Brominated and iodinated thiofluoresceins

Conditions were found for the synthesis of mono-, di-, tri-, and tetrabromo- and -iodo-substituted thiofluoresceins. Iodination and bromination of thiofluorescein with molecular iodine and bromine in 1 N aqueous sodium hydroxide gave mixtures of the corresponding 2,4,5,7-tetra- and 2,4,5-trihalo derivatives in 71/14 (Y = I) and 73/13% yield (Y = Br), respectively. In the reactions of thiofluorescein with bromine in acetic acid and with iodine in methanol at a substrate-to-halogen ratio of 1 : 2, 4,5-dibromo- and 4,5-diiodothiofluoresceins were isolated in 56 and 67% yield. Analogous reactions with equimolar amounts of the reactants produced 59% of 4-bromothiofluorescein and 51% of 4-iodothiofluorescein.     

Bromine cyanide as titrimetric oxidant in non-aqueous media

Bromine cyanide has been used for the potentiometric determination of sulphide, sulphite, thiocyanate, iodide, tin(II), arsenic(III),hydrazine hydrate, phenylhydrazine, 1,1-methylphenyldrazine and chloralhydrazine in glacial acetic acid and 1 : 1 acetic acid-acetic anhydride mixture, of thiourea, ethylthiourea, isopropylthiourea, benzylthiourea, alpha-phenylthiourea and o-tolythiourea in methanol, and of sodium methyl-, ethyl-,dimethyl-, diehtyl- and isopropyldithiocarbamates in ehtanol and acetonitrile media. The behaviour of bromine cyanide in these non- aqueous solvents has been compared with its behaviour in aqueous medium and with that of iodine cyanide in these non-aqueous solvents.     

Application of differential pulse polarography to the assay of ascorbic acid

A polarographic method for the determination of ascorbic acid in pharmaceutical preparations and fruit juices is described. The method is based on the oxidation of ascorbic acid by iodine, and the resulting iodide, after removal of excess iodine, is oxidized with bromine to iodate which is measured polarographically. The method enables analysis of solutions as dilute as 1.7 × 10^?6M ascorbic acid.     

笼形聚偕氨肟树脂吸附溴和碘

用酸、碱处理的笼形聚偕氨肟树脂（ACAO、BCAO）吸附溴和碘,发现它们的吸附能力无显著差别。吸附客量与溴和碘浓度关系符合Freundlich方程．从扫描电子显微镜观察到碘在树脂表面形成微晶．联系到溴和碘的超当量吸附现象,初步认为,它们是通过物理吸附在树脂表面富集。     

Titrimetric microdetermination of uric acid and thioglycollic acid by amplification reactions

A simple amplification method for determination of 0.05-2 mg of uric acid or thioglycollic acid has been worked out. It depends on iodine oxidation of the uric acid or thioglycollic acid solutions, removal of the excess of iodine, oxidation of the resulting iodide with bromine, and iodometric titration of the resulting iodate. The coefficient of variation ranges from 0.7 to 2.4% for uric acid and from 0.5 to 1.9% for thioglycollic acid, depending on the amount of the acid.     

Titrimetric determination of some organic compounds with bromine chloride

Bromine chloride is used in hydrochloric acid medium as a standard reagent for the rapid and precise determination of organic compounds by direct or indirect titrimetric methods. Hydrazine and its aryl derivative undergo a 4-electron change. Carbonyl compounds are determined by reaction with excess of 2,4-dinitrophenylhydrazine and estimation of the surplus. Sulphanilamide undergoes a substitution reaction in 1:3 molar ratio to bromine chloride. Thiobarbituric acid and thiourea or its alkyl derivatives show an 8-electron change but aryl thioureas also undergo nuclear bromination. Thiosemicarbazide and semicarbazide give a 10- and a 2-electron change respectively. In the direct titration, methionine is oxidized to its sulphoxide whereas cystine and cysteine form cysteic acid. In presence of bromide, glutathione forms the sulphonic acid but in the presence of iodide the product is the disulphide. The analytical results obtained by bromine chloride method are compared favourably with those afforded by established procedures.     

Iodimetric determination of organolead compounds

A sensitive, rapid and accurate titrimetric method has been developed for the determination of 50-5000 mug of ethyl-lead or phenyl-lead compounds, based on their oxidation with a chloroform solution of iodine, removal of the excess of iodine, oxidation of the resulting iodide with bromine, and iodometric titration of the iodate formed. The coefficient of variation does not exceed 1.2% for amounts > 1000 mug of the organolead compound, but increases to 2.8% for the 50-mug level. The ethyl- and phenyl-lead compounds can be determined independently in mixtures.     

