Bromine In Aqueous Solution Research Articles

Kinetics and Mechanism of Selenium(IV) Oxidation by Aqueous Bromine Solution.

The bromine-selenite reaction at strongly acidic conditions was investigated by monitoring the absorbance-time traces at the isosbestic point of the bromine-tribromide system at a constant ionic strength (0.5 M adjusted by sodium perchlorate) and temperature. Despite the simplicity of the stoichiometry, the kinetics was found to be very complex. Although the formal kinetic orders of the reactants bromine and selenite are strictly 1, that of the hydrogen ion varies from -2 to less than -3 and notably depends on the initial bromide concentration as well. The bromide ion also inhibits the reaction, making the whole system as a sound example of efficient autoinhibition. We have clearly shown that the inhibitory effect of the bromide ion cannot be explained quantitatively by either exclusively considering the unreactivity of the tribromide ion over elemental bromine or driving the reaction via hypobromous acid formed from the well-known hydrolysis of bromine in aqueous solutions. Instead of that, bromonium ion transfer initiating equilibrium is suggested between the selenium(IV) and bromine species to produce bromide ion and SeO3Br- followed by the hydrolysis of this short-lived intermediate. This hydrolytic transformation was found to be catalytic with respect to hydroxide and bromide ions as well. We have also demonstrated that, among the wide variety of selenium species present in the acidic aqueous solution, the best result can be obtained by considering HSeO3 - as the kinetically active species toward bromine. The proposed mechanism containing 10 acid-base equilibria with known equilibrium constants, the above-mentioned initiating equilibrium, and the hydrolysis of SeO3Br- is able to fit all 49 kinetic absorbance-traces simultaneously, taking into account properly the most important characteristics of the measured data at strongly acidic conditions. Furthermore, this kinetic model was further extended by the direct reactions of hypobromous acid with selenium(IV) species suggested previously with reasonably modified rate coefficients to describe the pH dependence of the apparent second-order rate coefficients over the pH = 1-13 range, providing a useful tool to predict more accurately the kinetic behavior of selenium(IV) species in water treatment process conditions.

Bromine‐Terminated β‐Alkyl‐Substituted Tripyrrin: Reactivity, Coordination Ability, and Role as Extendable Acyclic Oligo‐Pyrrole Ligand

AbstractBromine‐terminated tripyrrin, a partial porphyrin structure, is synthesized by saponification of tripyrrane dimethyl ester and subsequent treatment with an aqueous bromine solution. In this reaction, bromine serves as a decarboxylating, oxidizing, and brominating agent. The resulting ligand can be coordinated with a metal ion such as Re+, which is not easily encapsulated in porphyrin cores. Nucleophilic substitution reactions at the brominated positions were also investigated, particularly the substitution with diethylamino and/or ethoxy groups. Structural elucidation was carried out by X‐ray crystallography, which revealed the flatter frameworks of the free bases and distorted geometries of the metal complexes. Such chemical modifications dramatically influence the photophysical properties, such as UV‐visible absorption, and are promising for bio‐related applications such as SPECT imaging probes.

A reversible absorption-based supported gas membrane process for enriching bromine from brine by using thin PTFE hollow fibers

Enrichment of bromine from brine using a PTFE hollow fiber-based supported gas membrane (SGM) process was studied. The experimental data demonstrated that the overall mass transfer coefficient obtained for feed containing Cl− such as real brine was much smaller than that for a simple aqueous bromine solution, which was mainly due to the association of Br2 with Cl− in the brine. Based on the stronger association between Br2 and Br− than that of Br2 and Cl−, NaBr instead of NaOH was selected as an absorbent for enrichment of bromine from brine. The results showed that NaBr as absorbent for enriching bromine using the SGM process was feasible and bromine could be enriched for > 14 times. Conventional distillation could be further applied to regenerate the stripping solution used, and a bromine-enriched stream was obtained as a raw product. A mathematical model was established to characterize the mass transfer of bromine when brine containing chloride ions was used as feed and NaBr or NaOH served as absorbents and the association between Br2 and Br− or Cl− was considered. The lab and pilot-scale study demonstrated that the PTFE membrane contactor was stable for a long-term operation of > 12 months.

Membrane extraction performances and simulation of bromine recovery with poly(vinylidene fluoride) hollow fibre membranes

In this work, the extraction performance of poly(vinylidene fluoride) hollow fibre membranes during bromine recovery from aqueous bromine solution was studied. The results showed that feed volume flow, feed solution concentration and temperature were vital for both flux and mass transfer coefficient; however, the stripping volume flow and stripping played a negligible role on both flux and mass transfer coefficient. A mathematical model was developed to predict the bromine recovery behaviour, and the results of this model agreed well with the experimental data.

