Asymmetric hydrogenation ofN-acetyldehydrodipeptide complexes with Mg(II) and Ca(II) ions

N-Ac--Phe-AA form labile complexes with Mg(II) ions. Potentiometric titration data show that the carboxyl group of the dehydrodipeptide in them scarcely participates in complexation, unlike the complexes with Ca(II) ions. The hydrogenation of these complexes over Pd/C occurs asymmetrically, the diastereomeric excess being as high as 58%.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 601–602, March, 1993.     

Complex Formation of Acetic Acid with Ca(II) and Mg(II) Under Physiological Conditions

Potentiometric titrations of aqueous acetic acid alone and in the presence of Ca(II) or Mg(II) ions have been carried out under physiological conditions at the temperature 37 °C and ionic strength 0.15 mol⋅dm⁻³ (NaCl) at different ligand-to-metal ratios. Changes in pH were monitored with a glass electrode calibrated daily in terms of the hydrogen ion concentrations. Titration data within the pH range 2.5 to 6.6 were analyzed to determine stability constants using the SUPERQUAD program. Different combinations of complexes were considered during the calculation procedure for both systems, but evidence was found only for mononuclear ML and ML₂ species. Speciation calculations based on the corresponding constants were then used to simulate the species’ distributions.     

Reaction of N-acetyldehydrophenylalanyl-S-proline with Ca(II) and Ni(II) ions and its role in asymmetric hydrogenation

N-Ac-Phe-S-Pro forms strong coordination complexes with the CO₂H group of the proline residue and weak coordination complexes through the -C(=O)-N groups with Ca(II) and Ni(II) ions in 95% aqueous methanol as indicated by the pK _a values, PMR spectroscopy, and paramagnetic broadening of the¹³C NMR signals in the nickel complex. Complex formation enhances the rigidity of the dehydrodipeptide conformation, leading to a strong increase in the optical yield upon hydrogenation over achiral catalysts.Institute of Food Substances, Russian Academy of Sciences, 117813 Moscow. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 7, pp. 1667–1670, July, 1992.     

Degradation of ampicillin in the presence of cadmium (II) ions

Cadmium (II) ion-catalyzed degradation of ampicillin in methanol at 20 degrees C has been studied. It has been observed that the rate values tend to saturate when the concentration of ampicillin or the metal ion is increased. The results obtained in the present study suggest that ampicillin degradation occurs through the formation of a 1:1 (SM) and 2:1 (S(2)M) ampicillin-metal complexes. These complexes decompose giving a single product (absorption maximum at 285 nm; ((p)=1.82x10(4) l mol(-1) cm(-1)) that has been isolated and identified (Cd(II) (L(2-))(2) (H(2)O)(4) Na(2)). The appearance of this product reflects a first order reaction with respect to the 1:1 complex, with a rate constant of 3.87x10(-2) min(-1) and the existence of an equilibrium between the 1:1 and 2:1 initial complexes. The equilibrium constant value, calculated from kinetic data, is 1.7x10(3) l mol(-1).     

Photoprocess in AgBr microcrystals in the presence of Pt(II) and Pd(II) complex ions

Results of a systematic study of the chemical sensitization of cubic-faceted AgBr emulsion microcrystals with complex compounds K₂[XY₄] and Na₆[XZ₄] [X = Pd, Pt; Y = Br^?, Cl^?, SCN^?; Z =(SO₃)_2?] were considered. The role of secondary dissociation of complex ions during the chemical sensitizing was established. Conditions were determined in which the compounds specified can be used as chemical sensitizers of AgBr. The effect of these complexes on the basic photographic characteristics was demonstrated.     

Sorption of copper(II) ions with soybean crush modified with sodium monochloroacetate

The effect of chemical modification on sorption properties of soybean crush with respect to copper(II) ions was examined. The optimal parameters of soybean crush treatment with sodium monochloroacetate to ensure the maximal sorption capacity of the sorbent were determined.     

Preparation and characterization of Mg(II)-, Ca(II) and Cd(II) complexes of 1,2-ethanediol and water

Mixed ligand complexes of different compositions were prepared with water, sulfate ion and 1,2-ethanediol as ligand. IR spectra and the thermoanalytical curves of the complexes were recorded. Oxygen atoms bound by one or two coordinate bonds to the metal ion, or by hydrogen-bonds in the crystal, were observed. As for the water molecule, 1,2-ethanediol molecules of crystal and monohydrate type were found, depending on the type of binding of the oxygen atoms.This revised version was published online in November 2005 with corrections to the Cover Date.     

The influence of metal ions on the synthesis of MeAPO-5 (Me-Co,Mg) in the presence of acetate ions

Metal-substituted type 5 aluminophosphate structures have been prepared hydrothermally in a buffer solution consisting of acetic acid and a high concentration of template. The acetate ion added to the reaction mixture decreases the interaction of the metal ions with the gel and keeps the initial pH of the mother liquor. There was almost no change in the pH of the reaction mixture during the preparation. The most suitable pH range to synthesize single crystals of MeAPO-5 (Me = Co, Mg) was found to be around pH 5.5. The morphologies of the as-synthesized MeAPO-5 crystals were strongly dependent on the pH of the solution. The size of the crystals increased with increasing metal contents. Owing to the roles of acetate ions, MeAPO-5 crystals were obtained at high concentrations of template and metal ion. Increasing the amount of water and reducing the reaction temperature resulted in the formation of CHA-type structures.     

