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多溴苊是一类潜在的有机污染物。本文采用密度泛函理论在B3LYP/6-311G**水平上优化35个多溴苊化合物的分子几何结构,并获得它们在理想气态的一些热力学性质的数值,研究这些性质与取代的溴原子数目和位置的关系,根据各异构体的标准生成Gibbs自由能的相对大小,求得它们的热力学稳定性顺序。计算结果表明:在大部分多溴苊分子中,除4个氢原子外的其他原子在同一平面上。多溴苊最稳定及最不稳定异构体的ΔfH及ΔfG,都随Br原子数目增加而逐渐增加。溴原子数目相同的多溴苊异构体的ΔfH和ΔfG与溴原子的取代位置有很大的关系,其相对稳定性主要由分子内的处在不同六元环上的邻近Br...Br核排斥作用决定。所有多溴苊化合物在热力学上都比其母体化合物苊相对较难形成。
Polybrominated carbazole is a type of potential organic pollutant. In this paper, the molecular geometric structure of 35 polybrominated biphenyls compounds was optimized by using density functional theory at B3LYP / 6-311G ** level and their thermodynamic properties were obtained in the ideal gas state. The relationship between these properties and the number of substituted bromine atoms And the position of the Gibbs free energy generated according to the relative standard size of each isomer to obtain their order of thermodynamic stability. The calculation results show that in most polybromophthalic molecules, all but four hydrogen atoms are in the same plane. ΔfH and ΔfG of the most stable and most unstable isomers of polybromochlorite increased with the increase of Br atom number. ΔfH and ΔfG of polybromochlorine isomers with the same number of bromine atoms have a great relationship with the substitution position of bromine atoms, and their relative stability mainly consists of intramolecular adjacent Br ... Br Nuclear exclusion decision. All polybrominated compounds are thermodynamically more difficult to form than their parent compounds.