Reactions of alkoxyl radicals in the atmosphere

The products of the gas-phase reactions of the OH radical with n-pentane and [H-2(12)]pentane have been studied at 296 +/- 2 K and 740 Torr total pressure of N-2-O-2 diluent gas in the presence of NO. Direct air sampling, atmospheric-pressure ionisation tandem mass spectrometry showed the formation of the previously predicted C-5-hydroxycarbonyl product, together with pentanones. The effect of varying the O-2 concentration on the C-5-hydroxycarbonyl and pentanones was consistent with the hydroxy-carbonyl 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 O-2, to be determined.