Catalytic oxidation of Fe(II) aqua ions with atmospheric oxygen in the presence of Pd(II) tetraaqua complex and an aromatic compound

The effect of a series of aromatic compounds (toluene, benzyl alcohol, benzonitrile, phenylacetonitrile, and o-cyanotoluene) in a concentration of 0.01 M on the oxidation of Fe(II) aqua ions with oxygen in the presence of Pd(II) tetraaqua complex at 25–70°C was revealed. In the presence of an aromatic compound, palladium black is not formed, which results in an increased yield of Fe(III) in the Pd-catalyzed oxidation of Fe(II) with oxygen in a perchloric acid medium. A scheme involving the formation of a complex of palladium species in an intermediate oxidation state with arene and molecular oxygen was suggested.     

Stability of solubilized solutions in quaternary system in presence of sodium oleate and phenol

Summary Specific conductivity of solubilized solutions has been measured in quaternary system having water + sodium oleate + phenol + benzene at 30°, 40°, 50 °C and the results have been compared both with the heat of solubilization and the depression in freezing point measurements. It is observed that during solubilization, changes in specific conductivity are not regular, inflexion points are obtained, clusters or loose combinations of molecules may be formed due to interaction. Hence such solubilized solutions may be unstable in strictly thermodynamical sense, and are unsuitable for industrial or pharmaceutical purposes.The autor is highly obliged to Prof.A. C. Chatterji Emeritus Scientist, Chemistry Department Luoknow and to Prof.A. B. Sen for working in his department and to Prof. Dr.A. Weiss, Institut für Anorganische Chemie der Universität, München-2 (West Germany) for necessary suggestion and advice.     

Mechanism of the catalytic ozonization of lignin in the presence of Mn(II) ions

The reaction between ozone and lignin in aqueous solutions catalyzed by Mn(II) ions is studied. The rate of destruction for aromatic structures of lignin is found to increase in the presence of Mn(II) ions. However, the greatest catalytic effect is observed upon the transformation of aliphatic acids that are difficult to oxidize with ozone. The introduction of catalyst raises the total consumption of ozone from 3 to 7 mol per each structural unit of lignin. A scheme is proposed for the transformation of phenol fragments of lignin using ozone with the participation of Mn(II) ions: at the initial stage, we observe the ozone oxidation of lignin and Mn(II) to Mn(III) ions stabilized with products of lignin oxidation and accompanied by the formation of chelate complexes, and the Mn(III) chelate complexes act as low-molecular mediators, attacking phenol structures and initiating radical processes.     

The spherical oil agglomeration of barite suspensions in the presence of surfactant and cosurfactant

The spherical agglomeration of barite particles using oil in the presence of both surfactant and cosurfactant was studied. It was found that the mineral suspension needed a critical surfactant concentration to initiate oil agglomeration. The addition of long-chain aliphatic alcohols to the organic phase decreased the critical surfactant concentration. This phenomenon was ascribed to a screening effect of alcohol molecules in the adsorption layer of surfactant. When sodium chloride was added to the solution the spherical agglomeration disappeared even though the surfactant adsorption at the barite/solution interface increased. It was concluded that the disappearance of oil agglomeration was caused by a bilayer of the surfactant which was formed on the barite surface. In the barite—surfactant—alcohol—oil—brine system the agglomeration process is only realized with the long-chain alcohols. This behaviour can be explained by microemulsion formation at the mineral/solution interface.     

On the effect of copper (II) and chloride ions on the iodate-hydrogen peroxide reaction in the presence and absence of manganese (II)

The effect of copper (II) and chloride ions on the manganese (II) catalyzed iodate-peroxide reaction has been examined with reference to the hydrogen peroxide-iodic acid-manganese (II)-organic species oscillatory reaction. The observations are considered to provide evidence for iodine dioxide as the key intermediate in the manganese (II) catalyzed reaction. Kinetic data for the copper (II) catalyzed reaction are reported.     

Synthesis and characterization of some metal(II) and sodium ions with cyclopentane-1,2,3,4-tetracarboxylate anion

New divalent metal cyclopentane-1,2,3,4-tetracarboxylate (CPTC) hydrates of empirical formula M₂C₅H₆(COO)₄ · nH₂O, where M = Ni, Co, Cu, or Zn and n = 3?6, and sodium CPTC Na₃C₅H₆COOH(COO)₃ · 7H₂O have been prepared and characterized by elemental analysis, magnetic measurements, thermal, and infrared spectral studies. For the sodium salt, a single crystal (Na₃C₅H₆COOH(COO)₃ · 8H₂O) was also obtained. IR spectra of the metal(II) complexes indicate the coordination of metal ions through all carboxylates. For the sodium compound, a band at 1681 cm^?1 indicates that some carboxylic groups have not been deprotonated. The presence of protonated carboxylic group was also confirmed by an X-ray single crystal analysis. On heating in air atmosphere, all complexes lose water molecules and next anhydrous compounds decompose to corresponding metal oxides and sodium carbonate.     

