SYNTHESES AND CRYSTAL-STRUCTURES OF 2,5-B IS(2-ARYLVINYL)-1,4-BENZOQUINONES AND THEIR PHOTOCHEMICAL REACTIVITY IN THE CRYSTALLINE STATE

The 2,5-bis(2-arylvinyl)-1,4-benzoquinones 1a-1e are formed from hydro lysis of their corresponding ketals 5 which are generated by anodic ox idation of the corresponding 1,4-dimethoxybenzene derivatives 4. The c rystal structures of the quinone compounds 1a, 1d and 1e have been det ermined by X-ray analyses. The bond lengths of the quinone system are influenced by polar resonance structures. An alpha-type packing mode i s observed for the three crystal structures of compounds 1. The vinyli c double bonds have short intermolecular distances (1a: 4.417(5), 1d: 3.653(2), 1e: 4.224(5) angstrom). Only the crystals of 1d with the sho rtest contacts are photoreactive.