A combined thermodynamic and crystallographic study of 1,3-diisopropylnaphthalene

Abstract The thermodynamic properties and phase behaviour of 1,3-diisopropylnaphthalene were studied for the first time using static vapour pressure measurements, Tian-Calvet calorimetry, and differential scanning calorimetry (DSC). Polymorphic behaviour of the compound was detected and studied in detail by combination of DSC and variable-temperature X-ray powder diffraction. The crystal structure of the disordered metastable phase was obtained using a single-crystal X-ray diffraction for the first time. The experimental study was supplemented by calculating thermodynamic properties in the ideal-gas state using a combination of statistical thermodynamics and quantum-chemical calculations. Recommended vapour pressure equation was derived by simultaneous treatment of vapour pressures, experimental heat capacities of the condensed phases, calculated ideal-gas heat capacities, and temperature and enthalpy of fusion, assuring their mutual thermodynamic consistency.