Dithionite disulfide

Herz salts (89) made from 3-aminopyrazoles (Section 4.11.8.5) give pyrazolo[3,4-r/]-l,2,3-thia-diazoles (90) when subjected to reduction by sodium dithionite followed by nitrozation (Equation (12)) <84JOCl224>. If the reduction is carried out in an inert atmosphere the disulfide (91) is formed which upon nitrozation gives (90) in 63% yield. Notably, benzo-fused Herz salts give benzo-1,2,3-thiadiazoles simply on treatment with nitrozating mixture <84CHEC-I(6)916>. 

Disulfide bridges (crosslinkages) 65, 80 cleavage of 115-116 cleavage with performic acid 115 locating 119 in proteins 80 reduction of 115, 785 Dithioerythritol 115 Dithionite ion 779 Dithiothreitol 98,115, 822 Dityrosine linkages 81 DMSO reductase 890 DNA... 

The most efficient system of this type is obtained by the reduction of bovine serum albumin in the presence of molybdate. Apparently disulfide links in the peptide are broken and form thiolate groups which then bind molybdenum. In a borate buffer, this system will reduce dinitrogen and acetylene, although not using dithionite as an electron source. The turnover is similar to that of the iron-molybdenum cofactor (see Section XII), and dinitrogen reduction is inhibited by carbon monoxide and stimulated by ATP. The yield of ammonia is linearly dependent upon PN2, and the yield is also depressed in the presence of fumarate and, more surprisingly, succinate. It is calculated that the... 

A new heterocyclic ring system, 5//-pyrazolo[3,4- /]-l, 2,3-thiadiazoles (41), results from a one-pot, two-step reaction of the pyrazolodithiazolium chlorides (29). Sequential treatment of the derivatives (29) with base, sodium dithionite, and sodium nitrite followed by acidification afforded (41) (Scheme 3). For substrates (29a,b) potassium hydroxide was chosen, whilst for (29c,d) sodium bicarbonate was found to be superior. In the latter cases, potassium hydroxide caused appreciable hydrolysis of the ester substituent. A further point of interest is the significant quantity of disulfide (43) which can form on reaction of 6-carboethoxy-5-methylpyrazolodithiazolium chloride (29c). This, however, need not represent a problem since compound (43) can be converted in situ or isolated and converted to the desired product (41c) in good yield (Scheme 4) <84JOCl224>. 

There are only a few reports in this area. Reaction of a pyrazolyl disulfide 377 with bromotrifluoromethane and ethyl bromide in the presence of sodium dithionite at room temperature afforded pyrazolyl sulfides 378. Oxidation of these with hydrogen peroxide in trifluoroacetic acid afforded sulfenylpyrazoles 379 in excellent yields (Scheme 41) <2006JFC(127)948>. Pyrazole-4-carbaldehyde 380 has been utilized in the efficient synthesis of... 

Absorphon of CO2 in aqueous solutions of MEA absorption of H2S and mercaptans in aqueous soluhons of alkanolatnines and caushc soda absorption of carbon monoxide in aqueous cuprous ammonium chloride solutions absorphon of lower olefins in aqueous soluhons of cuprous ammonium compounds absorption of pure chlorine in aqueous solutions of sodium carbonate or sodium hydroxide conversion of dithiocarbamates to thiuram disulfides sulfonation of aromatic compounds with lean SO3 recovery of bromine from lean aqueous solutions of bromides reactions of importance in pyrometallurgy absorphon of CO2 in aqueous solutions of caustic alkahes and amine absorption of O2 in aqueous solutions of sodium dithionite absorphon of O2 in aqueous sodium sulfite soluhons absorption of O2 in alkaline solutions containing the sodium salt of 1,4-napthaquinone- 2-sulfonic acid (NQSA) special case role of diffusion in the absorption of gases in blood in the human body. 

Experiments were performed with various sulfoxylate radical anion precursors sodium dithionite, sodium hydroxymethanesulfinate or a mixture of sulfur dioxide with a reductant, such as zinc or sodium formate (refs. 29, 30).In contradistinction with the trifluoromethylation of aromatic compounds (Figs. 19,20), a stoiechiometric amount of the sulfoxylate radical anion precursor was necessary. In the disulfide case, there is no intermediate able to reduce back the sulfur dioxide which is formed in the medium (Fig. 22). 

Disulfides do not appear to be capable of reducing Fe(III) Lb to Fe(II) Lb (135). Reaction with sulfide itself appears to be different and gives rise to a Fe(III) Lb-sulfide complex rather than reduction or nucleophilic attack (135). The complex is, however, susceptible to reduction by strong reducing agents such as dithionite and ascorbic acid. 

Batteries exposed to certain abusive conditions may experience thermal runaway - a series of coupled exothermic chemical reactions involving metallic lithium, lithium dithionite and possibly sulfur, resulting in the formation of sulfides. At the elevated temperatures resulting from these reactions, these products may further react with the carbon in the cathode to form carbon dioxide (CO2) and carbon disulfide (CS2). Carbon... 

Of the many other methods we can mention the preparation of biospecific adsorbents utilizing trichloro-5-triazine [120], coupling via thiol-disulfide interchange with activated thiolated support [121] or via azide formation [122]. The attachment of affinants containing the aromatic residues can be carried out by means of diazonium groups [87,123]. The coupling of the affinant onto the silinized glass after the reactions with p-nitrobenzoylchloride followed by reduction with sodium dithionite was described by Weetall and Filbert [124]. 

The crystal structure shows a marked difference in the copper environments in the two monomers. In one of the subunits two electron density maxima are observed riding the cuprous ion in place of the usual density expected for the weakly bound water molecule. This is a two-center density that can be modeled with two water molecules at full occupancy, each being at coordinating distance from the metal ion, resulting in the imusual geometry shown in Fig. 11. The electron density could not be unambiguously interpreted because it can be modeled as well by a disulfide anion at about half occupancy. Such an anion may have been originated from the dithionite used for copper reduction. 

In addition to mercaptans and sulfites, compounds that have been used for nucleophilic cleavage of the disulfide bond in hair and/or wool fiber are sulfides, hydroxide, water (steam), a phosphine, borohydride, dithionite (hydrosulfite), and sulfoxylate. The interactions of some of these compounds with the disulfide bond in hair are described next. 

Alternatively protohemin was coupled with bis(3-aminopropyl)-disulfide (81). The resultant disulfide 82 was treated with sodium dithionite, the iron being reduced faster than the disulfide. Addition of CO then furnished the carbonmonoxy complex 80. 

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