多溴苊烯化合物的分子结构和热力学性质

Molecular structures and thermodynamic properties of polybrominated acenaphthylene compounds

多溴苊烯是潜在的一类有机污染物，本文采用密度泛函理论在B3LYP／6-311G水平上，优化这类化合物的分子几何结构135个，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，求出它们热力学稳定性的顺序。结果表明：大部分多溴苊烯分子具有平面的几何构型。最稳定及最不稳定异构体的△fG^Φ及△fG^Φ，都随Br原子数目增加而逐渐增加。溴原子数目相同的△fH^Φ和△fG^Φ与溴原子的取代位置有很大的关系，其相对稳定性由分子内Br…Br核排斥作用的强弱而决定。

Polybrominated acenaphthylene （PBAC） compounds are one type of latent chemical pollutants, of which thermodynamic properties, however, have not been reported. In this article, molecular geometric structures of 135 PBAC compounds 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, frorn which the relative stability of PBAC congeners was theoretically proposed according to the magnitude of the relative standard Gibbs free energy of formation （△r,fG^Φ）. The results show that most of PBAC isomers are in planar configuration. The values of △fG^Φ and △fG^Φ of both most stable and least stable PBAC isomers increase with increasing the number of bromine atoms. The values of △fG^Φ and ArGO for PBAC isomers with the same number of bromine atoms show a strong dependence on the position of bromine atoms and the relative stability of PBAC congeners are mainly determined by intramolecular Br…Br nuclear repulsive interaction.