Extraction of silver into nitrobenzene using cesium dicarbollylcobaltate in the presence of 18-crown-6

From several cesium distribution experiments with ¹³⁴ Cs tracer, the exchange extraction constant corresponding to the equilibrium Ag⁺ (aq)+CsL⁺ (nb)AgL⁺ (nb)+Cs⁺ (aq) in the two-phase water-nitrobenzene system (L = 18-crown-6; aq = aqueous phase, nb = nitrobenzene phase) was determined as log K _ex (Ag⁺ ,CsL⁺ ) = -0.6±0.1. Furthermore, the stability constant of the silver — 18-crown-6 complex in nitrobenzene saturated with water was evaluated for a temperature of 25 °C: log _nb (AgL⁺ ) = 8.2±0.1. Finally, the individual extraction constant of the species AgL⁺ in the water-nitrobenzene system corresponding to the equilibrium AgL⁺ (aq)AgL⁺ (nb) was calculated: K _AgL+ = O1.2±0.1.     

Extraction of certain actinide and lanthanide elements from different acid media by polyurethane foams loaded with di-(2-ethylhexyl)phosphoric acid (HDEHP)

The effect of added TBP on the extraction of uranium(VI) with a solution of di-(2-ethylhexyl)-phosphoric acid (HDEHP) in o-dichlorobenzene from nitric acid solutions has been investigated at varying concentrations of nitric acid, HDEHP, TBP and uranium(VI). The mechanism of the synergistic effect of TBP is discussed on the basis of the results and can be summarized in the following equation: UO _2(aq) ²⁺ +0.67(HX)_3(o)+2TBP_(o)UO₂X₂·2TBP_(o)+2H _(aq) ⁺ where HX denotes HDEHP and the HDEHP loaded on the foam is trimerized.     

Bestimmung der Gleichgewichtskonstanten des Zwischenphasen-Anionenaustausches in Aminsalzsystemen

It has been shown that in particular cases the ion exchange constants, _{x, x i, i} , of the reactions(QA) _x+iBQ_xA_x–iB_i may be calculated from the value of the constant ₁₀₁ referring to the equilibriumQA+BQB+A. The method proposed has been applied in investigating the exchange between methyltrioctyl-ammonium chloride and nitrate ions.     

Study of the multipositional conformational exchange in 2,2-dimethyl-1,3-dithiepin and its 5,6-benz analog by two-dimensional NMR spectroscopy

Conclusions Two-dimensional NMR spectroscopy was used to establish that the chair chair-inversion process in 2,2-dimethyl-1,3-dithiepin and its 5,6-benz derivative is a function of transitions between intermediate boat and twist structures, while the role of direct chair chair transitions is small.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 7, pp. 1696–1699, July, 1989.     

Thermal dissociation of diatomic molecules

The establishment of equilibrium in the chemical reaction X₂+M 2X+M is examined. All possible transitions between the vibrational levels and the continuous spectrum are considered. Taking account of two relaxation times, an expression is obtained for the concentration of the X atoms and the chemical reaction rate as a function of time. The conditions under which the dependence of the chemical reaction rate on time acquires an exponential nature are determined. An expression free from the requirement that the initial concentrations of X-atoms and X₂ molecules should be close to their equilibrium values is obtained for the rate constant.In conclusion, the authors thank Prof. N. D. Sokolov for discussion of the work.     

Spektrophotometrische Titanbestimmung mit Chromotrops?ure

Zusammenfassung Die Chromotropsäure ist ein analytisch wertvolles Reagens auf Eisen (III)₂₃, Chrom (VI)⁹, Kupfer, Niob²⁴ und besonders auf Titan (IV). Die Reaktion mit Chromotropsäure ist die empfindlichste (pD 5,9) und in Gegenwart von Ascorbinsäure weitgehend selektive Titanreaktion.In den Titan(IV)-lösungen bilden sich mit Chromotropsäure abhängig von der Zusammensetzung und dem p_H-Wert der Lösung sowie von der Konzentration der Reaktionspartner stufenweise mehrere Chelate. In den Lösungen mit Reagensüberschuß liegen folgende Chelatgleichgewichte vor: TiO²⁺ + 2 H₂R² TiO(RH)₂ ^4– + 2 H⁺ (Absorptionsmaximum470 m), P_H 0–2; TiO²⁺ + 2 H₂R^2– TiOR₂ ^6– + 4 H⁺ (470 m), p_H1–3,5; TiOR₂ ^6– + H₂R² TiOR₃ ^10– + 2 H⁺ (420 m), p_H 3,2–7,0; TiOR₂ ⁶ + 2H₂R^2– TiR₄ ^12– + 2 H + H₂O (470 m), p_H 1,7–2,4.Die beiden stabilen Chelate TiOR₂ ^6– und TiOR₃ ^10– können bei begrenzten Reaktionsbedingungen zur spektrophotoinetrischen Titanbestimmung ausgenutzt werden. Die Bestimmung bei p_H 2,9–3,2 und 467m in Gegenwart von Ascorbinsäure ermöglicht die Titanbestimmung neben einer Zahl von fremden Ionen. Sie ist die für die Praxis geeignetste Methode.Herrn Prof. Dr. A. Oká zum 55. Geburtstag gewidmet.Den Firmen E. Merck, Darmstadt und Reagencia, Kralupy, bin ich für das freundliche Überlassen der Präparate der Chromotropsäure mit herzlichem Dank verpflichtet.     

