Heat Capacity and Thermodynamic Functions of Diphenylacetylene

The heat capacity of diphenylacetylene was measured by vacuum adiabatic calorimetry over the temperature range from (8 to 371) K. The temperature and the enthalpy and entropy of fusion have been determined. The standard thermodynamic functions (changes of the entropy, enthalpy, and Gibbs free energy) were obtained for the crystal and liquid states in the temperature interval studied and for the ideal gas state at T = 298.15 K. The ideal gas entropies in wide temperature range were also calculated by the principle of additivity and statistical thermodynamics using molecular constants determined by the density functional theory (DFT) method on the level B3LYP/cc-pVTZ. The S-m(0)(g)(298.15K) values derived from the experimental and calculated data agree within (0.3 to 0.2) % which confirms their reliability. The data on thermodynamic properties of diphenylacetylene studied earlier and in this work were critically analyzed for verification of their reliability and mutual consistency.