Temperature-Dependent Rate Constants and Product Branching Ratios for the Gas-Phase Reaction Between CH3O2 and ClO

Article abstract of DOI:10.1021/j100146a020

Kinetic and product branching data have been measured for the reaction of CH3O2 radicals with ClO in the temperature range 225-355 K using the discharge-flow/mass spectrometry technique.The pressure-independent overall reaction rate constant is described by k₍₁₂₎(225-355 K) = (3.25 +/- 0.50) * 10^-12 exp((-114 +/- 38)/T) cm³ molecule^-1 s^-1.Two reaction channels were identified, leading to CH3O + ClOO (12a) and CH3OCl + O2 (12b), respectively.The branching ratios, α_12a = k_12a/k₁₂ and α_12b = k_12b/k₁₂, are also independent of pressure and are described by α_12a = (1.51 +/- 0.56) exp((-218 +/- 93)/T) and α_12b = (0.080 +/- 0.059) exp((-377 +/- 178)/T).These expressions yield roughly equal rate constants of k_12a and k_12b of ca. 1 * 10^-12 cm³ molecule^-1 s^-1 at the low temperatures prevalent in the polar winter and early springtime stratosphere.We thus identify CH3OCl as a potentially important species in ozone hole chemistry.