Bisulfite radical

Once sulfur dioxide has escaped into the atmosphere, it undergoes a series of reactions by which it is converted to sulfuric acid. Those reactions are somewhat complex and may follow at least three different courses. In the first of these reaction sequences, sulfur dioxide reacts with hydroxyl radicals in the atmosphere in the presence of some metallic catalyst (M) to form the bisulfite radical (HSO3 ) ... 

The bisulfite radical then reacts with molecular oxygen to produce sulfur trioxide and the hydroperoxyl (HO2 ) radical ... 

We assume that the bisulfite radical, HOSO2, is the product because the reaction has been shown to be third order. Unfortunately this species has never been detected and nothing is known about its chemistry, so the remaining steps in the mechanism are speculative. A typical scheme is as follows ... 

Here the bisulfite radical is oxidized by O2 to a peroxybisulfate radical which is reduced by NO to a bisulfate radical. The H-R molecule is some species such as H2O2 or HO2 with a relatively weakly bound hydrogen. 

Free radicals can also be generated by transition metal ion interaction. Thus, ferric ions can oxidize the bisulfite ion to the bisulfite radical (see Eq. 2.6). 

For both SO2 and NOx, a major reaction pathway is with hydroxyl radical (OH), a highly reactive molecule. xhe reaction between SO2 and (OH) produces the unstable bisulfite radical... 

In tanneries, sodium bisulfite is used to accelerate the unhairing action of lime. It is also used as a chemical reagent ia the synthesis of surfactants (qv). Addition to alpha-olefins under radical catalyzed conditions yields sodium alkylsulfonates (wetting agents). The addition of sodium bisulfite under base-catalyzed conditions to dialkyl maleates yields the sulfosucciaates. 

The reversible addition of sodium bisulfite to carbonyl groups is used ia the purification of aldehydes. Sodium bisulfite also is employed ia polymer and synthetic fiber manufacture ia several ways. In free-radical polymerization of vinyl and diene monomers, sodium bisulfite or metabisulfite is frequentiy used as the reduciag component of a so-called redox initiator (see Initiators). Sodium bisulfite is also used as a color preventative and is added as such during the coagulation of crepe mbber. 

Sodium alkanesulfonates for detergent manufacture can also be produced from the free-radical addition of sodium bisulfite and alpha olefins ... 

A branched, high-molecular-weight condensation product of cardanol, an alkylphenol, and an aldehyde can be further ethoxylated and may be sul-fonated by the addition of sodium bisulfite in the presence of a free radical... 

Taurog et al. [216] showed that contrary to previous suggestions, both iodination and coupling are catalyzed by the oxoferryl porphyrin Tr-cation radical of TPO Compound I and not the oxoferryl protein radical. HRP catalyzed the oxidation of bisulfite to sulfate with the intermediate formation of sulfur trioxide radical anion S03 [217] HPO, MPO, LPO, chloroperoxidase, NADH peroxidase, and methemoglobin oxidized cyanide to cyanyl radical [218],... 

Microsomes are capable of oxidizing not only organic substrates but also inorganic ones. An interesting example is the metabolism of bisulfite (aqueous sulfur dioxide) in microsomes. Although mitochondrial sulfite oxidase is responsible for the in vivo oxidation of bisulfite by a two-electron mechanism, cytochrome P-450 is also able to reduce bisulfite to the sulfur dioxide radical anion [56] ... 

The living radical polymerization process is also valid for the polymerization of water-soluble monomers. The polymerization of sodium styrenesulfonate in aqueous ethylene glycol (80%) in the presence of TEMPO using potassium per-sulfate/sodium bisulfite as the initiator at 125 °C gave a water-soluble polymer with well-controlled molecular weight and its distribution [207]. 

Photolytic. Plimmer and Hummer (1969) studied the irradiation of chloramben in water (2-4 mg/L) under a 450-W mercury vapor lamp (7, >2,800 A) for 2-20 h. Chloride ion was released and a complex mixture of colored products was observed. It was postulated that amino free radicals reacted with each other via polymerization and oxidation processes. The experiment was repeated except the solution contained sodium bisulfite as an inhibitor under a nitrogen atmosphere. Oxidation did not occur and loss of the 2-chloro substituent gave 3-amino-5-chlorobenzoic acid (Plimmer and Hummer, 1969). 

Mendiara, S. N., E. Ghibaudi, L. J. Perissinotti, and A. J. Colussi, Free Radicals and Diradicals in the Reaction between Nitrous Acid and Bisulfite in Acid Aqueous Media, . /. Phys. Chem., 96, 8089-8091 (1992). 

Synthesis from a-Pinene. a-Pinene from turpentine oil is selectively hydrogenated to cis-pinane [35], which is oxidized with oxygen in the presence of a radical initiator to give a mixture of ca. 75% cis- and 25% tran -pinane hydroperoxide. The mixture is reduced to the corresponding pinanols either with sodium bisulfite (NaHS03) or a catalyst. The pinanols can be separated by... 

Hayon, E.,Treinin, A., and Wilf, J. (1972), Electronic spectra, photochemistry, and autoxi-dation Mechanism of the sulfite-bisulfite-pyrosulfite systems. The SO2, SO3, SO4 radicals, J. Am. Chem. Soc., 94,47-57. 

With small latex particles ( 400 a) the rate of free radical generation (varied by varying the persulfate level) did not affect the polymerization rate over the range of conversions investigated. In addition, small amounts of sodium bisulfite were added to increase radical generation at low temperatures ( 25°C) at various conversion levels. This also did not change the... 

The autoxidation of S02 solutions is known to involve free radicals. Recent work on the reaction of free radicals with sulfite and bisulfite and on the reaction of the sulfite and peroxysulfite radicals is beginning to allow this complex system to be understood better. This is particularly true of the effect of added chemicals on S02 autoxidation and chemical transformations induced by this system. 

The autoxidation of aqueous solutions of sulfur dioxide (sulfite, bisulfite) is a classic problem in chemistry. Basic features of this reaction have been known since early in this century, when it was established that the reaction is trace metal ion catalyzed (1 ) and most likely involves free radicals (2). Certain chemical effects associated with sulfite autoxidation were noted also. Before the turn of the century, it was noted that sulfite would induce the oxidation of transition metal ions (3) and it was reported later that the oxidation of organic compounds was brought about during sulfite autoxidation ( 0. Conversly, organic compounds were also shown to serve as inhibitors of sulfite autoxidation (5). 

Recently, we have carried out studies on the free radical chemistry of sulfite. These studies have included kinetic measurements on the reactions of organic and inorganic free radicals with sulfite and bisulfite, and on the reactions of the sulfite derived radicals SO and S0 with organic and inorganic substrates. In this paper, I will review some of our results and results from other laboratories on the radical chemistry of sulfite and discuss these results in relation to the problem of S02 autoxidation. 

The small amount of H atoms produced usually does not interfere.) The OH reacts with sulfite or bisulfite to produce the SO radical... 

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