Alternative Etching for Improved Cu-rich CuInSe2 Solar Cells

ABSTRACTTwo alternative chemical etchings (aqueous solution of bromine and bromine methanol solution) have been here tested to replace the KCN etching step in Cu-rich CuInSe2 based solar cells fabrication process. This new oxidative etch aims also at smoothing and thinning the as-grown films. This directly affects the interface between the absorber and the CdS buffer, interface which causes problems for Cu-rich solar cells. We present here the effect of these two alternative etchings on both the absorber surface and the solar cells parameters: whereas the bromine methanol etching destroys the solar cell, the aqueous solution of bromine leads to an improvement of the device through reduced interface and tunneling enhanced recombination.

OXIDATION OF AQUEOUS SOLUTION OF BROMIDE USING H2O2 , UV AND PEROXONE

In this study , aqueous solutions of bromine were prepared with different concentration ranging from (0.025, 0.030, 0.035, 0.040, 0.045 to 0.050 N ) . At the beginning the oxidation was done using only Hydrogen peroxide then only ultraviolet radiation at 254nm wave length with different periods of time as for an interval of 10 minutes each hour. Consequently , the Oxidation was done by using hydroen peroxide with ultraviolet radiation at the same wave length and at periodic time .The final used method , peroxone which includes , ozone added to hydrogen peroxide at rate of 40 g/L to 70 g/L for ozone was full fitted . Finally the production of each method for all concentrations and period was titrated with 0.1 N Sodium Thiosulfat to determine the concentration of Ion bromate BrO- 3 The results show that the ratio of the transformed ion bromide to ion Bromate the highest using hydrogen peroxide with ultraviolet radiation . As such peroxone method and finally the method followed where Hydrogen peroxide was specifically used .

A kinetic study of d-glucose oxidation by bromine in aqueous solutions

The kinetics of the oxidation of d-glucose to d-gluconic acid by bromine in aqueous solution were studied using potentiometric techniques and theoretical considerations of complex bromine–bromide–pH equilibria. The pH has a strong influence on reaction rate. At pH < 8 the reaction is very slow, while in the pH range pH 8–9.5 the reaction is sufficiently fast and seems optimal for the reaction. The proposed active species at that pH region is hypobromous acid. At pH > 9.5, the reaction is further accelerated due to the formation of hypobromite. The proposed kinetics expression for gluconic acid formation, based on the determined kinetic parameters at pH 9.24, is of the form d c(GA)/d t = 160 c 2(G) c 0(HOBr) c 0(H +) c 0(Br −)

Atomic force microscopic study of the chemical oxidation of silver crystals immobilized on platinum and on quartz

When silver crystals immobilized on a platinum surface are oxidized with a diluted aqueous solution of bromine, the morphological reaction scenario resembles very much that of the electrochemical oxidation described earlier [U. Hasse, F. Scholz, Electrochem. Commun. 6 (2004) 409–412], i.e., the oxidation can be described by a nucleation–growth kinetics via an oversaturated solution. In that reaction the platinum serves as local cathode for bromine reduction and the silver as the local anode. When the silver crystals are immobilized on an electronic insulator like quartz, the loci of reducing the bromine and oxidizing the silver are obviously the silver crystals. In that case one observes for sub-micrometer size Ag crystals that each crystal is converted to a silver bromide crystal. However, crystals of micrometer size leave ring-shaped structures of silver bromide.

Superconductivity and cobalt oxidation state in metastableNaxCoO2−δ∙yH2O(x≈1∕3;y≈4x)

We report the synthesis and superconducting properties of a metastable form of the known superconductor NaxCoO2*yH2O (x ~ 1/3, y ~ 4x). Instead of using the conventional bromine-acetonitrile mixture for sodium deintercalation, we use an aqueous bromine solution. Using this method, we oxidize the sample to a point that the sodium cobaltate becomes unstable, leading to formation of other products if not controlled. This compound has the same structure as the reported superconductor, yet it exhibits a systematic variation of the superconducting transition temperature (Tc) as a function of time. Immediately after synthesis, this compound is not a superconductor, even though it contains appropriate amounts of sodium and water. The samples become superconducting with low Tc values after ~ 90 h. Tc continually increases until it reaches a maximum value (4.5 K) after about 260 h. Then Tc drops drastically, becoming non-superconducting approximately 100 h later. Corresponding time-dependent neutron powder diffraction data shows that the changes in superconductivity exhibited by the metastable cobaltate correspond to slow formation of oxygen vacancies in the CoO2 layers. In effect, the formation of these defects continually reduces the cobalt oxidation state causing the sample to evolve through its superconducting life cycle. Thus, the dome-shaped superconducting phase diagram is mapped as a function of cobalt oxidation state using a single sample. The width of this dome based on the formal oxidation state of cobalt is very narrow - approximately 0.1 valence units wide. Interestingly, the maximum Tc in NaxCoO2*yH2O occurs when the cobalt oxidation state is near 3.5. Thus, we speculate that the maximum Tc occurs near the charge ordered insulating state that correlates with the average cobalt oxidation state of 3.5.

