Hydrogen sulfite radical

The carbon-oxygen double bond of the carbonyl group is opened, and the hydrogen sulfite radical is added. An increase in temperature reverses the reaction more easily for ketones than for aldehydes. 

Both cationic and anionic precursors were used to generate the 02SOH radical (44) which is the presumed intermediate of OH radical attack on S02 to form S03 in the last step of the sulfur oxidation cascade [198]. The hydrogen sulfite cation was produced by dissociative ionization of methanesulfonic acid and used to generate radical 44, albeit in a low yield [209]. A improved preparation and NR mass spectrometric characterization of 44 relied on an anion precursor, 02SOH , which was made by termolecular associative reaction of S02 with OH-[210]. Neutralization with Xe of 02SOH- produced stable radical 44 that gave rise to a dominant survivor cation in the -NR+ mass spectrum [211]. 

The free radical initiator may be a redox catalyst such as ammonium persulfate-sodium hydrogen sulfite, a perfluorocarboxylic acid peroxide (RfC00)2, or an azo bis type compound such as azob isisobutylonitrile. 

Among nucleophiles used are enols " (including mono- and bis-TMS ethers, which are particularly favorable ) derivatives of P N and S in hydrogen sulfite dithionate and sulfide Si, Ge, Sn and alkyl or aryl in derivatives of Cd, Zn or Li . The Li reagents in particular require special experimental conditions, including dichloro methane as solvent and radical scavengers. Many nucleophiles cause electron addition to the cations, with formation of radicals. Aromatic substitutions displace not only H but SnMej or SiMe3 . Allylsilanes and trialkyl alkynylborates provide synthetically useful products. 

The elemental sulfur becomes colloidally stable in Sg molecules but can also add to sulfite and form thiosulfate S + S (0)3 S - S (0)3 (S203 ), which also loses the sulfur via disproportionation into H2S and SO4 . In hydrometeors and interfacial waters, however, sulfur reacts with oxygen (reactions 5.265 and 5.262) via SO2 to form hydrogen sulfite HSO3. Thiosulfate is an important intermediate in biological sulfur chemistry from both sulfate reduction and sulfide oxidation. Many hypothetical so-called lower sulfuric acids (Table 5.19) might appear as intermediates or in the form of radicals (such as SOH, HSO, HSO2, HSS and HS as seen from the structure formulas) in the oxidation chain from sulfide to sulfate ... 

The sulfite radical is a sulfur-centered radical and would form a S-H bond if it undergoes a hydrogen abstraction reaction. These bonds are weaker than typical C-H bonds and indeed hydrogen abstraction reactions, for example from 2-propanol, have been found to be very slow k < 10 L mol" s ) [53]. SOf does, however, add to unsaturated bonds, not only carbon-carbon double and triple bonds, but also C=S and C=N bonds [68]. The rate constants for the addition of 803" to unsaturated fatty acids were found to increase from about 3x10 L mol" s" for non-conjugated, straight chain fatty acids (linoleate, linolenate, and arachidonate) to about 1 x lO L mol" s for branched chain, conjugated fatty acids (crocin and crocetin) [69]. 

Subsequent reactions of this radical, HSO3 not the hydrogen sulfite ion), perhaps... 

The (8O3) radical is essentially the sulfur trioxide anion-radical. It is named the sulfite anion-radical because it is obtained from sodimn sulfite on reaction with titanimn trichloride in water. This reaction usually proceeds in the presence of ethylene diamine tetraacetic acid as a complexing agent and hydrogen peroxide as an oxidant (Bradic and Wilkins 1984). Under these conditions, the... 

The sulfite anion radical (SOI) is obtained from sodium sulfite upon the action of titanium trichloride in water in the presence of ethylene diamine tetraacetic acid (as a complexing agent) and hydrogen peroxide (Bradic Wilkins 1984). Scheme 1-91 below shows this type of SOI generation. 

Campanella et al. [1] Superoxide radical polyphenols Sulfite Ascorbic acid Wine Superoxide dismutase (SOD), or tyrosinase, or sulfite oxidase, or ascorbate axidase/in a gel-like kappa-carrageenan membrane sandwiched between a cellulose acetate membrane and a dialysis membrane Amperometric Pt electrode for hydrogen peroxide (for superaxide determination)/ +650 mV vs. Ag/AgCl/ Amperometric oxygen electrode (for the rest)/-650 mV vs. Ag/AgCl... 

We have found that sulfite and bisulfite undergo one-electron oxidation by many free radicals to produce S03. Rate constants determined for selected radicals are given in Table 1. Measurement of the rate constant over a wide range of pH has, in some cases, allowed the separate determination of rate constants for the oxidation of sulfite and bisulfite. The very strong oxidant OH reacts very rapidly and oxidizes bisulfite faster than sulfite, possibly due to a contribution from hydrogen atom abstraction. For radicals which are relatively weaker oxidants, the reaction with sulfite is the faster. For example, with Br2 the ratio of rate constants for sulfite to bisulfite is about 4 for the even weaker... 

Whatever the actual reagents might be, it has been shown that O2 can oxidize sulfite and initiate a free-radical chain reaction, or oxidize iron-containing clusters present in enzymes, such as aconitase and fumarases, freeing Fe(II), which in turn initiates a Fenton-like chemistry hy interacting with hydrogen peroxide (317). Fe(II) release from transferrin has also been observed following O2 secretion by stimulated human neutrophils (318). 

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