载溴树脂作为活泼芳香族化合物的溴化剂

用载溴树脂作为间甲基茴香醚、间甲酚等活泼芳香化合物的溴化剂，得到一溴代产物，产率为75～85%。该试剂反应条件温和，选择性好，是一种有效的活泼芳环的溴化剂。离子交换树脂可回收使用。     

The bromine catalysed oxidation of arsenic trifluoride by antimony pentafluoride

Antimony pentafluoride dissolves in excess arsenic trifluoride presumably with the formation of AsF₃·SbF₅ [1,2] and possibly (AsF₃)_nSbF₅ n = 2, [3], 3, [4], in equilibrium with one another and the solvent. However, O. Ruff [5] found in 1906 that in the presence of bromine, antimony pentafluoride oxidises arsenic trifluoride to arsenic pentafluoride with formation of a solid he suggested was SbBrF₄. In the course of our work we investigated this reaction and found that trace quantities of bromine (<0.1 mole per cent) catalyse the formation of arsenic pentafluoride and SbF₃·SbF₅ [6], according to equation (1).AsF₃ + 2SbF₅ = AsF₅ + SbF₃·SbF₅ (1)Reaction (2) is endothermic to the extent of ca. 33 Kcals mole^?1 [7–9], but reaction (1) occurs spontaneously in presence of bromine, being more favourable than reaction (2) by the heat of reaction (3).AsF₃ + SbF₅ = AsF₅ + SbF₃ (2)SbF₃ + SbF₅ = SbF₃·SbF₅ (3)     

Effect of bromide ion on the kinetics of bromination of o-hydroxy benzoic acid by bromine in aqueous solution

The kinetics of the bromination of o-hydroxy benzoic acid has been studied by rotating platinum electrode (RPE) technique. The bromide ion has been found to remarkably enhance the specific reaction rate. This is associated with a fall in energy of activation. The other added ions like nitrate, acetate and bicarbonate have shown that the base catalysis or salt effect is improbable. The mechanism suggested to explain the catalytic effect of bromide ions.     

Kinetics and mechanism of the oxidation of lower oxyacids of phosphorus by hexamethylenetetramine bromine

The oxidation of lower oxyacids of phosphorus by hexamethylenetetramine bromine (HABR) in glacial acetic acid resulted in the formation of corresponding oxyacids with phosphorus in a higher oxidation state. The reaction exhibited 2:1 stoichiometry. The reaction is first order with respect to HABR. Michaelis–Menten‐type kinetics were observed with respect to the acids. The formation constant of the phenylphosphinic acid–HABR complex also has been determined spectrophotometrically. The thermodynamic parameters for the complex formation and the activation parameters for their decomposition were calculated. The reaction showed the presence of a substantial kinetic isotope effect. It is proposed that the HABR itself is the reactive oxidizing species. It has been shown that the pentacoordinated tautomer of the phosphorus oxyacid is the reactive reductant. A suitable mechanism has been proposed. © 2000 John Wiley & Sons, Inc. Int J Chem Kinet 32: 165–170, 2000     

Kinetics and mechanism of the oxidation of substituted benzaldehydes by hexamethylenetetramine‐bromine

The oxidation of thirty‐six monosubstituted benzaldehydes by hexa‐methylenetetramine‐bromine (HABR), in aqueous acetic acid solution, leads to the formation of the corresponding benzoic acids. The reaction is first order with respect to HABR. Michaelis‐Menten–type kinetics were observed with respect to aldehyde. The reaction failed to induce the polymerization of acrylonitrile. There is no effect of hexamethylenetetramine on the reaction rate. The oxidation of [²H]benzaldehyde (PhCDO) indicated the presence of a substantial kinetic isotope effect. The effect of solvent composition indicated that the reaction rate increases with an increase in the polarity of the solvent. The rates of oxidation of meta‐ and para‐substituted benzaldehydes showed excellent correlations in terms of Charton's triparametric LDR equation, whereas the oxidation of ortho‐substituted benzaldehydes correlated well with tetraparametric LDRS equation. The oxidation of para‐substituted benzaldehydes is more susceptible to the delocalization effect but the oxidation of ortho‐ and meta‐substituted compounds displayed a greater dependence on the field effect. The positive value of γ suggests the presence of an electron‐deficient reaction center in the rate‐determining step. The reaction is subjected to steric acceleration when ortho‐substituents are present. © 2000 John Wiley & Sons, Inc. Int J Chem Kinet 32: 615–622, 2000     

Debundling of carbon single-walled nanotubes at oxidation of bromine ions

An electrochemical method of modification of carbon single-walled nanotubes at anodic polarization in aqueous solutions of potassium bromide is proposed. Bundles of nanotubes disperse under superposition of anodic potentials without damage of structure of individual nanotubes as revealed by cyclic voltammetry, electron microscopy, and small-angle X-ray scattering. On the basis of elemental and thermogravimetric analyses data obtained for the initial and processed samples, the mechanism of nanotube modification is proposed for potassium bromide electrolysis in aqueous solution.     

