Kinetic studies on fast reactions in solution III : photoreduction of anthracene derivatives

Abstract

The photoreduction of 9-acetylanthracene by stannane in benzene was studied. By the analysis of UV and IR spectra of the reaction products, it was found that the carbonyl group of 9-acetylanthracene was not photoreduced, and that the addition of hydrogen atom occurred at the meso position. For several anthracene derivatives, this photoreduction reaction at the meso positions was investigated by the method of the flash photolysis. The reduction rate constants are of the order of 10^4 l mole^-1 sec^-1. The trend of the substituent effect is reverse to that found by other investigators for the photo-oxidation of anthracene derivatives. Namely, the electron donating substituents decrease the rate of the photoreduction and the electron attracting substituents increase it, The activation energy for the reaction of 9-acetylanthracene was found to be 10.4kcal/mole. The reason why the carbonyl group of 9-acetylanthracene was not photoreduced by stannane will be discussed.