科研之友
微信
新浪微博
Facebook
分享链接
摘要
Geometric molecular structures of 527 polychlorinated phenanthrenes (PCPhen) have been optimized using density functional theory (DFT) at the B3LYP/6-311G(d, p) level and their thermodynamic properties in the ideal gas state, such as heat capacity at constant volume (C(v)(circle minus)), entropy (S(circle minus)), standard enthalpy of formation (Delta(f)H(circle minus)) and standard Gibbs free energy of formation (Delta(f)G(circle minus)), have been computed. The relations of C(v)(circle minus), S(circle minus), Delta(f)H(circle minus) and Delta(f)G(circle minus) with the number and position of chlorine atoms have also been explored, from which the relative stability of PCPhen congeners was theoretically proposed according to the magnitude of the relative standard Gibbs free energy of formation (Delta(r,f)G(circle minus)). It was found that most of PCPhen isomers are in a nonplanar configuration, with three kinds of intramolecular weak interactions, i.e., H center dot center dot center dot H, C-H center dot center dot center dot Cl and Cl center dot center dot center dot Cl interactions. With increasing the number of chlorine atoms, the values of Delta(f)H(circle minus) and Delta(f)G(circle minus) of the most stable PCPhen isomers decrease initially and then increase quickly. The values of Delta(f)H(circle minus) and Delta(f)G(circle minus) of PCPhen congeners with the same number of chlorine atoms show a strong dependence on the positions of chlorine atoms. The relative thermodynamic stability of PCPhen isomers is determined mainly by relative magnitude of intramolecularly delocalized pi bond and Cl center dot center dot center dot Cl nuclear repulsive interaction.
