The kinetics of the singlet oxygen oxidation of diethyl sulfide in the presence of diphenyl sulfoxide and diphenyl sulfide in various solvents (methanol, benzene, and acetonitrile) have been investigated. The results show that competitive trapping of a single intermediate species by diethyl sulfide, diphenyl sulfide, and diphenyl sulfoxide occurs in protic solvent (methanol), while in aprotic solvents (benzene, acetonitrile) only diphenyl sulfide competes with diethyl sulfide. Diphenyl sulfoxide traps an earlier intermediate; the same intermediate also leads to quenching. A mechanism is proposed in which an initial nucleophilic intermediate 2 can be trapped by electrophiles (diphenyl sulfoxide), lose singlet oxygen, or collapse to an electrophilic intermediate 3 that can be trapped by sulfide nucleophiles.

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Sensitized photooxidation of 1,5-dithiacyclooctane (1,5-DTCO) has been investigated in various solvents. At high conversions, a novel C-S bond cleavage occurs. Significant solvent effects are also observed. At high concentration (0.05-0.1 M) in methanol, more than 90% of the corresponding monosulfoxide and a mixture of cis-and tra/w-bissulfoxides are produced.In aprotic solvents (benzene, chloroform, acetone, and acetonitrile), novel cleavage products (1,2-dithiolane 1-oxide, 1,2-dithiolane 1,1-dioxide, and acrolein) were obtained in addition to the monosulfoxide and bissulfoxides. The cleavage products derive mostly from reaction of the primary monosulfoxide (1,5-DTCO 1-oxide) with singlet oxygen. Unstable compounds oxidized a to the sulfur atom were detected by NMR spectroscopy and shown to be intermediate in the formation of the cleavage products.