CH3CN: X-ray structural investigation of a unique single crystal. beta --> alpha phase transition and crystal structure.

The phase transition from the low- (beta) to the high-temperature (alpha) form of acetonitrile, CH(3)CN, has been directly observed and studied on a unique single crystal. Both the beta and alpha structures have been determined at temperatures close to the transition temperature (206 K and 201 K), taking advantage of the hysteresis. A single crystal of the beta form was obtained for the first time.