A two-step mimic for direct, asymmetric bromonium- and chloronium-induced polyene cyclizations

Although direct, asymmetric, halonium-induced cyclizations have proven difficult to achieve in the absence of enzymes, this report provides a two-step alternative based on reacting polyenes with chiral mercury(II) complexes to afford a number of polycyclic organomercurials that can be subsequently converted, with retention, into their corresponding chlorine, bromine, and iodine derivatives in good yield and enantioselectivity. A five-step asymmetric total synthesis of the natural product 4-isocymobarbatol is also described.     

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     

Titrimetric microdetermination of salicylic, acetylsalicylic, and p-hydroxybenzoic acids by amplification reactions

A novel titrimetric method with amplification has been developed for the determination of 0.05–2.0 mg of salicylic, acetylsalicylic, or p-hydroxybenzoic acid. It depends on bromination of these compounds by bromine to tribromophenylhypobromite, which liberates iodine when treated with iodide. The liberated iodine is extracted with chloroform, reduced to iodide, oxidation of the resulting iodide with bromine, and iodometric titration of the iodate produced gives the sixfold amplification method. The coefficient of variation does not exceed 1% for above 0.5 mg of the studied compounds, but increases to 2.8% at the 0.05-mg level.     

Characterization and analysis of new catalysts for a direct ethanol fuel cell

A direct ethanol fuel cell offers an attractive, fairly high density, energy source, if an electrochemical system can be developed that efficiently carries out the 12-electron oxidation of ethanol to carbon dioxide and water. To that end, new catalyst systems must be developed along with fuel cell operating conditions that encourage the complete oxidation of ethanol, as opposed to the presently available platinum on carbon systems that tend to produce acetaldehyde (two-electron oxidation) or acetic acid (four-electron oxidation) products. It is found that a composite nanoparticulate catalyst containing platinum and tin oxide or platinum indium tin oxide allows the partial conversion of ethanol to its 12-electron oxidation products. Catalysts of this type can be formed using a modified polyol process. Elevation of the operating temperature of a proton exchange membrane fuel cell using the indicated catalysts to 130 degrees C facilitates the production of carbon dioxide and provides an improved current-voltage response.     

Estimation of glutathione with chloramine-T and dichloramine-T

A simple but accurate method for the estimation of glutathione in aqueous solution has been developed, based on its oxidation with chloramine-T and dichloramine-T at room temperature. The direct titration with a visual or potentiometric end-point involves a one-electron change, corresponding to the oxidation of the thiol group to disulphide. Most amino-acids do not interfere, but cysteine, methionine and thiourea are oxidized under these conditions. A back-titration procedure in which glutathione is oxidized by excess of chloramine-T with a 10-electron change at pH 5 has also been developed.     

N-Bromosuccinimide assisted oxidation of 5-aminopyrazoles: formation of bis diazenylderivatives

Treatment of 5-amino-4-cyanopyrazoles with N-bromosuccinimide, in DMF at rt gave azo dyes resulting from dimerization through the amino groups and further oxidation.With bromine water the dimer was also formed but, bromination occurred on the aryl ring, either at reflux or rt. Reduction of the azo group with zinc in acetic acid originated the corresponding pyrazoles.     

Decomposition Studies of Aqueous Phase Ligands Used in Advanced Reprocessing Flowsheets

Two potential methods for decomposing organic ligands in nitric acid have been studied using acetic acid and diethylenetriaminepentaacetic acid (DTPA) as examples; these methods were oxidation by nitric acid at elevated temperatures (70-110 °C) and electrochemical oxidation, both direct and mediated electrochemical oxidation. Based on total carbon measurements, acetic acid proved to be rather stable against nitric acid oxidation whereas 60-80% of DTPA was decomposed at 100-110°C. Electrochemical oxidation methods were generally more effective in decomposing acetic acid and DTPA with mediated electrochemical oxidation using Ag(II) ions the most effective method under the conditions tested, with ∼80 and >90% loss of carbon from acetic acid and DTPA solutions respectively, at ambient temperature in 6 M HNO₃.     

Preparation and some reactions of halomagnesium diorganocuprates

Bromomagnesium diphenylcuprate and iodomagnesium dimethylcuprate have been prepared, and their thermal stability and some of their reactions investigated. In diethyl ether, 50% of the BrMgPh₂Cu decomposes in 12h at room temperature and 50% of the IMgMe₂Cu decomposes at 0°C in 14 but the cuprates are more stable in THF at or below 0°C. They react with acid chlorides to give 16–76% yields of the corresponding ketones. With bromine and iodine, BrMgPh₂Cu gives bromobenzene and iodobenzene in 56 and 48% yield, respectively. Oxidation of BrMgPh₂Cu with nitrobenzene or copper(II) chloride gives, respectively, 61 and 34% of biphenyl. Reaction of BrMgPh₂Cu with acetic or benzoic anhydride yields 46–55% of the corresponding ketone and 34–37% of the corresponding carboxylic acids.     

