Low-temperature heat capacity, phase transitions and thermodynamic functions of 2-furfurylamine

Heat capacities of 2-furfurylamine were measured by low-temperature adiabatic calorimetry in the temperature range from 5.6 to 356.1 K. Two phase transitions, solid phase transition and melting, were revealed at temperatures of 180.4 K and 228.17 K. Thermodynamic characteristics determined from experimental data show that the mechanism of solid phase transition is intermediate between order-disorder and displacive type. This conclusion is in agreement with X-ray crystallography data (Seidel et al., 2019). The standard thermodynamic functions in the condensed state (molar heat capacity, enthalpy, entropy and Gibbs energy) were calculated in the temperature range 5 - 350 K. Using the determined value of entropy for liquid 2-furfurylamine and available value of ${\Delta }_f{H}_m^{\circ }\left(l\right)$, the properties of formation, ${\Delta }_f{S}_m^{\circ }\left(l\right)$ and ${\Delta }_f{G}_m^{\circ }\left(l\right)$, were obtained. The thermodynamic functions of gaseous 2-furfurylamine were calculated taking into account the internal rotation in this molecule. The required molecular constants were determined from quantum chemical calculations.