Complex formation in concentrated sulfuric acid between selenium(iv) and 1,1'-dianthrimide

The complex formation in concentrated sulfuric acid between selenium(IV) and 1,1'-dianthrimide (Di) was studied by spectrophotometry, infrared spectroscopy and chemical analysis. The system was found to contain two species, a Se₂Di complex and aselenium-1,2,7,8-diphthaloylcarbazole complex. The primary complex reaction was assumed to be the formation of the Se₂Di compound; unter certain experimental conditions one selenium atom is split off, resulting in the irreversible formation of a carbazole bond. The selenium-1,2,7,8-diphthaloylcarbazole was prepared in the solid state.     

The composition of the complex formed in concentrated sulfuric acid between boric acid and 1,1'-dianthrimide

The complex formed in concentrated sulfuric acid between boric acid and 1,1'-dianthrimide was isolated in the solid state. It was found to consist of one six-membered boron-containing ring of the type reported by Gillespie and rohinson and two 1,1'-dianthrimide molecules, the molecular formula being C₅₆H₂₈N₂O₁₃B₂S. It is suggested that other reagents reacting with boric acid in concentrated sulfuric acid form complexes of the same type.     

Complex formation in concentrated sulfuric acid between boric acid and quinalizarin or alizarin

The complex formation in concentrated sulfuric acid between boric acid and quinalizarin (1,2,5,8-tetrahydroxyanthraquinone) or alizarin (1,2-dihydroxyanthraquinone) was studied by spectrophotometry. Both systems contained only one species, viz. a complex between one boric acid and one hydroxyanthraquinone molecules. The reactions of boric acid with hydroxyanthraquinones are discussed and compared with the reaction of boric acid with 1,1'-dianthrimide.     

o-Diamines as reagents for selenium : Part I. 4-dimethylamino-1,2-phenylenediamine

4-Dimethylamino-1,2-phenylenediamine is investigated as a photometric and qualitative reagent for selenium. With this reagent selenium (IV) forms 5-dimethylamino-2,1,3-benzoselenadiazole, a red colored compound, with an absorption maximum in the visible region at 500 mμ. Variables such as reagent stability, extinction stability, reaction rate, influence of acidity, foreign ions, validity of Beer's law are discussed. The reagent is highly selective for selenium, has good sensitivity and recproducibility, and is also useful for qualitative purposes.     

Complex formation in concentrated sulfuric acid between 1,1'-dianthrimide and germanium(IV) or tellurium(IV)

The complex formation in concentrated sulfuric acid between I,I'-dianthrimide (Di) and germanium or tellurium (IV) was studied by spectrophotometry. The systems contained only one species, GeDi or TeDi; the stability constants in 93.2% sulfuric acid were calculated to be 221 and 228, respectively.     

Polybrominated oxydiphenol derivatives from the sponge dysidea herbacea: Structure determination by analysis of 13C spin-lattice relaxation data for quaternary carbons and 13C-1H coupling constants

Five polybrominated oxydiphenol derivatives have been isolated from various Great Barrier Reef collections and one Fijian collection of the sponge Dysidea herbacea: 3,4',5,6,6'-hexabromo-2, 2'-oxydiphenol (11), 3,4',5,6,6'-pentabromo-2,2'-oxydiphenol (12), 3.4',5,6,6'-pentabromo-2,2'-oxydiphenol 1-methyl ether (13), 3,4,4',5,6'-pentabromo-2,2'-oxydiphenol 1,1'-dimethyl ether (14) and 3,4',5,6'-tetrabromo-2,2'-oxydiphenol 1'-methyl ether (15).The structure of the first member of this series is determined by a new method involving ¹³C spin-lattice relaxation data. The contributions of nearby hydrogens to quaternary carbon spin-lattice relaxation times are calculated for various possible structures and compared with the experimental data, leading to an unequivocal proof of structure. The structures of the remaining compounds in the series are established principally by analysis of ¹³C chemical shifts and ¹³C-¹H coupling constants.     

Enantioselective Oxidation of Thioethers. An Improved Route to the Resolution of [1,1′-Binaphthalene]-2,2′-Dithiol

Abstract

(±)-[1,1′-Binaphthalene]-2,2′-bis-methylthioether (±)-1 was oxidized with high enantioselectivity by using our asymmetric reagent [Ti(IV) : (+)-DET : TBHP = 1 : 4 : 2]. An appropriate substrate/oxidant ratio afforded such a product distribution that allowed us to obtain, after chromatographic separation and chemical transformations, optically pure [1,1′-binaphthalene]-2,2′-dithiol in ca. 80% yield based on the racemic starting material.     

