Absolute and Relative Rate Constants for the Reactions CH3C(O)O2 + NO and CH3C(O)O2 + NO2 and Thermal Stability of CH3C(O)O2NO2

Abstract

A pulse-radiolysis system was used to measure absolute rate constants for the reactions of CH3C(O)O2 radicals with NO and NO2 at 295 K and 1000 mbar total pressure of SF6. When the rate of formation and decay of NO2 using its absorption at 400.5 and 452 nm were monitored, the rate constants k(CH3C(O)O2 + NO) = (2.0 ± 0.3) × 10-11 and k(CH3C(O)O2 + NO2) = (1.0 ± 0.2) × 10-11 cm3 molecule-1 s-1 were determined. Long path-length Fourier transform infrared spectrometers were used to study the rate-constant ratio k(CH3C(O)O2 + NO)/k(CH3C(O)O2 + NO2) in 6−700 Torr total pressure of N2 diluent at 243−295 K. At 295 K in 700 Torr of N2 diluent k(CH3C(O)O2 + NO)/k(CH3C(O)O2 + NO2) = 2.07 ± 0.21. The results are discussed in the context of the atmospheric chemistry of acetylperoxy radicals.