Kinetics of the reactions of CH3 with O(3P) and O2 at 295 K

✍ Scribed by I. C. Plumb; K. R. Ryan

• Publisher: John Wiley and Sons
• Year: 1982
• Tongue: English
• Weight: 662 KB
• Volume: 14
• Category: Article
• ISSN: 0538-8066
• DOI: 10.1002/kin.550140806

✦ Synopsis

The reactions of CH3 radicals with O(3P) and 0 2 have been studied at 295 K in a gas flow reactor sampled by a mass spectrometer. For the reaction between CH3 and 0, conditions were such that [O] >> [CH3] and the methyl radicals decayed under pseudo-first-order conditions giving a rate coefficient of (1.14 f 0.29) X cm3/s. The reaction between CH3 and 0 2 was studied in separate experiments in which CH3 decayed under pseudo-first-order conditions. In this case, the rate coefficient obtained increased with increasing concentration of the helium carrier gas. This was varied over the range of 2.5-25 X 10l6 C I Y -~, resulting in value8 for the apparent two-body rate coefficient ranging from 1 X lo-" to 5.2 X cm3/s. No evidence was found for the production of HCHO by a direct two-body process involving CH3 + 0 2 , and an upper limit of 3 X cm3/s was placed on the rate coefficient for this reaction. The experimental results for the apparent two-body rate Coefficient exhibit the curvature one would expect for an association reaction in the fall-off region. Calculations used to extrapolate these measurements to the low-pressure limit yield a value for ko of (3.4 f 1.1) X lO-3l cm6/s, which is more than a factor of 2 higher than previous estimates.