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| Titel |
Kinetics of the reactions of isoprene-derived hydroxynitrates: gas phase epoxide formation and solution phase hydrolysis |
| VerfasserIn |
M. I. Jacobs, W. J. Burke, M. J. Elrod |
| 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 ; 14, no. 17 ; Nr. 14, no. 17 (2014-09-01), S.8933-8946 |
| Datensatznummer |
250118992
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| Publikation (Nr.) |
 copernicus.org/acp-14-8933-2014.pdf |
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| Zusammenfassung |
| Isoprene, the most abundant non-methane volatile organic compound (VOC)
emitted into the atmosphere, is known to undergo gas phase oxidation to form
eight different hydroxynitrate isomers in "high-NOx"
environments. These hydroxynitrates are known to affect the global and
regional formation of ozone and secondary organic aerosol (SOA), as well as
affect the distribution of nitrogen. In the present study, we have
synthesized three of the eight possible hydroxynitrates: 4-hydroxy-3-nitroxy
isoprene (4,3-HNI) and E / Z-1-hydroxy-4-nitroxy isoprene (1,4-HNI).
Oxidation of the 4,3-HNI isomer by the OH radical was monitored using a flow
tube chemical ionization mass spectrometer (FT-CIMS), and its OH rate
constant was determined to be
(3.64 ± 0.41) × 10−11 cm3 molecule−1 s−1.
The products of 4,3-HNI oxidation were monitored, and a mechanism to explain
the products was developed. An isoprene epoxide (IEPOX) – a species
important in SOA chemistry and thought to originate only from
"low-NOx" isoprene oxidation – was found as a minor, but
significant, product. Additionally, hydrolysis kinetics of the three synthesized isomers
were monitored with nuclear magnetic resonance (NMR). The bulk, neutral solution hydrolysis rate constants
for 4,3-HNI and the 1,4-HNI isomers were
(1.59 ± 0.03) × 10−5 s−1 and
(6.76 ± 0.09) × 10−3 s−1, respectively. The
hydrolysis reactions of each isomer were found to be general acid-catalyzed.
The reaction pathways, product yields and atmospheric implications for both
the gas phase and aerosol phase reactions are discussed. |
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