Heat capacity and thermodynamic functions of 2-methylbiphenyl and 3,3'-dimethylbiphenyl in the range of 6 to 372 K

The heat capacities of 2-methylbiphenyl and 3,3'-dimethylbiphenyl are measured by means of low-temperature adiabatic calorimetry in the temperature range of 6 to 372 K. The thermodynamic characteristics of fusion and the glass transition of the investigated compounds are determined. The saturation vapor pressure and enthalpy of vaporization of 3,3'-dimethylbiphenyl are determined according to the dynamic method based on the transfer of a substance vapor in a helium flow. The absolute entropies and changes in Gibbs energies of biphenyl derivatives are calculated from the data obtained in the condensed and ideal gas states. The contribution of the C-b-(C-b) group is determined using the Benson additive method for calculating the absolute entropies of biphenyl derivatives in the liquid state (where C-b is the carbon atom in a benzene ring).