Heat capacities and thermodynamic properties of trans-(R)-3-(2,2-dichloroethenyl)-2,2-dimethylcyclopropanecarboxylic acid

Abstract

The heat capacities of trans-(R)-3-(2,2-dichloroethenyl)-2,2-dimethylcyclopropanecarboxylic acid in the temperature range from 78 to 389 K were measured with a precise automatic adiabatic calorimeter. The sample was prepared with the purity of 0.9874 mole fraction. A solid-liquid fusion phase transition was observed in the experimental temperature range. The melting point, T _m, enthalpy and entropy of fusion, Δ_fus H _m, Δ_fus S _m, were determined to be 344.75±0.02 K, 13.75±0.07 kJ mol⁻¹, 39.88±0.21 J K⁻¹ mol⁻¹, respectively. The thermodynamic functions of the sample, H _(T)-H _(298.15), S _(T)-S _(298.15) and G _(T)-G _(298.15), were reported with a temperature interval of 5 K. The thermal decomposition of the sample was studied by TG analysis, the thermal decomposition starts at ca. 421 K and terminates at ca. 535 K, the maximum decomposition rate was obtained at 525 K. The order of reaction, pre-exponential factor and activation energy, are n=0.14, A=1.15·10⁸ min⁻¹, E=66.27 kJ mol⁻¹, respectively.