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首页> 外文期刊>Environmental Science & Technology >Metallocoenzyme-Mediated Reductive Transformation of Carbon Tetrachloride in Titanium(III) Citrate Aqueous Solution
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Metallocoenzyme-Mediated Reductive Transformation of Carbon Tetrachloride in Titanium(III) Citrate Aqueous Solution

机译：金属酶在柠檬酸钛（III）水溶液中四氯化碳的还原性转化

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摘要

Transformation pathways for carbon tetrachloride (CCl_4) catalyzed by hematin or vitamin B_(12) in aqueous titanium(III) citrate solution are proposed. The reaction of CCl_4 with B_(12) was zero order in CCl_4 and first order in B_(12), and the rate constant was measured from pH 7.3 to pH 10.3. The proposed rate-limiting step is the reduction of the stable trichloromethylcobalamin (CCl_3-Cbl) intermediate by titanium(III) citrate at alkaline pH and the sterically induced CCl_3-Cbl decomposition at neutral pH. The reaction kinetics can be described by a modified Michaelis-Menten model in the saturated regime. With hematin, only the pseudo-first-order rate constant was determined due to the significant deactivation of the coenzyme. The turnover number of hematin (molecules of CCl_4 transformed/molecule of hematin deactivated) was 27 at pH 8.0 and 42 at pH 9.9. Vitamin B_(12) was a more stable and more effective catalyst (on a molar basis) than hematin with respect to CCl_4. Chloroform (CHCl_3) was the primary product in titanium(III) citrate solution, and the yield was a function of pH, Ti(III) concentration, and organic content regardless of whether a coenzyme was present or which coenzyme was used. Although B_(12) and hematin can both enhance the CCl_4 transformation rate, they have little effect on the CHCl_3 yield. Titanium(III) citrate, on the other hand, controls not only the transformation rate but also CHCl_3 formation.
机译：提出了血红素或维生素B_（12）在柠檬酸钛（III）水溶液中催化四氯化碳（CCl_4）的转化途径。 CCl_4与B_（12）的反应在CCl_4中为零级，在B_（12）中为一级，从pH 7.3到pH 10.3测量了速率常数。拟议的限速步骤是在碱性pH下柠檬酸钛（III）还原稳定的三氯甲基钴胺素（CCl_3-Cbl）中间体，在中性pH下空间诱导的CCl_3-Cbl分解。反应动力学可以通过饱和状态下的改进的Michaelis-Menten模型来描述。对于血红素，由于辅酶的显着失活，仅确定了伪一级速率常数。血红素的周转数（转化的CCl_4分子/失活的血红素分子）在pH 8.0为27，在pH 9.9为42。相对于CCl_4，维生素B_（12）是比血红素更稳定，更有效的催化剂（基于摩尔）。氯仿（CHCl_3）是柠檬酸钛（III）溶液中的主要产物，其收率是pH，Ti（III）浓度和有机物含量的函数，而与是否存在辅酶或使用哪种辅酶无关。尽管B_（12）和血红素均可提高CCl_4的转化率，但它们对CHCl_3的收率影响很小。另一方面，柠檬酸钛（III）不仅控制转化率，而且还控制CHCl_3的形成。

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  • 来源
    《Environmental Science & Technology》 |1995年第3期|p.595-603|共9页
  • 作者

    PEI-CHUN CHIU; MARTIN REINHARD;

  • 作者单位

    Environmental Engineering and Science, Department of Civil Engineering, Stanford University, Stanford, California 94305-4020;

  • 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);
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 环境化学;
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