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The thermodynamic properties and molecular volumes (Vm) of 76 polychlorophe- nazines (PCPZs) have been calculated at the B3LYP/6-31G* level by using density functional theory. The isodesmic reactions were designed to calculate standard enthalpy of formation (△fHθ) and standard free energy of formation (△fGθ) of PCPZ congeners. According to the relative magnitude of their △fGθ, the order of relative stability of PCPZ congeners was theoretically proposed. Comparing the results with those of polychlorinated dibenzo-p-dioxin (PCDD) isomers, it was found that Sθ, △fHθ, △fGθ, Vm and the order of relative stability of PCPZ congeners were quite similar to those of PCDDs.
The isodynamic reactions were designed to calculate standard enthalpy of formation (ΔfHθ). The thermodynamic properties and molecular volumes (Vm) of 76 polychlorophenes (PCPZs) have been calculated at the B3LYP / 6-31G * level by using density functional theory. and standard free energy of formation (ΔfGθ) of PCPZ congeners. According to the relative magnitude of their ΔFGθ, the order of relative stability of PCPZ congeners was theoretically proposed. Comparing the results with those of polychlorinated dibenzo-p-dioxin (PCDD ) isomers, it was found that Sθ, ΔfHθ, ΔfGθ, Vm and the order of relative stability of PCPZ congeners were quite similar to those of PCDDs.