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Kinetics and Products from Heterogeneous Oxidation of Squalene with Ozone

机译：臭氧对角鲨烯进行异质氧化的动力学及产物

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Motivated by the importance of the heterogeneous chemistry of squalene contained within skin oil to indoor air chemistry, the surface reaction of squalene with gas-phase ozone has been investigated. Using direct analysis in real time mass spectrometry (DART-MS) to monitor squalene, the reactive uptake coefficients were determined to be (4.3 ± 2.2) × 10~(-4) and (4.0 ± 2.2) × 10~(-4) for ozone mixing ratios (MR_(O_3)) of 50 and 25 ppb, respectively, on squalene films deposited on glass surfaces. At an MR_(O_3) of 25 ppb, the lifetime for oxidation was the same as that in an indoor office with an MR_(O_3) between 22 and 32 ppb, suggesting that O_3 was the dominant oxidant in this indoor setting. While the heterogeneous kinetics of squalene and O_3 were independent of relative humidity (RH), the RH significantly affected the reaction products. Under dry conditions (＜5% RH), in addition to several products between m/z 300 and 350, the major condensed-phase end products were levulinic acid (LLA) and succinic acid (SCA). Under humid conditions (50% RH), the major end products were 4-oxopentanal, 4-oxobutanoic acid, and LLA. The molar yields of LLA and SCA were quantified as 230 ± 43% and 110 ± 31%, respectively, under dry conditions and 91 ± 15% and ＜5%, respectively, at 50% RH. Moreover, high-molecular weight (molecular weight of ＞450 Da) products were observed under dry conditions with indications that LLA was involved in their formation. The mechanism of squalene oxidation is discussed in light of these observations, with indications of an important role played by Criegee intermediates.
机译：由于皮肤油中所含角鲨烯的非均相化学对室内空气化学的重要性，因此对角鲨烯与气相臭氧的表面反应进行了研究。使用实时质谱直接分析（DART-MS）监测角鲨烯，确定反应吸收系数为（4.3±2.2）×10〜（-4）和（4.0±2.2）×10〜（-4）在沉积在玻璃表面的角鲨烯薄膜上的臭氧混合比（MR_（O_3））分别为50和25 ppb。在MR_（O_3）为25 ppb的情况下，氧化寿命与室内办公室的MR_（O_3）在22至32 ppb之间的氧化寿命相同，这表明O_3是该室内环境中的主要氧化剂。角鲨烯和O_3的异质动力学与相对湿度（RH）无关，但RH显着影响反应产物。在干燥条件下（相对湿度<5％），除了m / z 300和350之间的几种产物外，主要的冷凝相终产物是乙酰丙酸（LLA）和琥珀酸（SCA）。在潮湿条件下（相对湿度50％），主要的最终产物是4-氧戊醛，4-氧丁酸和LLA。在干燥条件下，LLA和SCA的摩尔产率分别定为230±43％和110±31％，在50％RH时分别为91±15％和＜5％。此外，在干燥条件下观察到高分子量（分子量> 450 Da）产物，这表明LLA参与了其形成。根据这些观察结果，对角鲨烯氧化的机理进行了讨论，并指出了克里基中间体的重要作用。

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  • 来源
    《Environmental Science & Technology》 |2016年第21期|11688-11697|共10页
  • 作者

    Shouming Zhou; Matthew W. Forbes; Jonathan P. D. Abbatt;

  • 作者单位

    Department of Chemistry, University of Toronto, 80 St. George Street, Toronto, ON, Canada M5S 3H6;

    Department of Chemistry, University of Toronto, 80 St. George Street, Toronto, ON, Canada M5S 3H6;

    Department of Chemistry, University of Toronto, 80 St. George Street, Toronto, ON, Canada M5S 3H6;

  • 收录信息 美国《科学引文索引》(SCI);美国《工程索引》(EI);美国《生物学医学文摘》(MEDLINE);美国《化学文摘》(CA);
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