多氯咔唑系列化合物的热力学性质的密度泛函理论研究

Thermodynamic Properties of Polychlorinated Carbazoles by Density Functional Theory

采用Gaussian 03程序中的密度泛函(DFT)方法,在B3LYP/6-31G*水平上对135个多氯咔唑系列化合物(PCCZs)进行了全优化计算,得到了298.15K,1.013×105Pa标准状态下各分子的热力学性质.设计等键反应,计算了PCCZs系列化合物的标准生成热(ΔfH)和标准生成自由能(ΔfG),研究了这些参数与氯原子的取代位置及取代数目(NPCS)之间的关系,结果表明:熵(S),ΔfH,ΔfG与NPCS之间有很强的相关性.并根据ΔfG的相对大小,从理论上求得异构体的相对稳定性的顺序.此外,以Gaussian 03程序的输出文件为基础,采用统计热力学程序计算了PCCZs化合物在200至1800K的摩尔恒压热容(Cp,m),并用最小二乘法求得Cp,m与温度之间的相关方程,发现Cp,m与T,T-1和T-2之间有着很好的相关性.

The thermodynamic properties of 135 polychlorinated carbazoles （PCCZ） in the ideal gas state at 298.15 K and 1.013 × 10^5 Pa have been calculated at the B3LYP/6-31G^＊ level using Gaussian 03 program. The isodesmic reactions were designed to calculate the standard enthalpy of formation （△fH^θ） and standard free energy of formation （△fG^θ of PCCZ congeners. The relations of these thermodynamic parameters with the number and position of Cl atom substitution （NPCS） were discussed, and it was found that there existed high correlation between thermodynamic parameters （entropy （S^θ, △fH^θ and △fG^θ） and NPCS. According to the relative magnitude of their AfGe, the relative stability order of PCCZ congeners was theoretically proposed. Moreover, using a statistical thermodynamics calculation program based on Gaussian 03 output files, the values of molar heat capacity at constant pressure （Cp,m） from 200 to 1800 K for the PCCZ congeners were calculated, and the temperature dependence relation of them was obtained using the least-squares method, which suggested that there be very good relationships between Cp,m and temperature （T, T^-1 and T^-2） for almost all the PCCZ congeners.