Rate constants for the reactions of Br atoms with a series of alkanes, alkenes, and alkynes in the presence of O₂

Abstract

Rate constants of Br atom reactions have been determined using a relative kinetic method in a 20 1 reaction chamber at total pressures between 25 and 760 torr in Nz + Oz diluent over the temperature range 293-355 K. The measured rate constants for the reactions with alkynes and alkenes showed dependence upon temperature, total pressure, and the concentration of O2 present in the reaction system.

Evaluated kinetic and photochemical data for atmospheric chemistry: Volume II – gas phase reactions of organic species

“…The rate coefficients from these studies Baker et al, 1970;Baldwin and Walker, 1979;Hucknall et al, 1975; are fitted to the three parameter expression, k=CT 2 exp(-D/T ), resulting in k=1.81×10 −17 T 2 exp(114/T ) cm 3 molecule −1 s −1 over the temperature range 230-760 K. The preferred Arrhenius expression, k=A exp(-B/T ), is centered at 260 K and is derived from the three parameter expression with A = Ce 2 T 2 and B = D + 2T . The preferred values are in good agreement with the room temperature absolute and relative rate coefficients of Greiner (1970), Stuhl (1973, , Paraskevopoulos and Nip (1980), , , , , Barnes et al (1986), Behnke et al (1988) and Chuong and Stevens (2002), which were not used in the evaluation of the rate coefficient.…”

Addition of Peroxyl Radicals to Alkenes and the Reaction of Oxygen with Alkyl Radicals

“…Also, the bond formed by OH addition to alkenes is not unusually strong, with the addition being reversible at the relatively low temperature of 500 -600 K. 51 Similarly, radical atoms are know to undergo barrierless addition to alkenes, [52][53][54] this is consistent with the above explanation for hydroxyl, as they are of even higher symmetry than OH. …”

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

“…This is also the case for the analogue C1 reactions. Product data for reaction of Br with hydrocarbons is currently only available for ethene and acetylene [29,31]. The reactions of Br-atoms with alkanes are slow, proceed via a hydrogen abstraction mechanism producing alkyl radicals and HBr and are of negligible importance for the atmosphere.…”