Thermodynamic Properties and Relative Stability of Polychlorinated Thianthrenes by Density Functional Theory

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Thermodynamic parameters, including total electronic energy (Et), enthalpy (H⊖), entropy (S⊖), Gibbs free energy (G⊖), and standard heat capacity at constant volume (C⊖v) for 75 polychlorinated thianthrenes (PCTAs) in the ideal gas state at 298.15 K and 101.325 kPa, have been computed using density functional theory at the B3LYP/6-31G* level with the Gaussian 98 program. The relations of these thermodynamic parameters with the number and position of chlorine substitution (NPCS) were discussed. It was suggested that Et, S⊖, H⊖, G⊖, and C⊖v of PCTAs vary greatly with the number and position of chlorine substitution. The values of molar heat capacity at constant pressure (Cp,m) at temperatures from (200 to 1800) K for PCTA congeners were calculated using a statistical thermodynamics calculation program based on Gaussian output files, and the temperature dependence relation of them was obtained using the least-squares method. The standard enthalpy of formation (ΔfH⊖) and the standard Gibbs energy of formation...