Direct kinetic studies on the unimolecular decomposition of the 2-butoxy radical and its reactions with NO/NO2 and O2.
In: Transport and Chemical Transformation in the Troposphere, Proceedings of EUROTRAC Symposium, 7th, Garmisch-Partenkirchen, Germany, Mar.11-15, 2002, (2002), S. 464-467
Zeitschriftenaufsatz / Fach: Chemie
The temp. and pressure dependence of the unimol. decompn. of 2-butoxy radicals has been studied by a combined laser photolysis/laser-induced fluorescence (LIF) technique following the generation of the radicals by excimer laser photolysis of 2-Bu nitrite at l = 351 nm. Expts. have been performed at total pressures between 5 and 520 Torr nitrogen (N2) and in a temp. range between 260 and 300 K. The low- and the high-pressure limiting rate consts. have been extd. from a fall-off anal. of the exptl. results to be: k0 = 4.4 * 10-4exp(-(56.4 +-5.4) kJ mol-1/RT) cm3 s-1, k... = 1.2 * 1010exp(-(31.1 +-4.4) kJ mol-1/RT)cm3 s-1. In addn., the kinetics of the 2-butoxy radical reaction with NO/NO2 and O2 at temps. between 223 and 305 K and pressures between 5 and 80 Torr have been detd. The rate coeffs. for the reactions were found to be independent of total pressure with kNO = (3.9 +-0.3) * 10-11 cm3 s-1, kNO2 = (3.6 +-0.3)10-11 cm3 s-1, and ko2 = (1.39 +-0.30) * 10-14 cm3 s-1 at T = 295 K. The Arrhenius expressions have been detd. to be kNO = (9.1 +-2.7 ) * 10-12exp((3.4 +-0.6) kJ mol-1/RT) cm3 s-1, kNO2 = (8.6 +-3.3 ) * 10-12exp((3.3 +-0.8) kJ mol-1/RT) cm3 s-1, and kO2 = (2.3 +-1,0) * 10-14exp(-(1.4 +-0.8) kJ mol-1/RT) cm3 s-1, resp.