Oxidation Of Bromide Ions Research Articles

紅藻由来含臭素環状エーテルの生合成

Various halogenated organic compounds, originated from marine livings, have been well-known over five decades. Particularly, cyclic bromo-ether have attracted many chemists to study their existence, biogenetic syntheses and artificial syntheses, owing to their unique structures. Laurencia species produce eight-membered ethers as major products, although their syntheses by chemical procedures are generally difficult. These compounds are divided into laurenan and lauthisan groups based on the type of ring formation. The laurenan compounds are characteristic in respect of C6-S and C7-S configurations, while the lauthisan series haveR and R at the requisite positions. It has been proposed without any proof that the bromine atoms in the marine compounds could be introduced via bromo cationic species, generated by the two-electron oxidation of bromide ion with bromoperoxidase (BPO) and hydrogen peroxide. We studied on the enzymatic formation of these bromo-ethers, and found that both series of laurenan and lauthisan compounds could be biosynthesized directly from linear C15 compounds, laurediols. Herein, we mention our study of these natural products, and the recent studies around this field.

Radiation-chemical oxidation of bromide ions and formation of tribromide ions in weakly acidic aqueous solutions

The formation of the Br 3 − ion in the radiation-chemical oxidation of Br − ions in an aqueous solution was detected by pulse radiolysis, and its optical characteristics and the equilibrium constant were found.

The oxidation of bromide ion by [(FeTPP)2O]+SbF6− in dichloromethane ‡

The oxidation of cetyltrimethylammonium bromide (CTAB) by mono-oxidised iron(III) tetraphenylporphyrin μ-oxo-dimer, [(FeTPP)2O]+SbF6−, has been found to be much slower than the corresponding oxidation of iodide ion, but can still be studied by stopped-flow techniques. The stoichiometry of the reaction has been established as 2 [Fe(TPP)2O]+ + 3Br− → 2(FeTPP)2O + Br3−. The rate law for the reaction is d [(FeTPP)2O]/dt = [Fe(TPP)2O+]·

Inactivation of Glucose Oxidase by Diperoxovanadate-Derived Oxidants

Inactivation of glucose oxidase occurred in the presence of bromide, vanadate, H2O2, and phosphate (the bromide system), and this was prevented by NADH or phenol red, a bromine acceptor. Glucose oxidase present during the reaction between diperoxovanadate and a reduced form of vanadate, vanadyl (the vanadyl system), but not added after mixing the reactants, was inactivated, and this was accompanied by a loss of binding of the dye, Coomassie blue, to the protein. The transient intermediate of the type OVOOV(O2), known to form in these reactions and used in the oxidation of bromide ion and NADH, appears to be responsible for inactivating glucose oxidase. In both systems, the inactivation of the enzyme was prevented by histidine and DTT, known to quench singlet-oxygen. By direct measurement of 1270-nm emission of singlet-oxygen, its generation was demonstrated in the bromide system, and in the reaction of hypohalous acids with diperoxovanadate, but not in the vanadyl system. By themselves both hypohalous acids, HOCl and HOBr inactivated glucose oxidase, and their prior reaction with H2O2 during which singlet-oxygen was released, protected the enzyme. The results provide support for possible oxidative inactivation of glucose oxidase by diperoxovanadate-derived oxidants.

Kinetics and thermodynamics of the reaction of aliphatic N-bromamines with bromide ion in acid media, and the pKa of N-bromamines †

The kinetics of the oxidation of bromide ions by aliphatic N-bromamines in aqueous acid media were studied using a pH jump technique. The reaction is first order in both bromide ion and total bromamine concentrations, and takes place only through the protonated N-bromamine. For two of the N-bromamines studied (N-Br-dimethylamine and N-Br-diethylamine), hydrolysis competed with the reaction with bromide ions, whereas in all the other cases hydrolysis was too slow to be detected. The pKa values obtained from the kobsvs. [H+] data at 25 °C are 2.88 for N-Br-dimethylamine, 3.24 for N-Br-diethylamine, 3.33 for N-Br-piperidine (all at I = 0.1 M), 2.26 for N-Br-iso-butylamine and 2.92 for N-Br-sec-butylamine (both at I = 0.5 M).

