Environment-related properties of polyhydroxylated dibenzo-p-dioxins.
Environment-related properties of polyhydroxylated dibenzo-p-dioxins.
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DOI：
10.1016/j.scitotenv.2011.10.063
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发表时间：
2012
期刊：
影响因子：
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通讯作者：
Jia-Qi Shi;Ruijuan Qu;A. Flamm;Hong-Xia Liu;Ying Xu;Zunyao Wang
中科院分区：
文献类型：
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作者：
Jia-Qi Shi;Ruijuan Qu;A. Flamm;Hong-Xia Liu;Ying Xu;Zunyao Wang
多羟基二苯并二恶英（PHODDs）是多氯二苯并二恶英（PCDDs）的重要代谢和合成产物。在PHODD分子中存在两种类型的氢键：一种在羟基（HO）和醚键的氧原子之间，另一种在苯环的两个邻位羟基之间。通过密度泛函理论（DFT）的全优化计算，通过比较不同分子的标准生成吉布斯自由能（ΔfGθ），确定了它们的键能分别约为9- 14 kJ/mol和15- 19 kJ/mol，并得到了实验验证。这两种类型的氢键影响分子的亲水性和稳定性。得到了羟基的扭转势和使同系物最稳定的取向。基于基团贡献法计算了正辛醇-水分配系数（logKows），并结合密度泛函计算和等键反应得到了稳定PHODD同系物的标准状态熵（Sθ）、标准生成焓（ΔfHθ）和ΔfGθ。以羟基取代的数目和位置（NPHOS）为描述符，建立了定量结构-性质相关（QSPR）模型。虽然PHODD的亲水性随着羟基的增加而增加，但它被分子内氢键削弱。PHODDs的logKow远小于PCDDs的logKow，且随取代基数目的变化趋势不同。此外，从理论上提出了PHODD同系物的相对稳定性顺序，这与PCDDs的相对稳定性顺序有很大不同。考虑水中的电离作用，根据自洽反应场理论（SCRF）的SMD方法计算了PHODDs的一级电离常数，并分析了氢键对PHODDs一级电离常数的影响。
Polyhydroxylated dibenzo-p-dioxins (PHODDs) are important metabolic and synthetic products of polychlorinated dibenzo-p-dioxins (PCDDs). Two types of hydrogen bonds exist in PHODD molecules: one between a hydroxyl group (HO) and an oxygen atom of the ether bond, and the other between two ortho hydroxyls of a benzene ring. By fully optimized calculation with density functional theory (DFT), their bond energies were ascertained to be approximately 9–14kJ/mol and 15–19kJ/mol respectively by the comparison of standard Gibbs energy of formation (ΔfGθ) between different molecules, which was experimentally verified. The two types of hydrogen bonds affect the hydrophilicity and stability of the molecules. The torsional potential of hydroxyls and the orientation making the congener most stable were obtained. The octanol-water partition coefficients (logKows) were calculated based on the group contribution method, and the standard state entropy (Sθ), standard enthalpy (ΔfHθ) of formation and ΔfGθwere obtained from the combination of DFT calculation and isodesmic reaction for the stable PHODD congeners. The number and position of hydroxyl substitution (NPHOS) were employed as descriptors to establish quantitative structure–property relationship (QSPR) models. Although the hydrophilicity of PHODDs increases with the number of hydroxyl groups, it is impaired by the intramolecular hydrogen bonds. The logKows of PHODDs are much smaller than those of PCDDs, and the variation trend with the number of substituents is different. In addition, the relative stability order of PHODD congeners was theoretically proposed, which is quite different from that of PCDDs. Considering the ionization in water, first-order ionization constants of PHODDs were calculated according to the results of SMD method of Self-Consistent Reaction Field Theory (SCRF), and they were influenced by the hydrogen bonds.