Photosensitized oxidation of phenyl and tert-butyl sulphides

S. M. BONESI, M. FAGNONI, S. MONTI, A. ALBINI

Photochemical and Photobiological Sciences

The Royal Chemical Society and Owners Societies

Año: 2004 vol. 3 p. 489 - 493

1474-905X

The photosensitized oxygenation of diphenyl (1), di-tert-butyl (2) and phenyl tert-butyl sulfide (3) was studied. Bimolecular rate constants of singlet oxygen quenching are low (1 to 5 104 M-1s-1) since the sulfides are poor nucleophiles due to sterical hindrance (2,3) or the HOMO on the sulfur atom being a less accessible pz orbital (1). The quenching is mainly physical, but chemical reaction leading to sulfoxides also takes palce in methanol and, to a lower degree, in acetonitrile. Catalysis by carboxylic acids considerably anhances the rate of sulfoxidation. Inefficiency in the chemical reaction is again due to the poor nucleophilicity of the sulfides, which limits oxygen transfer by electrophilic intermediates such as the protonated persulfoxide.