Kinetics and mechanism of the oxidation of nitrous acid by bromine in aqueous sulfuric acid

The kinetics and mechanism of the reaction between nitrous acid and bromine are studied in dilute sulfuric acid medium, using both the stopped‐flow method and conventional spectrophotometry. The partial reaction order with respect to Br₂ moderately differs from 1, showing a saturation at a higher concentration of bromine. The second order of the reaction towards nitrous acid has been observed. Hydrogen and bromide ions significantly suppress the rate of reaction. Despite the apparent simplicity, the mechanism is rather complex, with two reaction pathways proposed. The first one is represented by the reaction of bromine with the intermediate dinitrogen trioxide. A direct nucleophilic attack of NO₂⁻ ion towards the bromine molecule is suggested as the second pathway. The proposed mechanism accounts for the observed behavior; in almost all cases a satisfactory quantitative agreement with the experiments is obtained. © 2000 John Wiley & Sons, Inc. Int J Chem Kinet 32: 279–285, 2000     

Visible light-mediated photocatalytic bromination of 2-arylimidazo[1,2-a]pyridines using CBr4 as bromine source

Abstract

The photocatalytic bromination of 2-arylimidazo[1,2-a]pyridines is described in this paper. This reaction uses the readily accessible and shelf-stable CBr₄ as a bromine source. This photocatalytic system is shown to serve as a convenient and practical synthetic protocol for the preparation of 2-aryl-3-bromoimidazo[1,2-a]pyridines.     

S-oxygenation of thiocarbamides IV: Kinetics of oxidation of tetramethylthiourea by aqueous bromine and acidic bromate

The kinetics and mechanism of oxidation of tetramethylthiourea (TTTU) by bromine and acidic bromate has been studied in aqueous media. The kinetics of reaction of bromate with TTTU was characterized by an induction period followed by formation of bromine. The reaction stoichiometry was determined to be 4BrO(3)(-) + 3(R)(2)C═S + 3H(2)O → 4Br(-) + 3(R)(2)C═O + 3SO(4)(2-) + 6H(+). For the reaction of TTTU with bromine, a 4:1 stoichiometric ratio of bromine to TTTU was obtained with 4Br(2) + (R)(2)C═S + 5H(2)O → 8Br(-) + SO(4)(2-) + (R)(2)C═O + 10H(+). The oxidation pathway went through the formation of tetramethythiourea sulfenic acid as evidenced by the electrospray ionization mass spectrum of the dynamic reaction solution. This S-oxide was then oxidized to produce tetramethylurea and sulfate as final products of reaction. There was no evidence for the formation of the sulfinic and sulfonic acids in the oxidation pathway. This implicates the sulfoxylate anion as a precursor to formation of sulfate. In aerobic conditions, this anion can unleash a series of genotoxic reactive oxygen species which can explain TTTU's observed toxicity. A bimolecular rate constant of 5.33 ± 0.32 M(-1) s(-1) for the direct reaction of TTTU with bromine was obtained.     

The kinetics and mechanism of the oxidation of formic acid by bromine in acid aqueous media

The reaction between formic acid and bromine in strongly acid aqueous media at 298 K was studied by absorption spectrophotometry (λ = 447 nm). Reaction rates, expressed as R = -d[Br₂]/dt, depend on the concentrations of HCOOH (0.3–2.4M), Br₂[(2.7–13.6) × 10^?3M], H⁺ (0.03–2.0M), and Br^? (up to 0.6M). The mechanism with k₁ = 20.2 ± 1.2 M^?1 sec^?1, pK₂ = 3.76, pK₃ = ?1.20, accounts for all experimental observations. Br₃^? and HCOOH can be considered unreactive within experimental error. Apparent deviations from the basic mechanism at higher acidities can be quantitatively ascribed to the nonideality of ionic species.     

过氧化氢氧化酸性铬兰K催化动力学光度法测定溴离子

在中性条件下,游离的Br-对H2O2氧化酸性铬兰K褪色反应具有催化作用。基于此建立了测定微量Br-的催化光度分析方法。结果表明,该方法最大吸收波长为525 nm,测定的线性范围为0.4μg/mL～11.2μg/mL,检出限为0.321μg/mL。方法用于河水中微量Br-的测定,结果令人满意     

Anomalous kinetic hydrogen isotope effect in the oxidation of formate by bromine: Tunneling via an intermediate

Rates of oxidation of XCOO^? (X = H, D) by Br₂ in acid aqueous media were measured between 274 and 332 K. The derived Arrhenius parameters for both reactions where θ = 4.575T × 10^?3 kcal/mol, with (k_H/k_D)_298K = 2.85, reveal a primary isotope effect, but the difference (E_D - E_H) = 3.29 kcal/mol and the ratio A_D/A_H = 91 fall beyond the limits imposed by semiclassical transition-state theory, suggesting tunneling or a multiple-stage mechanism. However, it can be shown that either tunneling in a single step or a three-step, internal return mechanism can be ruled out as alternative models, since both require unreasonable kinetic parameters to fit the data. The simplest scheme accounting for the present observations involves tunneling in the decomposition of a charge transfer complex in equilibrium with the reactants.     

Selective oxidation of sulfides and oxidative bromination of organic substrates catalyzed by polymer anchored Cu(II) complex

A new polymer-anchored Cu(II) complex has been synthesized and characterized. The catalytic performance of the complex has been tested for the oxidation of sulfides and in oxidative bromination reaction with hydrogen peroxide as the oxidant. Sulfides have been selectively oxidized to the corresponding sulfoxides in excellent yields and in the presence of KBr as the bromine source, organic substrates have been selectively converted to mono bromo substituted compounds using polymer-anchored Cu(II) catalyst. This catalyst showed excellent catalytic activity, high selectivity, and recyclability. The polymer-anchored Cu(II) catalyst could be easily recovered by filtration and reused more than five times without appreciable loss of its initial activity.