Abstract:
A study of the 1 : 1 solid compound hexafluorobenzene–benzene using a differential scanning calorimeter has enabled an estimate to be made of the enthalpy of formation of the compound when it is formed from the two pure solids. The measured value, + 1.0 ± 0.3 kJ mol–1, is small and positive and is good evidence that the compound is stabilized by preferred geometrical packing effects probably enhanced by weak electrostatic forces rather than by any of the normal specific intermolecular interactions of the charge transfer type. A solid–solid transition was detected at 249.2 K. This is thought to be a genuine order–disorder transition brought about by a partial disordering of the regular alternate packing sequence observed at lower temperatures.
