Measurements of the gas phase UV absorption spectrum of C2H5O2· radicals and of the temperature dependence of the rate constant for their self-reaction

✍ Scribed by Timothy J. Wallington; Philippe Dagaut; Michael J. Kurylo

• Publisher: Elsevier Science
• Year: 1988
• Tongue: English
• Weight: 937 KB
• Volume: 42
• Category: Article
• ISSN: 1010-6030
• DOI: 10.1016/1010-6030(88)80061-3

✦ Synopsis

A flash photolysis technique has been used to measure the gas phase UV absorption cross-sections for C2H,02* radicals over the wavelength range 215 -300 nm. Kinetic absorption spectroscopy was then employed to study the self-reaction of these radicals. The measured absorption cross-section at 250 nm, (3.89 + 0.54) X lo-l8 cm2 molecule-i, was used to derive an observed self-reaction rate constant at room temperature, defined as -d[C2Hs02-]/dt = 2k,bs[C2H,0z*]2, of kobs = (9.87 f 0.74) X lo-l4 cm3 molecule-l s-l, independent of pressure over the range 25 -400 Torr. Experiments were performed over the temperature range 228 -380 K and the kinetic data were fit by the Arrhenius expression (kobs = (1.41 f 0.19) X lo-l3 exp{-(110 + 40)/T} cm3 molecule-' s-l) where the error limits represent 20 from linear least-squares analysis. A modeling assessment of the effects of secondary reactions involving CZH502-radicals indicates that these measured values for !z,,,~ could be higher than the true rate constant for the self-reaction by as much as a factor of 1.7 depending on the branching ratio for the various product channels for the reaction C2H,02* + C,H,O,-+ Products. Thus k, = (0.6)k,b,.