Perborates, formation

Perborates, formation of, 28. Percarbonates, formation of, 22. Permanganates, formation of, 25. Persolpburio aoid, formation of, 17. Phenantbrene, oxidation of, 66. Potaaainm fenioyanide, 28. 

Precipitate formation can occur upon contact of iajection water ions and counterions ia formation fluids. Soflds initially preseat ia the iajectioa fluid, bacterial corrosioa products, and corrosion products from metal surfaces ia the iajectioa system can all reduce near-weUbore permeability. Injectivity may also be reduced by bacterial slime that can grow on polymer deposits left ia the wellbore and adjacent rock. Strong oxidising agents such as hydrogen peroxide, sodium perborate, and occasionally sodium hypochlorite can be used to remove these bacterial deposits (16—18). 

Applications of oxaziridine rearrangements in asymmetric syntheses have been reviewed,596 and the formation of A,A-disubstituted formamides (462) on sodium perborate oxidation of alkyl A-arylaldimines (460) has been rationalized597 in terms of an intermediate oxaziridine (461) that rearranges via acid-catalysed O—N cleavage. 

The ability of other peracids28, sodium perborate and sodium percarbonate29, to release oxidative species in an organic medium has made them useful reagents in organic synthesis. The oldest organic reaction reported with sodium perborate concerns the formation of peracids (equation 5). 

The formation of peracids as the effective oxidizing species has often been proposed for oxidations with sodium percarbonate in the presence of organic acids or acid anhydrides30-32. It was observed that at room temperature and in dichloromethane as solvent, the addition of acetic anhydride induced the epoxidation by sodium perborate of mono-, di- and trisubstituted alkenes, including a,/i-unsaturated ketones in a slightly exothermic reaction33 (equation 6). 

A saturated solution of sodium tetraborate, also containing both carbonate and bicarbonate of sodium, is used as the eleotrolyte. The presenoe of excessive solid borax guarantees that the solution is continuously resaturated with this compound during electrolysis. The eleotrolyte is also saturated with perborate so that this salt, which is formed by anodic oxidation of borax, is separated from the solution immediately after its formation in the form of small crystals. 

Carbonate is neoessary for electrolysis, as otherwise perborate could not be formed. For this reason its formation is supposed to take place in such a way that sodium per carbonate is first formed at the anode ... 

Many heterocyclic bases can be oxidized to A-oxides with sodium perborate and acetic acid in the absence of metal catalysts.352 Use of a smaller excess of oxidant leads to diazo compounds.353 Aliphatic amines can be converted to nitroso products. Sodium perborate/acetic acid systems can also cleave hydra-zones, regenerating carbonyl compounds which have been protected by hydrazine formation.354... 

Cystine, which contains a disulfide bond, is reported to be the most numerous and reactive amino acid present in hair keratin. Disulfide bonds in cystine are reduced by mercaptans and phosphines, and oxidized by perborates, bromates, and bleach. These reactions result in structural rearrangements within keratin which may affect the physiochemical properties of hair, since disulfide bonds in cystine contribute to the stability of hair. For example, hydrogen peroxide bleaching of hair is an oxidative process which occurs readily in an alkaline medium. This results in the formation of perhydroxy anions which have been proposed to react with cystine to form cysteic acid residues. The process of bleaching results in the loss of approximately 15% of the cystine bonds originally present in keratin and may explain the increased permeability of bleached hair to chemicals. - ... 

Sodium perborate (NaB03 nH20 n = 1-4) is a cheap and widely used industrial chemical. If sulfuric acid is added to a mixture of the perborate and an alkene in acetic anhydride, an exothermic reaction occurs leading to anti addition to the double bond with formation of the corresponding l-hydroxy-2-ace-toxy derivative in moderate yield. Peroxybis(diacetoxy)borane, (AcO)2BOOB(OAc)2, may be the reactive species in this oxidation and it seems likely that the epoxide is an intermediate. 

Sodium perborate has been recommended for the oxidation of alkenyldialkoxyboranes to aldehydes. In particular, the reagent avoids the formation of possibly hazardous 2 1 aldehyde-4iydrogen peroxide adducts as well as C—C bond cleavage. Sodium percarbonate is an air-stable solid, inexpensive and self-buffered, that appears to be a promising oxidant. ... 

The first step, the formation of sodium metaborate from borax and sodium hydroxide, is carried out at temperatures up to 90°C. When impure borax is used the solution is filtered. The second step is carried out at 25 °C and the mixture subsequently cooled to 15°C and the precipitated sodium peroxoborate hexahydrate filtered off. Stabilizers for the perborate, such as silicates or magnesium salts, may be added to the reaction mixture. Residual moisture (3 to 10%) is removed in a hot air drier. The mother liquor from the second step can be returned to the first step. 

Step I Formation of nietaborate from borax and sodium hydroxide Step 2 Reaction of metaborate with H2O2 forming perborate, which is then filtered off from the cooled solution and dried... 

Green, D. A., Rogers, J.M., Robertson, D.C., and Tolbert, L.F. (1995). Formation of Attrition- and Breakage-Resistant Polycrystalline Sodium Perborate Tetrahydrate Particles, In Proceedings of the 1995 Topical Conference "Recent Developments and Future Opportunities in Separations Technology, AIChE, New York. 

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