摘要
多溴代芴化合物是一类潜在的化学污染物,其热力学性质数据对于进一步研究这些化合物的其它物理、化学性质以及它们在环境中的形成、分布及迁移转化机制有重要价值,但这些热力学性质数据极其缺乏。本文采用密度泛函理论在B3LYP/6-311G^(**)水平上优化135个多溴代芴分子的几何结构,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,根据各异构体的相对标准生成Gibbs自由能的大小,得它们热力学稳定性的顺序。结果表明:多溴代芴分子的几何构型,取决于溴原子的取代位置。多溴代芴最稳定及最不稳定异构体的△_fH^(?)及△_fG^(?),都随Br原子数目增加而逐渐增加。溴原子数目相同的多溴代芴异构体的△_fH^(?)和△_fG^(?)与溴原子的取代位置有很大的关系,其相对稳定性看离域π键和Br…Br核排斥作用的强弱而决定。
Polybrominated fluorene （PBFR） compounds are one type of latent chemical pollutants, of which thermodynamic properties are of significant meaning to study PBFR＇s other physical and chemical properties and their formation, distribution and transfer and transformation in environment. The data of PBFR＇s thermodynamic properties, however, are very scarce. In this article, geometric structures of 135 PBFR molecules were optimized using density functional theory （DFT） at the B3LYP/6-311G＊＊ level and some thermodynamic properties of them in the ideal gas state were calculated. The relations of these thermodynamic properties with the number and position of bromine atoms were also explored, from which the relative stability of PBFR congeners was theoretically proposed according to the magnitude of the relative standard Gibbs free energy of formation （△rfGe）. The results show that the geometric configuration of PBFR isomers is determined by the position of bromine atoms. The values of △fHe and △fGe of both most stable and least stable PBFR isomers increase with increasing the number of bromine atoms. The values of △fHe and △fGe for PBFR isomers with the same number of bromine atoms show a strong dependence on the position of bromine atoms and the relative stability of PBFR congeners are mainly determined by intramolecular delocalized bond and Br…Br nuclear repulsive interaction.
出处
《计算机与应用化学》
CAS
CSCD
北大核心
2010年第9期1242-1246,共5页
Computers and Applied Chemistry
基金
河南省教育厅自然科学研究项目(2009A150022)
信阳师范学院青年骨干教师资助计划项目
关键词
多溴代芴
分子结构
热力学性质
相对稳定性
密度泛函理论
polybrominated fluorenes, molecular structures, thermodynamic properties, relative stability, density functional theory （DFT）
