Oxidation of selenite by alkaline ferricyanide using osmium tetroxide as a catalyst

Summary Oxidation of selenite to selenate by alkaline ferricyanide catalysed by osmium tetroxide was followed by direct and indirect procedures. Either the ferrocyanide was titrated with selenite solution at 8–10% overall alkalinity or vice versa using amperometric or potentiometric end point. In the indirect procedure the excess ferricyanide was determined by amperometric titration with arsenious oxide at 10–15% alkalinity, and the ferrocyanide with ceric sulphate using o-phenanthroline or amperometric indicator. A cerimetric determination of ferricyanide based on this reaction is described.Sincere thanks of the authors are due to Dr. S. S. Joshi, D. Sc. (London), for kind interest in the work.     

Conductometric and ph studies on cobalt tellurite

Summary Conductometric and p_H titration procedures for the determination of cobalt over a wide range of concentrations of cobalt solutions are described. Direct, as well as reverse titration procedure are shown to be possible and the effect of varying ethanol concentrations is reported. Both conductometric and p_H studies lend support to the 11 molar ratio of Co and Te.Sincere thanks of the authors are due to Prof. S. S. Joshi, D. Sc. (London), Head of the Chemistry Department for keen interest and facilities. The award of a scholarship to one of us (V.D.A.) by the Ministry of Scientific Research and Cultural Affairs is also acknowledged.     

Kinetics and mechanisms of the oxidation of the octacyanoniobate(III)ion by oxyanions in alkaline aqueous media

Summary The kinetics and mechanisms of the oxidation of Nb(CN) _inf8 ^sup5– by the oxyanions S₂O _inf8 ^sup2– , BrO _inf3 ^sup– , and IO _inf4 ^sup– have been investigated in alkaline aqueous media (pH 12). The second-order rate constant for the electron transfer reaction between Nb(CN) _inf8 ^sup5– and S₂O _inf8 ^sup2– at 25.0 °C, I = 0.36m (K⁺), is 11.1± 0.3 m ^–1 s ^–1 with H = 30 ± 2kJmol^–1 and S = - 125 + 7JK^–1 mol^–1. The rate constant for the oxidation of Nb(CN) _inf8 ^sup5– by BrO _inf3 ^sup– at 25.0 °C, I = 0.20m (Na⁺), is 2.39 ± 0.08m ^–1 s ^–1 with H = 28 ± 2kJmol^–1 and S = -139 ± 7JK^–1mol^–1. The oxidation of Nb(CN) _inf8 ^sup5– by IO _inf4 ^sup– proceeds by two parallel pathways involving the monomeric IO _inf4 ^sup– ion and the hydrated dimer H₂I₂O _inf10 ^sup4– . The second-order rate constant for the oxidation of Nb(CN) _inf8 ^sup5– by monomeric IO _inf4 ^sup– at 5.0 °C, I = 0.050m (Na⁺), is (3.3 ± 0.6) × 10³ m ^–1 s ^–1 with H = 75 ± 6 kJ mol^–1 and S = 94 ± 15 J K^–1 mol^–1, while the rate constant for the oxidation by H₂I₂O _inf10 ^sup4– is (1.8 ± 0.1) × 10³ m ^–1 s ^–1 with H = 97 ± 5 kJ mol^–1 and S = 166 ± 16 J K^–1 mol^–1 under the same reaction conditions. The rate constants for each of the oxidants employed display specific cation catalysis with the order of increasing rate constants: Li⁺ < Na+ < NH _inf4 ^sup+ < K⁺ < Rb⁺ < Cs⁺, in the same direction as the electronic polarizability of the cations. The results are discussed in terms of the outer-sphere electron-transfer processes and compared with the corresponding data and mechanisms reported for other metal-cyano reductants.     

Spectrophotometric determination of ruthenium(III) using diphenylcarbazone

Summary The purple violet ruthenium(III)-diphenylcarbazone complex which is formed at p _h 5–7, and has an absorption maximum at 530 nm with molar absorption coefficient 16.2·10⁴l.cm^–1.mole^–1 is suggested for the estimation of 20–125g ruthenium(III) spectrophotometrically in 30–60% ethanol. The complex is stable over p _h range 3.2–8.4. The limits of interference due to foreign ions have been studied.

