Rubrene, direct photooxygenation

Mechanistic studies were started by Gaffron15-17 in 1926. At this time Moureu, Dufraisse, and Dean18 discovered the direct photooxygenation of rubrene and Windaus and Brunken19 discovered the photosensitized oxygenation of ergosterol. The structures of both the products formed were elucidated some years later and shown to be those of transannular peroxides (endoperoxides).20-23... 

Already in his early investigations on type II direct and indirect photooxygenation reactions, Gaffron18,32 33 showed that the quantum yields of these processes are independent of the intensity as well as of the exciting wavelength of light. He also showed that in the direct photooxygenation of rubrene, two rubrene molecules have to take part in the reaction sequence which bads to the stable endoperoxide. 

The direct photooxygenation of rubrene was also studied by two other groups of investigators.35-37 Schumacher36 confirmed the participation of two molecules of rubrene in this reaction. However, he postulated the formation of an unstable, electronically excited rubrene-... 

Values for Polymer and Model Compounds. 1,4-Polyisoprene and 1,4-polybutadiene are so sufficiently reactive toward singlet oxygen that we can conveniently obtain / -values by three methods (a) from oxygen-uptake rates by photosensitized oxidation at different polymer concentrations (b) by the initial disappearance rate of rubrene on photooxygenation of solutions with and without polymer (or model olefin) and (c) for 1,4-polyisoprene, by the amount of rubrene consumed upon addition of aliquots of triphenyl phosphite ozonide in the presence and absence of olefin or polymer. The treatment of data from methods (b) and (c) was modified to give /3-values directly from the following equations ... 

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