Reactions of alkoxyl radicals in the atmosphere

Abstract

The products of the gas-phase reactions of the OH radical with n-pentane and [²H₁₂] pentane have been studied at 296 ± 2 K and 740 Torr total pressure of N₂–O₂ diluent gas in the presence of NO. Direct air sampling, atmospheric-pressure ionisation tandem mass spectrometry showed the formation of the previously predicted C₅-hydroxycarbonyl product, together with pentanones. The effect of varying the O₂ concentration on the C₅-hydroxycarbonyl and pentanones was consistent with the hydroxycarbonyl being the product formed after isomerisation of the pentan-2-oxyl radical. Gas chromatographic analyses of pentan-2-one and pentan-3-one and pentan-2-yl and pentan-3-yl nitrates allowed rate constants for the decomposition and isomerisation reactions of the pentan-2-oxyl and pentan-3-oxyl radicals, relative to their reactions with O₂, to be determined.