Bromate, oxidation with

For producing bromates, oxidation with hypochlorite as shown here is a useful reaction ... 

Better results are obtained by oxidation with potassium bromate in the presence of hydrochloric acid ... 

Impurities in CL have also been destroyed by oxidation with ozone22 followed by distillation. Ozonation treatment of waste CL leaves no ionic impurities. However, the most commonly used oxidizing agents are potassium permanganate, perboric acid, perborate, and potassium bromate. Treatment of CL with these oxidizing agents is carried out in a neutral medium at 40-60°C. Strongly alkaline or acidic conditions accelerate the oxidation of CL to form isocyanates. Hie undesirable oxidation reaction is fast above pH 7 because of the reaction with isocyanate to form carbamic acid salts, which shifts the equilibrium to form additional isocyanate. 

Catalytic Ce(IV) reagent combined with an additional oxidant such as sodium bromate oxidizes hydroquinones, catechols, and their derivatives to quinones in aqueous acetonitrile (e.g., Eq. 7.18).43... 

An acidic bromate solution can oxidize various organic compounds and the reaction is catalyzed by species like cerous and manganous ions that can generate 1-equivalent oxidants with quite positive reduction potential. Belousov (1959) first observed oscillations in Celv]/[Cem] during Ce (III) catalysed oxidation of citric acid by bromate ion. Zhabotinskii made extensive studies of both temporal and spatial oscillations and also demonstrated that instead of Ce (III), weak 1- equivalent reductants like Mn(II) and Fe (II) can also be used. The reaction is called Belousov-Zhabotinskii reaction. This reaction, most studied and best understood, can be represented as... 

Calcium hydride ignites in air on heating and can explode violently if mixed and rubbed with a strong oxidizing agent such as perchlorate or bromate. Contact with water produces hydrogen which can create a fire hazard in a confined space. 

All the early work on plutonium was done with unweighable amounts on a tracer scale. When it became apparent that large amounts would be needed for the atomic bomb, it was necessary to have a more detailed knowledge of the chemical properties of this element. Intensive bombardment of hundreds of pounds of uranium was therefore begun in the cyclotrons at Berkeley and at Washington University in St. Louis. Sepa-ration of plutonium from neptunium was based on the fact that neptunium is oxidized by bromate while plutonium is not, and that reduced fluorides of the two metals are carried down by precipitation of rare earth fluorides, while the fluorides of the oxidized states of the two elements are not. Therefore a separation results by repeated bromate oxidations and precipitations with rare earth fluorides. 

The main processes occurring in this system are the following [219] bromate oxidizes trivalent cerium to tetravalent cerium Ce4+ oxidizes bromomalonic acid, and is reduced to Ce3+. The bromide ion, which inhibits the reaction, is isolated from the oxidation products of bromomalonic acid. During the reaction, the concentration of the Ce4+ ions (and Ce3+) oscillates several times, passing through a maximum and a minimum. The shape of the peaks of concentrations and the frequency depend on the reaction conditions. The autooscillation character of the kinetics of the cerium ions disappears if Ce4+ or Br are continuously introduced with a low rate into the reaction mixture. The autooscillation regime of the reaction takes place only in a certain interval of concentrations of the reactants [malonic... 

Zinc Bromate. Zn(Br03)2.6H20 mw 429.28 white deliq crysts mp 100° sp grav 2.566. V sol in w. Prepn is by treating Zn oxide with bromine w. Intimate mixts of the bromate with finely divided Al, As, Cu, C, P, S hydrides of alkali and alkaline earth metals, Sb sulfide, metal cyanides, K thiocyanate or impure Mn dioxide can react explosively (spontaneously in the pre-... 

Although NaI04 or KI04 are the secondary oxidants used in the vast majority of cases in which alcohols are oxidized with catalytic Ru04, the employment of sodium hypochlorite (NaOCl),31 sodium bromate (NaBrOj )32 or Cl+, electrolytic-ally generated by oxidation of chloride ion,33 have also been reported. 

The periodinane (10) may also be prepared from o-iodobenzoic acid by oxidation with potassium bromate and then treatment with acetic anhydride18 (see Expt 6.36 for detailed formulation). It should be noted that the organic derivatives of pentacoordinate iodine(v) are termed periodinanes.18b This compound (the systematic name is l,l,l-triacetoxy-2,l-benzoxiodol-3(3//)-one) has found use as an oxidant of primary alcohols to aldehydes and alicyclic ketones to secondary alcohols it is claimed to have advantages over the chromium-based oxidation reagents. 