Threshold Levels for Bromate Formation In Drinking Water

Ozone is a sufficiently strong oxidant to cause the oxidation of bromide ion and formation of bromate ion. In this study, bromate ion formation in a wide variety of drinking water sources was analyzed, with bromate ion formed in all sources under drinking water treatment conditions. Threshold levels for pH, bromide ion concentration, and ozone dose were found to be source-specific. Two non-linear empirical models were developed to predict bromate ion formation; these models are easy to use and require only several water quality and treatment variables. The models were tested against several literature data and a good simulation was found in other bench-scale tests, whereas the model tended to under-predict bromate ion formation in pilot-scale and full-scale programs.

In-Situ Imaging of Ionic Crystal Dissolution Using an Integrated Electrochemical/AFM Probe

The kinetics and mechanism controlling dissolution from the (100) cleavage face of potassium bromide single crystals in acetonitrile solutions have been identified using a novel integrated electrochemical/AFM probe and a scanning electrochemical microscope (SECM). With both techniques, dissolution is induced by perturbing the dynamic dissolution/growth equilibrium at the crystal/solution interface through the electrochemical oxidation of bromide ions. SECM measurements demonstrate that the dissolution reaction is diffusion-limited under the experimental conditions, suggesting that the surface reaction is characterized by a rate constant in excess of 5 cm s-1 (assuming a first-order dissolution process). The topography of the dissolving surface has been imaged in situ, under conditions which closely mimic those of the SECM measurements, using an electrochemically active AFM probe. These studies provide the first direct experimental evidence of the operation of the spiral mechanism in the dissolution of an ...

Electrochemical Haloform Reaction Efficient Transformation of Methyl Ketones to Carboxylates.

Electrolysis of aliphatic, aromatic, and α, β-unsaturated methyl ketones in an anhydrous alcohol containing sodium or lithium bromide using an undivided cell equipped with carbon rods as the anode and the cathode brought about electrochemical Haloform reaction to give the corresponding carboxylates in good to excellent yields. The reaction was found to be mediated with bromonium ion, generated by anodic oxidation of bromide ion. Absence of bromoform in the product mixtures of this reaction may be attributed to ready reduction of bromoform to highly volatile compounds, which may provide high simplicity of reaction procedure.Facile and efficient introduction of carboalkoxyl groups to aromatic rings and olefinic bonds was accomplished in two steps through initial Friedel-Crafts acetylation followed by the present electrochemical method.

Studies on the oxidation of ?-amino acids by N-Bromo oxidants: Kinetics of the reaction of bromide ion with N-Bromoacetamide

The rate of oxidation of amino acids (AA) by N-Bromoacetamide (NBA) was studied in aqueous buffered medium at 35°C. The rate of disappearance of [NBA] is catalyzed by the Br− produced from the reduction of NBA. Analysis of the autocatalyzed reaction gives the kinetic data for the oxidation of bromide ion by NBA. The results suggest that the protonated NBA reacts with Br− to form Br2 which rapidly oxidizes amino acids. The rate constant for the reaction between protonated NBA and Br− at 35°C is estimated. © 1996 John Wiley & Sons, Inc.

ChemInform Abstract: Non‐Metal Redox Kinetics: Oxidation of Bromide Ion by Nitrogen Trichloride.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Non-Metal Redox Kinetics: Oxidation of Bromide Ion by Nitrogen Trichloride

Bromide ion reacts with NC13 to generate NBrC12 with the rate expression d[NCl3]/dt = 12[Br-][NC13] (M s-' at 25.0 C, y = 0.50 M). The NBrC12 intermediate subsequently reacts with Brto give N2, Br2, and C1with the rate expression -d[NBrClz]/dt = (0.05 + 5.3[Br-])[NBrC12]. The overall stoichiometry from pH 3.2 to 6.5 corresponds to 2NC13 + 6BrN2 + 3Br2 + 6C1-. Rate constants for NCl3 reactions show extreme sensitivity to nucleophilic strength with so32> CN> I>> Br-. Aqueous absorption spectra are determined for NC13 with maxima at 336 nm ( E 190 M-' cm-I) and 220 nm ( E 5320 M-' cm-') and for NBrC12 with a maximum at 228 nm ( E 4800 M-' cm-I). Spectral bands for NCl3, NBrC12, NBr2C1, and NBr3 shift systematically with the number of bromine atoms from 220 to 256 nm. The rate constants for the reactions of NHCl2 with Br2, HOBr, and Brare much larger than that for the reaction of NCl3 with Br-.

