Peroxodisulphate

A detailed study has been made of the oxidation of vanadium(iv) by peroxodisulphate in weakly acidic media  

In the hydrogen-ion concentration range 0.1—0.5 mol 1, with the oxidant in large excess, the rate becomes independent of vanadium(iv) concentration at levels greater than 10 mol 1. The rate of formation of vanadium(v) was also shown to be twice the rate of disappearance of oxidant, the order with respect to hydrogen ion being unity. At sufficiently high concentrations of reductant, the rate law conforms to the expression 

The copper(n)-catalysed oxidation of hypophosphite by SaO in perchloric acid media has been described, the rate law having the form 

The mechanisms of decomposition of peroxomono-sulphates and -phosphates in alkaline media have been investigated, the rates being first-order with respect to hydroxide ion and the peroxo-species. The reaction is considered to proceed via a one-electron transfer from the OH to the peroxo-anion, 

The reduction of iridium(rv) by ascorbic acid has been studied in 80% acetone-water mixtures, the rate being first-order with respect to each reactant and inversely proportional to [H+] . The reaction involves the formation of an ascorbate free radical, AH  

The kinetics of oxidation of six iron(ii) complexes containing 2,2 -bipyridyl or 1,10-phenanthroline as ligands have been studied, the mechanism postulated being  

Moiseev, N. G. Satsko, and Y. K. Sirkin, Izvest. Akad. Nauk, 

Studies on the kinetics and mechanism of the oxidation of ascorbic acid show the rate to be independent of the concentration of organic substrate. A chain mechanism is proposed with reaction between the radical anion of ascorbic acid and the peroxodisulphate ion. Although the influence of neutral salts is negligible and that of acid slight, the presence of allyl acetate strongly inhibits the rate, suggesting the formation of radical ions. In the reaction with lactic acid, a similar rate expression is observed although the description of the mechanism is different. 

The oxidation of vanadium(iv) by peroxodiphosphate has been reported in aqueous acidic solutions, two vanadyl ions being oxidised per P20g  

The reaction is first-order in both vanadium(iv) and oxidant, the mechanism being  

At low persulphate concentrations, the order of 0.5 observed with respect to oxidant may be accounted for by the mechanism 

The oxidation of the copper(ii)-hydrazine complex has been investigated, the rate law being of the form 

The silver(i)-catalysed oxidation of americium(iii) by SgOg has been studied using Am tracer techniques, coprecipitation with lanthanum trifluoride representing a good method of monitoring the micromolar 

Ohyoshi, A. Jyo, T. Shinohara, and E. Ohyoshi, Radiochem. Radioanalyt. Letters, 

Osmometric measurements on the nature of the interaction with ferro-cyanides have been made in the presence of different counter ions, extensive ion-pairing being observed, although the extent of interaction varies from one cation to another. In all, four reaction paths have been identified  

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Electrolysis of the hydrogensulphate of potassium or ammonium can yield a peroxodisulphate and thence hydrogen peroxide. 

It can also be precipitated in a hydrated form by the oxidation of a manganese(II) salt, by, for example, a peroxodisulphate ... 

Thus, for example. peroxodisulphate(VI) will oxidise Mnlll) to Mn(VII) ... 

Peroxodisulphate salts in air Lab method using mobile phase ion chromatography 79... 

Peroxomonosulphate and peroxodisulphate have also been used to oxidize sulphoxides to sulphones in good yields at room temperature. Potassium persulphate (KHS05) readily oxidizes a range of sulphoxides to sulphones at 0°C in yields greater than 90%, in the presence of hydroxy, keto and alkene groups82-84. The mechanism is similar to that observed for other peroxy species, as discussed above. Peroxomonosulphate oxidation has been used as an analytical procedure for the estimation of dimethyl sulphoxide84. 

Potassium peroxodisulphate (K2S2Og) also oxidizes sulphoxides to sulphones in high yield, either by catalysis with silver(I) or copper(II) salts at room temperature85 or in pH 8 buffer at 60-80 °c86-88. The latter conditions have been the subject of a kinetic study, and of the five mechanisms suggested, one has been shown to fit the experimental data best. Thus, the reaction involves the heterolytic cleavage of the peroxodisulphate to sulphur... 

Peroxodisulphates are particularly dangerous oxidants because of their reactivity. 

Potassium peroxodisulphate decomposes violently when it is heated above 100°C by releasing oxygen. The same violent decomposition takes place at temperatures lower than 100°C, if water is present. The salt combusts spontaneously if soda is present. 

Potassium peroxodisulphate reacts violently with hydrazine in a basic medium. The danger is aggravated by the formation of nitrogen, which can represent a risk of overpressure if the apparatus used creates the substances containment. 

Ammonium peroxodisulphate detonates when it is heated above 75°C, but there is the same result at ambient temperature in the presence of water, carbon dioxide or sodium peroxide. 

Detonation occurs during the reaction of molten aluminium with ammonium peroxodisulphate in the presence of water. However, since the temperature is above 75°C, the presence of water is sufficient to decompose it and the water/molten aluminium interaction has aiready been mentioned as being explosive. 

Finally, there is an extremely violent reaction during the action of ammonia on ammonium peroxodisulphate in the presence of Ag- ions. 

Moist potassium peroxodisulphate was accidentally exposed to traces of potassium hydroxide. It combusted spontaneously, causing the installations to catch fire. It is impossible to put out a fire involving this peroxydic compound with carbon dioxide or extinguishing powders although these agents are suitable for fires of chemical substances. Only water, which is usually not recommended in this case, can put out this type of fire. 

Potassium pemnanganate Potassium nitrite Potassium nitrate Potassium sulphite Potassium stannate IV Potassium sulphate Poptassium metabisulphite Potassium peroxodisulphate Potassium tellurate (IV) Potassium pyrophosphate... 

Pyridinediylbisphosphonium salts react with methanol in the presence of ammonium peroxodisulphate to give the 5-hydroxymethylated compound when radical conditions were absent, nucleophiles gave the 4-substituted products selectively746. 

Mark G, Schuchmann MN, Schuchmann H-P, von Sonntag C (1990) The photolysis of potassium peroxodisulphate in aqueous solution in the presence of tert-butanol a simple actinometer for 254 nm radiation. J Photochem Photobiol A Chem 55 157-168 Mark G, Korth H-G, Schuchmann H-P, von Sonntag C (1996) The photochemistry of aqueous nitrate revisited. J Photochem Photobiol A Chem 101 89-103 Mark G, Tauber A, Laupert R, Schuchmann H-P, Schulz D, Mues A, von Sonntag C (1998) OH-radical formation by ultrasound in aqueous solution, part II. Terephthalate and Fricke dosimetry and the influence of various conditions on the sonolytic yield. Ultrason Sonochem 5 41-52 MarkG, Schuchmann H-P, von Sonntag C (2000) Formation of peroxynitrite by sonication of aerated water. J Am Chem Soc 122 3781-3782... 

Schuchmann H-P, von Sonntag C (1988) The oxidation of methanol and 2-propanol by potassium peroxodisulphate in aqueous solution free-radical chain mechanisms elucidated by radiation-chemical techniques. Radiat Phys Chem 32 149-156 Schwarz HA, Bielski BHJ (1986) Reactions of H02 and 02 with iodine and bromine and l2 and I atom reduction potentials. J Phys Chem 90 1445-1448... 

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