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Zusammenfassung Der bei p _h 5 bis7 entstehende Ruthenium(III)-Diphenylcarbazon-Komplex hat ein Absorptionsmaximum bei 530 nm und einen Absorptionskoeffizienten von 16,2·10⁴ l.cm^–1.Mol^–1. Die spektrophotometrische Bestimmung von 20 bis 125g Ruthenium(III) in 30 bis 60%igem Äthanol mit Hilfe dieses zwischen p _h 3,2 und 8,4 beständigen Komplexes wurde vorgeschlagen. Die Störung durch Fremdionen wurde geprüft.

     

Natriumchlorit als Oxydationsmittel in der quantitativen analytischen Chemie

Zusammenfassung Es wird eine photocolorimetrische Methode zur Bestimmung von Atebrin mit Natriumchlorit bei pH 5,5–6 ( _max=485 nm) beschrieben. Das Lambert-Beersche Gesetz wird zwischen den Konzentrationsgrenzen 0,2 und 1,4 mg/10 ml befolgt. Die Methode wurde sowohl für reines Atebrin als auch für Atebrintabletten angewandt.

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Summary Sodium chlorite has been employed as a reagent for the photocolorimetric determination of atebrin (pH 5.5–6, _max=485 nm). Lambert-Beers's law is obeyed within the range of 0.2 to 1.4 mg/10 ml. The method has been applied to pure atebrin and to atebrin tablets.

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VI. Mitt.: Spacu, P., C. Gheorghiu u. I. Paralescu: diese Z. 195, 321 (1963).     

Supernucleophilic Reactivity of Hypobromite Ion toward 4-Nitrophenyl Diethylphosphonate in Water and Micelles of Cetyltrimethylammonium Bromide

The nucleophilic reactivity of the typical -nucleophile hypobromite ion, generated by the organic complexes of the tribromide ion, toward 4-nitrophenyl diethylphosphonate in water and micelles of cetyltrimethylammonium bromide (CTAB) was studied. The BrO^––CTAB system is one of the most effective for the decomposition of organophosphorus compounds; the concentrating effect of the reagents secures the rapid break down of 4-nitrophenyl diethylphosphonate in an aqueous–micellar medium with t _1/2 20 s (in water t _1/2 600 s).Yu. S. Simanenko: Deceased     

Flow injection chemiluminescence determination of l-cysteine in amino acid mixture and human urine with the BrO3 −–quinine system

In this paper, a novel flow injection chemiluminescence (CL) determination of l-cysteine is proposed. The method is based on the CL reaction of l-cysteine and KBrO₃ in acidic medium. The CL intensity was greatly enhanced in the presence of quinine. The CL intensity was linear with l-cysteine concentration in the range of 0.2–80 g L^–1, and the detection limit was 0.1 g L^–1 (3). A complete analysis, including sampling and injecting, could be performed in 1 min, giving a throughput of about 60 h^–1. The relative standard deviation was 1.6% for 0.8 g L^–1 l-cysteine (n=11). The proposed method was satisfactorily applied to the determination of cysteine in an amino acid mixture and human urine. The mechanism of the CL reaction is also discussed.     

Kinetics of anation of hexaaquachromium(III) by thiocyanates – specific salt effects

The kinetics of anation of hexaaquachromium(III) by thiocyanates follows the rate law: –d[complex]/dt=k[NCS] (20–40°C, [NCS^–]=0.1–0.6M, I=2.0M, pH=1.0). The specific salt effect has been studied for five media: NaCl, NaBr, NaClO₄, KCl and CsCl. The series of chloride (Na⁺, K⁺ and Cs⁺) salts show a negligible effect on the anation rate. On the contrary, the series of sodium salts (Cl^–, Br^– and ClO ₄ ^– ) reveal a marked difference in the reaction rate. The anation rate decreases sharply with the ionic strength increase (I=0.2–2.0M, NaCl). The results were interpreted within the frame of fast equilibria of ion-pair formation followed by an interchange mechanism step. The difference of reaction rate is a result of competition between anions (thiocyanates and supporting electrolyte anions) to the complex cation at an ion-pair formation process.     

