Rate constants for the reactions of OH with CH4 and fluorine, chlorine, and bromine substituted methanes at 296 K

Abstract

The absolute rate constants for the reactions of OH radicals with CH₄ and fifteen fluorine, chlorine, and bromine substituted methane molecules have been measured using a discharge flow system and laser magnetic resonance detection of OH. Measurements were made at 296 K and at pressures between 107 and 1300 Pa. The results indicate that the reaction mechanism involves the abstraction of a hydrogen atom and formation of H₂O and a methyl type radical product. Completely halogenated methane molecules are found to be relatively unreactive. Hydrogen containing molecules react with rate constants ranging from about 0.2 to 160×10⁻¹⁵ cm³/molecule⋅sec. The reactivity increases with decreasing carbon–hydrogen bond energies. Rough estimates are made of the Arrhenius parameters for the reactions.