Measuring Rate Constants for Reactions of the Simplest Criegee Intermediate (CH2OO) by Monitoring the OH Radical

While generating the CH2OO molecule by reacting CH2I with O2, significant amounts of the OH radical were observed by laser-induced fluorescence. At least two different processes formed OH. A fast process was probably initiated by a reaction of vibrationally hot CH2I radicals. The second process appeared to be associated with the decay of the CH2OO molecule. The addition of molecules known to react with CH2OO increased the observed decay rates of the OH signal. Using the OH signals as a proxy for the CH2OO concentration, the rate constant for the reaction of hexafluoroacetone with CH2OO was determined to be (3.33 ± 0.27) × 10−11 cm3 molecule−1 s−1, in good agreement with the value measured by Taatjes et al.1 The rate constant for the reaction of SO2 with CH2OO, (3.53 ± 0.29) × 10−11 cm3 molecule−1 s−1, showed no pressure dependence over the range of 50−200 Torr and was in agreement with the value at 4 Torr reported by Welz et al.2