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.)