Syntheses of dibenzo[c,e][1,2]diselenin and related novel chalcogenide heterocyclic compounds

Reaction of 2,2′-dilithio-1,1′-binaphthyl with selenium followed by air oxidation gives a mixture of dinaph-thoselenophene and dimer and oligomers of 2,2′-diseleno-1,1′-binaphthyl. 2,2′-Dilithio-1,1′-biphenyl reacts with selenium to afford dibenzo[c,e][1,2]diselenin. Structures of the dimeric 2,2′-diseleno-1,1′-binaphthyl and dibenzo[c,e][1,2]diselenin have been confirmed by X-ray crystallographic analyses. Similar reaction of 2,2′-dilithio-1,1′-binaphthyl with sulfur or tellurium gives a mixture of dinaphthothiophene and dinaphtho[2,1-c:-1′,2′-e][1,2]dithiin or a mixture of dinaphthotellurophene and oligomer of 2,2′-ditelluro-1,1′-binaphthyl, respectively. Dibenzotellurophene and oligomer of 2,2′-ditelluro-1,1′-biphenyl are obtained from reaction of 2,2′-dilithio-1,1′-biphenyl with tellurium.     

Scandium triflate-catalyzed 6,6′-diiodination of 2,2′-dimethoxy-1,1′-binaphthyl with 1,3-diiodo-5,5-dimethylhydantoin

Scandium triflate-catalyzed iodination of 2,2′-dimethoxy-1,1′-binaphthyl with 2 equiv of 1,3-diiodo-5,5-dimethylhydantoin (DIH) proceeded to give 6,6′-diiodo-2,2′-dimethoxy-1,1′-binaphtyl in 98% yield and subsequent deprotection of methyl groups provided 6,6′-diiodo-1,1′-binaphthol, which is a useful ligand or reagent for many enantioselective transformations. Use of 2 equiv of NIS in place of DIH in the presence of scandium triflate, however, did not successfully yield 6,6′-diiodo-2,2′-dimethoxy-1,1′-binaphtyl, indicating that one of two types of iodine atoms in DIH is more reactive toward the iodination than iodine in NIS.     

Trennung von Selen und Tellur mit Hilfe von Bismuthiol II

Zusammenfassung Tellur(IV) läßt sich von Selen(IV) durch Ausschütteln der Bismuthiol II-Verbindung mit Chloroform trennen. Der pH-Wert der Ausgangslösung muß zwischen pH 4,5 und 4,7 liegen, die Reagenszugabe darf erst nach der pH-Einstellung erfolgen.

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Separation of selenium and tellurium by means of Bismuthiol II

Tellurium(IV) can be separated from selenium(IV) by extracting the Bismuthiol II complex with chloroform at pH 4.5–4.7 of the aqueous solution. The addition of the organic reagent must be made after adjusting the pH.

     

Measurements of sub-nanosecond lifetimes by means of nanosecond laser pulses

It is shown that the lifetimes of excited states of molecules which give a reasonably strong absorption (molar decadic extinction coefficient ∈ > 10⁴M^?1cm^?1) at the frequency of the ruby laser can be determined from the saturation of the optical transitions. This is illustrated for DDI (1,1'-diethyl-2,2'-dicarbocyanine iodide) in glycerol, which appears to have a lowest excited state with a lifetime of 110 psec. This value agrees fairly well with that calculated from the formula for the rate of internal conversion derived from Siebrand's work. Under favourable conditions lifetimes as short as 10 psec can be measured.     

Investigation of the iron(II) complex of bis-3,3'-(5,6-dimethyl-1,2,4-triazine)

The reagent, bis-3,3'-(5,6-dimethyl-1,2,4-triazine) (BDMT), forms intensely colored complexes with selected transition metal ions. The reagent is water-soluble and easily prepared. An intense orange complex, Fe(BDMT)₃²⁺;is formed on reaction of iron(II) with the reagent in aqueous solution at pH 4.0–7.0. Nuclear magnetic resonance data show that chelation occurs between the 2,2'-nitrogens of the reagent. The complex exhibits absorption maxima at 408 mμ, with molar absorptivities of 12,000 and 15,000 respectively. The perchlorate salt of the complex is readily extracted into nitrobenzene. A proposed spectrophotometric method for the determination of iron is both accurate and precis     

