Acid bromate, oxidation with

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. 

Experimental results on velocity of trigger waves in acidic bromate oxidation of ferroin have been reported by Field and Noyes [18] and Showalter [24]. A semi-quantitative comparison with experimental results shows that the observed velocity is proportional to square root of the product of [H+] and [BrOj ] as theoretically predicted. However, deviations have been observed depending on experimental conditions. Thus, in the case of malonic acid -I- bromate -t- manganous sulphate -1- ferroin in H2SO4 medium, the wave velocity is found [25] to be proportional to [Br03 ]y [H+]. Similar results are obtained for citric acid -I- BrOj -I- Mn - - H2SO4 system [26]. 

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. 

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... 

Mechanisms involving glycol bond fission have been proposed for the oxidation of vicinal diols, and hydride transfer for other diols in the oxidation of diols by bromine in acid solution.The kinetics of oxidation of some five-ring heterocyclic aldehydes by acidic bromate have been studied. The reaction of phenothiazin-5-ium 3-amino-7-dimethylamino-2-methyl chloride (toluidine blue) with acidic bromate has been studied. Kinetic studies revealed an initial induction period before the rapid consumption of substrate and this is accounted for by a mechanism in which bromide ion is converted into the active bromate and hyperbromous acid during induction and the substrate is converted into the demethylated sulfoxide. 

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... 

The closely related o-iodylbenzoic acid (IBX) and Dess-Martin oxidations have proved to be effective methods for the synthesis of peptide aldehydes (Table 7, Scheme 6) 9 38 39] 2-Iodobenzoic acid is oxidized by potassium bromate to form 2-iodylbenzoic acid (IBX), which can be used directly for IBX oxidation. IBX can be further treated with acetic anhydride and TosOH at 100 °C for 40 minutes to form the more stable Dess-Martin periodinane reagent 45 46]... 

The uncatalysed Belousov-Zhabotinsky (B-Z) reaction between malonic acid and acid bromate proceeds by two parallel mechanisms. In one reaction channel the first molecular products are glyoxalic acid and carbon dioxide, whereas in the other channel mesoxalic acid is the first molecular intermediate. The initial reaction for both pathways, for which mechanisms have been suggested, showed first-order dependence on malonic acid and bromate ion.166 The dependence of the maximal rate of the oxidation of hemin with acid bromate has the form v = [hemin]0-8 [Br03 ] [H+]12. Bromate radical, Br02, rather than elemental bromine, is said to play the crucial role. A mechanism has been suggested taking into account the bromate chemistry in B-Z reactions and appropriate steps for hemin. Based on the proposed mechanism, model calculations have been carried out. The results of computation agree with the main experimental features of the reaction.167... 

Chloric acid, in conjunction with catalysts (particularly vanadium pentaoxide), is used for the oxidation of aldonic acids or lactones to the 2-glyculosonic acids. Thus, D-glucono-1,4-lactone (9) and potassium D-galactonate in methanol, in the presence of phosphoric acid and vanadium pentaoxide, are oxidized by chloric acid to methyl D-arabino-2-hexulosonate (10) and methyl D-/yxo-2-hexulosonate, respectively.38 At moderate temperatures in the absence of a catalyst, aldoses, ketoses, and sucrose are inert to the action of chlorates over a several weeks time period 39 bromates in alkaline solution also exert no oxidative action (Scheme 5). 

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. 

The seawater is acidified with sulfuric acid to a pH of 3.5, 130 g of 100% sulfuric acid being necessary per t of seawater. The slight excess of chlorine necessary to oxidize the bromide is fed in at the same time as the sulfuric acid. The bromine formed is expelled by air in so-called blowout towers. The bromine (and possibly chlorine or bromine chloride)-containing air is fed into absorption towers in which it is brought into contact with a sodium carbonate solution, whereupon the bromine is disproportionated into bromide and bromate according to the above equation. The bromine in the absorption solution is then converted into elemental bromine with sulfuric acid and expelled with steam ... 

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. 

Gupta et al. (1981) studied uncatalyzed and catalyzed oscillatory behavior in the redox potential during the oxidation of 3-alizarinsulfonic acid sodium salt by KBr03—H2S04 and suggested a mechanism. Gupta and Srinivasulu (1981) reported a comparative study of oscillatory behavior in the redox potential in a slowly stirred closed system of salicyclic and 5-sulfosalicyclic acid (5-SSA) with acidic (H2S04) bromate in the presence and absence of catalysts. Ferroin (l,10-phenanthrolineiron(II) sulfate) as catalyst enhances the oscillatory behavior of 5-SSA considerably. 

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 ... 

ACETIC ACID, LEAD(II) SALT TRIHYDRATE (6080-56-4) Pb(C2H302)2 3H20 Contact with acids forms acetic acid. Incompatible with oxidizers, bases, acetic acid alkalis, aUcylene oxides, ammonia, amines, bromates, carbonates, citrates, chlorides, chloral hydrate cresols, epichlorohydrin, hydrozoic acid, isocyanates, methyl isocyanoacetate, phenols, phosphates, salicylic acid sodium salicylate, sodium peroxyborate, potassium bromate resorcinol, salicylic acid, strong oxidizers, sulfates, sulfites, taimin, tartrates, tinctures trinitrobenzoic acid, urea nitrate. On small fires, use dry chemical, Halori, or CO2 extinguishers. 

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