Photochemical Hydrolysis of Barbitals

Abstract

The irradiation of barbital (BA) and N,N'-dimethylbarbital (DMBA) in aqueous alkaline media gave diethylacetylurea and N,N'-dimethyldiethylmalonamide respectively. On the basis of the results of kinetic studies, the above photochemical hydrolyses of BA and DMBA were shown to be an attack of the hydroxide ion on the singlet excited states of BA monoanion and DMBA respectively. Such nucleophilic reagents as amines, mercaptide, and cyanide ions retarded the photochemical hydrolyses by quenching the excited state of the substrates.

Photoinduced Electron Transfer Reaction of 2-Thiobarbituric Acid and Methylene Blue: Mechanism and Kinetics

“…Otsuji et al 14 The cationic dye methylene blue -photo sensitizer -absorbs the visible radiation and goes to the singlet excited state and is converted to the triplet state by ISC (Intersystem Crossing). The excitation energy of the sensitizer molecule is transferred to 3 O 2 molecule and converts it to the singlet state, while photo sensitizer molecule returns to the ground state.…”