Crown ethers with converging neutral binding sites: Synthesis and complexation with t-butylammonium hexafluorophosphate

The influence of substituents in close proximity to crown ether cavities, on the stability of complexes of the crown ethers with t-butylammonium salts, has been investigated. Crown ethers with intra-annular donor substituents (2–4) were prepared by the reaction of 2-acetylresorcinol (1) with polyethylene glycol ditosylates and subsequent modification of the acetyl group. Crown ethers with substituents above and below the plane of the crown ether 0 atoms were synthesized by the reaction of 2,2'-dihydroxy-1,1'-biphenyls with polyethylene glycol ditosylates. Chloromethylation of 5,5'-dimethyl-1,1'-biphenyl crown ethers (6) yielded 4,4'-bis(chloromethyl)-1,1'-biphenyl crown ethers (10). 3,3'-Disubstituted-1,1'-biphenyl crown ethers (13–24) were synthesized by the reaction of 3,3'-diallyl-2,2'-dihydroxy-1,1'-biphenyl (12) with polyethylene glycol ditosylates. The allyl groups of 13 were isomerized with sodium hydride to propen- 1-yl groups. Ozonolysis of 13 and 14 gave the corresponding dialdehydes (15 and 18) which were converted into other 3,3'-disubstituted biphenyl-20-crown-6 derivatives (RCH₂COOMe, CH₂COOH, CH₂OH, CH₂Cl, CH₂OMe, OH and Me) by standard operations. The thermodynamic stability of the complexes of these functionalized crown ethers with t-butylammonium hexafluorophosphate has been studied in deuterochloroform in competition experiments with m-xyleno-18-crown-5 and benzo-15-crown-5 as the reference compounds. The nature of the 2-substituents in the crown ethers 2 and 3 has little effect on the stability of the complexes. The stability of the complexes of 3,3'-disubstituted biphenyl crown ethers depends of ringsize and the size and nature of the substituents. The most stable complexes are those of 24 (R = Me) and 14 (R=CH=CHMe).The Me groups in 24 represent the optimum between relief of O-O repulsion in the polyether ring and steric hindrance of complexation. The propen-1-yl substituents of 14 stabilize the complex because they provide extended π-electron donor stabilization. Substitution at the 4- and 4'-positions of the aryl groups has little effect on the stability of the complexes.     

Fabrics and papers modified with analytical reagents for the test determination of selenium(IV) and tellurium(IV)

It is shown that Malachite Green and Crystal Violet immobilized on viscose fabrics can be used as reagents for the rapid determination of selenium(IV) and tellurium(IV). Selenium is determine by the color intensity of ion associates formed by the reagents with the triiodide ion formed upon the reduction of selenium(IV) with potassium iodide and tellurium, by the color intensity of reagent ion associates with telluromolybdic heteropoly acid. The analytical ranges for selenium and tellurium(IV) were 0.005–0.5 and 0.01–0.1 mg/L upon passing 20 and 100 mL of a test solution through the indicator matrix, respectively. The duration of analysis does not exceed 15–20 min. The relative standard deviation is 50%. Test strips were proposed for determining 0.1–100 mg/L selenium(IV) and 1–1000 mg/L tellurium(IV) by the length of the colored zone. The determination of selenium(IV) is based on the oxidation of 4-nitrophenylgydrazine to its diazonium salt and salt interaction with naphthylamine chemically immobilized on paper with the formation of a red azo compound. The determination of tellurium(IV) is based on its reaction with Bismuthol II immobilized on a paper.     

State mixing and cd spectra of chiral molecules consisting of two identical chromophores

A study is reported of the effect of electronic state mixing on circular dichroism spectra of chiral molecules containing two identical chromophores. The CD spectrum of dimethyl-1,1'-bianthry1-2,2' dicarboxylate is intepreted in terms of such mixing between the ¹L_a and ¹B_b states of the anthracene moicty.     

