Thermodynamic properties of 1-bromoadamantane in the condensed state and molecular disorder in its crystals

The heat capacities of 1-bromoadamantane in the condensed state were measured in calorimeters of two types: an adiabatic vacuum calorimeter was used in the temperature range from (6 to 320) K and a differential scanning calorimeter of the heat bridge type - between T = (290 and 430) K. Three solid-to-solid phase transitions and fusion were found to occur in the mentioned temperature range. The thermodynamic parameters of the solid-to-solid phase transitions were determined by the adiabatic calorimetry and of the crII → crI transition and fusion - in the scanning calorimeter. The molar thermodynamic functions of 1-bromoadamantane in the crystalline and liquid states were obtained. The two-stage development of the orientational disorder in the crystalline phases up to the formation of the plastic crystals was established for the compound under study. Thermal behaviour of adamantane and 1-haloadamantanes and parameters of orientational disorder in their isotropic plastic crystals were discussed.