Kurtén, T., Hyttinen, N., D'Ambro, E. L., Thornton, J., and Prisle, N. L.: Estimating the saturation vapor pressures of isoprene oxidation products C5H12O6 and C5H10O6 using COSMO-RS, Atmos. Chem. Phys., 18, 17589-17600, https://doi.org/10.5194/acp-18-17589-2018, 2018.
Estimating the saturation vapor pressures of isoprene oxidation products C₅H₁₂O₆ and C₅H₁₀O₆ using COSMO-RS
|Author:||Kurtén, Theo1; Hyttinen, Noora1; D’Ambro, Emma2,3;|
1University of Helsinki, Department of Chemistry and Institute for Atmospheric and Earth System Research (INAR), P.O. Box 55, 00014 Helsinki, Finland
2Department of Chemistry, University of Washington, Seattle, Washington 98195, USA
3Department of Atmospheric Sciences, University of Washington, Seattle, Washington 98195, USA
4University of Oulu, Nano and Molecular Systems Research Unit, P.O. Box 3000, 90014 Oulu, Finland
|Online Access:||PDF Full Text (PDF, 1.2 MB)|
|Persistent link:|| http://urn.fi/urn:nbn:fi-fe201902226041
|Publish Date:|| 2019-02-22
We have used COSMO-RS (the conductor-like screening model for real solvents), as implemented in the COSMOtherm program, to compute the saturation vapor pressures at 298 K of two photo-oxidation products of isoprene: the dihydroxy dihydroperoxide C₅H₁₂O₆, and the dihydroperoxy hydroxy aldehyde, C₅H₁₀O₆. The predicted saturation vapor pressures were significantly higher (by up to a factor of 1000) than recent experimental results, very likely due to the overestimation of the effects of intramolecular hydrogen bonds, which tend to increase saturation vapor pressures by stabilizing molecules in the gas phase relative to the liquid. Modifying the hydrogen bond enthalpy parameter used by COSMOtherm can improve the agreement with experimental results — however the optimal parameter value is likely to be system-specific. Alternatively, vapor pressure predictions can be substantially improved (to within a factor of 5 of the experimental values for the two systems studied here) by selecting only conformers with a minimum number of intramolecular hydrogen bonds. The computed saturation vapor pressures were very sensitive to the details of the conformational sampling approach, with the default scheme implemented in the COSMOconf program proving insufficient for the task, for example by predicting significant differences between enantiomers, which should have identical physical properties. Even after exhaustive conformational sampling, COSMOtherm predicts significant differences in saturation vapor pressures between both structural isomers and diastereomers. For C₅H₁₂O₆, predicted differences in psat between structural isomers are up to 2 orders of magnitude, and differences between stereoisomers are up to a factor of 20 — though these differences are very likely exaggerated by the overestimation of the effect of intramolecular H-bonds. For C₅H₁₂O₆, the maximum predicted differences between the three studied structural isomers and their diastereomer pairs are around a factor of 8 and a factor of 2, respectively, when only conformers lacking intramolecular hydrogen bonds are included in the calculations. In future studies of saturation vapor pressures of polyfunctional atmospheric oxidation products using COSMOtherm, we recommend first performing thorough conformational sampling and subsequently selecting conformers with a minimal number of intramolecular H-bonds.
Atmospheric chemistry and physics
|Pages:||17589 - 17600|
|Type of Publication:||
A1 Journal article – refereed
|Field of Science:||
114 Physical sciences
116 Chemical sciences
115 Astronomy and space science
Theo Kurtén, Noora Hyttinen, and Emma Louise D'Ambro thank the Academy of Finland for funding. Emma Louise D'Ambro was supported by the National Science Foundation Graduate Research Fellowship under grant no. DGE-1256082. Nønne Lyng Prisle thanks the European Research Council under the European Union's Horizon 2020 research and innovation programme (Project SURFACE, grant agreement no. 717022) and the Academy of Finland (grant 308238) for funding. We thank the CSC – IT Center for Science, Finland, for computational resources and Frank Eckert from COSMOLogic GmbH for technical support and helpful discussions. We thank Ben H. Lee and Felipe Lopez-Hilfiker (UW) and John Shilling and Jiumeng Liu (PNNL) for their contributions to the observations.
|EU Grant Number:||
(717022) SURFACE - The unexplored world of aerosol surfaces and their impacts.
|Academy of Finland Grant Number:||
308238 (Academy of Finland Funding decision)
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.