Triplet-Triplet Energy Transfer Reaction of 5-Methylthiazole and Benzophenone: Mechanism and Kinetics

The photosensitized reaction of 5–Methylthiazole (5MT) with benzophenone (BP) in aqueous alkaline medium using visible light has been studied to mineralize 5MT to less toxic ions. 5MT shows the λmax at 240 nm in the pH range of 2-12. The triplet–triplet energy transfer from the triplet excited state of the aromatic ketone BP to the substrate molecule takes place during the photosensitized reaction. The triplet excited 5MT breaks down on further exposure and photoproduct formation takes place. The reaction shows the participation of singlet oxygen during the photoreaction. The sulfate has been observed as photoproduct. The apparent rate of the reaction has been calculated and the effect of pH, concentration of the sensitizer, the light intensity on the apparent rate of the reaction has been studied. The quantum efficiency of the photochemical reaction is calculated using potassium ferri oxalate actinometer and the effect of the concentration of the substrate on the quantum efficiency is calculated. The reaction mechanism and the excited states involved have been suggested.