Novel Immobilized Hydrosilylation Catalysts Based on Rhodium 1,3-Bis(2,4,6-trimethylphenyl)-3,4,5,6-tetrahydropyrimidin-2-ylidenes

The reactivity of a well defined Rh (I) complex, i.e. Rh(CF₃COO)(NHC)(COD) (1, NHC=1,3-bis(2,4,6-trimethylphenyl)-3,4,5,6-tetrahydropyrimidin-2-ylidene, COD=⁴-cycloocta-1,5-diene) in the hydrosilylation of 1-alkenes, alkynes, and ,-unsaturated carbonyl compounds, respectively, is described. With this complex, excellent reactivity was observed and turn-over numbers (TONs) up to 1000 were reached. A supported version of 1 was realized by reaction of RhCl(NHC)(COD) with PS-DVB–CH₂–O–CO–CF₂–CF₂–CF₂–COOAg (PS-DVB=poly(styrene-co-divinylbenzene) to yield PS-DVB–CH₂–O–CO–CF₂–CF₂–CF₂–COORh(NHC)(COD). This supported version of 1 exhibited at least comparable, in some cases increased reactivity compared to 1 and allowed the rapid removal of the catalyst from the reaction mixture. Due to reduced catalyst bleeding, the synthesis of target compounds with a Rh-content of less than 130ppm was accomplished.     

Products and kinetics of the thermal decomposition of (l-(−)-menthyl)[2,2′-methylene-bis-(4-methyl-6-tert-butylphenyl)] phosphite ozonide

Two conformers (chair, boat) of [l-(–)-menthyl)]-[2,2-methylene-bis-(4-methyl-6-tert-butylphenyl)] phosphite ozonide have been obtained by the low temperature ozonization (–80 °C) of [l-(–)-menthyl)]-[2,2-methylene-bis-(4-methyl-6-tert-butylphenyl)] phosphite. It was determined that decomposition of the ozonide is first order with the rate constant logk ₀ = (10.92±1.10)–(14.02±1.25)/gq ( = 2.303RT, kcal mol^–1), leading to [l-(–)-menthyl)]-[2,2-methylene-bis-(4-methyl-6-tert-butylphenyl)] phosphate and oxygen (including singlet oxygen). Conformational transitions (chair-boat) for [l-(–)-menthyl)]-[2,2-methylene-bis-(4-methyl-6-tert-butylphenyl)] phosphate have been registered by³¹P NMR spectroscopy.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1758–1761, October, 1994.This work was supported by Russian Foundation for Basic Research (Project No. 93-03-532l).     

Amperometric determination of cobalt as tellurite

Summary The precipitation of cobalt as the normal tellurite has been made the basis of an amperometric titration procedure for the determination of cobalt. Potassium chloride (0.1 M) was used as the supporting electrolyte with gelatin as the maximum suppressor. The titrations were performed in a 10% ethanolic medium. E _1/2 for cobalt and tellurium were found to be –1.21 and –1.10 volts vs. S.C.E. respectively. Titrations were performed at an applied potential of –1.5 volts vs. S.C.E. at which both cobalt and tellurium are reducible. Effect of ethanol on the equivalence point of the titration was also studied. The procedure described is simple and accurate, and is applicable over a wide range of cobalt concentrations varying from 0.1–10 millimolars. The results support the molar ratio 11 for Co and Te in agreement with earlier findings of the author.     

Potassium ferrocyanide as a spectrophotometric reagent for the determination of uranium

Potassium ferrocyanide gives a colour reaction with U(VI), which is suitable for its determination. The complex absorbs in the wavelength range of 390–397 nm. The optimum pH range for colour development was 1.5–3.5. The molar absorptivity was found to be 4.65·10³ 1·mol^–1·cm^–1. Most of the anions up to 1000 g did not interfere. The method was made selective by extracting U(VI) first with DOSO from the mixture of interfering cations from 1–2M HNO₃ medium and then determining uranium in the back-extracted solution by developing the colour with ferrocyanide. 20 g/10 ml of U(VI) in the final solution could be satisfactorily determined within an RSD of ±2%.     

