Issue 7, 2021

Chemical functionality at the liquid surface of pure unsaturated fatty acids


The C[double bond, length as m-dash]C double bonds in unsaturated fatty acids found within atmospheric aerosols play an important role in tropospheric pollution cycles. An understanding of the affinity of such double bonds for the surface of these aerosols is thus vital to the accurate modelling of reactions occurring at these interfaces. To simulate the structures of the liquid surfaces of a series of C18 fatty acids with increasing degrees of unsaturation molecular dynamics calculations have been carried out using the GROMACS suite of programs, employing the general Amber force field. The relative surface coverage of HC[double bond, length as m-dash]CH, carboxylic acid, methyl and CH2 groups has been probed and found to be significantly different from that predicted based on a purely statistical distribution of groups or assumed based on X-ray diffraction data. HC[double bond, length as m-dash]CH, methyl, and CH2 groups dominate the surface, with the methyl groups being found disproportionally at the surface relative to their bulk concentration. The HC[double bond, length as m-dash]CH surface exposure does not increase linearly as the acids become more unsaturated. The distinct structure found at the interface extends only a few nanometers into the sample, suggesting that surface order only affects the first layer of molecules at the interface, but is key to the exposure of highly reactive chemical functional groups to atmospheric oxidants.

Graphical abstract: Chemical functionality at the liquid surface of pure unsaturated fatty acids

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Article information

Article type
02 Jun 2021
23 Aug 2021
First published
09 Sep 2021
This article is Open Access
Creative Commons BY license

Environ. Sci.: Atmos., 2021,1, 498-507

Chemical functionality at the liquid surface of pure unsaturated fatty acids

A. C. Stewart, M. J. Paterson and S. J. Greaves, Environ. Sci.: Atmos., 2021, 1, 498 DOI: 10.1039/D1EA00043H

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