Oxidation of Bromide by the Human Leukocyte Enzymes Myeloperoxidase and Eosinophil Peroxidase: FORMATION OF BROMAMINES

Myeloperoxidase and eosinophil peroxidase catalyzed the oxidation of bromide ion by hydrogen peroxide (H2O2) and produced a brominating agent that reacted with amine compounds to form bromamines, which are long-lived oxidants containing covalent nitrogen-bromine bonds. Results were consistent with oxidation of bromide to an equilibrium mixture of hypobromous acid (HOBr) and hypobromite ion (OBr-). Up to 1 mol of bromamine was produced per mole of H2O2, indicating that bromamine formation prevented the reduction of HOBr/OBr- by H2O2 and the loss of oxidizing and brominating activity. Bromamines differed from HOBr/OBr- in that bromamines reacted slowly with H2O2, were not reduced by dimethyl sulfoxide, and had absorption spectra similar to those of chloramines, but shifted 36 nm toward higher wavelengths. Mono- and di-bromo derivatives (RNHBr and RNHBr2) of the beta-amino acid taurine were relatively stable with half-lives of 70 and 16 h at pH 7, 37 degrees C. The mono-bromamine was obtained with a 200-fold excess of amine over the amount of HOBr/OBr- and the di-bromamine at a 2:1 ratio of HOBr/OBr- to the amine. In the presence of physiologic levels of both bromide (0.1 mM) and chloride (0.1 M), myeloperoxidase and eosinophil peroxidase produced mixtures of bromamines and chloramines containing 6 +/- 4% and 88 +/- 4% bromamine. In contrast, only the mono-chloramine derivative (RNHCl) was formed when a mixture of hypochlorous acid (HOCl) and hypochlorite ion (OCl-) was added to solutions containing bromide and excess amine. The rapid formation of the chloramine prevented the oxidation of bromide by HOCl/OCl-, and the chloramine did not react with bromide within 1 h at 37 degrees C. The results indicate that when enzyme-catalyzed bromide or chloride oxidation took place in the presence of an amine compound at 10 mM or higher, bromamines were not produced in secondary reactions such as the oxidation of bromide by HOCl/OCl- and the exchange of bromide with chlorine atoms of chloramines. Therefore, the amount of bromamine produced by myeloperoxidase or eosinophil peroxidase was equal to the amount of bromide oxidized by the enzyme. Bromide was preferred over chloride as the substrate for both enzymes.

Mimicking the vanadium bromoperoxidases reactions:Mild and selective bromination of arenes and alkenes in a two-phase system

Vanadium bromoperoxidases catalyze the oxidation of bromide ion by hydrogen peroxide to a bromine-equivalent intermediate. This, in turn, brominates organic molecules. The hypothesis is made that the former reaction takes place in the hydrophilic portion of the enzyme whereas the latter proceeds in a hydrophobic one in which the brominating intermediate is rapidly transferred. We have reproduced such situation by employing a two-phase (H 2O/CHCl 3) system. In the aqueous acid phase H 2O 2 and catalytic amounts of NH 4VO 3 are present, together with KBr. The substrates, i.e. aromatic hydrocarbons and alkenes are dissolved in CHCl 3. The bromination proceeds smoothly with stirring, at 25°C, providing high yields of the corresponding brominated products.

Superconducting thallium cuprates obtained by substitution of copper for thallium in the double-thallium layer cuprate (T12212)

A new series of superconducting thallium cuprates of nominal composition, (Tl 2− x Cu x )Ba 2CaCu 2O 8 (0<x<1.0), where copper seems to substitute for thallium in Tl2212, is reported. These materials, which are synthesized at 920K-1120K in sealed silver tubes, exhibit T c s in the range 110-99K. The phases are metastable, decomposing at higher temperatures (≈1150K) to a mixture of thallium cuprates, CuO and BaCuO 2. Significantly, x=1 member decomposes at 1150K to mixture of Tl2223, CuO and BaCuO 2. Chemical titrations involving oxidation of bromide ions reveal that the copper substituting for thallium in (Tl 2− x Cu x )Ba 2CaCu 2O 8 most likely occurs in the III oxidation state for x≤0.25 and in a mixed state (II, III) state for x>0.25.

Kinetics and mechanism of oxidation of bromide ions by sodium perborate by transforming to a Landolt process

Sodium perborate was used for oxidation of bromide ions at pH 3.64. The reaction was conducted by potentiometric measurements. The orders with respect to perborate and bromide ions were found to be unity in each reagent and a plausible mechanism was postulated. The effect of temperature was studied in the range of 20–40 °C and the Arrhenius parameters were evaluated.

