Abstract
Using tailor-made organic compounds tethered to solid substrates through organo-silane chemistry, we present a reductionist model study aimed at understanding the mechanisms of heterogeneous organic oxidation reactions at solid/air interfaces. The surface vibrational spectra of glass slides functionalized with the tropospherically relevant olefins 1-pentene, 2-hexene, cyclopentene, cyclohexene, and a menthenol derivative via aniline-silane linkers have been obtained through polarization-resolved broadband vibrational sum frequency generation (SFG). The olefinic and aliphatic CH stretches located above and below 3000 cm-1, respectively, are clearly discernable and their spectral intensities are used to track, with 10 s time resolution, C{double bond, long}C double bond oxidation reactions of surface-bound cyclohexene at room temperature and with low ppm amounts of ozone at 1 atm. The olefinic CH stretching mode disappears at a rate of 0.05(1) s-1, and the aliphatic asymmetric stretch modes increase at a rate of 0.04(1) s-1. Analogous experiments show the formation of methyl groups even for those olefins under investigation that do not originally possess methyl groups. The implications for heterogeneous organic oxidation chemistry involving tropospheric dust particles are discussed.
Original language | English (US) |
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Pages (from-to) | 86-98 |
Number of pages | 13 |
Journal | Vibrational Spectroscopy |
Volume | 50 |
Issue number | 1 |
DOIs | |
State | Published - May 26 2009 |
Funding
GYS gratefully acknowledges support by NASA Headquarters under the NASA Earth and Space Science Fellowship program (Grant 07-Earth07R-0084). JMG-D gratefully acknowledges a fellowship from the Camille and Henry Dreyfus Postdoctoral Program in Environmental Chemistry. Support for this project is provided by the National Science Foundation Atmospheric Chemistry division and the ACS Petroleum Research Fund. This work was supported by the Director, Chemical Sciences, Geosciences and Biosciences Division, of the U.S. Department of Energy as well as the National Science Foundation CAREER grant in Experimental Physical Chemistry. Support from the DOE-funded Northwestern University Institute for Catalysis in Energy Processes (ICEP) and the Northwestern University International Institute for Nanotechnology (IIN) is greatly appreciated. We thank Mark A. Anderson and Professor R.P.H. Chang for ellipsometry analysis. The authors also acknowledge donations, equipment loans and the technical support of Spectra Physics, a Division of Newport Corporation, and helpful discussions with Dr. Michael J. Musorrafiti. FMG is the Northwestern University Dow Chemical Company professor. KAS and FMG are both Sloan Foundation Fellows.
Keywords
- Cyclohexane
- Cyclohexene
- Cyclopentene
- Hexene
- Olefins
- Ozone
- Pentene
- Sum frequency generation
- Terpene
- Tropospheric chemistry
ASJC Scopus subject areas
- Spectroscopy