Concomitant Polymorphism in 3-Acetylcoumarin: Role of Weak C−H···O and C−H···π Interactions

An analysis of structural features associated with polymorphism in 3-acetylcoumarin has been made in terms of morphology, infrared spectroscopy, crystal structure, powder X-ray diffraction, and differential scanning calorimetric measurements. The appearance of concomitant polymorphs is found to depend on the crystallization temperature in the 1:1 chloroform/hexane solvent system. C−H···O and C−H···π interactions stabilize one form in a head to head configuration, while only C−H···O interactions stabilize the other in a head to tail configuration of the molecules in the crystal lattice.