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| Titel |
Mechanistic study of secondary organic aerosol components formed from nucleophilic addition reactions of methacrylic acid epoxide |
| VerfasserIn |
A. W. Birdsall, C. R. Miner, L. E. Mael, 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. 23 ; Nr. 14, no. 23 (2014-12-08), S.12951-12964 |
| Datensatznummer |
250119218
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| Publikation (Nr.) |
 copernicus.org/acp-14-12951-2014.pdf |
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| Zusammenfassung |
| Recently, methacrylic acid epoxide (MAE) has been proposed as a precursor to
an important class of isoprene-derived compounds found in secondary organic
aerosol (SOA): 2-methylglyceric acid (2-MG) and a set of oligomers, nitric
acid esters, and sulfuric acid esters related to 2-MG. However, the specific
chemical mechanisms by which MAE could form these compounds have not been
previously studied with experimental methods. In order to determine the
relevance of these processes to atmospheric aerosol, MAE and 2-MG have been
synthesized and a series of bulk solution-phase experiments aimed at studying
the reactivity of MAE using nuclear magnetic resonance (NMR) spectroscopy
have been performed. The present results indicate that the acid-catalyzed MAE
reaction is more than 600 times slower than a similar reaction of an
important isoprene-derived epoxide, but is still expected to be kinetically
feasible in the atmosphere on more acidic SOA. The specific mechanism by
which MAE leads to oligomers was identified, and the reactions of MAE with a
number of atmospherically relevant nucleophiles were also investigated.
Because the nucleophilic strengths of water, sulfate, alcohols (including
2-MG), and acids (including MAE and 2-MG) in their reactions with MAE were
found to be of similar magnitudes, it is expected that a diverse variety of
MAE + nucleophile product species may be formed on ambient SOA. Thus, the
results indicate that epoxide chain reaction oligomerization will be limited
by the presence of high concentrations of non-epoxide nucleophiles (such as
water); this finding is consistent with previous environmental chamber
investigations of the relative humidity dependence of 2-MG-derived
oligomerization processes and suggests that extensive oligomerization may not
be likely on ambient SOA because of other competitive MAE reaction
mechanisms. |
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