Spectroscopic and differential scanning calorimetric studies of the phase transitions in oxanorbornane

Oxanorbornane (7-oxabicyclo[2.2.1]heptane, C6H10O) resembles other bicycloheptane-like molecules by exhibiting order-disorder transitions in the solid state. Differential scanning calorimetric studies show that five different phases may occur, with hysteresis in the transition temperatures. The vibrational spectra have been examined, and a factor group analysis of the vibrational splittings indicates that the crystal structure of the ordered phase has D2d symmetry. Activation energies for molecular motions were derived from proton spin-lattice relaxation time measurements.Key words: oxanorbornane, order-disorder, phase transitions.