Thermodynamic model for the solubility of NdPO4(c) in the aqueous Na+-H+-H2PO4–HPO42–OH–Cl–H2O system

The solubility of NdPO₄(c) was studied at 23±2 °C from both the over and undersaturation directions, with pH ranging from 0 to 9, P concentrations ranging from 0.0003 to 1.00M, and equilibration periods ranging from 6 to 57 days. Equilibrium was reached in <6 days. From the H⁺, Nd, and P concentrations in equilibrated solutions, the logarithm of the thermodynamic equilibrium constant for the reaction (NdPO₄(c) Nd³⁺+PO₄ ^3-) was calculated to be -24.65±0.23 and the value of the Pitzer ion-interaction parameter ⁽²⁾for Nd³⁺-H₂PO₄ ^- was determined to be -92.9. Predictions based on these thermodynamic quantities were in excellent agreement with the experimental data.     

Extraction of Pb2+ with sodium dicarbollylcobaltate in the presence of 15-crown-5

From extraction experiments with ²² Na as a tracer, the exchange extraction constant corresponding to the equilibrium Pb²⁺ (aq)+2 NaL⁺ (nb)PbL₂ ²⁺ (nb)+2 Na⁺ (aq) in the two-phase water-nitrobenzene system (L = 15-crown-5; aq = aqueous phase, nb = nitrobenzene phase) was evaluated as log K_ex (Pb²⁺ , 2NaL⁺ ) = 4.7±0.1. Moreover, the stability constant of the complex PbL₂ ²⁺ in nitrobenzene saturated with water was calculated for a temperature of 25 °C as log _nb (PbL₂ ²⁺ ) = 17.9±0.1.     

Complete synthesis of serratamolide

Summary 1. A method for the separation and quantitative determination of - and -DNP derivatives of , -DABA, ornithine, and lysine has been proposed.2. A quantitative evaluation of the N N migration in four peptides of , -DABA has been carried out.3. The degree of migration in inactive polymyxin M and the DNP-peptides from a partial hydrolyzate of the inactivated antibiotic has been determined.4. The amino acid composition of the DNP peptide B1 from a partial hydrolyzate of active DNP-polymyxin M has been established.5. The quantitative aspect of the conversion of and diketopiperazines has been studied.Khimiya Prirodnykh Soedinenii, Vol. 2, No. 4, pp. 277–284, 1966     

Stability of the valinomycin-rubidium complex in water saturated nitrobenzene

From the extraction experiments and -activity measurements, the extraction constant corresponding to the Rb⁺(aq)+CsL⁺(nb)RbL⁺(nb)+Cs⁺(aq) equilibrium in the two-phase water-nitrobenzene system (L=valinomycin; aq=aqueous phase, nb=nitrobenzene phase) was evaluated in the form logK _ex (Rb⁺, CsL⁺)=0.9. Further, the stability constant of the valinomycin-rubidium complex in nitrobenzene saturated with water was calculated as log _nb(RbL⁺)=11.7.     

Concentrations of Active Species in the Flowing Afterglow of a Nitrogen Microwave Plasma

Measurements of nitrogen atom density, by means of NO chemical titration, along with an evaluation of the densities of some excited species N ₂ (B, v=11), N ₂ (B, v=2), N ₂ (C, v=0), and N ₂ ⁺ (B,v=0), by means of a spectroscopic study of some bands of dinitrogen, are achieved along the flowing afterglow of a dinitrogen microwave plasma (2450 MHz) for several pressures. The concentrations obtained are in the following range: [N]10 ⁺¹⁵ , [N ₂ (B, 2)]10 ⁺⁹ –10 ⁺¹⁰ , [N ₂ (B, 11)]10 ⁺⁸ –10 ⁺⁹ , [N ₂ (C, 0)]10 ⁺⁶ –10 ⁺⁷ , [N ₂ ⁺ (B,0)]10 ⁺⁶ -10 ⁺⁸ (cm^-3). From a kinetic study of the formation and decay of excited and charged species, an estimation of N ₂ (A, v), N ₂ (X, v, and N ₂ ⁺ (X) densities can be derived: [N ₂ (A, v)]10 ⁺¹² , [N ₂ (X, v6)]10 ⁺¹⁵ –10 ⁺¹⁶ , [N ₂ (X, v12)]10 ⁺¹⁴ –10 ⁺¹⁵ , [N ₂ ⁺ (X)]10 ⁺¹⁰ (cm ^-3 ).     

