Sulphite radical

The presence of the denominator term in the rate equation (17) suggests that the equilibrium (18) precedes the oxidation step. Two sequences of reactions are proposed (see below), depending on whether the sulphite radical ion dimerises (20) or attacks further acid chromate ion (21). It should be noted that of the species prevalent in dilute aqueous chromic acid, namely CrOj , Cr207, HCrO and H2Cr04, only the last is regarded as possessing oxidising powers. This fact, noted by Westheimer , is tacitly assumed in all recent discussion of... 

Reaction of nitrosyl disulphonate, 0N(S03), with hydroxylamine-N-sulphonate is reported to be subject to catalysis by ferric salts at low concentrations, and to depend on the alkalinity through the hydrolysis of the catalyst . In mildly alkaline solution (pH 6-11), the rates of decomposition of this sul-phonate have been shown to be consistent with the existence of two reaction paths, one forming NO and the other sulphite radicals . The processes are assumed to represent bimolecular nucleophilic substitution by water. 

Chloro-l-hydroxynaphthalene is converted into the sulphonate 246 on eosin-sensitized irradiation in the presence of sodium sulphite. A study of the chain substitution of the chloro group in 4-chloro-l-hydroxynaphthalene by aqueous sodium sulphite has shown that two mechanisms for the photoinitiation have been identified and two intermediates have been detected a radical anion of 4-chloro-l-naphthoxide and the sulphite radical anion. Thus, an SjjajI mechanism is suggested and is one that involves reaction with the radical anion of sulphite. An example of the S n 1 process between a phenol and the (2-cyanoaryl)azo-f-butylsulphides has been reported. The 1 reactivity of several compounds (Scheme 27) have demonstrated that 247 is a product however, this is also photochemically reactive and is converted into the cyclic ether 248 . 

The real value of k2,iso was anticipated close to the upper limit. The errors given in (4) are just standard errors and do not reflect the errors that could originate from the assumption that isoprene reacted exclusively with sulphate radicals. Approximate analysis showed that if isoprene reacted also with sulphite radicals, the upper limit in (4) is overestimated by a few percent, and if isoprene reacted also with peroxymonosulphate radicals as well, the upper limit is overestimated by not more than 30%. 

The selective ability of higher-valent metal ions to oxidize organic free radicals has been examined and two mechanisms have been proposed for the decomposition of cerium(iv) carboxylates in the presence of olefins and aromatic hydrocarbons (i) involving a non-decarboxylative route with the generation of carboxyalkyl radicals via thermal decomposition, and ( ) the formation of alkyl radicals and COg in the decarboxylation reaction. E.s.r. studies using cerium(iv) have been used to provide evidence for the formation of the sulphite radical anion SO3 in the oxidation of sulphite. ... 

The presence of sulphonic and carboxylic groups enables the iron ions to be in the vicinity of the cellulose backbone chain. In this case, the radicals formed can easily attack the cellulose chain leading to the formation of a cellulose macroradical. Grafting of methyl methacrylate on tertiary aminized cotton using the bi-sulphite-hydrogen peroxide redox system was also investigated [58]. 

When an alkali sulphite is allowed to react with the bromide or iodide of an organic radical, for example with ethyl iodide, the resulting compound, ethylsulphonic acid, undoubtedly possesses the unsym-0. OH... 

Constantin, D., A.Bini, E.Meletti, P.Moldeus, D.Monti, and A.Tomasi. 1996. Age-related differences in die metabolism of sulphite to sulphate and in the identification of sulphur trioxide radical in human polymorphonuclear leukocytes. Mech. Ageing. Dev. 88(1—2) 95—... 

There is brief mention of some iodide-induced exchange of bromate oxygen If correct, this would imply that the rate is limited by (13) or (16). Since, in the reaction with sulphite"the sulphate formed takes oxygen from bromate, that reaction is related to (14), not to (11). In addition to catalysis by chromate , vanadium(V) has been shown to be effective . When oxalate is also present, radicals appear to be produced , as shown by polymerization of acrylonitrile. Vanadium(VI) is suggested as an intermediate . This is of some interest since most authors have regarded one-electron oxidation steps in this whole class of reactions as highly improbable. 

