A temperature-dependent relative-rate study of the OH initiated oxidation of n-butane: the kinetics of the reactions of the 1- and 2-butoxy radicals.
The kinetics of the reactions of 1-and 2-butoxy radicals have been studied using a slow-flow photochemical reactor with GC-FID detection of reactants and products. Branching ratios between decomposition, CH3CH(O*)CH2CH3 --> CH3CHO + C2H5, reaction (7), and reaction with oxygen, CH3CH(O*)CH2CH3+ O2 --> CH3C(O)C2H5+ HO2, reaction (6), for the 2-butoxy radical and between isomerization, CH3CH2CH2CH2O* --> CH2CH2CH2CH2OH, reaction (9), and reaction with oxygen, CH3CH2CH2CH2O* + O2 --> C3H7CHO + HO2, reaction (8), for the 1-butoxy radical were measured as a function of oxygen concentration at atmospheric pressure over the temperature range 250-318 K. Evidence for the formation of a small fraction of chemically activated alkoxy radicals generated from the photolysis of alkyl nitrite precursors and from the exothermic reaction of 2-butyl peroxy radicals with NO was observed. The temperature dependence of the rate constant ratios for a thermalized system is given by k7/k6= 5.4 x 10(26) exp[(-47.4 +/- 2.8 kJ mol(-1))/RT] molecule cm(-3) and k9/k8= 1.98 x 10(23) exp[(-22.6 +/- 3.9 kJ mol(-1))/RT] molecule cm(-3). The results agree well with the available experimental literature data at ambient temperature but the temperature dependence of the rate constant ratios is weaker than in current recommendations.
Cassanelli
Paola
P
University Chemical Laboratory, Lensfield Road, Cambridge, UKCB2 1EW. pc254@hermes.cam.ac.uk
Johnson
D
D
Anthony Cox
R
R
D002073:Butanes / Q000032:analysis / Q000737:chemistry*; D002849:Chromatography, Gas; D003198:Computer Simulation; D005609:Free Radicals / Q000032:analysis / Q000737:chemistry; D017665:Hydroxyl Radical / Q000032:analysis / Q000737:chemistry*; D007700:Kinetics; D008956:Models, Chemical; D010084:Oxidation-Reduction; D013696:Temperature
D002073:Butanes; D005609:Free Radicals; D017665:Hydroxyl Radical; C046888:butane