The overall rate constants of the NO reaction with hydroxyalkylperoxy radicals derived from the OH-initiated oxidation of several atmospherically abundant alkenes-ethene, propene, 1-butene, 2-butene, 2-methyl propene, 1,3-butadiene, and isoprene (2-methyl-1,3-butadiene)-were determined using the turbulent flow technique and pseudo first-order kinetic conditions with high pressure chemical ionization mass spectrometry for the direct detection of hydroxyalkylperoxy radical reactants. The individual 100 Torr, 298 K rate constants for each alkene system were found to be identical within the 95% confidence interval associated with each separate measurement. The average overall rate constant for the reaction of all alkene-derived hydroxyalkylperoxy radicals with NO was determined to be 9.1 AE 0.5 (2s) Â 10 À12 cm 3 molecule À1 s À1 . Previous studies of this reaction for the ethene, 2-methyl propene and isoprene systems reported varying rate constant values that ranged from a factor of two lower to a factor of two higher than the present result. However, the invariant nature and value of the present rate constant determination closely parallels the results obtained in the measurement of rate constants for the reactions of several alkane-derived peroxy radicals with NO.

A direct kinetics study of the product-forming channels of the reaction of isoprenederived hydroxyalkylperoxy radicals with NO has been performed at 100 Torr pressure and 298 K using the turbulent flow technique with high-pressure chemical ionization mass spectrometry for the detection of reactants and products. For comparative purposes, a similar study was also performed for the reaction of 1-and 2-butene-derived hydroxyalkylperoxy radicals with NO. The measured hydroxyalkylnitrate product channel branching ratios were determined to be 0.061, 0.068, and 0.070 for the 1-butene, 2-butene, and isoprene systems, respectively. The results are compared to previous measurements of the hydroxyalkylnitrate-branching ratios for these systems, and the atmospheric significance of the results is discussed.