Tetrathionates, formation

At high ratios of reductant to oxidant, conditions which favour tetrathionate formation at the expense of sulphate, the Cr(Vl) oxidation of thiosulphate follows kinetics ... 

A final method of forming disulfide crosslinks between toxins and targeting molecules is the use of S-sulfonate formation using sodium sulfite (Na2SC>3) in the presence of sodium tetrathion-ate (Na2S40g). Tetrathionate reacts with sulfhydryls to form sulfenylthiosulfate intermediates (section 1.1.5.2). These derivatives are reactive toward other thiols to create disulfide linkages... 

Electrolysis of a thiosulphate in neutral solution causes the formation of tetrathionate at the anode 3... 

In aqueous solution alkali trithionates gradually undergo decomposition with formation of sulphate, hydrogen sulphite and tetrathionate. The course of the main reaction may be expressed ionically as follows 7... 

Tetrathionic Acid, H2S4Oe.—Formation.—(l) From Thiosulphates As is well known, sodium tetrathionate is produced by the interaction of sodium thiosulphate and iodine ... 

Chlorine, bromine, hypoehlorous acid and hypobromous acid also convert thiosulphate into tetrathionate, but their activity is so great that the reaction tends to proceed still further, with formation of sulphate.2... 

The pentathionates are not stable, decomposing spontaneously alone or in aqueous solution with gradual formation of tetrathionate, tri-thionate and sulphur, the change being retarded by the addition of a little hydrochloric or sulphuric acid. When heated in the dry condition they yield sulphate, sulphur and sulphur dioxide ... 

Sodium carbonate causes deposition of sulphur and formation of tetrathionate ... 

Mercury fulminate dissolves readily in an aqueous solution of potassium cyanide to form a complex compound from which it is reprecipitated by the addition of strong acid. It dissolves in pyridine and precipitates again if the solution is poured into water. A sodium thiosulfate solution dissolves mercury fulminate with the formation of mercury tetrathionate and other inert compounds, and this reagent is used both for the destruction of fulminate and for its analysis.10 The first reaction appears to be as follows. 

Sodium tetrathionate (Na2S406) is a redox compound that under the right conditions can facilitate the formation of disulfide bonds from free sulfhydryls. The tetrathionate anion reacts with a sulfhydryl to create a somewhat stable active intermediate, a sulfenylthiosulfate (Fig. 102). Upon attack of the nucleophilic thiolate anion on this activated species, the thiosulfate (S203 =) leaving group is removed and a disulfide linkage forms (Pihl and Lange, 1962). The reduction of tetrathionate to thiosulfate in vivo was a subject of early study (Theis and Freeland, 1940 Chen et al., 1934). 

Tetrathionate of sodium, as already remarked, is produced by addition of a solution of iodine to a thiosulphate it is precipitated on addition of alcohol. The acid forms a colourless solution, with strong acid taste. The method of its formation gives a clue to its constitution NaO—S(02)—S—Na I Nal Na0-S(02)-S... 

In agreement with the statements of Trueper (1) one can say that principally different dissimilatory sulfur metabolic pathways exist in Anoxyphotobacteria for the oxidation of sulfite to sulfate (via APS or directly), the utilization of thiosulfate (splitting or formation of tetrathionate), and the oxidation of sulfide or elemental sulfur (by a "reverse" siroheme sulfite reductase or other mechanisms). 

The reaction in neutral solution probably involves two stages, the solution becoming temporarily alkaline through the formation of sodium cyanide, which reacts with the generated tetrathionate in accordance with the equation... 

Potassium tetrathionate, K2S406.—The tetrathionate is formed by the interaction of potassium thiosulphate in aqueous solution and iodine, the salt being precipitated from the reaction-mixture by addition of alcohol. It is crystalline, and has a density of 2-296. The heat of formation from the elements is 897-21 Cal.7... 

The rate law for the formation of tetrathionate turns out to involve the square of the concentration of the ion 8203 . At low concentrations of iodide (below 0.003 M) the stoichiometry is no longer exact, because some sulfate is formed by the reaction... 

It should be noted that the formation of a stable sulfenylthiosulfate is a phenomenon observed with native proteins (Pihl and Lange 1962). When simple thiols such as cysteine are reacted with an excess of tetrathionate, S-sulfocysteine is formed (Inglis and Liu 1970). If thiol is in excess, the sulfenylsulfonate can react with a second molecule of thiol to form a disulfide. 

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