Singlet oxygen production from the reactions of superoxide ion in aprotic solvents: implications for hydrophobic biochemistry.

A number of reactions of superoxide ion in aprotic solvents have been reported to produce singlet oxygen. There is strong evidence for singlet oxygen generation from the reactions of superoxide ion with chlorine-containing halocarbons, bromine-containing halocarbons, hexafluorobenzene, diacylperoxides, lead tetraacetate, iodobenzene diacetate, cerium (IV) cation and tetranitromethane. Earlier studies reporting singlet oxygen generation from the reactions of superoxide ion with iodine, ferricenium ion, thianthrene cation radical, tris (N,N'-dioxobipyridyl) manganese (III) cation and di-mu-oxo-bis[phenanthrolinato manganese (IV)] cation need to be repeated because of the methods used to detect singlet oxygen had low specificity. The results of studies of superoxide ion chemistry in aprotic solvents should not be uncritically extrapolated to hydrophobic biological microenvironments, such as the cell membrane.