Experimental thermochemical study of 2-chloroacetophenone and 2,4’-dichloroacetophenone

Abstract

The standard (p∘=0.1MPa) molar enthalpies of formation of 2-chloroacetophenone and 2,4’-dichloroacetophenone, in the gaseous phase, at T=298.15K, were derived from the combination of the values of the standard molar enthalpies of formation in the crystalline phase, at T=298.15K, and the standard molar enthalpies of sublimation of each compound, at the same temperature. The standard molar enthalpies of formation, in the crystalline phase, were derived from the corresponding standard massic energies of combustion, in oxygen, at T=298.15K, measured by rotating-bomb combustion calorimetry. The standard molar enthalpy of sublimation of 2-chloroacetophenone was measured by Calvet microcalorimetry whereas the standard molar enthalpy of sublimation for 2,4’-dichloroacetophenone was calculated by application of the Clausius–Clapeyron equation to the vapor pressures at several temperatures measured by the Knudsen effusion technique.Compound-ΔfHm∘(cr)/kJ·mol−1ΔcrgHm∘/ kJ·mol−12-Chloroacetophenone179.6±1.387.7±1.72,4’-Dichloroacetophenone223.2±1.797.8±0.5The values of the standard molar enthalpies of formation, in the gaseous phase, at T=298.15K, were compared with the same parameters estimated by the empirical scheme developed by Cox. The estimation schemes were extended to others chloro-substituted acetophenones.