 |
| Titel |
Ozonolysis of surface-adsorbed methoxyphenols: kinetics of aromatic ring cleavage vs. alkene side-chain oxidation |
| VerfasserIn |
E. M. O'Neill, A. Z. Kawam, D. A. Ry, R. Z. Hinrichs |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1680-7316
|
| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 14, no. 1 ; Nr. 14, no. 1 (2014-01-02), S.47-60 |
| Datensatznummer |
250118242
|
| Publikation (Nr.) |
 copernicus.org/acp-14-47-2014.pdf |
|
|
|
|
|
| Zusammenfassung |
| Lignin pyrolysis products, which include a variety of substituted
methoxyphenols, constitute a major component of organics released by biomass
combustion, and may play a central role in the formation of atmospheric brown
carbon. Understanding the atmospheric fate of these compounds upon exposure
to trace gases is therefore critical to predicting the chemical and physical
properties of biomass burning aerosol. We used diffuse reflectance infrared
spectroscopy to monitor the heterogeneous ozonolysis of 4-propylguaiacol,
eugenol, and isoeugenol adsorbed on NaCl and α-Al2O3 substrates.
Adsorption of gaseous methoxyphenols onto these substrates produced near-monolayer surface concentrations of
3 × 1018 molecules m−2. The subsequent dark
heterogeneous ozonolysis of adsorbed 4-propylguaiacol cleaved the aromatic
ring between the methoxy and phenol groups with the product conclusively
identified by GC-MS and 1H-NMR. Kinetic analysis of eugenol and
isoeugenol dark ozonolysis also suggested the formation of ring-cleaved
products, although ozonolysis of the unsaturated substituent groups forming
carboxylic acids and aldehydes was an order of magnitude faster. Average
uptake coefficients for NaCl-adsorbed methoxyphenols were
γ = 2.3 (± 0.8) × 10−7 and
2 (± 1) × 10−6 for ozonolysis of the aromatic ring and
the unsaturated side chain, respectively, and reactions on
α-Al2O3 were approximately two times slower. UV–visible
radiation (λ > 300 nm) enhanced eugenol ozonolysis of the
aromatic ring by a factor of 4(± 1) but had no effect on ozonolysis of
the alkene side chain. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|