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首页> 外文期刊>Environmental Science & Technology >Molecular Mechanism of NDMA Formation from N,N-Dimethylsulfamide During Ozonation: Quantum Chemical Insights into a Bromide-Catalyzed Pathway
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Molecular Mechanism of NDMA Formation from N,N-Dimethylsulfamide During Ozonation: Quantum Chemical Insights into a Bromide-Catalyzed Pathway

机译：N，N-二甲基亚磺酰胺在臭氧化过程中形成NDMA的分子机制：量子化学见解到溴化物催化的途径。

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摘要

During ozonation of drinking water, the fungicide metabolite N,N-dimethyIsulfamide (DMS) can be transformed into a highly toxic product, N-nitrosodimethylamine (NDMA). We used quantum chemical computations and stopped-flow experiments to evaluate a chemical mechanism proposed previously to describe this transformation. Stopped-flow experiments indicate a pK_a = 10.4 for DMS. Experiments show that hypobromous acid (HOBr), generated by ozone oxidation of naturally occurring bromide, brominates the deprotonated DMS~- anion with a near-diffusion controlled rate constant (7.1 ± 0.6 × 10~8 M~(-1) s~(-1)), forming Br-DMS~- anion. According to quantum chemical calculations, Br-DMS has a pK_a ～ 9.0 and thus remains partially deprotonated at neutral pH. The anionic Br-DMS~- bromamine can react with ozone with a high rate constant (10~(5±2.5) M~(-1) s~(-1)), forming the reaction intermediate (BrNO)(SO_2)N(CH_3)_2~-. This intermediate resembles a loosely bound complex between an electrophilic nitrosyl bromide (BrNO) molecule and an electron-rich dimethylaminosulfinate ((SO_2)N(CH_3)_2~-) fragment, based on inspection of computed natural charges and geometric parameters. This fragile complex undergoes immediate (10~(10±2.5) s~(-1)) reaction by two branches: an exothermic channel that produces NDMA, and an entropy-driven channel giving non-NDMA products. Computational results bring new insights into the electronic nature, chemical equilibria, and kinetics of the elementary reactions of this pathway, enabled by computed energies of structures that are not possible to access experimentally.
机译：在饮用水的臭氧化过程中，杀菌剂代谢物N，N-二甲基亚磺酰胺（DMS）可以转化为剧毒产品N-亚硝基二甲胺（NDMA）。我们使用量子化学计算和停流实验来评估先前提出的描述这种转变的化学机理。停止流实验表明DMS的pK_a = 10.4。实验表明，由天然溴化物的臭氧氧化产生的次溴酸（HOBr）以近扩散控制的速率常数（7.1±0.6×10〜8 M〜（-1）s〜（）溴化去质子化的DMS〜-阴离子。 -1）），形成Br-DMS-阴离子。根据量子化学计算，Br-DMS的pK_a〜9.0，因此在中性pH值下部分脱质子。阴离子Br-DMS〜-溴胺可以与臭氧以高速率常数（10〜（5±2.5）M〜（-1）s〜（-1））反应，形成反应中间体（BrNO）（SO_2）N （CH_3）_2〜-。基于对计算的自然电荷和几何参数的检查，该中间体类似于亲电的亚硝酰基溴（BrNO）分子和富电子的二甲基氨基亚磺酸盐（（SO_2）N（CH_3）_2〜-）片段之间的松散结合复合物。这种易碎的复合物通过两个分支立即发生（10〜（10±2.5）s〜（-1））反应：产生NDMA的放热通道和产生非NDMA乘积的熵驱动通道。计算结果为该途径的基本反应的电子性质，化学平衡和动力学带来了新的见解，这是由无法通过实验获得的结构的计算能量实现的。

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  • 来源
    《Environmental Science & Technology》 |2015年第7期|4163-4175|共13页
  • 作者

    Daniela Trogolo; Brijesh Kumar Mishra; Michele B. Heeb; Urs von Gunten; J. Samuel Arey;

  • 作者单位

    Environmental Chemistry Modeling Laboratory (LMCE), ENAC, Ecole Polytechnique Federale de Lausanne (EPFL), Lausanne CH-1015, Switzerland;

    Environmental Chemistry Modeling Laboratory (LMCE), ENAC, Ecole Polytechnique Federale de Lausanne (EPFL), Lausanne CH-1015, Switzerland,International Institute of Information Technology, Bangalore (IIIT-B) 560100 Bangalore, Karnataka, India;

    Laboratory for Water Quality and Treatment (LTQE), ENAC, Ecole Polytechnique Federale de Lausanne (EPFL), Lausanne CH-1015, Switzerland;

    Laboratory for Water Quality and Treatment (LTQE), ENAC, Ecole Polytechnique Federale de Lausanne (EPFL), Lausanne CH-1015, Switzerland,Eawag, Swiss Federal Institute of Aquatic Science and Technology, Duebendorf 8600, Switzerland;

    Environmental Chemistry Modeling Laboratory (LMCE), ENAC, Ecole Polytechnique Federale de Lausanne (EPFL), Lausanne CH-1015, Switzerland,Eawag, Swiss Federal Institute of Aquatic Science and Technology, Duebendorf 8600, 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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