A Gas-Phase Kinetic Study of the Reaction between Bromine Monoxide and Methylperoxy Radicals at Atmospheric Temperatures

Abstract

The rate constant of the reaction of BrO with CH(3)O(2) was determined to be k1 = (6.2 +/- 2.5) x 10(-12) cm3 molecule(-1) s(-1) at 298 K and 100-200 Torr of O2 diluent. Quoted uncertainty was two standard deviations. No significant pressure dependence of the rate constants was observed at 100-200 Torr total pressure of N2 or O2 diluents. Temperature dependence of the rate constants was further investigated over the range 233-333 K, and an Arrhenius type expression was obtained for k1 = 4.6 x 10(-13) exp[(798 +/- 76)/T] cm3 molecule(-1) s(-1). The product branching ratios were evaluated and the atmospheric implications were discussed.

A computational investigation of the atmospheric reaction CH3O2+ClO

“…A similar thermodynamically feasible pathway leading to CH 2 O + HOOOI has been computed for the CH 3 O 2 + IO reaction [21]. Nevertheless, a recent experimental study of the reaction CH 3 O 2 + BrO [22] has not detected bromine atoms, a finding which has been interpreted as an evidence for a small probability of stabilization of the CH 3 OOOBr intermediate and the formation of the decomposition products CH 2 O + HOOBr. Instead, yield of methyl bromide, CH 3 Br, has been discussed as taking place to a limited degree [22].…”

“…Nevertheless, a recent experimental study of the reaction CH 3 O 2 + BrO [22] has not detected bromine atoms, a finding which has been interpreted as an evidence for a small probability of stabilization of the CH 3 OOOBr intermediate and the formation of the decomposition products CH 2 O + HOOBr. Instead, yield of methyl bromide, CH 3 Br, has been discussed as taking place to a limited degree [22]. The analogous pathway in the CH 3 O 2 + ClO reaction leading to the formation of CH 3 Cl + O 3 species (channel 1c) has been examined [10].…”

Measurement and interpretation of gas phase formaldehyde concentrations obtained during the CHABLIS campaign in coastal Antarctica

“…Rate constants for BrO+CH 3 O 2 reaction of 9.14×10 −12 molec −1 cm 3 s −1 (267 K) and 5.7×10 −12 (298 K) have been reported by Enami et al (2007) and Aranda et al (1997) respectively, but the products of the reaction are not fully constrained: Evidence from the kinetic studies indicates that the likely products are CH 2 O 2 +HOBr, or CH 3 OBr+O 2 , rather than (for example) CH 3 O+BrO 2 , which would yield HCHO+Br+O 2 . In this paper we assume that the reaction does not produce HCHO.…”

Coupling of HO<sub>x</sub>, NO<sub>x</sub> and halogen chemistry in the antarctic boundary layer

“…7 indicates that two key factors are the kinetics/products of the IO + CH 3 O 2 reaction, and the aerosol surface area. IO + CH 3 O 2 competes with the peroxy-radical termination reactions, and with the CH 3 O 2 + NO propagation step; laboratory measurements of the rate constant for this reaction vary by a factor of 30, from the "slow" results of Dillon et al (2006), k = 2×10 −12 molec −1 cm 3 s −1 , to the faster data from Bale et al 2005and Enami et al (2007), both giving k ∼ (6-7)…”