Thermodynamic function derivation of dioxin substances using semi-empirical molecular orbital theory

In this investigation, respective thermodynamic parameters of heats of formation, standard entropy and specific heat capacity at constant pressure for PCDDs, PCDFs, Co-PCB and PCBs as well as polychlorinated-benzens and polychlorinated-phenols have been evaluated by quantum chemical calculation using a semi-empirical molecular orbital method with the PM3 Hamiltonian and statistical thermodynamic correlation. The values of heats of formation for the dioxin substances and their precursors are calculated in the range of ±200 kJ/mol. The tolerance analysis indicates that the maximum discrepancy with experimental values would be reasonably estimated to be ±28 kJ/mol. The values of standard entropy for these compounds would be in the range of + 270 to + 500 J/mol K, and the estimated discrepancy between the calculated experimental heats of formation would be in the range of + 1 to + 9 J/mol K.