Stopped‐flow investigation of the reaction of hexabromoiridate(III) with bromine in aqueous solution

AbstractThe reaction of hexabromoiridate(III) with bromine to form hexabromoiridate(IV) and bromide ion was studied using a Durrum stopped‐flow spectrophotometer. Special precautions were taken while studying this reaction. All of the experiments were carried out within 3 min after preparation of the hexabromoiridate solution throughout this investigation in order to limit the amount of conversion of hexabromoiridate(III) to aquapentabromoiridate(III) before reaction with bromine. Very dilute solutions were used because of the rapidity of the reaction. The rate constant for the reaction at 24 ± 1°C was determined to be (3.2 ± 0.4) × 103 L mol−1 s−1. © 2004 Wiley Periodicals, Inc. Int J Chem Kinet 36: 623–626, 2004

Chemical elaboration of well defined Cu(In,Ga)Se 2 surfaces after aqueous oxidation etching

The present work is an attempt to prepare well defined surfaces of Cu(In,Ga)Se 2 (CIGS) thin films in order to answer to basic questions about the relationship between bulk and surface composition. The approach is to use an oxidative etch with an aqueous bromine solution, known to lead to specular surfaces. The CIGS surface is then analyzed by mechanical profilometry, SEM and XPS, allowing for determination of the surface roughness and the nature of surface species. After short time bromine etch, a Se 0 film is formed on the CIGS surface which can be completely removed by KCN treatment, leaving a CIGS specular surface. An highlight result is that under specific conditions, the surface composition is close to the stoichiometry of the Cu(In,Ga) 3Se 5 copper deficient phase. This is the first time that such a study is conducted on technology relevant thin polycrystalline CIGS film. It is expected that the method described will help conducting experiments (e.g. Angle resolved XPS, SIMS, etc.) with an improved resolution.

Evidence for cyclodextrin dioxiranes

α-Cyclodextrin, β-cyclodextrin, 2,6-di- O-methyl- β-cyclodextrin, methyl- β-cyclodextrin and sucrose have been oxidised by aqueous bromine solution at neutral pH. Both ketone and carboxylic acid containing materials are among the products of the oxidations. For α-cyclodextrin there is clear 13C NMR evidence for the presence of a ketone group and its hydrate form. This together with the continued ability of the product to complex p-nitrophenol indicates that the ketone is present at the secondary rim of an intact cyclodextrin ring. A pH dependence for the reaction of bromine with cyclodextrin shows that the maximum rate of bromine loss roughly coincides with the maximum concentration of hypobromous acid, HOBr, indicating that this is the reactive species in these oxidations. The results are consistent with a mechanism involving attack by one of the secondary hydroxyls of cyclodextrin on HOBr, with Br - leaving to yield an intermediate dehydroxy hydroperoxy cyclodextrin that subsequently decomposes to a keto-cyclodextrin via a Kornblum–De La Mare-type reaction. An alternative pathway prevails when the reaction is carried out under alkaline conditions, where carboxylic acids are the principle products. The keto derivatives produced by bromine oxidation at neutral pH are capable of catalysing the oxidation of p-nitrophenol and aryl–alkyl sulfoxides by peroxomono-sulfate in an analogous way to cyclohexanone, which is known to form a dioxirane upon reaction with peroxomonosulfate. It is likely that dioxirane formation is responsible for the observed catalysis in the present case also.

Oxidation of some organic compounds by aqueous bromine solutions

Oxidation of some organic compounds by aqueous bromine solutions

The reaction of perfluoroalkanesulfonyl halides VII. Preparation and reactions of trifluoromethanesulfonyl bromide

AbstractThe reaction between sodium trifluoromethanesulfinate, which was prepared from trifluoromethyl bromide, with bromine in aqueous solution resulted in the formation of trifluoromethanesulfonyl bromide (CF2SO2Br). CF3SO1Br reacted with alkenes and alkyne to give the corresponding adducts with the loss of SO2 in good yields, and with compounds containing active hydrogen to give brominated derivatives. A radical reaction mechanism was proposed and confirmed by EPR study.

Gemischt ionisch und elektronisch leitende derivate des polyvinylalkohols

By reacting poly(vinylalcohol) with elemental bromine in aqueous solution a partially oxidized copolymer of vinyl alcohol, β-bromo-vinyl alcohol, ketene, and bromo-ketene units obtained, which on treatment with aqueous alkali hydroxide yield salts with electric and ionic conductivity ( K 140°C⩽10 −3S cm −1).

ChemInform Abstract: Etching of GaP Single Crystals in Aqueous Bromine Solutions.

