10-HYDROXYANTHRONE PHOTOCHEMISTRY IN FLUID SOLUTION AND IN HYDROGELS

Reaction schemes are proposed to a better account for the published re sults of studies on the photochemistry of 10-hgdroxyanthrone (oxanthro ne) in alcohol solution, and for the much different product distributi ons observed in 2-hydroxyethylmethacrylate hydrogels. In a fluid solut ion, oxanthrone simultaneously phototautomerizes to anthrahydroquinone and photoreduces to 9-hydroxyanthracene, and an unstable, intermediat e pinacol is proposed to account for this. This is based partly on rep orted product distributions and partly on results of studies on the cl osely related. compounds anthrone and benzophenone, both of which form pinacols. In the hydrogels, neither photoproduct forms and the pendan t oxanthrone photooxidizes to anthraquinone only. Restricted diffusion of photoproducts and the greater order in tile polymer environment ar e proposed to explain this.