The standard molar enthalpy of formation of 2-chlorodibenzo-p-dioxin

The standard molar energy of combustion of crystalline 2-chlorodibenzo-p-dioxin was determined by rotating-bomb calorimetry: ΔcUm°= −(5573.6±2.8)kJ·mol−1. The standard molar enthalpy of sublimation was measured in a Calvet microcalorimeter: ΔsubHm°= (97.24±0.55) kJ·mol−1. Using these results, the values of the standard molar enthalpies of formation of 2-chlorodibenxo-p±dioxin in the crystalline and gaseous states were found to be −(171.3 ±3.2)kJ·mol−1and −(74.1±3.3)kJ·mol−1and −(74.1-3.3)kJ·mol−1, respectively.