Products of the gas phase reactions of the OH radical with α‐ and β‐pinene in the presence of NO

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Abstract
Products of the gas phase reactions of the OH radical with α‐ and β‐pinene in the presence of NO have been investigated using gas chromatography and in situ atmospheric pressure ionization mass spectrometry (API‐MS). Acetone was identified and quantified by gas chromatography with flame ionization detection and combined gas chromatography‐mass spectrometry, with formation yields of 0.110±0.027 from the α‐pinene reaction and 0.085±0.018 from the β‐pinene reaction. Acetone is a first‐generation product and may arise after initial H atom abstraction from the tertiary allylic C‐H bond at the 1 position and/or after OH radical addition at the 2 and 3 positions. Using API‐MS and API‐MS/MS analyses, in addition to the formation of pinonaldehyde from α‐pinene and nopinone from β‐pinene, we have observed the formation of hydroxynitrates, dihydroxynitrates and dihydroxycarbonyl products of molecular weights 215, 231 and 184, respectively, from both α‐ and β‐pinene. Reaction schemes leading to the formation of these multifunctional product species, consistent with our understanding of the atmospheric chemistry of organic peroxy and alkoxy radicals, are presented.