Thermodynamic properties of 2-adamantanone in the condensed and ideal gaseous states

The results of a comprehensive study of thermodynamic properties of 2-adamantanone in different phase states are reported. The heat capacity of the compound in the condensed state was measured from 5 to 310 K with an adiabatic calorimeter and between 290 and 610 K with a differential scanning calorimeter of the heat-bridge type. Adamantanone undergoes a solid-to-solid phase transition at 216.4 +/- 0.1 K with Delta H-trs(m)degrees = 7.627 +/- 0.014 kJ mol(-1) and fusion at 557.5 +/- 0.2 K with Delta H-fus(m)degrees = 11.77 +/- 0.24 kJ mol(-1). The solid-phase transition is associated with formation of orientationally disordered (plastic) crystal. The thermodynamic functions of the compound in the crystalline and liquid states were obtained. The saturated vapour pressure for crystalline adamantanone between 280 and 333 K was determined by the Knudsen effusion method, the undersaturation of the vapours in the effusion cell being taken into account. The sublimation enthalpy of the compound was measured with a differential Calvet-type calorimeter. The weighted average value of the sublimation enthalpy was Delta H-sub(m)degrees(298.15 K) = 66.38 +/- 0.25 kJ mol(-1). The thermodynamic properties of the compound in the ideal gaseous state were calculated by statistical thermodynamics. (C) 2006 Elsevier B.V. All rights reserved.