Sulfite free radical generation

F8. Fridovich, I., and Handler, P., Detection of free radicals generated during enzymatic oxidations by the initiation of sulfite oxidation. J. Biol. Chem. 235, 1835-1838 (1960). 

Thiosulfate is believed to inhibit sulfite oxidation by reacting with free radicals generated in the chain reactions involved in sulfite oxidatirm. The chain reactions are catalyzed by transition metal ions such as Fes, and the use of a chelating agent such as ethyloiediaminete-traacetate (EDTA) to remove the metal ions has been shown to augment the oxidation inhibition properties of thiosulfate (Mailer et al., 1990). 

Singlet iodocarbene is probably generated in this reaction. To remove iodine, the process is carried out in the presence of aqueous sulfurous acid," aqueous sodium hydroxide, or sodium sulfite." The competitive reaction observed during photolysis of iodoform is the free radical cleavage of the C-I bond the free radical thus formed undergoes addition to an alkene. 

In addition to the products of lipid oxidation, methanethiol and dimethyl trisulfide were shown to contribute to the complex odor characteristic of soy protein products such as SPI and soy protein concentrates (Boatright Lei, 2000 Lei Boatright, 2001) and soymilk (Lozano et al., 2007) at concentrations comparable to hexanal. Since the threshold in water for methanethiol was reported at 0.02 ppb compared to hexanal at 4.5 ppb (MacLeod C Ames, 1988), these sulfur compounds are intense flavor notes in soy protein products. Lei and Boatright (2007) provided evidence that methanethiol is generated in aqueous slurries of SPI or defatted soy flake from methionine by a free radical mechanism involving manganese, sulfite, and... 

The peroxysulfate radical, SO," is a key intermediate in the autoxidation of sulfite/bisulfite solutions, but is also the intermediate about which the least is known. It is formed subsequent to the one-electron oxidation of sulfite/bisulfite by the reaction of the sulfite radical with molecular oxygen (Reaction (29)). It is also generated in the metal ion-induced free radical decomposition of peroxy-monosulfate, H8O5" [107]. Its production in the oxidation of H8O5" by Ce(IV) has been confirmed by ESR spectroscopy [108], where a g factor of 2.0145 was... 

---