2. Academic Validation
  3. Ozone initiated heterogeneous oxidation of unsaturated carboxylic acids by ATR-FTIR spectroscopy

Ozone initiated heterogeneous oxidation of unsaturated carboxylic acids by ATR-FTIR spectroscopy

  • Spectrochim Acta A Mol Biomol Spectrosc. 2019 May 5;214:177-183. doi: 10.1016/j.saa.2019.02.025.
Xiaoyan Gao 1,  Chunbo Leng 2,  Guang Zeng 3,  Dong Fu 4,  Yunhong Zhang 5,  Yong Liu 6
Affiliations

Affiliations

  • 1 Department of Chemistry, University of Colorado Denver, Denver, CO, 80217, USA; School of Chemical Engineering, Key Laboratory for Palygorskite Science and Applied Technology of Jiangsu, Huaiyin Institute of Technology, Huaian 223003, China. Electronic address: [email protected].
  • 2 Department of Chemistry, University of Colorado Denver, Denver, CO, 80217, USA; The Institute of Chemical Physics, Key Laboratory of Cluster Science, School of Chemistry and Chemical Engineering, Beijing Institute of Technology, Beijing 100081, China.
  • 3 Department of Chemistry, University of Colorado Denver, Denver, CO, 80217, USA; Institute of Nuclear Physics and Chemistry, China Academy of Engineering of Physics, Mianyang 621900, China.
  • 4 Department of Chemistry, University of Colorado Denver, Denver, CO, 80217, USA.
  • 5 The Institute of Chemical Physics, Key Laboratory of Cluster Science, School of Chemistry and Chemical Engineering, Beijing Institute of Technology, Beijing 100081, China.
  • 6 Department of Chemistry, University of Colorado Denver, Denver, CO, 80217, USA. Electronic address: [email protected].
PMID: 30776719 DOI: 10.1016/j.saa.2019.02.025
Abstract

Despite considerable effort has been directed to ozone-initiated heterogeneous oxidation of unsaturated organic species in atmospheric environment, current knowledge about how chemical structure of unsaturated carboxylic acids affects their reaction kinetics remains very limited. Here, kinetics of heterogeneous reaction of ozone with six unsaturated fatty acids (oleic acid, vaccenic acid, eladic acid, myristoleic acid, palmitoleic acid and 2-hexadecenoic acid) were studied via a flow system combined with attenuated total reflection Fourier-transformed infrared spectroscopy (ATR-FTIR). Pseudo-first-order rate constants (kapp) and overall reactive uptake coefficients (γ) values were derived according to the changes in absorbance from infrared spectra. Results have shown reaction rates are highly dependent on structures of unsaturated fatty acids. Cis-isomer has faster reaction kinetics than trans-isomer, and conjugated system between CC and CO bonds can greatly inhibit reactivity. Also, it is found that a longer carbon chain length between CC bond and COOH group or a shorter chain length between CC bond and last carbon seemingly enhances reaction kinetics. In addition, changes in redox activity and hydrophilicity of oleic acid samples before and after exposure ozone have been reported for the first time. Results have revealed that ozone-initiated heterogeneous reaction can markedly increase redox activity and hydrophilicity of unsaturated carboxylic acids.

Keywords

Heterogeneous oxidation; Reaction kinetics; Unsaturated fatty acids; Uptake coefficient.

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