Heat capacities and thermodynamic properties of (-)-2,3-O-Isopropylidene-2,3-dihydroxy-1,4-bis (diphenylphosphino) butane [(-)-DIOP]

Heat capacities of (-)-DIOP have been measured with a precision automatic adiabatic calorimeter in the temperature range from 78 to 380 K. A solid–solid phase transition for the compound was observed at 348.65 K and the molar enthalpy and entropy of the transition were determined to be 3.415 kJ mol−1 and 9.795 J mol−1, respectively. A solid–liquid phase transition was found at 364.23 K and the molar enthalpy and entropy of fusion were determined to be 38.606 kJ mol−1 and 106.0 J K−1 mol−1, respectively. The purity of the sample under investigation was determined to be 0.9837 molar fraction by the fractional melting method.