SOLID-STATE PHOTOCHEMISTRY OF THE MIXED-CRYSTALS BETWEEN BENZOQUINONES AND POLYMETHYLBENZENES

Nine mixed crystals combined 1,4-benzoquinone (1), 2,5-xyloquinone (2) and duroquinone (3) with durene (a), pentamethylbenzene (b) and hexamethylbenzene (c) were prepared by a melting-resolidifying process and characterized by powder X-ray diffractometry, DDC and IR. Only the mixed crystal of 3 and a formed a 2:1 novel molecular crystal (4); other eight mixed crystals were simple polycrystalline mixtures of the two components. Irradiation of the molecular crystal 4 (3/a) and the mixed crystals 1/a, 1/b and 3/b caused intermolecular hydrogen abstraction to give hydroquinones and in some cases adducts. Product selectivities in the solid state were different from those in solution. Correlation between the crystal structure and the reactivity of 4 is discussed.