Mechanism and thermal rate constants for the complete series reactions of chlorophenols with H.
Mechanism and thermal rate constants for the complete series reactions of chlorophenols with H.
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DOI：
10.1021/es9001778
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发表时间：
2009-04
影响因子：
11.4
通讯作者：
Qingzhu Zhang;X. Qu;Hui Wang;Fei Xu;Xiangyang Shi;Wen-xing Wang
中科院分区：
文献类型：
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作者：
Qingzhu Zhang;X. Qu;Hui Wang;Fei Xu;Xiangyang Shi;Wen-xing Wang
氯酚与氢原子的反应是焚烧炉中生成多氯二苯并对二恶英和二苯并呋喃(PCDD/Fs)的重要初始步骤。对关键基本步骤的机理和动力学性质的详细了解是理解多氯二苯并二恶英形成的先决条件。本文用密度泛函理论(DFT)方法和直接动力学方法对19种氯苯酚同系物与H原子的全系列反应进行了理论研究。势能面在MPWB1K/6-311+G(3df，2p)//MPWB1K/6-31+6(d，p)水平上建立。多氯二苯并二恶英/二恶英形成的模型需要有关元素反应的动力学信息。用正则变分过渡态理论(CVT)和小曲率隧穿贡献(SCT)计算了600-1200K温度范围内的速率常数。首次对速率-温度公式进行了拟合。研究表明，苯酚的取代方式对氯酚中O-H键的强度和反应活性有显著影响。分子内氢键在决定邻位取代苯酚O-H键的反应活性中起着决定性的作用。
Reactions of chlorophenols with atomic H are important initial steps for the formation of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in incinerators. Detailed insight into the mechanism and kinetic properties of crucial elementary steps is a prerequisite for understanding the formation of PCDD/Fs. In this paper, the complete series reactions of 19 chlorophenol congeners with atomic H have been studied theoretically using the density functional theory (DFT) method and the direct dynamics method. The profiles of the potential energy surface were constructed at the MPWB1K/6-311+G(3df,2p)//MPWB1K/6-31+6(d,p) level. Modeling of the PCDD/Fs formation requires kinetic information aboutthe elemental reactions. The rate constants were deduced over a wide temperature range of 600-1200 K using canonical variational transition-state theory (CVT) with small curvature tunneling contribution (SCT). The rate-temperature formulas were fitted for the first time. This study shows that the substitution pattern of the phenol has a significant effect on the strength and reactivity of the O-H bonds in chlorophenols. Intramolecular hydrogen bonding plays a decisive role in determining the reactivity of the O-H bonds for ortho-substituted phenols.