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α-Pinene Autoxidation Products May Not Have Extremely Low Saturation Vapor Pressures Despite High O : C Ratios

Kurtén, Theo; Tiusanen, Kirsi; Roldin, Pontus LU ; Rissanen, Matti; Luy, Jan Niclas; Boy, Michael; Ehn, Mikael and Donahue, Neil M. (2016) In The Journal of Physical Chemistry Part A: Molecules, Spectroscopy, Kinetics, Environment and General Theory 120(16). p.2569-2582
Abstract

COSMO-RS (conductor-like screening model for real solvents) and three different group-contribution methods were used to compute saturation (subcooled) liquid vapor pressures for 16 possible products of ozone-initiated α-pinene autoxidation, with elemental compositions C10H16O4-10 and C20H30O10-12. The saturation vapor pressures predicted by the different methods varied widely. COSMO-RS predicted relatively high saturation vapor pressures values in the range of 10-6 to 10-10 bar for the C10H16O4-10 "monomers", and 10-11 to 10-16 bar for the C20H30O10-12 "dimmers".... (More)

COSMO-RS (conductor-like screening model for real solvents) and three different group-contribution methods were used to compute saturation (subcooled) liquid vapor pressures for 16 possible products of ozone-initiated α-pinene autoxidation, with elemental compositions C10H16O4-10 and C20H30O10-12. The saturation vapor pressures predicted by the different methods varied widely. COSMO-RS predicted relatively high saturation vapor pressures values in the range of 10-6 to 10-10 bar for the C10H16O4-10 "monomers", and 10-11 to 10-16 bar for the C20H30O10-12 "dimmers". The group-contribution methods predicted significantly (up to 8 order of magnitude) lower saturation vapor pressures for most of the more highly oxidized monomers. For the dimers, the COSMO-RS predictions were within the (wide) range spanned by the three group-contribution methods. The main reason for the discrepancies between the methods is likely that the group-contribution methods do not contain the necessary parameters to accurately treat autoxidation products containing multiple hydroperoxide, peroxy acid or peroxide functional groups, which form intramolecular hydrogen bonds with each other. While the COSMO-RS saturation vapor pressures for these systems may be overestimated, the results strongly indicate that despite their high O:C ratios, the volatilities of the autoxidation products of α-pinene (and possibly other atmospherically relevant alkenes) are not necessarily extremely low. In other words, while autoxidation products are able to adsorb onto aerosol particles, their evaporation back into the gas phase cannot be assumed to be negligible, especially from the smallest nanometer-scale particles. Their observed effective contribution to aerosol particle growth may therefore involve rapid heterogeneous reactions (reactive uptake) rather than effectively irreversible physical absorption.

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publication status
published
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in
The Journal of Physical Chemistry Part A: Molecules, Spectroscopy, Kinetics, Environment and General Theory
volume
120
issue
16
pages
14 pages
publisher
The American Chemical Society
external identifiers
  • scopus:84968880413
  • wos:000375521500009
ISSN
1089-5639
DOI
10.1021/acs.jpca.6b02196
language
English
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yes
id
66effeae-d05b-4962-a86e-9147d49a9491
date added to LUP
2017-02-06 08:50:34
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2017-11-19 04:37:23
@article{66effeae-d05b-4962-a86e-9147d49a9491,
  abstract     = {<p>COSMO-RS (conductor-like screening model for real solvents) and three different group-contribution methods were used to compute saturation (subcooled) liquid vapor pressures for 16 possible products of ozone-initiated α-pinene autoxidation, with elemental compositions C<sub>10</sub>H<sub>16</sub>O<sub>4-10</sub> and C<sub>20</sub>H<sub>30</sub>O<sub>10-12</sub>. The saturation vapor pressures predicted by the different methods varied widely. COSMO-RS predicted relatively high saturation vapor pressures values in the range of 10<sup>-6</sup> to 10<sup>-10</sup> bar for the C<sub>10</sub>H<sub>16</sub>O<sub>4-10</sub> "monomers", and 10<sup>-11</sup> to 10<sup>-16</sup> bar for the C<sub>20</sub>H<sub>30</sub>O<sub>10-12</sub> "dimmers". The group-contribution methods predicted significantly (up to 8 order of magnitude) lower saturation vapor pressures for most of the more highly oxidized monomers. For the dimers, the COSMO-RS predictions were within the (wide) range spanned by the three group-contribution methods. The main reason for the discrepancies between the methods is likely that the group-contribution methods do not contain the necessary parameters to accurately treat autoxidation products containing multiple hydroperoxide, peroxy acid or peroxide functional groups, which form intramolecular hydrogen bonds with each other. While the COSMO-RS saturation vapor pressures for these systems may be overestimated, the results strongly indicate that despite their high O:C ratios, the volatilities of the autoxidation products of α-pinene (and possibly other atmospherically relevant alkenes) are not necessarily extremely low. In other words, while autoxidation products are able to adsorb onto aerosol particles, their evaporation back into the gas phase cannot be assumed to be negligible, especially from the smallest nanometer-scale particles. Their observed effective contribution to aerosol particle growth may therefore involve rapid heterogeneous reactions (reactive uptake) rather than effectively irreversible physical absorption.</p>},
  author       = {Kurtén, Theo and Tiusanen, Kirsi and Roldin, Pontus and Rissanen, Matti and Luy, Jan Niclas and Boy, Michael and Ehn, Mikael and Donahue, Neil M.},
  issn         = {1089-5639},
  language     = {eng},
  month        = {04},
  number       = {16},
  pages        = {2569--2582},
  publisher    = {The American Chemical Society},
  series       = {The Journal of Physical Chemistry Part A: Molecules, Spectroscopy, Kinetics, Environment and General Theory},
  title        = {α-Pinene Autoxidation Products May Not Have Extremely Low Saturation Vapor Pressures Despite High O : C Ratios},
  url          = {http://dx.doi.org/10.1021/acs.jpca.6b02196},
  volume       = {120},
  year         = {2016},
}