Sulfite, formation from sulfate

It has been shown that the addition of a small amount of the anionic surfactant sodium dodecyl sulfate (SDS) to a microemulsion based on nonionic surfactant increased the rate of decyl sulfonate formation from decyl bromide and sodium sulfite (Scheme 1 of Fig. 2) [59,60]. Addition of minor amounts of the cationic surfactant tetradecyltrimethylammonium gave either a rate increase or a rate decrease depending on the surfactant counterion. A poorly polarizable counterion, such as acetate, accelerated the reaction. A large, polarizable counterion, such as bromide, on the other hand, gave a slight decrease in reaction rate. The reaction profiles for the different systems are shown in Fig. 12. More recent studies indicate that when chloride is used as surfactant counterion the reaction may at least partly proceed in two steps, first chloride substitutes bromide to give decyl chloride, which reacts with the sulfite ion to give the final product [61]. 

Kobayashi, K., Seki, Y. and Ishimoto,M., 1974. Biochemical studies on sulfate-reducing bacteria. XIII Sulfite reductase from Desulfovibrio vulgaris — mechanism of trithio-nate, thiosulfate and sulfide formation and enzymatic properties. J. Biochem., Tokyo, 75 519—529. 

The reaction of polysulfides with peroxide depends on the polysulfide ion present (see above). Once higher polysulfides are produced, the reaction should result in a peroxide-polysulfide intermediate (similar to II) that transfers two electrons from the polysulfide ion to the peroxide as readily as the sulfide and peroxide reaction. At low peroxide levels, partial oxidation of the polysulfide ions should result in the direct formation of sulfate (through thiosulfate and perhaps sulfite) and S ... 

Inorganic sulfur in the environment (primarily sulfate, but also sulfur, and sulfite) must undergo fixation to be ulitized by organisms. The fixation of sulfate is largely confined to plants and bacteria. Fixation begins with the formation of PAPS (3 -phosphoadenosine-5 -phosphosulfate) (see here). PAPS is formed in a two-step reaction from sulfate ion and two molecules of ATP (see here). 

A primary experimental fact relating to this reaction is the formation of sulfate (under aerobic conditions) from cysteine sulfinic acid by the action of ground or extracted rat livers (85). This oxidation was carried out by Medes (85) in order to study the existence of a sulfinic acid oxidase responsible for the action. But it is difficult to assume that a single enzyme would have the ability to split the cysteinesulfinic acid into an organic molecule without sulfur and into inorganic sulfur, and then oxidize the latter to sulfate. Numerous explanations have been proposed to resolve this difficulty. According to Pirie (95), the removal of the sulfur from cysteine-sulfenic acid would take place as sulfite, which in turn would be oxidized spontaneously to sulfate (reaction 31). Medes and Floyd (86) have two other theories to explain the sulfate formation. The first of these two theories may be written ... 

Barium sulfide solutions undergo slow oxidation in air, forming elemental sulfur and a family of oxidized sulfur species including the sulfite, thiosulfate, polythionates, and sulfate. The elemental sulfur is retained in the dissolved bquor in the form of polysulfide ions, which are responsible for the yellow color of most BaS solutions. Some of the mote highly oxidized sulfur species also enter the solution. Sulfur compound formation should be minimized to prevent the compounds made from BaS, such as barium carbonate, from becoming contaminated with sulfur. 

If the snlfate anion-radical is bonnd to the snrface of a catalyst (sulfated zirconia), it is capable of generating the cation-radicals of benzene and tolnene (Timoshok et al. 1996). Conversion of benzene on snlfated zirconia was narrowly stndied in a batch reactor under mild conditions (100°C, 30 min contact) (Farcasiu et al. 1996, Ghencin and Farcasin 1996a, 1996b). The proven mechanism consists of a one-electron transfer from benzene to the catalyst, with the formation of the benzene cation-radical and the sulfate radical on the catalytic snrface. This ion-radical pair combines to give a snrface combination of sulfite phenyl ester with rednced snlfated zirconia. The ester eventually gives rise to phenol (Scheme 1.45). Coking is not essential for the reaction shown in Scheme 1.45. Oxidation completely resumes the activity of the worked-out catalyst. 

Furthermore, the cleavage of organic sulfites and sulfates by hydrogen fluoride gives the corresponding alkyl or acyl fluorides in fair to good yield,287 e.g. formation of acetyl fluoride from the mixed anhydride287 or sulfonyl fluorides from sulfonic acid anhydrides.287... 

IZV118) and the formation of (31) is analogous to the reaction (197)->(98) via a four-membered 1,2-oxathietane 2,2-dioxide intermediate. Subsequent products derived from (31) by electrophilic addition reactions at the alkenic double bond have been described in Section 4.33.3.2.2 and the synthesis of 4,5-dichloro-l,3,2-dioxathiolane 2,2-dioxide (154) by chlorination of ethylene sulfate (18) is discussed in Section 4.33.3.5. Cyclic sulfites, on the other hand, cannot be halogenated without ring opening (cfSection 4.33.3.2.4). 

In humans, age-related differences have been observed in metabolism of sulfite to sulfate and in formation of sulfur trioxide (Constantin et al. 1996). Constantin et al. (1996) measured sulfur trioxide radicals and sulfite oxidase activity in polymorphonuclear leukocytes (PMNs) from four groups young adults (average age 25), older adults (average age 65), 3 centenarians (older than 100), and Down syndrome patients. They found significantly increased amounts of sulfur trioxide radicals in PMNs from healthy adults who had low sulfite oxidase activity. In centenarians and Down syndrome patients, generation of the sulfur trioxide radical was the primary mechanism for detoxification of sulfite. There was no correlation between the sulfur trioxide radical and sulfite oxidase activity. 

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