Structure Determination of Brominated Morphinan-6-ones by 13C-NMR. Spectroscopy: A novel closure of the oxygen bridge using 4-acetoxymorphinan-6-ones

Bromination of (?)-4-hydroxy-N-methylmorphinan-6-one ( 3 ), prepared from natural morphine, with 1 mol of bromine in acetic acid, afforded the 1-bromo ketone 5 . The structure of 5 was assigned by ¹³C-NMR.spectroscopy, and confirmed by X-ray diffraction analysis of its hydrobromide salt. It is suggested that monobromination of synthetic (±)-2,4-dihydroxy-N-formylmorphinan-6-one ( 7 ) takes in principle a similar course, although the ¹³C-NMR.spectrum of the primary reaction product 9 could not be measured because of insolubility in commonly used solvents. Monobromination of (?)-4-acetoxy-N-formylmorphinan-6-one ( 12 ) of the natural series, and of (±)-2,4-diacetoxy-N-formylmorphinan-6-one ( 8 ) of the synthetic series, followed by treatment of the monobrominated ketones with potassium carbonate in methanol resulted in closure of the O-bridge, and afforded after acid hydrolysis, the corresponding 4,5-epoxy-morphinan-6-ones (?)- 16 and (±)- 17 respectively. This variation of the ring closure reaction represents a novel and convenient method to convert 4-hydroxymorphinan-6-ones into their corresponding 4,5-epoxymorphinan-6-ones, without involving aromatic bromination and with only 1 mol of bromine.     

Degree of solid-phase oxidation of nickel and cobalt phthalocyanines by halogens

Electronic and IR transmission spectroscopy and ESR have been used to investigate the products obtained in the oxidation of layes of nickel and cobalt phthalocyanines by halogen vapors. It has been established that cobalt phthalocyanine in chlorine or bromine vapor forms stable cation radicals in which one electron has been detached from the cobalt and the other from the phthalocyanine ligand; in iodine vapor, a partially oxidized product is formed, with a positive charge on the ligand. Nickel phthalocyanine in bromine vapor at high pressure of bromine, and also in chlorine or iodine vapor, nickel phthalocyanine forms partially oxidized products with various degrees of oxidation of the ligand. An interpretation is given for the spectra of the ionic species that have been investigated; the interpretation can be used in particular to determine the degree of the ionic species on the basis of their spectra.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 25, No. 5, pp. 528–534, September–October, 1989.The authors wish to thank A. V. Baranov for measuring the Raman spectrum of the bromine-oxidized Copc.     

Effect of bromine oxidation on high-performance thin-layer chromatography multi-enzyme inhibition assay detection of organophosphates and carbamate insecticides

Following high-performance thin-layer chromatography, thiophosphate pesticides, which inhibit choline esterases, are detectable using a multi-enzyme inhibition assay (HPTLC-EI) based on rabbit liver esterase (RLE), Bacillus subtilis (BS2) esterase, or cutinase (from Fusarium solani pisi). Because choline esterase inhibition is more effective after conversion of thiophosphate thions into their corresponding oxons, a pre-oxidation step was added to the HPTLC-EI assay. Bromine vapour was found to be more effective than iodine or UV irradiation for oxidation. Following oxidation, the inhibitory strength of parathion, parathion-methyl, chlorpyrifos, chlorpyrifos-methyl, and malathion, expressed as HPTLC enzyme inhibition factors (f(i)), increased by approximately 2 orders of magnitude. In contrast, bromine oxidation of organophosphate and carbamate insecticides resulted in a slight reduction in their inhibition factors, due to partial bromination and degradation of the parent compounds, while bromine oxidation increased the inhibition factors for demeton-S-methyl and propoxur. Apple juice and water samples spiked with paraoxon (0.001 mg/L), parathion (0.05 mg/L), and chlorpyrifos (0.5 mg/L) were used to test the HPTLC-EI system, resulting in mean recoveries of 95-106% and 91-102% for RLE and cutinase, respectively.     

对叔丁基甲苯的直接电解氧化

由对叔丁基甲苯合成对叔丁基苯甲醛,主要有化学氧化法、空气(或氧气)催化氧化法和电化学氧化法。化学氧化法通常使用二氧化锰作氧化剂,在浓硫酸中氧化合成对叔丁基苯甲醛。此法的主要缺点是产生大量的硫酸锰,需回收处理。另外,浓硫酸介质腐蚀设备且对环境有一定影响。空气催化氧化     

2,4-Dioxohexahydropyrimidine derivatives V. 5-Bromo-6-alkoxydihydroorotic acids,amides, and esters

The corresponding 5-bromo-6-alkoxydihydroorotic acid derivatives were obtained by reaction of orotic acid, its methyl ester, and amide with bromine in methanol and ethanol. The reaction of methyl and butyl orotates with methyl and ethyl hypobromites gives 5,5-dibromo-6-alkoxydihydroorotic acid esters. Isoorotic acid reacts with methyl hypobromite to give 5,5-dibromo-6-methoxydihydrouracil.