermediate, of which the reactivity has been a hot topic. Here we investigated the kinetics of CH 2 OO reaction with dimethyl sulfoxide (DMSO) under 278–349 K and 10–150 Torr. DMSO is an important species formed in the oxidation of dimethyl sulfide in the biogenic sulfur cycle. The concentration of CH 2 OO was monitored in real‐time via its mid‐infrared absorption band at about 1,286 cm −1 (Q branch of the ν 4 band) with a high‐resolution quantum cascade laser spectrometer. The 298 K bimolecular rate coefficient was determined to be k 298 = (2.3 ± 0.3) × 10 −12 cm 3 /s at 30 Torr with an Arrhenius activation energy of −3.9 ± 0.2 kcal/mol and a weak pressure dependence for pressures higher than 30 Torr ( k 298 = (2.8 ± 0.3) × 10 −12 cm 3 /s at 100 Torr). The reaction is speculated to undergo a five‐membered ring intermediate, analogous to that of CH 2 OO with SO 2 . The negative activation energy indicates that the rate‐determining transition state is submerged. The magnitude of the reaction rate coefficient lies in between those of CH 2 OO reactions with (CH 3 ) 2 CO and with SO 2 .