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

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

Kinetic studies on fast reactions in solution : I. Photoreduction of 2-acetonaphthone

The photoreduction of 2-acetonaphthone by (Bu)_3SnH and (Bu)_3SiH were investigated by the method of flash photolysis and compared with the results obtained from the steady state method. The rate constant of the reduction by (Bu)_3SnH was found to be 1.3×10^6/mole^-1 sec^-1, which is close to that of Linschitz et al. The temperature dependence of the rate constant gives the activation energy of 1.7kcal mole^-1. The reduction by (Bu)_3SiH was found not to occur even after a long exposure to sunlight. Furthermore we discuss qualitatively about the activation energy and the reactivity of reducing agents