Products and Mechanisms of the Gas-Phase Reactions of OH Radicals with 1-Octene and 7-Tetradecene in the Presence of NO

Abstract

Products of the gas-phase reactions of OH radicals with 1-octene and 7-tetradecene have been investigated at 296 +/- 2 K and atmospheric pressure of air, using gas chromatography, direct air sampling atmospheric pressure ionization tandem mass spectrometry, and in situ Fourier transform infrared spectroscopy. We observe the hydroxynitrate(s) formed from reaction of the hydroxyalkylperoxy radicals with NO; heptanal and 4-hydroxyhexanal from decomposition of the 1,2-hydroxyoctoxy and 7-hydroxy-8-tetradecoxy radicals; and dihydroxynitrates and dihydroxycarbonyls formed after isomerization of the intermediate 1,2-hydroxyalkoxy radicals. Formic acid formation was also observed from the 1-octene reaction, in approximately 3% yield. In the presence of approximately 1.5 x 10(14) molecules cm(-3) of NO, the respective molar formation yields of heptanal and 4-hydroxyhexanal were 28 +/- 3% and 4% from 1-octene, and 86 +/- 11% and 6% from 7-tetradecene. The 4-hydroxyhexanal yield increased with increasing NO concentration, and we attribute 4-hydroxyhexanal + HC(O)OH formation to a minor pathway of the RC(*)HOH + O(2) reaction in the presence of NO. The reaction pathways occurring are discussed.