Perbromates are obtained by oxidation of bromates in aqueous solution. Electrolytic oxidation, the best method of preparing perchlorates and periodates, is not very satisfactory in the case of perbromates. The most practical synthesis involves oxidation with elemental fluorine in sodium hydroxide solution. The procedure is somewhat hazardous, and the experimenter should familiarize himself with the precautions necessary for safely handling fluorine before undertaking the synthesis.1... 

Thiocyanate ion frequently reacts in oxidation with a rate-determining step reminiscent of those with the halides, and this oxidation is no exception. A study based on measurements of the limiting polarographic currents for thiocyanate in the presence of hydrochloric acid and bromate gives clear evidence of first-order dependence on bromate and on thiocyanate ion concentrations and of second-order dependence on hydrogen ion concentration. The authors report the Arrhenius parameters as, AH = 11.4 kcal.mole and AS = 28.0 caLmole . deg . One strange, and unexplained, anomaly is present. The experimental first-order coefficient for bromate reaction appears to be constant over about one half-life for equimolar initial thiocyanate and bromate concentrations. Yet these rate coefficients depend linearly on thiocyanate ion concentration for [SCN ] > [BrOj ], but non-linearly below. It seems improbable that the postulated mechanism with first steps (1 )-(3), is capable of explaining this, viz. 

In the BZ reaction, malonic acid is oxidized in an acidic medium by bromate ions, with or without a catalyst (usually cerous or ferrous ions). It has been known since the 1950s that this reaction can exhibit limit-cycle oscillations, as discussed in Section 8,3. By the 1970s, it became natural to inquire whether the BZ reaction could also become chaotic under appropriate conditions. Chemical chaos was first reported by Schmitz, Graziani, and Hudson (1977), but their results left room for skepticism—some chemists suspected that the observed complex dynamics might be due instead to uncontrolled fluctuations in experimental control parameters. What was needed was some demonstration that the dynamics obeyed the newly emerging laws of chaos. 

Original B-Z reaction where metal ion catalyzed organic substrate is brominated by enolization and bromide is liberated when the organic bromate reacts with the oxidized form of the catalyst, [See G G]. 

In section C we summarize the recent contributions under subsections. The general considerations on the mechanism of the B-Z reaction are in four subsections. Following these general considerations, we have sections C.2. Mathematical models and techniques, C.3. Experiments with different substrates, C.4. Experiments with different catalysts, and C.5. Horatian oscillations in bromate oxidations. The name horatian has recently been proposed for replacing the term chaotic. Here we simply state that throughout this article instead of chaotic oscillations, the term horatian oscillations will be used. 

Oxidation of the 1,1-disubstituted hydrazine, 3-amino-2-oxazolidinone (1), with bromine water, with potassium iodate-HN03, or with potassium bromate in 6 N HC1 affords a compound melting at 299° and now recognized as the trans-3,3 -azobis(2-oxazolidinone) of formula (2). Forgione et al. 5 explored oxidation with yellow mercuric oxide in dioxane or THF at 25° and obtained an isomeric product, m.p. 171°, in 50% yield along with a little of the trans isomer (2). Infrared, UV,... 

The use of bromine in alkaline media resulted in the formation of uronic acids.416,417 Oxidation to some non-uronic acid products, (carbonyl compounds) accompanied the major oxidation pathway.418-420 The 2,2,6,6-tetramethyl-l-piperidinyloxy-mediated oxidation by hypobromite was highly selective for the 6-OH groups of the glucose residues.421 Potassium bromate (HB1-O3) was also used.338 The kinetics of oxidation with bromine at pH 6-8 has been studied 422 It was observed that oxidation decreases the heat and temperature of gelation as the oxidation proceeds. Simultaneously, the molecular weight of starch and the viscosity of its aqueous solutions decreased. Subsequent reduction of the oxidation products increased the viscosity. Microscopic observations revealed that the starch granularity vanished at a low level of oxidation.423... 

Oxidations with bromine-bromate Carboxylic acid esters from alcohols ... 

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