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H. Hein, Holger Somnitz, A. Hoffmann, Reinhard Zellner
A Combined Experimental and Theoretical Investigation of the Reactions of 3-Pentoxy Radicals: Reaction with O2 and Unimolecular Decomposition
The reactions of 3-pentoxy radicals with O2 and their unimolecular decomposition were investigated using time-resolved and simultaneous detection of NO2 and OH in the laser flash initiated oxidation of bromopentane combined with numerical simulation of the experimentally obtained concentration-time profiles. NO2 was monitored by cw-LIF, whereas OH was detected by laser long-path absorption at 308 nm. 3-pentoxy radicals were produced selectively by the excimer-laser photolysis of 3-bromopentane at 248 nm and subsequent reaction of the 3-pentyl radicals with O2 in the presence of NO. All experiments were performed at a temperature of 293&plusm;3 K and 50 mbar total pressure. The following rate coefficients for reaction with oxygen (kO2) and for thermal decomposition (kdecomp) of 3-pentoxy radicals were obtained: kO2 = (7.2&plusm;3.5)× 10-15 cm3 molecule-1 s-1 and kdecomp = (5.0&plusm;2.5)× 103 s-1.
In addition to the experimental investigation, the unimolecular reaction channels of 3-pentoxy radicals were also analyzed by a combined ab initio/RRKM treatment. From the ab initio calculations structures of the 3-pentoxy radical and its decomposition transition states as well as energy barriers were determined. This information was used to solve the J-independent Master Equation which allowed thermal decomposition rate coefficients to be determined. The calculated rate constants are in good agreement with those determined experimentally.
Zeitschrift für Physikalische Chemie, Oldenbourg Wissenschaftsverlag
Print ISSN: 0942-9352
Volume: 214, 04/2000
Pages: 449