FLASH-PHOTOLYSIS STUDY OF THE CH3O2 + HO2 REACTION BETWEEN 248 AND 573-K

The kinetics of the reaction CH3O2 + HO2 → products (1) has been investigated between 248 and 573 K, using the flash photolysis-UV absorption technique. The rate constant, k1, was found to be independent of the presence of up to 12.8 Torr of water vapor at 298 K and of pressure between 210 and 760 Torr and can be represented by the Arrhenius expression k1/cm3 molecule-1 s-1 = (4.4 ± 0.7) × 10-13 exp[(780 ± 55)/T]. Absolute uncertainties, including experimental scatter and uncertaintites in the analysis parameters used to derive k1, are estimated to be 32% at 248 K, falling to 26% at 573 K. New results on the HO2 + HO2 → H2O2 + O2 (11) reaction, obtained between 248 and 573 K and 100 and 760 Torr total pressure, are presented, with k11/cm3 molecule-1 s-1 = (3.8 ± 0.4) × 10-13 exp[(580 ± 32)/T] + (1.2 ± 0.4) × 10-33[M] exp[(1150 ± 97)/T]. The UV absorption cross sections for HO2 and CH3O2 are critically reviewed. The rate constant for the reaction of atomic chlorine with methanol, Cl + CH3OH → HCl + CH2OH (6), was obtained relative to that with methane, Cl + CH4 → HCl + CH3 (8). k6 was independent of temperature, within experimental error, from 248 to 573 K, with k6cm3 molecule-1 s-1 = (5.3 ± 1.2) × 10-11. Errors are 1σ. © 1990 American Chemical Society.