Structural and Thermodynamic Insight into Solid StatePhase Transition Mechanism of a 1,3,3′-Triketone.

A studyof a solid state phase transition in dipivaloyl(3-cyclopentylpropanoyl)methanewas undertaken by a combination of crystallographic and calorimetricmethods. The high temperature polymorph with two molecules in theasymmetric unit and a disordered cyclopentyl group undergoes a reversiblephase transition into an ordered structure with a single moleculein the asymmetric unit. The transition temperature is −20.80°C with a minimal hysteresis of 1 °C. The nucleation ofthe new phase was followed by differential scanning calorimetry andoccurs in a wide temperature range starting from ca. 0.5 °C aboveand below the transition temperature, and the crystallographic orientationof the crystals of the nascent phase is to a high degree in agreementwith that of the parent crystal. [ABSTRACT FROM AUTHOR]