Abstract:

Fully optimized calculation and frequency analysis of 135 polychlorinated dibenzothiophenes sulfoxide (PCDBTOs) compounds were carried out by using density functional theory(DFT) method at the BHandHLYP/6-31G* level and their thermodynamic parameters in the ideal gas state at 298.15 K and 101.3 kPa were obtained.The isodesmic reactions were designed to calculate standard enthalpy of formation (Δ_fH^θ) and standard free energy of formation (Δ_fG^θ) of PCDBTOs congeners.The relationships of these thermodynamic parameters with the number and the position of Cl atom substitution (N_PCS) were established.There exists good correlation between entropy (S^θ)，standard enthalpy of formation (Δ_fH^θ)，standard free energy of formation (Δ_fG^θ) and N_PCS.The stability of PCDBTOs congeners was obtained theoretically based on the relative magnitude of their Δ_fG^θ.The values of c_p,m were calculated by using statistical thermodynamic calculation program in the temperature range from 200 K to 1000 K based on Gaussian 03 output files.The relative equation between c_p,m and temperature was obtained by the least square method.It is found that c_p,m and T，T^-1 and T^-2 have a very good relationship (R²=1.000）.Furthermore，based on the relationship of molecular volume and toxicity，it is predicted that the TCDBTO isomers may be the most toxic among the PCDBTOs compounds.

Key words:

多氯代二苯并噻吩亚砜, 密度泛函理论, 氯原子取代位置方法, 热力学性质, 相对稳定性

摘要：

在BHandHLYP/6-31G*水平上对135个多氯代二苯并噻吩亚砜(PCDBTOs)系列化合物进行了全优化和振动分析计算，得到各分子在298.15 K、101.3 kPa标准状态下的热力学参数。设计等键反应，计算了PCDBTOs系列化合物的标准生成热(Δ_fH^θ)和标准生成自由能(Δ_fG^θ)。研究了热力学参数S^θ与氯原子的取代位置及取代数目(N_PCS)之间的关系，结果表明：PCDBTOs系列化合物的S^θ、Δ_fH^θ和Δ_fG^θ与N_PCS之间有较好的相关性。根据异构体标准生成自由能的相对大小，从理论上求得异构体的相对稳定性。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PCDBTOs化合物在200～1000 K的摩尔定压热容(c_p,m)，并用最小二乘法求得c_p,m与温度之间的相关方程，发现c_p,m与T、T^-1和T^-2之间有着很好的相关性(R²=1.000)。同时，根据分子体积推测了化合物的毒性，结果表明：PCDBTOs系列化合物中，毒性最大的异构体可能在4取代中。

关键词:

多氯代二苯并噻吩亚砜, 密度泛函理论, 氯原子取代位置方法, 热力学性质, 相对稳定性