Direct probing of acylperoxy radicals during ozonolysis of <i>α</i>-pinene: constraints on radical chemistry and production of highly oxygenated organic molecules
<p>Acylperoxy radicals (<span class="inline-formula">RO<sub>2</sub></span>) are key intermediates in the atmospheric oxidation of organic compounds and different from the general alkyl <span class="inline-formula">RO<sub>2</sub><...
| Main Authors: | , , , , , , |
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| Format: | Article |
| Language: | English |
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Copernicus Publications
2023-10-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://acp.copernicus.org/articles/23/12691/2023/acp-23-12691-2023.pdf |
| _version_ | 1797661944660885504 |
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| author | H. Zang D. Huang J. Zhong Z. Li C. Li H. Xiao Y. Zhao |
| author_facet | H. Zang D. Huang J. Zhong Z. Li C. Li H. Xiao Y. Zhao |
| author_sort | H. Zang |
| collection | DOAJ |
| description | <p>Acylperoxy radicals (<span class="inline-formula">RO<sub>2</sub></span>) are key intermediates in the atmospheric
oxidation of organic compounds and different from the general alkyl <span class="inline-formula">RO<sub>2</sub></span>
radicals in reactivity. However, direct probing of the molecular identities
and chemistry of acyl <span class="inline-formula">RO<sub>2</sub></span> remains quite limited. Here, we report a
combined experimental and kinetic modeling study of the composition and
formation mechanisms of acyl <span class="inline-formula">RO<sub>2</sub></span>, as well as their contributions to the
formation of highly oxygenated organic molecules (HOMs) during ozonolysis of
<span class="inline-formula"><i>α</i></span>-pinene. We find that acyl <span class="inline-formula">RO<sub>2</sub></span> radicals account for 67 %,
94 %, and 32 % of the highly oxygenated <span class="inline-formula">C<sub>7</sub></span>, <span class="inline-formula">C<sub>8</sub></span>, and <span class="inline-formula">C<sub>9</sub></span>
<span class="inline-formula">RO<sub>2</sub></span>, respectively, but only a few percent of <span class="inline-formula">C<sub>10</sub></span> <span class="inline-formula">RO<sub>2</sub></span>. The
formation pathway of acyl <span class="inline-formula">RO<sub>2</sub></span> species depends on their oxygenation
level. The highly oxygenated acyl <span class="inline-formula">RO<sub>2</sub></span> (oxygen atom number <span class="inline-formula">≥6</span>) are
mainly formed by the intramolecular aldehydic H shift (i.e., autoxidation)
of <span class="inline-formula">RO<sub>2</sub></span>, while the less oxygenated acyl <span class="inline-formula">RO<sub>2</sub></span> (oxygen atom number
<span class="inline-formula"><6</span>) are basically derived from the C–C bond cleavage of alkoxy (RO)
radicals containing an <span class="inline-formula"><i>α</i></span>-ketone group or the intramolecular H shift
of RO containing an aldehyde group. The acyl-<span class="inline-formula">RO<sub>2</sub></span>-involved reactions
explain 50 %–90 % of <span class="inline-formula">C<sub>7</sub></span> and <span class="inline-formula">C<sub>8</sub></span> closed-shell HOMs and 14 % of
<span class="inline-formula">C<sub>10</sub></span> HOMs, respectively. For <span class="inline-formula">C<sub>9</sub></span> HOMs, this contribution can be up
to 30 %–60 %. In addition, acyl <span class="inline-formula">RO<sub>2</sub></span> contribute to 50 %–95 % of
<span class="inline-formula">C<sub>14</sub></span>–<span class="inline-formula">C<sub>18</sub></span> HOM dimer formation. Because of the generally fast
reaction kinetics of acyl <span class="inline-formula">RO<sub>2</sub></span>, the acyl <span class="inline-formula">RO<sub>2</sub></span> <span class="inline-formula">+</span> alkyl <span class="inline-formula">RO<sub>2</sub></span>
reactions seem to outcompete the alkyl <span class="inline-formula">RO<sub>2</sub></span> <span class="inline-formula">+</span> alkyl <span class="inline-formula">RO<sub>2</sub></span> pathways,
thereby affecting the fate of alkyl <span class="inline-formula">RO<sub>2</sub></span> and HOM formation. Our study
sheds lights on the detailed formation pathways of the monoterpene-derived
acyl <span class="inline-formula">RO<sub>2</sub></span> and their contributions to HOM formation, which will help to
understand the oxidation chemistry of monoterpenes and sources of
low-volatility organic compounds capable of driving particle formation and
growth in the atmosphere.</p> |
| first_indexed | 2024-03-11T18:52:54Z |
| format | Article |
| id | doaj.art-b5015f665e0e4a518278bd67271dbfbc |
| institution | Directory Open Access Journal |
| issn | 1680-7316 1680-7324 |
| language | English |
| last_indexed | 2024-03-11T18:52:54Z |
| publishDate | 2023-10-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Atmospheric Chemistry and Physics |
