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首页> 外文期刊>Environmental Science & Technology >Reconciling Disparate Models of the Involvement of Vinyl Radicals in Cobalamin-Mediated Dechlorination Reactions
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Reconciling Disparate Models of the Involvement of Vinyl Radicals in Cobalamin-Mediated Dechlorination Reactions

机译：协调不同模型的钴自由基介导的钴自由基脱氯反应中的乙烯基自由基

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摘要

Inner-sphere (nonradical) and outer-sphere (radical-based) mechanisms have been suggested for cobalamin-mediated dechlorination of tetrachloroethylene (PCE) and trichioroethylene (TCE). In this study, the role of free vinyl radicals was investigated using deuterated radical traps: d_8-isopropanol and d_8-tetrahydrofuran. For both substrates, addition of trap resulted in production of deuterated dechlorination products, and higher concentrations of trap resulted in increased amounts of deuterated products. However, only a finite proportion of the products were trappable: 8% of the PCE-derived products and 86% of the TCE-derived products result from free radicals. The data show that the reaction does not proceed solely by either an inner-sphere or an outer-sphere mechanism and led to the hypothesis that caged radical intermediates were involved in the mechanism. The untrappable fraction of products are hypothesized to result from in-cage reactions. This hypothesis was investigated using d_5-glycerol as a radical trap and viscogen. Although increased viscosity resulted in decreased formation of free-radical-derived products, consistent with the cage hypothesis, these data were inconclusive. The role of d_8-isopropanol in enhancing the production of radicals in this system via an acetone ketyl radical chain mechanism was also investigated, and no evidence for such an effect was found.
机译：已提出内球蛋白（非自由基）和外球蛋白（基于自由基）机制用于钴胺素介导的四氯乙烯（PCE）和三氯乙烯（TCE）的脱氯。在这项研究中，使用氘代自由基捕集阱d_8-异丙醇和d_8-四氢呋喃研究了游离乙烯基自由基的作用。对于两种底物，添加捕集阱都会导致产生氘化的脱氯产物，而更高的捕集阱浓度则会导致增加的氘代产物的量。但是，只有有限比例的产品可捕获：8％的PCE衍生产品和86％的TCE衍生产品是自由基。数据表明，反应不仅是通过内球或外球机理进行的，而且导致了一个假设，即笼型自由基中间体参与了该机理。假设产品的不可捕获部分是由笼内反应引起的。使用d_5-甘油作为自由基捕获剂和粘胶原对这一假设进行了研究。尽管粘度增加导致自由基衍生产物的形成减少，这与笼子假设相符，但这些数据尚无定论。还研究了d_8-异丙醇在该系统中通过丙酮酮基自由基链机理增强自由基产生的作用，但没有发现这种作用的证据。

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  • 来源
    《Environmental Science & Technology》 |2009年第23期|8961-8967|共7页
  • 作者

    SARAH KLIEGMAN; KRISTOPHER MCNEILL;

  • 作者单位

    Department of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455-0431;

    Department of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455-0431 ETH Zurich, Department of Environmental Science, Untversitaetstrasse 16, 8092 Zurich, Switzerland;

  • 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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