Electronic spectra, photochemistry, and autoxidation mechanism of the sulfite-bisulfite-pyrosulfite systems. SO2-, SO3-, SO4-, and SO5- radicals

Abstract

The technique with inclusion of overlap charges, as described in previous papers of this series, has been extended to evaluate the -bond energies, heats of formation, and resonance energies of some conjugated hydrocarbons. The success of the method has been supported by comparing the results with experimental data and with results obtained by others using Pople's SCF-MO method.

Efficient degradation of sulfamethoxazole by the Fe(II)/HSO5− process enhanced by hydroxylamine: Efficiency and mechanism

“…Based on the radical reaction characteristics, methanol and TBA were selected as quenching compounds to investigate their inhibition effects on SMX degradation, and thus explore the degradation mechanism of SMX in HA/Fe(II)/PMS process. (Hayon et al, 1972), approximately 25% of SMX degradation in non-alcohol system could be attributed to the rapid degradation in the initial reaction or the contribution of SO5…”

Free-radical chemistry of sulfite.

“…The S03 radical has been produced by oxidation sulfite with Ce4+ in acid solution (39)(40)(41), by reacti of sulfite with rad.icals produced by Fenton-type i agents, e.g., OH, NH2, and S4-(from the reaction Ti + with H202, NH2OH, S2082, respeetively) (42), reaction with radiolytically produced OH radicals other oxidizing radicals (43)(44)(45)(46)(47) OH + S02 -R OH-+ SOgby photoionization of sulfite directly (3,48,49) or throu photosensitizers (49) S032-+ hv -SO-+ eor by photolysis of dithionate (50) or thiosulfate (5 The S03-single-line ESR spectrum has been detect by using all ofthe above techniques (39)(40)(41)(42)46,47,49,5 as well as in biochemical systems such as horseradi peroxidase-hydrogen peroxide (52) or prostaglan( hydroperoxidase (53). Most of these studies report a g factor for S03 around 2.0030, except experimer with Ce4+ in acid solutions, where g = 2.0022 has be measured (39)(40)(41).…”

“…The hydrated electron is unreactive toward So32-(k < 106 M-1sec-I) and reacts very slowly with HS03-to produce hydrogen atoms (k = 2 x 107WM-1sec-1) (3). On the other hand, SO2 is reported (66).…”

“…HSO-+ S02eaq -t HS20O PKa = 1.5 (4) (3) At any physiological pH, sulfite and bisulfite will both be important forms of S(IV). We will use primarily the term sulfite to refer to the equilibrium mixture, except when referring specifically to bisulfite.…”

Protein Radical Formation Resulting from Eosinophil Peroxidase-catalyzed Oxidation of Sulfite

“…It can be hydrated to bisulfite in the lung and upon contact with fluids lining the air passages as follows, where the second pKa ϭ 7.2 (2). Its two ionized forms in aqueous solution at physiological pH, bisulfite and sulfite (3), are widely used as preservatives and antioxidants to prevent food and beverage spoilage, as bleaching agents for certain products, and as medicine ingredients (4).…”