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

Oxanorbornane (7-oxabicyclo[2.2.1]heptane, C6H10O) resembles other bicycloh eptane-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 vibr ational spectra have been examined, and a factor group analysis of the vibr ational splittings indicates that the crystal structure of the ordered phas e has D-2d symmetry. Activation energies for molecular motions were derived from proton spin-lattice relaxation time measurements.