Improved Synthesis and Crystal Structure of 7H-Dibenz[a,kl]anthracen-7-one.

An improved synthetic method gives pure 7H-dibenz[a,kl]anthracen-7-one, C21H12O, in a higher yield than those reported so far. The crystal structure has been determined by X-ray analysis. The space group is Pn21a, with unit cell dimensions of a=23.325(5), b=14.149(3), c=3.986(1) A, and Z=4. The structure was solved by the direct method and refined by the block-diagonal least-squares method to an R value of 0.044. The molecule is greatly distorted from the planar conformation because of an intramolecular steric repulsion between the hydrogen atoms.