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| Titel |
Newly observed peroxides and the water effect on the formation and removal of hydroxyalkyl hydroperoxides in the ozonolysis of isoprene |
| VerfasserIn |
D. Huang, Z. M. Chen, Y. Zhao, H. Liang |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 13, no. 11 ; Nr. 13, no. 11 (2013-06-12), S.5671-5683 |
| Datensatznummer |
250018697
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| Publikation (Nr.) |
 copernicus.org/acp-13-5671-2013.pdf |
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| Zusammenfassung |
| The ozonolysis of alkenes is considered to be an
important source of atmospheric peroxides, which serve as oxidants,
reservoirs of HOx radicals, and components of secondary organic
aerosols (SOAs). Recent laboratory investigations of this reaction
identified hydrogen peroxide (H2O2) and hydroxymethyl
hydroperoxide (HMHP) in ozonolysis of isoprene. Although larger hydroxyalkyl
hydroperoxides (HAHPs) were also expected, their presence is not currently
supported by experimental evidence. In the present study, we investigated
the formation of peroxides in the gas phase ozonolysis of isoprene at
various relative humidities on a time scale of tens of seconds, using a
quartz flow tube reactor coupled with the online detection of peroxides. We
detected a variety of conventional peroxides, including H2O2,
HMHP, methyl hydroperoxide, bis-hydroxymethyl hydroperoxide, and ethyl
hydroperoxide, and interestingly found three unknown peroxides. The molar
yields of the conventional peroxides fell within the range of values
provided in the literature. The three unknown peroxides had a combined molar
yield of ~ 30% at 5% relative humidity (RH), which was
comparable with that of the conventional peroxides. Unlike H2O2
and HMHP, the molar yields of these three unknown peroxides were inversely
related to the RH. On the basis of experimental kinetic and box model
analysis, we tentatively assigned these unknown peroxides to C2−C4 HAHPs,
which are produced by the reactions of different Criegee intermediates with
water. Our study provides experimental evidence for the formation of large
HAHPs in the ozonolysis of isoprene (one of the alkenes). These large HAHPs
have a sufficiently long lifetime, estimated as tens of minutes, which
allows them to become involved in atmospheric chemical processes, e.g., SOA
formation and radical recycling. |
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