Spiro Compounds of Tin,Selenium and Tellurium Containing 1,3,2‐Diazaelement‐[3]ferrocenophane Units

The reactions of 1,1′‐bis[Li(trimethylsilyl)amino]ferrocene ( 2a ) with selenium‐ or tellurium tetrahalides gave the 1,1′,3,3′‐tetrakis(trimethylsilyl)‐1,1′,3,3′‐tetraaza‐2‐selene‐ and 2‐tellura‐2,2′‐spirobi[3]ferrocenophanes 5 and 6 , respectively. The analogous reaction with tin dichloride afforded the corresponding 2‐stanna‐2,2′‐spirobi[3]ferrocenophane ( 9 ) rather than the expected stannylene 8 . The reaction of 2,2‐dichloro‐1,3‐bis(trimethylsilyl)‐1,3,2‐diazastanna‐[3]ferrocenophane ( 10 ) with the dilithio reagent 2b also gave the spirotin compound 9 , of which the molecular structure was determined by X‐ray analysis. The formation of the products and their solution‐state structures was deduced from multinuclear magnetic resonance spectroscopic studies (¹H, ¹³C, ¹⁵N, ²⁹Si, ⁷⁷Se, ¹²⁵Te, ¹¹⁹Sn NMR spectroscopy).     

Applications of rare earth complexes as nmr shift reagents in elucidating the structure of organic molecules

The present state of affairs concerning shift reagents is reviewed and some new data on lanthanide-1,10-phenanthroline and lanthanide-2,2'-dipyridyl systems are presented. The use of Pr(TTA)₃ as an NMR shift reagent for benzylic systems has been reviewed and it is concluded that this complex possesses useful properties as a “two-way” shift reagent. Both high field and low field shifts for benzylic protons have been observed.     

Retention profile, kinetics and sequential determination of selenium(IV) and (VI) employing 4,4'-dichlorodithizone immobilized-polyurethane foams

Polyurethane foams (PUFs) loaded with the chromogenic reagent 4,4′-dichlorodithizone (Cl₂H₂D_Z) have been investigated for the quantitative retention, chemical speciation and sequential determination of traces of inorganic selenium(IV) and (VI) from aqueous media containing bromide ions. The retention profile of selenium(IV) onto the reagent loaded foam followed a dual-mode sorption mechanism involving both absorption related to “solvent extraction” and an added component for surface adsorption. The kinetics and thermodynamic characteristics of selenium(IV) uptake onto PUFs have been studied. The kinetics of selenium(IV) sorption onto PUFs was found fast, reached equilibrium in few minutes and followed a first-order rate constant in presence of bromide ions in the extraction media. The thermodynamic parameters, ΔH, ΔS and ΔG, indicated the exothermic and spontaneous nature of the sorption process. The sorption and the recovery percentages of inorganic selenium(IV) from fresh water by the proposed loaded foam columns were achieved quantitatively. The height equivalent to theoretical plate (HETP), the number of layers (N), breakthrough capacity and the critical capacity for selenium(IV) uptake onto Cl₂H₂D_Z loaded foams columns were found to be 1.3, 103, 8.6 and 7.2 mg/g, respectively. The method was successfully applied for the chemical speciation and sequential determination of inorganic selenium(IV) and/or (VI) species spiked to fresh and industrial wastewaters.     

Potentiometric redox determination of gold(III) and its application to alloys

The simple potentiometric method proposed for the indirect determination of 1–10 mg of gold(III) is based on reduction to the metal with excess of cobalt(II) in the presence of 1,10-phenanthroline or 2,2'-bipyridine at pH 3 and 50°C, and titration of the unused cobalt(II) complex with iron(III) chloride solution. Many metal ions can be tolerated; Ag(I) and Pd(II) are eliminated by precipitation with sodium chloride and 1,10-phenanthroline or 2,2'-bipyridine, respectively, but Hg(II), Fe(III) and Pt(IV) interfere. The method is applied to the determination of gold in alloys.     

The group extraction of noble metals with s-(1-decyl)-N,N'-diphenylisothiouronium bromide and their determination in the organic extract by atomic-absorption spectrometry

The distribution coefficients are given for the noble metals and associated base metals between S-(1-decyI)-N, N'-diphenylisothiouronium (DDTU) in diisobutyl ketone and aqueous solutions containing varying molarities of hydrochloric acid. DDTU is a satisfactory reagent for the extraction of noble metals as a group from most of the associated base metals. Base metals such as iron(III), tin(II), and selenium(IV), which are co-extracted, can be removed from the organic phase by washing with 0.1 M hydrochloric acid; this affects only the recovery of iridium. Although the noble metals cannot be recovered from the organic phase by back-extraction, direct measurement in the organic phase is possible in ths presence of zinc dibenzyldithiocarbamate added as a releasing agent. The final solution for analysis contains 6 mg of additive per 10 ml of solution.