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Ozonolysis of methyl oleate monolayers at the air-water interface: oxidation kinetics, reaction products and atmospheric implications

Pfrang, Christian; Sebastiani, Federica; Lucas, Claire O. M.; King, Martin D.; Hoare, Ioan D.; Chang, Debby LU and Campbell, Richard A. (2014) In Physical Chemistry Chemical Physics 16(26). p.13220-13228
Abstract
Ozonolysis of methyl oleate monolayers at the air-water interface results in surprisingly rapid loss of material through cleavage of the C=C bond and evaporation/ dissolution of reaction products. We determine using neutron reflectometry a rate coefficient of (5.7 +/- 0.9) x 10(-10) cm(2) molecule(-1) s(-1) and an uptake coefficient of similar to 3 x 10(-5) for the oxidation of a methyl ester monolayer: the atmospheric lifetime is similar to 10 min. We obtained direct experimental evidence that <2% of organic material remains at the surface on atmospheric timescales. Therefore known long atmospheric residence times of unsaturated fatty acids suggest that these molecules cannot be present at the interface throughout their ageing cycle,... (More)
Ozonolysis of methyl oleate monolayers at the air-water interface results in surprisingly rapid loss of material through cleavage of the C=C bond and evaporation/ dissolution of reaction products. We determine using neutron reflectometry a rate coefficient of (5.7 +/- 0.9) x 10(-10) cm(2) molecule(-1) s(-1) and an uptake coefficient of similar to 3 x 10(-5) for the oxidation of a methyl ester monolayer: the atmospheric lifetime is similar to 10 min. We obtained direct experimental evidence that <2% of organic material remains at the surface on atmospheric timescales. Therefore known long atmospheric residence times of unsaturated fatty acids suggest that these molecules cannot be present at the interface throughout their ageing cycle, i.e. the reported atmospheric longevity is likely to be attributed to presence in the bulk and viscosity-limited reactive loss. Possible reaction products were characterized by ellipsometry and uncertainties in the atmospheric fate of organic surfactants such as oleic acid and its methyl ester are discussed. Our results suggest that a minor change to the structure of the molecule (fatty acid vs. its methyl ester) considerably impacts on reactivity and fate of the organic film. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Physical Chemistry Chemical Physics
volume
16
issue
26
pages
13220 - 13228
publisher
Royal Society of Chemistry
external identifiers
  • wos:000337785400025
  • scopus:84902491381
ISSN
1463-9084
DOI
10.1039/c4cp00775a
language
English
LU publication?
yes
id
98df27b5-e83a-45c0-a652-602c4764ceb4 (old id 4609278)
date added to LUP
2014-08-26 11:38:23
date last changed
2017-10-01 04:18:22
@article{98df27b5-e83a-45c0-a652-602c4764ceb4,
  abstract     = {Ozonolysis of methyl oleate monolayers at the air-water interface results in surprisingly rapid loss of material through cleavage of the C=C bond and evaporation/ dissolution of reaction products. We determine using neutron reflectometry a rate coefficient of (5.7 +/- 0.9) x 10(-10) cm(2) molecule(-1) s(-1) and an uptake coefficient of similar to 3 x 10(-5) for the oxidation of a methyl ester monolayer: the atmospheric lifetime is similar to 10 min. We obtained direct experimental evidence that &lt;2% of organic material remains at the surface on atmospheric timescales. Therefore known long atmospheric residence times of unsaturated fatty acids suggest that these molecules cannot be present at the interface throughout their ageing cycle, i.e. the reported atmospheric longevity is likely to be attributed to presence in the bulk and viscosity-limited reactive loss. Possible reaction products were characterized by ellipsometry and uncertainties in the atmospheric fate of organic surfactants such as oleic acid and its methyl ester are discussed. Our results suggest that a minor change to the structure of the molecule (fatty acid vs. its methyl ester) considerably impacts on reactivity and fate of the organic film.},
  author       = {Pfrang, Christian and Sebastiani, Federica and Lucas, Claire O. M. and King, Martin D. and Hoare, Ioan D. and Chang, Debby and Campbell, Richard A.},
  issn         = {1463-9084},
  language     = {eng},
  number       = {26},
  pages        = {13220--13228},
  publisher    = {Royal Society of Chemistry},
  series       = {Physical Chemistry Chemical Physics},
  title        = {Ozonolysis of methyl oleate monolayers at the air-water interface: oxidation kinetics, reaction products and atmospheric implications},
  url          = {http://dx.doi.org/10.1039/c4cp00775a},
  volume       = {16},
  year         = {2014},
}