| spelling | doaj.art-b5015f665e0e4a518278bd67271dbfbc2023-10-11T08:26:06ZengCopernicus PublicationsAtmospheric Chemistry and Physics1680-73161680-73242023-10-0123126911270510.5194/acp-23-12691-2023Direct probing of acylperoxy radicals during ozonolysis of <i>α</i>-pinene: constraints on radical chemistry and production of highly oxygenated organic moleculesH. Zang0D. Huang1J. Zhong2Z. Li3C. Li4H. Xiao5Y. Zhao6School of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai, 200240, ChinaShanghai Academy of Environmental Sciences, Shanghai, 200233, ChinaDivision of Environment and Sustainability, Hong Kong University of Science and Technology, Hong Kong SAR, 999077, ChinaSchool of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai, 200240, ChinaSchool of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai, 200240, ChinaSchool of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai, 200240, ChinaSchool of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai, 200240, China<p>Acylperoxy radicals (<span class="inline-formula">RO<sub>2</sub></span>) are key intermediates in the atmospheric oxidation of organic compounds and different from the general alkyl <span class="inline-formula">RO<sub>2</sub></span> radicals in reactivity. However, direct probing of the molecular identities and chemistry of acyl <span class="inline-formula">RO<sub>2</sub></span> remains quite limited. Here, we report a combined experimental and kinetic modeling study of the composition and formation mechanisms of acyl <span class="inline-formula">RO<sub>2</sub></span>, as well as their contributions to the formation of highly oxygenated organic molecules (HOMs) during ozonolysis of <span class="inline-formula"><i>α</i></span>-pinene. We find that acyl <span class="inline-formula">RO<sub>2</sub></span> radicals account for 67 %, 94 %, and 32 % of the highly oxygenated <span class="inline-formula">C<sub>7</sub></span>, <span class="inline-formula">C<sub>8</sub></span>, and <span class="inline-formula">C<sub>9</sub></span> <span class="inline-formula">RO<sub>2</sub></span>, respectively, but only a few percent of <span class="inline-formula">C<sub>10</sub></span> <span class="inline-formula">RO<sub>2</sub></span>. The formation pathway of acyl <span class="inline-formula">RO<sub>2</sub></span> species depends on their oxygenation level. The highly oxygenated acyl <span class="inline-formula">RO<sub>2</sub></span> (oxygen atom number <span class="inline-formula">≥6</span>) are mainly formed by the intramolecular aldehydic H shift (i.e., autoxidation) of <span class="inline-formula">RO<sub>2</sub></span>, while the less oxygenated acyl <span class="inline-formula">RO<sub>2</sub></span> (oxygen atom number <span class="inline-formula"><6</span>) are basically derived from the C–C bond cleavage of alkoxy (RO) radicals containing an <span class="inline-formula"><i>α</i></span>-ketone group or the intramolecular H shift of RO containing an aldehyde group. The acyl-<span class="inline-formula">RO<sub>2</sub></span>-involved reactions explain 50 %–90 % of <span class="inline-formula">C<sub>7</sub></span> and <span class="inline-formula">C<sub>8</sub></span> closed-shell HOMs and 14 % of <span class="inline-formula">C<sub>10</sub></span> HOMs, respectively. For <span class="inline-formula">C<sub>9</sub></span> HOMs, this contribution can be up to 30 %–60 %. In addition, acyl <span class="inline-formula">RO<sub>2</sub></span> contribute to 50 %–95 % of <span class="inline-formula">C<sub>14</sub></span>–<span class="inline-formula">C<sub>18</sub></span> HOM dimer formation. Because of the generally fast reaction kinetics of acyl <span class="inline-formula">RO<sub>2</sub></span>, the acyl <span class="inline-formula">RO<sub>2</sub></span> <span class="inline-formula">+</span> alkyl <span class="inline-formula">RO<sub>2</sub></span> reactions seem to outcompete the alkyl <span class="inline-formula">RO<sub>2</sub></span> <span class="inline-formula">+</span> alkyl <span class="inline-formula">RO<sub>2</sub></span> pathways, thereby affecting the fate of alkyl <span class="inline-formula">RO<sub>2</sub></span> and HOM formation. Our study sheds lights on the detailed formation pathways of the monoterpene-derived acyl <span class="inline-formula">RO<sub>2</sub></span> and their contributions to HOM formation, which will help to understand the oxidation chemistry of monoterpenes and sources of low-volatility organic compounds capable of driving particle formation and growth in the atmosphere.</p>https://acp.copernicus.org/articles/23/12691/2023/acp-23-12691-2023.pdf |
| spellingShingle | H. Zang D. Huang J. Zhong Z. Li C. Li H. Xiao Y. Zhao Direct probing of acylperoxy radicals during ozonolysis of <i>α</i>-pinene: constraints on radical chemistry and production of highly oxygenated organic molecules Atmospheric Chemistry and Physics |
| title | Direct probing of acylperoxy radicals during ozonolysis of <i>α</i>-pinene: constraints on radical chemistry and production of highly oxygenated organic molecules |
| title_full | Direct probing of acylperoxy radicals during ozonolysis of <i>α</i>-pinene: constraints on radical chemistry and production of highly oxygenated organic molecules |
| title_fullStr | Direct probing of acylperoxy radicals during ozonolysis of <i>α</i>-pinene: constraints on radical chemistry and production of highly oxygenated organic molecules |
| title_full_unstemmed | Direct probing of acylperoxy radicals during ozonolysis of <i>α</i>-pinene: constraints on radical chemistry and production of highly oxygenated organic molecules |
| title_short | Direct probing of acylperoxy radicals during ozonolysis of <i>α</i>-pinene: constraints on radical chemistry and production of highly oxygenated organic molecules |
| title_sort | direct probing of acylperoxy radicals during ozonolysis of i α i pinene constraints on radical chemistry and production of highly oxygenated organic molecules |
| url | https://acp.copernicus.org/articles/23/12691/2023/acp-23-12691-2023.pdf |
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