Rate coefficients for the gas-phase reactions of bromine radicals with a series of alkenes, dienes, and aromatic hydrocarbons at 298 � 2 K

Abstract

Using the relative kinetic method rate coefficients have been determined for the gas-phase reaction of bromine (Br) radicals with a series of alkenes, chloroalkenes, dienes. and aromatic hydrocarbons in 1000 mbar of synthetic air at 298 ? 2 K. Both the UV photolysis of CH,Br, ( A = 254 n m ) and the visible photolysis of Br, (320 5 A 5 480) were used to generate Br radicals. For the alkenes and dienes the following rate coefficients were obtained ( i n units of cm3 molecule-' s -l ) : trans-2-butene 9.

Temperature-dependent rate coefficient measurements for the reaction of bromine atoms with trichloroethene, ethene, acetylene, and tetrachloroethene in air

“…This observation led us to report the following modified Arrhenius expressions: k 5 ϭ 7.9 ϫ 10 Ϫ12 exp(Ϫ580/T) and k 6 ϭ 2.7 ϫ 10 Ϫ11 exp(Ϫ567/T) cm 3 molecule Ϫ1 s Ϫ1 , which have been used in the determination of absolute rate coefficients in this article. The only previous measurements of k 1 have been made at room temperature [32,33]. Reasonably consistent data (differences Յ15%) are obtained from the two reference reactions over the range of overlap.…”

Artifacts in measuring aerosol uptake kinetics: the roles of time, concentration and adsorption

“…To further investigate the plausibility of this, experiments were performed in which Br 2 was added to the flow tube along with Cl 2 to determine whether Br 2 would adsorb and affect the rate of 2-ODA loss. Br 2 was used to decouple the effect of adsorption from the radical reactions since the Br radicals generated by photolysis of Br 2 should not react with the gas-phase reference, acetone, or the particles; for example, the Br + acetone rate constant is estimated to be only 1.0×10 −20 cm 3 molecule −1 s −1 at 298 K (King et al, 1970), and reactions between Br and gas-phase organic compounds are typically orders of magnitude slower than analogous reactions with Cl (Bierbach et al, 1996;Finlayson-Pitts et al, 1999;Ezell et al, 2002). In fact, no reaction of the 2-ODA particles is observed in the absence of Cl 2 indicating that, indeed, Br radicals do no react with 2-ODA to an appreciable extent.…”

The reaction of allyl radicals with oxygen atoms—rate coefficient and product branching

“…The competitive reactions of Cl atoms with the precursor and olefinic primary products [28][29][30] complicate the stable product analysis. Allyl bromide photolysis produces allyl radicals and bromine atoms whose reactions are comparatively slow and do not interfere with the fast radical-radical/fast atom chemistry [31][32][33]. The photodecomposition of 1,5-hexadiene yields besides two allyl radicals directly propene and allene [15].…”