Fully optimized calculation and frequency analysis of 135 polychloridized phenoxazine (PCPX) compounds derivatives were carried out by using a DFT method at the B3LYP/6-31G* level and their thermodynamic parameters were obtained. The isodemic reactions were designed to calculate standard enthalpy of formation (ΔfH ) and standard free energy of formation (Δf ) of the PCPX congeners. The relation of these thermodynamic parameters with the number and the position of Cl atom substitution (NPCS) was studied, and it was found that there existed high correlation between of thermal correction to heat capacity at constant volume, entropy ( ), standard enthalpy of formation (Δf ) and or standard free energy of (CVө)formation (Δf ) and with NPCS. The order of relative stability of the PCPX congeners was theoretically proposed based on the relative magnitude of their Δf . The values of Cp,m were calculated by using statistical thermodynamics calculation Program program at the temperatures between( 200 to and 1800) K based on Gaussian 03 output files, and a obtained relative equation between the Cp,m and temperature was obtained by the least square method, found finding that the Cp,m has and T、T-1、T-2 have a very good relationship with T, T－1, and T－2.

Key words: polychloridized phenoxazines,, density functional theory (DFT), , method of position of Cl atom substitution,, thermodynamic property,, relative stability