多氯二苯硫醚结构参数和热力学性质的密度泛函理论研究

在B3LYP/6-31G*水平上对209个多氯二苯硫醚(PCDS)系列化合物进行了全优化计算, 得到各分子的结构参数和热力学参数. 研究了这些参数与氯原子在苯环各位置的取代数目和相互位置(N_PCS)之间的关系发现: 分子平均极化率(α)、焓(H $)、自由能(G $)、恒容热容( )和熵(S $)与N_PCS之间有很强的相关性, 相关性系数r²＞0.988, 分子体积(V_m)、最高占据轨道能(E_HOMO)和最低未占据轨道能(E_LUMO)与N_PCS也有较好的相关性, 相关性系数r²分别为0.949, 0.894和0.915. 设计等键反应, 计算了PCDS各异构体的标准生成热(Δ_fH $)和标准生成自由能(Δ_fG $). 根据异构体自由能的相对大小, 求得异构体的相对稳定性顺序.

DFT Study on the Structural Parameters and Thermodynamic Properties of Polychlorinated Diphenyl Sulfides

Fully optimized calculation and frequency analysis of 209 polychlorinated diphenyl sulfide (PCDS) compounds were carried out at the B3LYP/6-31G* level and their structural and thermodynamic parameters were obtained. The relation of these parameters with the number and relative positions of Cl atom substitution (N_PCS) was studied, and it was found that there exists high correlation between the molecular mean polarizability (α), enthalpy (H $), free energy (G $), heat capacity at constant volume ( ) or entropy (S $) and N_PCS (correlative coefficients r²＞0.988). It was also found that the molecular volume (V_m), the energy of highest occupied molecular orbital (E_HOMO) and the energy of lowest unoccupied molecular orbital (E_LUMO) had good correlation with N_PCS and the correlative coefficients r² were 0.949, 0.894 and 0.915 respectively. The isodesmic reactions were designed to calculate standard enthalpy of formation (Δ_fH $) and standard free energy of formation (Δ_fG $) of PCDS congeners. The order of relative stability of these PCDS congeners was theoretically proposed based on the relative magnitude of their Δ_fG .