Ethylphosphinediacetic acid: synthesis,characterization and coordinating behaviour towards Ca(II), Ni(II) and Hg(II) ions in solution

The new ligand, ethylphosphinediacetic acid, H₂Z, was synthesized and characterized by spectral methods. The Z^2? anion is protonated in three steps with the pK values of 6.10 (phosphorus atom), 2.75 and 0.9 (carboxyl groups). The ligand is highly selective for soft metal ions as demonstrated by the stability constants of the water-soluble complexes CaHZ-(logβ_CaHZ^HZ 0.73), NiZ₂^2? (log β₂ 9.06) and HgZ₄^6? (log β₄ 40.9). The di in behaviour compared to related phosphineacetic acids are mainly consequences of the high basicity of the phosphorus atom.     

Organic acid solutions in the chromatography of inorganic ions. VII. Cation exchange of Mg(II), Ca(II), Sr(II), Ba(II), Mn(II), Cd(II), Co(II), Ni(II), Zn(II), Cu(II) and Fe(III) in succinate media

Summary The cation-exchange behaviour of Mg(II), Ca(II), Sr(II), Ba(II), Mn(II), Cd(II), Co(II), Ni(II), Zn(II), Cu(II) and Fe(III) in succinate media at various concentrations and pH, was studied with Dowex 50 WX8 resin (200–400 mesh) in the NH ₄ ⁺ form. As examples separations of Cd(II)/Co(II), Cd (II)/Ni(II), Fe(III)/Cu(II)/Ni(II) and Mg(II)/Ca(II)/Sr(II)/Ba(II) have been achieved.This work was supported by C.N.R. of Italy.     

Comparison of polymeric and ceramic membranes performance in the process of micellar enhanced ultrafiltration of cadmium(II) ions from aqueous solutions

A comparison of polymeric and ceramic membranes in the ultrafiltration process was studied and presented. This study was conducted on the separation of cadmium(II) ions, with particular reference to parameters such as hydrodynamic permeability coefficient, membrane fouling, amount of surfactant in the permeate, efficiency, and effectiveness of the process. The effect of ionic (SDS) and non-ionic (Rofam 10) surfactants or their mixture was investigated. The hydrodynamic permeability coefficient of the ceramic membrane was found to be much lower in comparison to those of the polymeric ones (1.69 × 10^?7 m³ h^?1 m^?2 Pa^?1, 5.66 × 10^?7 m³ h^?1 m^?2 Pa^?1, and 9.26 × 10^?7 m³ h^?1 m^?2 Pa^?1 for ceramic, CA, and PVDF, respectively). However, filtration of the surfactants solutions did not cause permanent blocking of pores and the surface of the ceramic membrane in contrast to the polymeric ones. No significant differences in surfactants permeation through the membranes tested were observed. Concentration of the surfactant in the permeate was lower than 1 CMC for the Rofam 10 solution and exceeded the CMC by about 40 % for the SDS solution. Better separation properties of polymer membranes for the separation of cadmium(II) ions from micellar systems were identified.     

Solvent extraction and spectrophotometric determination of palladium(II) with some nitrogen-containing heterocyclic hydrazones in the presence of chloride ions

Three terdentate hydrazones, all containing the 1-phthalazino grouping in the hydrazine moiety but differing in the heterocyclic substituent in the aldehyde moiety, have been used as analytical reagents for palladium(II), the optimal conditions for the extractive spectrophotometric determination of palladium(II) in the presence of chloride ions being deduced. These compounds are highly selective and sensitive reagents for palladium(II), since they are not extracted into chloroform from sulfuric acid solutions and do not react with other platinum group metals. The desirable spectral properties of the palladium(II) complex of benzothiazole-2-aldehyde-1-phthalazinohydrazone (BAPhH) have also been discussed with respect to preference of the C  N structural form in the heterocyclic ring on the aldehyde moiety of the ligand.     

The array and interfacial activity of sodium dodecyl benzene sulfonate and sodium oleate at the oil/water interface

There is a close correlation between the interfacial activity and the adsorption of the surfactant at the interface, but the detailed molecular standard information was scarce. The interfacial activity of two traditional anionic surfactants sodium dodecyl benzene sulfonate (SDBS) and sodium oleate (OAS) were studied by experimental and computer simulation methods. With the spinning drop method and the suspension drop method, the interfacial tension of oil/aqueous surfactant systems was measured, and the influence of surfactant concentration and salinity on the interfacial tension was investigated. The dissipative particle dynamics (DPD) method was used to simulate the adsorption of SDBS and OAS at the oil/water interface. It was shown that it is beneficial to decrease interfacial tension if the hydrophobic chains of the surfactant and the oil have similar structure. The accession of inorganic salts causes surfactant molecules to form more compact and ordered arrangements and helps to decrease the interfacial tension. There is an osculation relation between interfacial density and interfacial activity. The interfacial density calculated by molecular simulation is an effective parameter to exhibit the interfacial activity.