Marginal electron density and density-difference functions

Summary For visual analysis of the density reorganization and distortion, the one-dimensional cut (x, y ₀,z ₀) and the two-dimensional cut (x, y, z ₀) of the three-dimensional electron density difference function (x, y, z) are frequently employed. However, these cut functions do not satisfy any sum rules in contrast to the original difference function (x, y, z). To avoid this difficulty, the use of the marginal electron density functions _x (x) and _xy (x, y) and their difference functions _x (x) and _xy (x, y) is proposed. The marginal densities are condensation of the three-dimensional density onto a particular plane or line of our interest, and they satisfy the sum rule (i.e., the conservation of the number of electrons) exactly. Some basic properties of the marginal electron density are clarified for typical diatomic molecular orbitals. An illustrative application is given for the bonding and antibonding processes in the H₂ system.     

Redox equilibria in the In(III)-In(I)-In system in aqueous KBr solutions II. A rotating ring-disc electrode study

Summary The open-circuit behaviour of thick indium films formed onto gold by the electroreduction of In(III) has been investigated in acidified aqueous KBr solutions using the rotating ring-disc electrode technique. The spontaneous dissolution of indium metal immersed in the solution containing its own ions of higher valency yields In(I) ions. Information about the equilibrium and mechanism of the process studied was drawn from measurements of the limiting ring current and disc potential as a function of the electrode rotation rate. It was proved that the overall reaction 2In+In(III)3In(I) occurs as a coupling of two electrochemical steps: InIn(I)+e^–, and In(III)+2e^–In(I). The cathodic half-reaction is the rate-determining step, whereas the anodic half-reaction is reversible.

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Das Redox-Gleichgewicht im In(III)-In(I)-In-System in wäßrigen KBr-Lösungen, 2. Mitt. Untersuchungen mit der rotierenden Ring-Scheiben-Elektrode

Zusammenfassung Die spontane Auflösung von Indium unter der Wirkung von eigenen lonen (In(III)) wurde in sauren bromidhaltigen Lösungen mit Hilfe der rotierenden Ring-Scheiben-Elektrode untersucht. Die Angaben über das Gleichgewicht und den Mechanismus des untersuchten Prozesses wurden auf Grund der Abhängigkeit der Grenzströme an der Ring-Elektrode und der Elektrodepotentiale der Scheiben-Elektrode von der Umdrehungsgeschwindigkeit erreicht. Aus den Messungen folgt, daß die Bruttoreaktion 2In+In(III)3In(I) aus zwei überlagerten Durchtrittsreaktionen, InIn(I)+e^– und In(III)+2e^–In(I), besteht. Die kathodische Reaktion ist geschwindigkeitsbestimmend, während die anodische Teilreaktion reversibel abläuft.

     

Synthesis and the crystal structure of the triosmium cluster with the μ-dehydrobenzene ligand,Os3(μ-H)2(CO)7(μ-C6H4){μ3-Ph2PCH2P(C6H4)Ph}

The Os₃(-H)₂(CO)₇(-C₆H₄){₃-Ph₂PCH₂P(C₆H₄)Ph} complex, which was isolated from the products of thermolysis of Os₃(CO)₁₀(-dppm) (dppm is Ph₂PCH₂PPh₂) in toluene, was characterized by X-ray diffraction analysis. Protonation of the resulting complex with trifluoroacetic acid afforded the cationic complex [Os₃(-H)₃(CO)₇(-C₆H₄){₃-Ph₂PCH₂P(C₆H₄)Ph}]⁺.     

Conformational analysis of 2-phenyl-2-oxo-5,6-benzo-1,3,2-dioxaphosphepine with data from vibrational spectroscopy,dipole moments,and the kerr effect

2-Phenyl-2-oxo-5,6-benzo-1,3,2-dioxaphosphepine exists in a melt and solutions in polar solvents as a three-component equilibrium of two chair forms (C) with axial and equatorial arrangement of the phenyl group and the twist-boat form (TB) with a pseudoequatorial position of the phenyl substituent, a-C e-C e-TB. The two-component equilibrium e-C e-TB is observed in nonpolar solvents. The e-TB conformation occurs in the crystalline state. The dipole moment of the P=O groups is 3.5 D. The angle of rotation of the plane of the phenyl group with respect to the P=O bond in the e-TB conformation was 54 or 129.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 5, pp. 1039–1043, May, 1991.     

