Heat capacities of selected chlorohydrocarbons

Abstract

Isobaric heat capacities in the liquid phase of seven selected halogenated hydrocarbons (1,1,2-trichloroethylene, (Z)- and (E)-1,2-dichloroethylene, 1,1-dichloropropane, 1,2-dichloropropane, 2,2-dichloropropane, and (trichloromethyl)benzene) were measured by using a highly sensitive Tian–Calvet calorimeter in the temperature range from 260K to 340K. Due to high volatility of the studied compounds the correction for sample evaporation was applied. Vapor pressure equations required for applying this correction were iteratively developed by simultaneous correlation of the literature vapor pressures and related thermal data (calorimetrically obtained vaporization enthalpies, heat capacities in the liquid and ideal-gas state). The thermodynamic properties in the ideal gaseous state were calculated using the methods of statistical thermodynamics based on fundamental vibrational frequencies and molecular structure data calculated by DFT at the B3LYP/6-311+G(2df,p) level of theory. Data on liquid heat capacities obtained in this work were merged with available literature data, critically assessed and correlated as a function of temperature.