ChemInformVolume 21, Issue 42 Physical Inorganic Chemistry ChemInform Abstract: Etching of GaP Single Crystals in Aqueous Bromine Solutions. H. H. GOOSSENS, H. H. GOOSSENS Lab. Fys. Scheikd., Rijksuniv., B-9000 Gent, Belg.Search for more papers by this authorK. STRUBBE, K. STRUBBE Lab. Fys. Scheikd., Rijksuniv., B-9000 Gent, Belg.Search for more papers by this authorW. P. GOMES, W. P. GOMES Lab. Fys. Scheikd., Rijksuniv., B-9000 Gent, Belg.Search for more papers by this author H. H. GOOSSENS, H. H. GOOSSENS Lab. Fys. Scheikd., Rijksuniv., B-9000 Gent, Belg.Search for more papers by this authorK. STRUBBE, K. STRUBBE Lab. Fys. Scheikd., Rijksuniv., B-9000 Gent, Belg.Search for more papers by this authorW. P. GOMES, W. P. GOMES Lab. Fys. Scheikd., Rijksuniv., B-9000 Gent, Belg.Search for more papers by this author First published: October 16, 1990 https://doi.org/10.1002/chin.199042005Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume21, Issue42October 16, 1990 RelatedInformation

Aqueous bromine solutions from HBr by 3% hydrogen peroxide

The authors have found that ordinary 3% hydrogen peroxide purchased in any drugstore or supermarket is very effective in generating aqueous solutions of bromine for halogen displacement reactions.

On the etching of GaP single crystals in aqueous bromine solutions

The etch rate of n- and p-GaP single crystals was measured in aqueous Br 2 solutions, using a flow-cell set-up. The etching process was found to occur by a chemical mechanism, involving the formation of radical decomposition intermediates. The difference in etching kinetics between the (1̄1̄1̄)- and the (111)-face resulted in a difference in the morphology of the surface after etching. Incorporating the GaP crystals in an electrochemical cell gave a strong interrelationship was found between the cathodic reduction of Br 2, the chemical and the anodic etching of GaP.

Chemical Characterization of Bromine Oxidized Potato Starch

AbstractPotato starch was oxidized with a neutral aqueous bromine solution at seven different levels of molar ratios of bromine/starch (1/40–5/1). The molecular weight distribution of the products obtained was analysed by gel permeation chromatography on two different agarose gels, Sepharose CL‐2B and Superose 6. A gradually increased fragmentation of the molecules with increased oxidation level was noticed. Some of the modified samples were debranched and the products obtained were analysed by gel permeation chromatography. For comparison amylose and waxy maize starch were also treated at the 1/20 and 1/5 molar ratios. The results indicate that the amylose is more easily degraded to small fragments than amylopectin during the oxidation process. An enzymatic starch analysis method was applied on the oxidized samples. This method was found suitable for estimating the total content of introduced keto and carboxylic groups into the modified product.

Kinetics and mechanisms of the redox reaction of hexaaquotitanium(III) and the ethylenediamine tetraacetato titanium(III) complex by aqueous solutions of bromine

At 25°C, I = 1.0 M (CF 3SO 3 −Li ++CF 3SO 3H), [H +] = 0.034–0.274 M and λ = 453 nm, the rate equation for the oxidation of Ti(H 2O), 6 3+ by bromine was found to be: −d/[Br 2] T/d t= kK/[Br 2][Ti III]/[H +]+ K+ kK/[Br 3 −][Ti III]/[H ++ K, where k = 9.2 × 10 −3 M −1 s −1 and K = 4.5 × 10 −3 M. At [H +] = 1.0 M, [Br −] = 0.05–0.4 M, the apparent second-order rate constant decreases as [Br −] increases. The pH-dependence of the oxidation of Ti III-edta by bromine is interpreted in terms of the change in identity of the Ti III-edta species as the pH of the reaction medium changes. The second-order rate constants were fitted using a non-linear least-square computer program with (1/ k 0 edta) 2 weighting into an equation of the form: k 0 edta = k 1+ k 2 K 1[H +] −1+ k 3 K 1 K 2[H +] −2/1+ K 1[H +[H + −1+ K 1 K 2[H +] −2, with K 1 and K 2 fixed as earlier determined at 9.55 × 10 −3 and 2.29 × 10 −9 M, respectively, for the oxidation of bromine. k 1= k 2 =(3.1±0.32)×10 3M −1s −1 k 3=(2.3±0.45)×10 6N −1s −1. It is proposed that these electron transfer reactions proceed by univalent changes with the production of Br 2 .− as a transient intermediate. An outer-sphere mechanism is proposed for these reactions. The homonuclear exchange rate for Ti III-edta+Ti IV-edta is estimated at 32 M −1 s −1.