Sodium bromate reduction

Related oxidants that have been exploited to similar ends include l-(tert-butoxy)-l,2-benzoiodoxol-3(l//)-one292 and sodium bromate.293 Oxidation of benzyl ethers by l-(/erf-butoxy)-l,2-benzoiodoxol-3(l/f)-one followed by easy basic hydrolysis of the resultant benzoate ester provides a convenient alternative to the usual reductive deprotection. The reaction is carried out in the presence of alkali metal carbonates and the conditions are mild enough to be compatible with other hydroxyl protecting groups such as methoxymethyl, tetrahydropyranyl, TBS and acetate. 

A similar rearrangement occurs when a-epoxyketones are refluxed with 30% aqueous sodium hydroxide. Best directions ate those for benzilic acid (90%) from benzoin, sodium bromate, and sodium hydroxide. Oxidation of the benzoin to benzil and rearrangement of benzil to benzilic acid are accomplished in one step. a-Ketoaldehydes and potential a-ketoalde-hydes undergo a similar internal oxidation-reduction reaction in excellent yields, viz.,... 

Even though the reaction conditions may lead to formation of the metal enolate in high yield, further reduction may occur during the quenching step of the reaction. Alcohols such as methanol and ethanol convert metal enolates to saturated ketones much faster than they react with metals in ammonia, and quenching of reduction mixtures with these alcohols will usually lead to partial or complete conversion to alcoholic product rather than to the saturated ketone. Rapid addition of excess solid ammonium chloride is the commonly employed quench procedure if ketonic products are desired,but other reagents that destroy solvated electrons before neutralization may be employed, such as sodium ben-zoate, iron(III) nitrate, - sodium nitrite, bromobenzene, sodium bromate, 1,2-dibromoethane and acetone. 

Lactones have been converted to (hydroxyalkyljcyclopropyl phenyl ketones on reaction with phenylmagnesium bromide and phenyllithium. Reductive dimerization of ethyl cyclo-propanecarboxylate with sodium gave l,2-dicyclopropylethane-l,2-dione in 69% yield when thionyl chloride treatment was carried out prior to hydrolytic workup, and to dicyclopropyl ketone in 74% yield, when workup included sodium bromate treatment. A related reaction occurred during thermolysis of 6,6-dimethyl-5,7-dioxaspiro[2.5]octane-4,8-dione to give dispiro[2.1.2.1. ]octane-4,8-dione. ... 

Bromate and iodate salts are prepared on a much smaller scale than chlorates. Under appropriate conditions, these ions undergo oscillating chemical reactions known as chemical clocks. The best known clock reaction is observed when an acidified solution of sodium sulfite (Na2S03) is mixed with an excess of iodate in the presence of starch indicator. After a suitable induction period allowing for sodium sulfite reduction of iodate to iodide [Eq. (44)], the blue, starch-iodine color periodically appears and disappears as the iodide is oxidized to iodine [Eq. (45)], and the iodine is reduced back to iodide [Eq. (46)]. 

Other imaginative uses of rare earths include the reduction of alkenes, aldehydes and ketones with intermetalhc compounds containing absorbed hydrogen, viz. LaNijHg (Imamoto et al., 1984d). The use of duPont s Nafion polymer as a support for Cr(III) and Ce(IV) reagents useful in the oxidation of alcohols has also been reported (Kanemoto et al., 1984). Such conversions also involved the use of t-butylhydroperoxide or sodium bromate as cooxidant. 

Assays of bromate and perbromate concentrations are required during the procedure. Bromate concentrations that are at least comparable to the perbromate may be determined iodometrically by reaction with sodium iodide in acid solution containing molybdate, followed by titration with standardized thiosulfate. After reduction of the bromate the solution should be ca. 0.1 M each in H+ and in free iodide ion. Perchloric, hydrochloric, or sulfuric acids may be used. The molybdenum(VI) concentration should be ca. 10 3 M. 

These reactions may be accompanied by unwanted side-reactions, such as oxidation of hypobromite to bromate or its reduction to bromide. The electro-oxidation of 2,3 4,6-di-0-isopropylidene- -L-sorbofuranose (14) is affected by a number of factors, and here the method of mathematical planning of so-called extreme experiments for obtaining the optimal conditions for electrolysis was utilized the conditions are concentration of sodium bromide, 107.7 g per liter concentration of nickel chloride, 0.71 g per liter concentration of 2,3 4,6-di-0-isopropylidene-L-sorbose, 86 g per liter the amount of electric current passed, 1.912 A-hr/g of the diisopropylidene acetal current density, 4.56 A.dm pH of the solution, 9.83 the expected yield, 91.9 0.7%. A more-detailed survey of the mechanism and kinetics of the electrochemical oxidation of monosaccharides and their derivatives, as well as of the effect of experimental conditions on the yields of aldonic acids and of the di-O-isopropylidene-xylo-hexulosonic acid (15) formed, has been given. ... 

In addition, bromate and chlorate were determined by potentiometric titration after reduction with sodium nitrite." Sodium nitrite was added to... 

R. C. Duty and J. S. Ward, Determination of bromate and chlorate via reduction with sodium nitrite. Analyst, 1994, 119, 2141-2143. 

Electrolysis of aqueous bromide liquors ts one of the principal methods for production of sodium and potassium bromatc. The tnitiai reaction products are bromine at the anode and hydroxyl ions at the cathode. In an undivided cell, mixing of these species within the mterelMrode gap results in hypobromite formation. This species then decomposes to bromate. The chemistry is complex and analogous to the reactions for chlorate (section SJJ). Loss of the hypo-bromilc by cathodic reduction may be minimi by the addition of alkali metal... 

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