Infrarotspektroskopische Untersuchungen an Alkylverbindungen von Gallium, Indium und Antimon

Zusammenfassung Es werden die Absorptionsspektrogramme der Trialkyle (C₁-C₄) der Elemente Ga, In und Sb im Wellenzahlbereich von 4000-300 cm^–1 (2,5–33 Wellenlänge) gezeigt. Das große Massenverhältnis der drei in jedem der betrachteten Moleküle vorhandenen Atomarten bewirkt, daß nur eine schwache Kopplung zwischen den einzelnen Schwingungsformen besteht, wodurch die Zuordnung der Absorptionen zu den Schwingungen einzelner Atomgruppen im Molekül ermöglicht wird.Die C-H-Absorptionen sind vom Zentralatom weitgehend unabhängig und für die Art des Alkylrestes charakteristisch.Aus den Lagen der Metall-Kohlenstoff-Absorptionen ( _Ga-C540 cm^–1, _In-C470 cm^–1, _Sb-C500 cm^–1) lassen sich die Kraftkonstanten dieser Bindungen abschätzen. Bei den Isobutyl-Verbindungen liegen diese Absorptionen um etwa 100 cm^–1 höher als bei den anderen Gliedern der Reihe, was auf eine höhere Kraftkonstante der Metall-Kohlenstoff-Bindung dieser Verbindungen zurückgeführt wird.Die Spektrogramme werden zur Prüfung der Substanzen auf Reinheit sowie Feststellung eingetretener Veränderungen herangezogen. Bei thermischer Belastung der Isopropylverbindungen tritt zwar Zersetzung der Substanzen aber keine Isomerisierung der Alkylreste ein.Den Herren Dr. R. Dötzer, Dr. F. Engelbrecht, Dr. G. Raab und Dr. E. Todt bin ich für die Bereitstellung der Substanzen und für wertvolle Diskussionen zu Dank verpflichtet. Herrn Dr. E. Golling danke ich sehr für die Überlassung Ramanspektroskopischer Daten. Mein Dank gilt ferner Fräulein E. Vierhus und Herrn W. Regelsberger für die Aufnahme und Auswertung der Spektrogramme.     

A calculation of the spin-orbit splitting of the X 2Π state of NO

Using Brion, Moser and Yamazaki's SCF LCAO MO the spin orbit splitting of the X ² state of NO has been calculated using various potentials. Experimentally W (² _3/2) –W (² _1/2) is known to be 122 cm^–1. Using an unscreened nuclear field we find a value of 328 cm^–1. Inclusion of screening due to electronic repulsions reduces this value to 283 cm^–1. Agreement with the experimental value may be obtained by reducing the orbital exponents in the 2 molecular orbital by 30% over the value given by Slater's rules.

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Zusammenfassung Die Spin-Bahn-Aufspaltung des X ² -Zustandes von NO wurde mit verschiedenen Potentialen unter Verwendung der SCF LCAO MOs von Brion, Moser und Yamazaki berechnet. Der experimentelle Wert für W (² _3/2) –W (² _1/2) beträgt 122 cm^–1. Die Rechnung mittels eines reinen Kernfeldes liefert den Wert 328 cm^–1 und unter Einschluß der Abschirmung durch die Elektronen 283 cm^–1. Übereinstimmung mit dem experimentellen Wert läßt sich erzielen, wenn man den Exponenten des 2-Zustandes 30% kleiner als nach den Slater Regeln macht.

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Résumé Avec les orbitals moléculaires SCF LCAO de Brion, Moses et Yamazaki, nous avons calculé le dédoublement spin-orbitale de l'état X ² de NO. La valeur expérimentale W (² _3/2) –W (² _1/2) est 122 cm^–1. Dans un champ nucléaire «sans écran» on trouve 328 cm^–1. L'inclu-sion de l'effet d'écran dû aux répulsions interélectroniques réduit cette valeur à 283 cm^–1. La valeur expérimentale s'obtient, si l'on réduit de 30% les exposants d'après Slater dans l'orbi-tale moléculaire 2.