Determination of activity coefficients for ammonium chloride at 25°C

Precise values of the activity coefficients of aqueous ammonium chloride solutions at 25°C determined from emf measurements of cells with transference are reported for the concentration range 0 to 0.2m. The results show no anomalous behavior with respect to the Debye-Hückel limiting law. An interpretation of excess thermodynamic functions of potassium and ammonium chloride solutions is made in terms of ionic influences on solvent structure. The relative order of activity coefficients for the R ₄ NCl series up to 0.1m is shown to be (NH ₄ Cl)>(Me ₄ NCl)>(Et ₄ NCl)>(n-Bu ₄ NCl).     

Thermodynamic Modeling of Actinide Complexation with Acetate and Lactate at High Ionic Strength

The stability constants of NpO ₂ ⁺ , UO ₂ ²⁺ Am³⁺, and Th⁴⁺ with acetate and lactate anions has been measured in 0.3–5.0m NaCl media at 25°C by the solvent extraction technique. For the 1:1 complexation, the values of the stability constants increased in the order: NpO ₂ ⁺ < Am³⁺ < ₂ ²⁺ < Th⁴⁺, in accordance with the actinide charge density and reflecting the strongly ionic bonding of the complexes. The Pitzer ionic interaction parameters were calculated and used to estimate the thermodynamic stability constants at I = 0. Because our data were collected mainly in the high ionic strength region values of ⁽¹⁾ were estimated from values reported in the literature. For all stability constants the Pitzer model gives an excellent representation of the data using three interaction parameters ⁽⁰⁾, ⁽¹⁾, and COn leave from Institute of     

Redox Properties of Rhodium(III) Oxo-Bridged Carboxylate Complexes

Chemical and electrochemical oxidation of rhodium (III) oxo-bridged carboxylate complexes was studied. The chemical [with O₃ and Ce(IV) salts] or electrochemical (at potentials of 1.00-1.20 V) oxidations of the binuclear complexes [Rh₂(-O)(-O₂CCH₃)₂(H₂O)₆]^{2 +} and [Rh₂(-O)(-O₂CCF₃)₂(H₂O)₆]^{2 +} leads to the superoxo complexes [Rh₂(-O)(O₂-)(-O₂CCH₃)₂(H₂O)₅]⁺ and [Rh₂(-O)(O₂ ^-)(-O₂CCF₃)₂(H₂O)₅]⁺ with terminal coordination of O₂-. The trinuclear acetate [Rh₃(₃-O)(-O₂CCH₃)₆(H₂O)₃]⁺, unlike its trifluoroacetate analog [Rh3(₃-O)(-O₂CCF₃)₆(H₂O)₃]⁺, is oxidized only electrochemically at a potential of 1.38 V. The oxidation of [Rh₃(₃-O)(-O₂CCH₃)₆(H₂O)₃]⁺ is reversible and involves formation of an unstable superoxo group O₂ ^- between two Rh₃III(₃-O) cores.     

Nature of catalytic effect of Ni(O)- and BF3OEt2-based systems in propene dimerization

¹H NMR, EPR and IR spectroscopic studies of the products of the interaction between components of the Ni[PPh₃]₄+EtOH+BF₃.OEt₂ and Ni(PPh₃)₄+BF₃OEt₂ systems suggest the formation of two types of complexes [HNi(PP₃)₃L]⁺[BF₃OEt]^– and [Ni(PPh₃)₃L]⁺BF ₄ ^– , which are catalytically active in propene dimerization.

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¹H, , - Ni(PPh₃)₄+ EtOH+BF₃OEt₂ Ni(PPh₃)₄+BF₃·OEt₂ [HNi (PPh₃)₃L]⁺ [BF₃OEt]^– [Ni (PPh₃)L₂]⁺BF ₄ ^– .

     

A π-acceptor series for phosphines from51V N.M.R. data on [η5-CpV(CO)3L] complexes

Summary Qualitative molecular orbital considerations of the complexes [⁵-CPV(CO)₃ L] (L = substituted phosphane, SbPh₃, AsPh₃, CN^–) suggest that s' V chemical shift parameters () obtained for these compounds should correlate with the -acceptor abilities of L. Based on observed r-values, the ligands are arranged in sequence of their -acceptor ability, which lies in the order P(OR)₃ > CN^– > PR'₃3 SbPh₃ PPhF₂ > P(i-Bu)₃ P(NR ₂ )₃ > PPh₃ > AsPh₃ Nuclear spin-spin coupling constants J (⁵¹V-³¹ P), line widths H and i.r. data in the (CO) region are also presented.P(OR)₃ = P(OEt)₃, 4-Ethyl-l-phospha-2,6,7-trioxabicyclo[2.2.2]-octane; R = Me, n-Pr; R = Me, Et.