Direct investigations of reactions of 1-butoxy and 1-pentoxy radicals using laser pulse initiated oxidation: reaction with O-2 and isomerisation at 293 K and 50 mbar

The reactions of 1-butoxy and 1-pentoxy radicals were studied using time-re solved and simultaneous measurement of NO2 and OH concentrations in laser p ulse initiated oxidation studies followed by numerical simulations of the c oncentration profiles. The alkoxy radicals were produced selectively by the excimer-laser photolysis of 1-butyl bromide and 1-pentyl bromide at 248 nm and subsequent reaction of the 1-alkyl radicals with O-2 and NO. Whereas N O2 was detected by cw-LIF, OH was monitored by laser long-path absorption a t 308 nm. All experiments were performed at 293 +/- 3 K and a total pressur e of 50 mbar. The reactions with O-2 and the isomerisations via a 1,5-H-shi ft, viz., CH3CH2CH2CH2O + O-2 --> CH3CH2CH2CHO + HO2 (5) CH3CH2CH2CH2O --> CH2CH2CH2CH2OH (6) CH3CH2CH2CH2CH2O + O-2 --> CH3CH2CH2CH2CHO + HO2 (25) CH3CH2CH2CH2CH2O --> CH3CHCH2CH2CHOH (26) were investigated. Their rate coefficients were varied, utilizing the FACSI MILE integrator, until the best fits were obtained. Whereas in the case of 1-butoxy radicals absolute rate coefficients k(5) = (1.4 +/- 0.7) x 10(-14) cm(3) molecule(-1) s(-1) and k(6) = (3.5 +/- 2) x 10(4) s(-1) could be der ived, only limiting values for the 1-pentoxy radical reactions k(25) less t han or equal to 1 x 10(-13) cm(3) molecule(-1) s(-1) and k(26) greater than or equal to 1.0 x 10(5) s(-1) were obtained.