Peroxy radical chemistry and OH radical production during the NO<sub>3</sub>-initiated oxidation of isoprene
Peroxy radical reactions (RO<sub>2</sub> + RO<sub>2</sub>) from the NO<sub>3</sub>-initiated oxidation of isoprene are studied with both gas chromatography and a chemical ionization mass spectrometry technique that allows for more specific speciation of products t...
| Main Authors: | , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2012-08-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | http://www.atmos-chem-phys.net/12/7499/2012/acp-12-7499-2012.pdf |
| Summary: | Peroxy radical reactions (RO<sub>2</sub> + RO<sub>2</sub>) from the NO<sub>3</sub>-initiated oxidation of isoprene are studied with both gas chromatography and a chemical ionization mass spectrometry technique that allows for more specific speciation of products than in previous studies of this system. We find high nitrate yields (~ 80%), consistent with other studies. We further see evidence of significant hydroxyl radical (OH) formation in this system, which we propose comes from RO<sub>2</sub> + HO<sub>2</sub> reactions with a yield of ~38–58%. An additional OH source is the second generation oxidation of the nitrooxyhydroperoxide, which produces OH and a dinitrooxyepoxide with a yield of ~35%. The branching ratio of the radical propagating, carbonyl- and alcohol-forming, and organic peroxide-forming channels of the RO<sub>2</sub> + RO<sub>2</sub> reaction are found to be ~18–38%, ~59–77%, and ~3–4%, respectively. HO<sub>2</sub> formation in this system is lower than has been previously assumed. Addition of RO<sub>2</sub> to isoprene is suggested as a possible route to the formation of several isoprene C<sub>10</sub>-organic peroxide compounds (ROOR). The nitrooxy, allylic, and C<sub>5</sub> peroxy radicals present in this system exhibit different behavior than the limited suite of peroxy radicals that have been studied to date. |
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| ISSN: | 1680-7316 1680-7324 |