Many unsaturated chloro- and bromo-hydrocarbons and many polychloro and polybromo compounds decompose by radical-chain mechanisms, but only the chloro compounds have been studied in reasonable detail, presumably owing to the complex nature of the chain reactions in the case of the bromo compounds. Other examples of compounds which undergo radical-chain decompositions are 2,2-dichlorodiethyl ether oxalyl chloride alkyl hypochlorites alkyl peroxychloroformates and alkyl chloro-sulphites in the gas phase ... 

Nitrosolysis of camphor ethyl acetal with ethanolic ethyl nitrite in sulphur dioxide yields the orthoester oxime (205) which is rapidly dehydrated by excess acetal to the orthoester nitrile which then reacts with sulphur dioxide to form the ester nitrile and diethyl sulphite.Further papers in this section include the full paper on ozonolysis of silyl ethers (Vol. 5, p. 33), another synthesis of camphor-enol trimethylsilyl ether (cf. Vol. 6, p. 41)/°° the conversion of camphor oxime with Grignard reagents into the corresponding imine with no aziridine formation/° the preparation of (206) by treating bornylene with trichloroacetyl isocyanate/ the oxidation of thiocam-phor to the 5-oxide and alkylation in the presence of thallium(i) ethoxide to a/S-unsaturated sulphoxides/ and the free-radical C-3 alkylation of camphor with alkenes. " ... 

The reduction of the diazo-compounds to hydrazines may be accomplished by the method of Emil Fischer1 which led to the discovery of this class of compounds, and also by another method. If neutral sodium sulphite is allowed to act on a diazo-salt, the acid radical of the diazo-compound is replaced by a residue of sulphurous acid, eg. ... 

Derivative benzoates and parabenzoates have been used primarily in fruit juices, chocolate syrup, pie fillings, pickled vegetables, relishes, horseradish, and cheese (Barbosa-Canovas et al., 2003). Other foodstuffs where sodium benzoate is used include soft drinks, baked goods, and lollipops (Poulter, 2007). Benzaldehyde and benzoic alcohol are better known to be yeast inhibitors. Benzoic acid has been found to release fewer protons than sulphite, nitrite, or acetic acid and it may be speculated that benzoic acid is not a classic weak-acid preservative. However, due to a lower pKa value, benzoic acid releases three to four times more protons than sorbic acid. This is a sizable concentration of protons although not as much as other weak-acid preservatives (Stratford and Anslow, 1998). Inhibition of growth is strongly pH-dependent and most effective under acidic conditions. Under these conditions the protonated form of the acid is predominantly found (Visti, Viljakainen, and Laakso, 2003). Another unexpected discovery was that benzoic acid appears to be a pro-oxidant. This was unexpected as it is a well-known fact 2-hydroxybenzoic acid (or salicylic acid) acts as a scavenger of free radicals in vivo (Piper, 1999). 

The tentative mechanism of isoprene transformation accompanying the autoxidation of S(TV) was suggested, which started with the addition of a sulphate radical to a double bond in isoprene, followed by addition of oxygen and formation of a peroxy radical. The peroxy radical reacted with sulphite ion to the alkoxy radical, which in turn reacted either with oxygen or with a sulphite ion to give respectively /rfl s-3-methyl-4-sulphoxy-2-buten-l-al or trctns-3-methyl-4-sulphoxy-2-buten-l-ol (Rudzinski e/a/., 2002 Rudzinski, 2004). 

A chain (Sj, ) mechanism is proposed for the light initiated substitution of halogen by sulphite in halo-substituted naphthols. The reaction is initiated by electron transfer from sulphite to an excited sensitiser dye. The sulphite anion radical produced then attacks the halonaphthol loss of halide from this species to give the product is coupled with electron transfer from a second sulphite, so propagating the chain. 

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