Studies of Structural and Thermodynamic Properties for Polychlorinated Thianthrenes by Density Functional Theory

摘要

The structural and thermodynamic properties of 75 polychlorinated thianthrenes(PCTAs) in the ideal gas state at 298.15 K and 1.013 ×105 Pa have been calculated at the B3LYP/6-31G level using Gaussian 98 program.Based on the output data of Gaussian=the isodesmic reactions were designed to calculate standard enthalpy of formation(△fHθ) and standard free energy of formation(△fGθ) of PCTAs 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 exists high correlation between thermodynamic parameters(total energy(TE)=zero-point vibrational energy(ZPE)=thermal correction to energy(Eth)=heat capacity at constant volume(Cvθ)=entropy(Sθ)=enthalpy(Hθ)=free energy(Gθ)=standard enthalpies of formation(△fHθ) and standard Gibbs energies of formation(△fGθ)) and NPCS.On the basis of the relative magnitude of their △fGθ=the order of relative stability of PCTA congeners was theoretically proposed.In addition=the correlations between structural parameters and NPCS were also discussed.The good correlations were found between molecular average polarizability(α)=energy of the highest occupied molecular orbital(EHOMO)=molecular volume(Vm) and NPCS=and all R2 values are larger than 0.95.Moreover=it was supposed that the isomer groups with higher toxicity should be Tri-CTA and TCTA .