TEMPERATURE-DEPENDENCE OF THE GIBBS ENERGY ORDERING OF ISOMERS OF CL2O2

A computational evaluation of relative stabilities of ClOOCl (C2 symmetry), ClClO2 (C(s)), and ClOClO (C1) isomers of Cl2O2 in ideal gas phase has been carried out on the basis of recent quantum-chemical data. In the low-temperature region the C2 isomer represents a prevailing component of the equilibrium isomeric mixture. However, at high temperatures the relative stabilities of C2 and C(s) (and finally of C2 and C1) are interchanged. The relative stability approaching and interchanging is reflected in the overall thermodynamic functions of the system and in their isomerism contributions, especially in the temperature dependence (with a rather pronounced maximum) of the heat capacity terms. The results represent a good example of possible effects of enthalpy-entropy interplay in isomeric systems.