     

Potentiometric and spectroscopic study of selenomethionine complexes with copper(II) and zinc(II) ions

Summary The stepwise stability constants of 1:1 and 2:1 complexes of selenomethionine (SeMet) with Cu^II and Zn^II ions have been determined in NaNO₃ (0.1m) supporting electrolyte by potentiometric titration at 25 °C. The overall log stability constant (logML₂ = [ML₂]/[M²⁺][L^–1]²) for Cu^II and Zn^II complexes are 14.50 and 8.75, respectively. Two new solids were prepared and identified by elemental microanalysis as (SeMet)₂Cu and (SeMet)₂Zn. I.r. and Raman spectral studies indicated metal coordination with the nitrogen and oxygen atoms of the amino acidato group of SeMet. The corresponding stretching bands were assigned at 341.1cm^– for Cu-O, 352.9 cm^– for Zn-O, 497.3 cm^– for Cu-N and 475.2 cm^– for Zn-N bonds.     

Measurement of isothermal diffusion coefficients at 37°C in the systems glycine−NaCl−H2O,dl-α alanine−NaCl−H2O,anddl-α-aminobutyric acid−NaCl−H2O

Isothermal diffusion coefficients have been measured at 37°C in the systems glycine–NaCl–H₂O,dl--alanine–NaCl–H₂O, anddl--aminobytyric acid–NaCl–H₂O. Experiments were performed at 0.5 and 1.0M in both solutes. It was found that the cross-term diffusion coefficientsD ₁₂ andD ₂₁ increased and the main-term diffusion coefficientsD ₁₁ andD ₂₂ decreased as the length of the hydrocarbon chain of the amino acid increased. The cross-term diffusion coefficients for the system with glycine were only 2% of the values of the mainterm diffusion coefficients while those for the system withdl--aminobutyric acid approached 10% of the main-term diffusion coefficients at 1.0M.     

Electrochemical synthesis of halogen derivatives of bis(1,2-dicarbollyl)cobalt(III)

A convenient electrochemical method for the synthesis of 8,8-dihalogen derivatives of bis(1,2-dicarbollyl)cobalt(III) anion [8,8X₂-3,3-Co(1,2-C₂B₉H₁₀)]^– (X = Cl, Br, I) was developed. The method includes the electrolysis of a solution of alkaline metal halide and tetramethylammonium salt of bis(1,2-dicarbollyl)cobalt(III) in methanol at 50 °C in a one-compartment electrochemical cell with a nickel cathode and platinum anode.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2448–2451, November, 2004.     

The substitution kinetics of the aqua ligand by cyanide ions in [Ru(TPPS)(CO)(H2O)]4−

Summary The reaction between the title compound, ,,,-tetra(p-sulphonatophenyl)porphynatoaquacarbonylruthenate(II), [Ru(TPPS)(CO)(H₂O)]^4–, and CN^- revealed that only the aqua ligand is substituted even in the presence of a large excess of the nucleophile. The pK _a1 was spectrophotometrically determined as 13.4(5) (at 33.2 °C) and kinetically as 13.44(5) (at 33.6 °C). The rate of aqua substitution was determined as 89(4)m ^–1 s ^–1 at 35.1 °C and the activation enthalpy and entropy as 55.44(1) kJ mol^–1 and-27.90(4) J K^–1 mol^–1, respectively.     

Chronovoltammetry of electrolytic molybdenum oxides at the electrochemical intercalation/deintercalation of lithium ions

Chemical diffusion coefficients of lithium ions in processes of electrochemical intercalation/deintercalation in electrolytic molybdenum oxides and the parameter of interaction between the intercalated particles (g) have been obtained by the following methods: the galvanostatic intermittent titration technique (GITT), the potential relaxation technique after current interruption (PRT), and the potential intermittent titration technique (PITT). In the potential range 2.40–1.40 V the values of of the order of 10^–11–10^–13 cm²/s have been obtained for Mo₄O₁₁ oxide. Intercalation/deintercalation was realized in one phase when g>4.Presented at the 3rd International Meeting on Advanced Batteries and Accumulators, 16–20 June 2002, Brno, Czech Republic