Impact of organic molecular structure on the estimation of atmospherically relevant physicochemical parameters
<p>Many methods are currently available for estimating physicochemical properties of atmospherically relevant compounds. Though a substantial body of literature has focused on the development and intercomparison of methods based on molecular structure, there has been an increasing focus on met...
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| Format: | Article |
| Language: | English |
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Copernicus Publications
2021-04-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://acp.copernicus.org/articles/21/6541/2021/acp-21-6541-2021.pdf |
| _version_ | 1818411437686521856 |
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| author | G. Isaacman-VanWertz B. Aumont |
| author_facet | G. Isaacman-VanWertz B. Aumont |
| author_sort | G. Isaacman-VanWertz |
| collection | DOAJ |
| description | <p>Many methods are currently available for estimating physicochemical properties of atmospherically relevant compounds. Though a substantial body of literature has focused on the development and intercomparison of methods based on molecular structure, there has been an increasing focus on methods based only
on molecular formula. However, prior work has not quantified the extent to
which isomers of the same formula may differ in their properties or,
relatedly, the extent to which lacking or ignoring molecular structure
degrades estimates of parameters. Such an evaluation is complicated by the
fact that structure-based methods bear significant uncertainty and are
typically not well constrained for atmospherically relevant molecules. Using
species produced in the modeled atmospheric oxidation of three representative
atmospheric hydrocarbons, we demonstrate here that estimated differences
between isomers are greater than differences between three widely used
estimation methods. Specifically, isomers tend to differ in their estimated
vapor pressures and Henry's law constants by a half to a full order of
magnitude greater than differences between estimation methods, and they differ in
their rate constant for reaction with OH radicals (<span class="inline-formula"><i>k</i><sub>OH</sub></span>) by a
factor of 2. Formula-based estimation of these parameters, using certain
methods, is shown to agree with structure-based estimates with little bias and
approximately normally distributed error. Specifically, vapor pressure can be
estimated using a combination of two existing methods, Henry's law constants
can be estimated based on vapor pressure, and <span class="inline-formula"><i>k</i><sub>OH</sub></span> can be
approximated as a constant for all formulas containing a given set of
elements. Formula-based estimation is, therefore, reasonable when applied to a
mixture of isomers but creates uncertainty commensurate with the lack of
structural information.</p> |
| first_indexed | 2024-12-14T10:31:24Z |
| format | Article |
| id | doaj.art-d4cce0486d254c57b4deb0a92297fda2 |
| institution | Directory Open Access Journal |
| issn | 1680-7316 1680-7324 |
| language | English |
| last_indexed | 2024-12-14T10:31:24Z |
| publishDate | 2021-04-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Atmospheric Chemistry and Physics |
| spelling | doaj.art-d4cce0486d254c57b4deb0a92297fda22022-12-21T23:06:08ZengCopernicus PublicationsAtmospheric Chemistry and Physics1680-73161680-73242021-04-01216541656310.5194/acp-21-6541-2021Impact of organic molecular structure on the estimation of atmospherically relevant physicochemical parametersG. Isaacman-VanWertz0B. Aumont1Department of Civil and Environmental Engineering, Virginia Tech, Blacksburg, VA 24060, USALISA, UMR CNRS 7583, Université Paris-Est-Créteil, Université de Paris, Institut Pierre Simon Laplace, Créteil, France<p>Many methods are currently available for estimating physicochemical properties of atmospherically relevant compounds. Though a substantial body of literature has focused on the development and intercomparison of methods based on molecular structure, there has been an increasing focus on methods based only on molecular formula. However, prior work has not quantified the extent to which isomers of the same formula may differ in their properties or, relatedly, the extent to which lacking or ignoring molecular structure degrades estimates of parameters. Such an evaluation is complicated by the fact that structure-based methods bear significant uncertainty and are typically not well constrained for atmospherically relevant molecules. Using species produced in the modeled atmospheric oxidation of three representative atmospheric hydrocarbons, we demonstrate here that estimated differences between isomers are greater than differences between three widely used estimation methods. Specifically, isomers tend to differ in their estimated vapor pressures and Henry's law constants by a half to a full order of magnitude greater than differences between estimation methods, and they differ in their rate constant for reaction with OH radicals (<span class="inline-formula"><i>k</i><sub>OH</sub></span>) by a factor of 2. Formula-based estimation of these parameters, using certain methods, is shown to agree with structure-based estimates with little bias and approximately normally distributed error. Specifically, vapor pressure can be estimated using a combination of two existing methods, Henry's law constants can be estimated based on vapor pressure, and <span class="inline-formula"><i>k</i><sub>OH</sub></span> can be approximated as a constant for all formulas containing a given set of elements. Formula-based estimation is, therefore, reasonable when applied to a mixture of isomers but creates uncertainty commensurate with the lack of structural information.</p>https://acp.copernicus.org/articles/21/6541/2021/acp-21-6541-2021.pdf |
| spellingShingle | G. Isaacman-VanWertz B. Aumont Impact of organic molecular structure on the estimation of atmospherically relevant physicochemical parameters Atmospheric Chemistry and Physics |
| title | Impact of organic molecular structure on the estimation of atmospherically relevant physicochemical parameters |
| title_full | Impact of organic molecular structure on the estimation of atmospherically relevant physicochemical parameters |
| title_fullStr | Impact of organic molecular structure on the estimation of atmospherically relevant physicochemical parameters |
| title_full_unstemmed | Impact of organic molecular structure on the estimation of atmospherically relevant physicochemical parameters |
| title_short | Impact of organic molecular structure on the estimation of atmospherically relevant physicochemical parameters |
| title_sort | impact of organic molecular structure on the estimation of atmospherically relevant physicochemical parameters |
| url | https://acp.copernicus.org/articles/21/6541/2021/acp-21-6541-2021.pdf |
| work_keys_str_mv | AT gisaacmanvanwertz impactoforganicmolecularstructureontheestimationofatmosphericallyrelevantphysicochemicalparameters AT baumont impactoforganicmolecularstructureontheestimationofatmosphericallyrelevantphysicochemicalparameters |