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Kinetics of Elementary Steps in the Reaction of Atomic Bromine with...

Laine, P. L., Y. S. Sohn, J. M. Nicovich, M. L. McKee, and P. Wine (2012), Kinetics of Elementary Steps in the Reaction of Atomic Bromine with 2,3-Dimethyl-2-butene under Atmospheric Conditions, Int. J. Chem. Kinet., 44, 13-26, doi:10.1002/kin.20608.

We have employed the laser flash photolysis–resonance fluorescence technique to investigate the gas-phase kinetics of elementary steps in the Br-initiated oxidation of 2,3-dimethyl-2-butene (TME) under atmospheric conditions. At T ≥ 274 K, measured rate coefficients are independent of pressure suggesting hydrogen abstraction as the dominant pathway. The following Arrhenius expression adequately describes all kinetic data at 274 K ≤ T ≤ 420 K: k1a (T ) = (3.84 ± 0.84) × 10−11 exp[(−169 ± 61)/T ] cm3 molecule−1 s−1 (uncertainties are 2σ , precision only). At 203 K ≤ T ≤ 241 K, kinetic evidence for reversible addition, Br + TME ↔ Br−TME (k1b , k−1b ), is observed. Analysis of the approach to equilibrium data allows evaluation of the rate coefficients k1b and k−1b . At atmospheric pressure addition of Br to TME occurs at a near gas kinetic rate. Equilibrium constants are obtained from k1b /k−1b . Combining the experimental results with electronic structure calculations allows third-law analyses of the equilibrium data. The following thermochemical parameters for the addition reaction (1b) at 0 and 298 K are obtained

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Tropospheric Composition Program (TCP)
Upper Atmosphere Research Program (UARP)