Studies on singlet oxygen in aqueous solution. Part 1. Formation of singlet oxygen from hydrogen peroxide with two-electron oxidants

Abstract

Kinetic parameters are reported for the trapping of singlet oxygen by anthracene-9,10-bis(ethanesulphonate)(aes) in water and deuterium oxide solutions. The kinetics of the reactions of N-chloro-succinimide, chloramine T (N-chlorotoluene-p-sulphonamide), N-chloromethanesulphonamide, and N,N-dichloromethanesulphonamide with hydrogen peroxide have been studied. For chloramine T and N-chloromethanesulphonamide the rate-determining step is formation of the corresponding dichloro-compounds, which are the reactive species. Using aes as a trap, it is shown that both chloramine T and N-chlorosuccinimide with H₂O₂ produce singlet oxygen in essentially quantitative yield. Iodylbenzene reacts with H₂O₂ to give, in the rate-determining step, iodosylbenzene and oxygen and then iodobenzene and oxygen; 47% of the oxygen produced is in the singlet state. For the corresponding reaction with 4-iodosylbenzene-1-sulphonic acid, the yield of singlet oxygen is 45%, i.e. indistinguishable within experimental error. Periodate and H₂O₂ give lower yields of singlet oxygen, and it is considered that two concomitant processes are involved. With hypobromite and H₂O₂ the yield of singlet oxygen is 76%. These variations in yield are briefly discussed.