Thermodynamic Properties and Relative Stability of Polyhydroxylated Dibenzo-p-dioxins Calculated by Density Functional Theory  

作　　者：戴勇 石佳奇 郑清 王遵尧 

机构地区：[1]Department of Chemical and Biological Engineering,Yancheng Institute of Technology [2]State Key Laboratory of Pollution Control and Resources Reuse,Department of Environment,Nanjing University

出　　处：《Chinese Journal of Structural Chemistry》2011年第3期354-361,共8页结构化学（英文）

基　　金：supported by the National Natural Science Foundation of China (41071319, 20977046, 20737001)

摘　　要：In this work, partial thermodynamic properties of polyhydroxylated dibenzo-p-dioxins （PHODDs） are calculated by density functional theory （DFT） with the Gaussian 03 program at the B3LYP/6-311G^＊＊ level. By comparing the total energy Eθ values, it is found that two types of hydrogen bonds exist in PHODDs, one between a hydroxyl and the parent compound （dibenzop-dioxin） with bond energy of approximate 15.7 kJ/mol and the other between two ortho hydroxyl groups with higher bond energy of about 18.3 kJ/mol. Hydrogen bonds have an effect on the conformation stability. On the basis of evaluating the strength of these two types of hydrogen bonds, 75 most stable congeners are ascertained. The relations of calculated thermodynamic parameters （total energy E^θ, zero-point vibrational energy ZPE, correction value of thermal energy Ethθ, heat capacity at constant volume CV^θ） with the number and position of hydroxyl substitution （NPHOS） are also discussed. The results show that the NPHOS models can be used to predict the thermodynamic properties for PHODD congeners. In addition, the values of molar heat capacities at constant pressure （Cp,m） from 200 to 1000 K for PHODD congeners are calculated, and the temperature dependence relation of Cp,m is obtained with the least-squares method.In this work, partial thermodynamic properties of polyhydroxylated dibenzo-p-dioxins （PHODDs） are calculated by density functional theory （DFT） with the Gaussian 03 program at the B3LYP/6-311G^＊＊ level. By comparing the total energy Eθ values, it is found that two types of hydrogen bonds exist in PHODDs, one between a hydroxyl and the parent compound （dibenzop-dioxin） with bond energy of approximate 15.7 kJ/mol and the other between two ortho hydroxyl groups with higher bond energy of about 18.3 kJ/mol. Hydrogen bonds have an effect on the conformation stability. On the basis of evaluating the strength of these two types of hydrogen bonds, 75 most stable congeners are ascertained. The relations of calculated thermodynamic parameters （total energy E^θ, zero-point vibrational energy ZPE, correction value of thermal energy Ethθ, heat capacity at constant volume CV^θ） with the number and position of hydroxyl substitution （NPHOS） are also discussed. The results show that the NPHOS models can be used to predict the thermodynamic properties for PHODD congeners. In addition, the values of molar heat capacities at constant pressure （Cp,m） from 200 to 1000 K for PHODD congeners are calculated, and the temperature dependence relation of Cp,m is obtained with the least-squares method.

关 键 词：PHODDs DFT thermodynamic property NPHOS Cp m 

分 类 号：O621.3[理学—有机化学]