Solving the discrepancy between the direct and relative-rate determinations of unimolecular reaction kinetics of dimethyl- substituted Criegee intermediate (CH3)2COO using a new photolytic precursor

We have performed direct kinetic measurements of thermal unimolecular reaction of (CH3)2COO in the temperature 243–
340 K and pressure 5–350 Torr ranges using time-resolved UV-absorption spectroscopy. We have utilized a new photolytic
precursor, 2-bromo-2-iodopropane ((CH3)2CIBr), which photolysis at 213 nm in presence of O2 produces acetone oxide,
(CH3)2COO. The results show that the thermal unimolecular reaction is more important main loss process of (CH3)2COO in
the atmosphere than direct kinetic studies hitherto suggest. The current experiments show that the unimolecular reaction
rate of (CH3)2COO at 296 K and atmospheric pressure is 899 ± 42 s-1. Probably more importantly, current measurements
bring the direct and relative rate measurements of thermal unimolecular reaction kinetics of (CH3)2COO in quantitative
agreement.