Kinetics of the reaction of methyl radicals with oxygen
Abstract
The rate of reaction of methyl radicals (⩽ 5 × 10–7 mol dm–3) with oxygen [(1–40)× 10–6 mol dm–3] in an excess of argon has been studied in a flow-discharge tube at total pressures from 2 to 10 Torr and temperatures from 230 to 568 K using a competitive technique. Methyl radicals were produced by the addition of hydrogen atoms [(1–6)× 10–6 mol dm–3] to ethylene [(5–20)× 10–6 mol dm–3] and the radical combination products formed by the competing reactions were measured by gas chromatography.
The following rate constants have been measured: H + C2H5→ 2CH3(3) H + CH3+ Ar → CH4+ Ar (4) log10(k3/dm3 mol–1 s–1)=(10.68 ± 0.10)–(55 ± 35)/(T/K) log10(k4/dm6 mol–2 s–1)=(12.59 ± 0.01)+(113 ± 4)/(T/K) CH3+ O2+ Ar → CH3O2+ Ar (9) log10(k°9/dm6 mol–2 s–1)=(10.46 ± 0.06)+(243 ± 20)/(T/K) where the last value has been extrapolated to its low-pressure limit. (Errors throughout are one standard deviation.)