Bromide ion oxidation of various Pt surfaces

At variance with the absence of an orientation effect in the hydrogen evolution reaction, aclear difference in the electrocatalytic effect of various parts of the surface on bromide ion oxidation is observed.

Determination of hole concentration in superconducting thallium cuprates

A chemical method for the determination of hole concentration in superconducting thallium cuprates is described. The method is based on selective oxidation of bromide ion by holes on CuO 2 sheets. Application of this method to several thallium cuprates has provided some insight into the origin of holes in these materials.

Photosensitized oxidation of bromide in dead sea water

The photosensitized oxidation of bromide ions in acidified oxygenated Dead Sea water was studied by illumination with natural sunlight and with artificial light sources. No measurable oxidation of bromide to bromide was observed in the dark, in the absence of oxygen (or air), or without acidification of the brine. The rate of oxidation was enhanced by increasing acidity, and occurred also in sunlight-illuminated air-bubble films of the brine, simulating reactions at the sea-air interface. Some photo-oxidation was observed even in the absence of added photosensitizers or added acid, producing a non-volatile oxidant. The photo-oxidation of bromide was not inhibited by the addition of 1,4-diazabicyclo-[2,2]-octane (DABCO), indicating that singlet oxygen is probably not involved as an intermediate in this reaction. A search for dissolved organic compounds in the Dead Sea brine by n-hexane extraction and gas chromatography-mass spectrometry showed the presence of several distinct species with m/ e values of 308–378. These molecular weights are compatible with those of some saturated and some mono-unsaturated or monocyclic-saturated hydrocarbons. The observed photo-oxidation of bromide in the brine, which involves its natural photosensitizing properties, suggests a possible mechanism for the abiotic generation of halogenated organic compounds in the marine environment. The rate of photo-oxidation of bromide in the brine was markedly increased by the addition of aromatic ketones, such as anthraquinone derivatives.

Kinetic investigation of the oxidation of bromide ions by cobalt(III). Reaction in the presence of p-toluic acid

The rate of Co(III) reduction under inert atmosphere in the presence of p-toluic acid (PTA) and hydrobromide obeys the rate law d[Co(III)]/dt = k[Co(III)]2 [Co(II)]-1 [PTA] [HBr]. The proposed reaction mechanism involves the reduction of Co(III) by Br- ions and formation of a cation-radical from p-toluic acid. p-Xylene is attacked by bromine species and not directly by Co(III). The rate constants of Co(III) and Br- consumption as well as apparent activation energies were estimated.

Bromine derivatives of amino acids as intermediates in the peroxidase-catalyzed formation of singlet oxygen

Recently, J. R. Kanofsky et al. (1988, J. Biol. Chem. 263, 9692–9696 ) reported that human eosinophils generated modest amounts of singlet oxygen. In the mechanism proposed, hypobromous acid (made from the peroxidase-catalyzed oxidation of bromide ion) reacted with hydrogen peroxide to form singlet oxygen. In contrast, human neutrophils, which generate both hypochlorous acid and hydrogen peroxide, do not make singlet oxygen. The failure of human neutrophils to generate singlet oxygen is due in part to the trapping of hypochlorous acid by endogenous amines. In this paper, I show that amino acids are much more effective traps for hypochlorous acid than for hypobromous acid. Glycine totally inhibits singlet oxygen generation from a model enzyme system composed of chloroperoxidase, hydrogen peroxide, and chloride ion, but causes only a 35% reduction in singlet oxygen generation from an analogous enzyme system containing bromide ion instead of chloride ion. The products of the reaction of hypobromous and glycine (presumably an equilibrium mixture of N-bromoglycine, N,N-dibromoglycine, and hypobromous acid) retain the ability to react with hydrogen peroxide to form singlet oxygen. In contrast, the products of the reaction of hypochlorous acid and glycine do not react with hydrogen peroxide to produce singlet oxygen. Similar results were obtained for l-alanine, l-arginine, l-asparagine, l-aspartic acid, l-cystine, l-glutamic acid, l-glutamine, l-histidine, l-lysine, l-phenylalanine, l-proline, l-serine, and l-tyrosine. Thus, bromine derivatives of amino acids may act as intermediates in the peroxidasecatalyzed generation of singlet oxygen.