Kinetic study of the atmospheric oxidation of a series of epoxy compounds by OH radicals
<p>In this work, we study the kinetics of the gas-phase reactions of hydroxyl radicals with cyclohexene oxide (CHO), 1,2-epoxyhexane (EHX), 1,2-epoxybutane (12EB), <i>trans</i>-2,3-epoxybutane (<span class="inline-formula"><i>t</i></span>EB) and &l...
| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2022-05-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://acp.copernicus.org/articles/22/6989/2022/acp-22-6989-2022.pdf |
| Summary: | <p>In this work, we study the kinetics of the gas-phase
reactions of hydroxyl radicals with cyclohexene oxide (CHO), 1,2-epoxyhexane (EHX), 1,2-epoxybutane (12EB), <i>trans</i>-2,3-epoxybutane (<span class="inline-formula"><i>t</i></span>EB) and <i>cis</i>-2,3-epoxybutane (<span class="inline-formula"><i>c</i></span>EB) using the relative rate technique. The experiments
were conducted at (298 <span class="inline-formula">±</span> 3) K and (760 <span class="inline-formula">±</span> 10) Torr ((1.01 <span class="inline-formula">±</span> 0.01) <span class="inline-formula">×</span> 10<span class="inline-formula"><sup>5</sup></span> Pa) total pressure of synthetic air using different reference compounds in a 1080 L Quartz Reactor (QUAREC) and a 480 L Duran glass chamber. The following room temperature rate coefficients (cm<span class="inline-formula"><sup>3</sup></span> molecule<span class="inline-formula"><sup>−1</sup></span> s<span class="inline-formula"><sup>−1</sup></span>) were obtained: <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M11" display="inline" overflow="scroll" dspmath="mathml"><mrow><msub><mi>k</mi><mrow><mn mathvariant="normal">1</mn><mo>(</mo><mrow class="chem"><mi mathvariant="normal">OH</mi><mo>+</mo><mi mathvariant="normal">CHO</mi></mrow><mo>)</mo></mrow></msub><mo>=</mo><mo>(</mo><mn mathvariant="normal">5.93</mn><mo>±</mo><mn mathvariant="normal">1.13</mn><mo>)</mo><mo>×</mo><msup><mn mathvariant="normal">10</mn><mrow><mo>-</mo><mn mathvariant="normal">12</mn></mrow></msup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="165pt" height="17pt" class="svg-formula" dspmath="mathimg" md5hash="857005332b1380032da69f2cffc65dad"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-22-6989-2022-ie00001.svg" width="165pt" height="17pt" src="acp-22-6989-2022-ie00001.png"/></svg:svg></span></span>, <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M12" display="inline" overflow="scroll" dspmath="mathml"><mrow><msub><mi>k</mi><mrow><mn mathvariant="normal">2</mn><mo>(</mo><mrow class="chem"><mi mathvariant="normal">OH</mi><mo>+</mo><mi mathvariant="normal">EHX</mi></mrow><mo>)</mo></mrow></msub><mo>=</mo><mo>(</mo><mn mathvariant="normal">5.77</mn><mo>±</mo><mn mathvariant="normal">0.83</mn><mo>)</mo><mo>×</mo><msup><mn mathvariant="normal">10</mn><mrow><mo>-</mo><mn mathvariant="normal">12</mn></mrow></msup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="164pt" height="17pt" class="svg-formula" dspmath="mathimg" md5hash="a1a47fb6a3f89609a631c25caf4a212f"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-22-6989-2022-ie00002.svg" width="164pt" height="17pt" src="acp-22-6989-2022-ie00002.png"/></svg:svg></span></span>, <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M13" display="inline" overflow="scroll" dspmath="mathml"><mrow><msub><mi>k</mi><mrow><mn mathvariant="normal">3</mn><mo>(</mo><mrow class="chem"><mi mathvariant="normal">OH</mi><mo>+</mo><mn mathvariant="normal">12</mn><mi mathvariant="normal">EB</mi></mrow><mo>)</mo></mrow></msub><mo>=</mo><mo>(</mo><mn mathvariant="normal">1.98</mn><mo>±</mo><mn mathvariant="normal">0.29</mn><mo>)</mo><mo>×</mo><msup><mn mathvariant="normal">10</mn><mrow><mo>-</mo><mn mathvariant="normal">12</mn></mrow></msup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="167pt" height="17pt" class="svg-formula" dspmath="mathimg" md5hash="54c071a5c7436d461388590a4ec52d48"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-22-6989-2022-ie00003.svg" width="167pt" height="17pt" src="acp-22-6989-2022-ie00003.png"/></svg:svg></span></span>, <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M14" display="inline" overflow="scroll" dspmath="mathml"><mrow><msub><mi>k</mi><mrow><mn mathvariant="normal">4</mn><mo>(</mo><mrow class="chem"><mi mathvariant="normal">OH</mi></mrow><mo>+</mo><mi>c</mi><mi mathvariant="normal">EB</mi><mo>)</mo></mrow></msub><mo>=</mo><mo>(</mo><mn mathvariant="normal">1.50</mn><mo>±</mo><mn mathvariant="normal">0.28</mn><mo>)</mo><mo>×</mo><msup><mn mathvariant="normal">10</mn><mrow><mo>-</mo><mn mathvariant="normal">12</mn></mrow></msup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="163pt" height="17pt" class="svg-formula" dspmath="mathimg" md5hash="a70fb9f57a984bc593a7e2c23b2d6311"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-22-6989-2022-ie00004.svg" width="163pt" height="17pt" src="acp-22-6989-2022-ie00004.png"/></svg:svg></span></span> and <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M15" display="inline" overflow="scroll" dspmath="mathml"><mrow><msub><mi>k</mi><mrow><mn mathvariant="normal">5</mn><mo>(</mo><mrow class="chem"><mi mathvariant="normal">OH</mi></mrow><mo>+</mo><mi>t</mi><mi mathvariant="normal">EB</mi><mo>)</mo></mrow></msub><mo>=</mo><mo>(</mo><mn mathvariant="normal">1.81</mn><mo>±</mo><mn mathvariant="normal">0.33</mn><mo>)</mo><mo>×</mo><msup><mn mathvariant="normal">10</mn><mrow><mo>-</mo><mn mathvariant="normal">12</mn></mrow></msup></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="162pt" height="17pt" class="svg-formula" dspmath="mathimg" md5hash="52e5a95db4f8d8b805c074caecbdb359"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="acp-22-6989-2022-ie00005.svg" width="162pt" height="17pt" src="acp-22-6989-2022-ie00005.png"/></svg:svg></span></span>. Except for previous studies on 1,2-epoxybutane
and cyclohexene oxide, this is, to the best of our knowledge, the first
kinetic study of the reaction of these compounds with OH radicals. We
discuss the discrepancies found between the values obtained from the present
study with values estimated from the structure–activity relationship method
(SAR). Our findings indicate that pseudo-ethylenic character in the epoxy
ring is an important factor to be included in the improvement of the SAR
estimation method. Atmospheric lifetimes, reactivity trends and atmospheric
implications are discussed considering the epoxy compound rate coefficients
obtained in the present study.</p> |
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| ISSN: | 1680-7316 1680-7324 |