Kinetics of oxidation of ethyldigol by vanadium(V) in aqueous acidic medium

The kinetics of oxidation of ethyldigol by vanadium(V) in aqueous acidic medium has been carried out. The reaction is first order with respect to vanadium(V) and the substrate and is acid catalysed.Hammett acidity function (H ₀) andBunnett hypothesis have been applied. The formation of free radicals during the course of the reaction has been indicated. A probable reaction mechanism is proposed.

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Die Kinetik der Oxidation von Ethyldigol mit Vanadium(V) in wäßrigem saurem Medium

Zusammenfassung Es wurde die Kinetik der Oxidation von Ethyldigol mittels Vanadium(V) in wäßriger saurer Lösung untersucht. Die Reaktion ist erster Ordnung bezüglich Vanadium(V) und Substrat und ist säurekatalysiert. Es wurden dieHammett-Aciditätsfunktion (H ₀) und dieBunnett-Hypothese angewandt. Die Bildung von freien Radikalen während der Reaktion konnte bestätigt werden. Es wird ein Reaktionsmechanismus vorgeschlagen.

     

Hyperfine structure in the configuration 4f 115d6s 2 of Er I

Hyperfine constants of low lying levels of the configuration 4f ¹¹5d6s ² in Er I have been measured for the only stable odd isotope,¹⁶⁷Er, using high resolution laseratomic-beam spectroscopy. Hyperfine parameters were evaluated from the experimental data using the effective tensor operator formalism. For this purpose eigenfunctions have been determined from an analysis of the fine structure energies of Er I as well as from ab initio multiconfiguration Dirac-Fock calculations. With the latter method also ab initio hyperfine constants for the levels investigated were evaluated. A comparison of calculated fine structure energies, Landég _J -factors and hyperfine constants with the experimental data allowed a test of the reliability of the fine structure and multiconfiguration Dirac-Fock wavefunctions. Effective nuclear electric quadrupole moments for¹⁶⁷Er have been determined from the experimental hyperfine constants using both calculated relativistic electronic radial integrals and hyperfine parameters for the 4f and 5d electrons in the configuration 4f ¹¹5d6s ² in Er I. From a comparison with the nuclear quadrupole moment measured in the mesic atom Sternheimer shielding factors are calculated. Configuration-interaction contributions to the radial integrals 〈r ^?3〉 _nl ⁰¹ of the 4f and 5d electrons have been determined.     

Polymerization of w/o microemulsions for the preparation of transparent SiO2/PMMA nanocomposites

Reverse w/o microemulsions composed of methyl methacrylate (MMA) forming the oil phase, nonionic surfactants, and water are used for the synthesis of transparent SiO2/PMMA nanocomposites. An inorganic precursor, tetraethoxysilane (Si(OEt)(4), TEOS), is hydrolyzed in the reverse micelles containing aqueous ammonia. During the hydrolysis of TEOS, polymerization of the continuous MMA phase is initiated using AIBN (azobisisobutyronitrile), and after thermal polymerization at 333 K for 12 h, solid blocks of PMMA are obtained in which nanometer-sized silica particles are trapped in the solid polymer matrix. According to small-angle X-ray and dynamic light scattering experiments, the water droplets in MMA microemulsions are 12 nm (R(W) = 13) in diameter, whereas after polymerization of the microemulsion, the SiO2 particles in the transparent SiO2/PMMA composites are 26 nm in diameter. Transmission electron micrographs demonstrate a low degree of agglomeration in the composites. In comparison with materials generated from micelle-free solutions, the particle size distribution is narrow. The reverse micelle-mediated approach produces composites of high transparency comparable with that of pure PMMA.     

Determination of an aldosterone antagonist in urine by high-performance liquid chromatography using automated column switching

An automated high-performance liquid chromatographic assay for the determination of an aldosterone antagonist (I) is described using column switching for direct injection of urine samples. After dilution with buffered internal standard solution, the sample was injected onto a clean-up column (17 X 4.6 mm I.D.), dry-packed with C18 reversed-phase material (particle size 30 micron). Polar urine components were removed by flushing the clean-up column with water. Retained substances, including I and the internal standard, were desorbed by backflush elution onto a 5-micron ODS-silica analytical column (125 X 4 mm I.D.), separated with water-methanol-tetrahydrofuran, and detected at 295 nm. After backflushing the analytical column and re-equilibrating the clean-up column, the system was ready for the next injection. The limit of quantification was ca. 100 ng/ml, using a 100-microliter specimen of diluted urine. The mean inter-assay precision of the method up to 25.6 micrograms/ml was 2%. Practicability and accuracy of the new method were demonstrated by the application to excretion studies performed with human volunteers.     

Wachstum dünner Fluorkohlenstoffschichten auf der Anode einer Glühkathodenentladung

The polymerization of tetrafluorethylene on the anode of a hot glow discharge has been investigated. Rates of polymer deposition have been measured as a function of monomer pressure, discharge current density, and electrode surface temperature. A mechanism of polymer formation is suggested. The results are different from those obtained by polymerization of the same monomer in a glow discharge. It is concluded that negative ions have a great influence on mechanism of polymer formation. Additionally, monomer molecules adsorbed at the electrode are polymerized by electron bombardment.     

Study of the Properties of Electrodeposited Polypyrrole Films

Experimental and theoretical methods have been used for characterization of the properties of polypyrrole films. The AFM studies show that the morphology of polypyrrole (PPy) films on polycrystalline gold electrodes at the first stages of synthesis depends on the structure of the metal surface. It was established that mobility of anions depends remarkably on the rate of electrodeposition of the polymer film. If PPy film was deposited at relatively low current density, mobility of ClO^- ₄ anion was not high enough to guarantee electroneutrality during redox cycling and cations take part in this process especially when Li⁺ cations were replaced by more mobile ⁺ cations. Semiempirical (AM1 and PM3) quantum-chemical methods were used for theoretical studies. It was established that different size and charge of the anions together with the variation in doping levels give rise to a different optimal conformation of oligopyrrole cations which, in turn, define the resulting polymer to be either all-anti (common linear chains) or all-syn (formation of helical structures) or a combination of the two.     

Novel iron(III) complexes of tripodal and linear tetradentate bis(phenolate) ligands: close relevance to intradiol-cleaving catechol dioxygenases

Four new iron(III) complexes of the bis(phenolate) ligands N,N-dimethyl-N',N'-bis(2-hydroxy-3,5-dimethylbenzyl)ethylenediamine [H2(L1)], N,N-dimethyl-N',N'-bis(2-hydroxy-4-nitrobenzyl)ethylenediamine [H2(L2)], N,N'-dimethyl-N,N'-bis(2-hydroxy-3,5-dimethylbenzyl)ethylenediamine [H2(L3)], and N,N'-dimethyl-N,N'-bis(2-hydroxy-4-nitrobenzyl)ethylenediamine [H2(L4)] have been isolated and studied as structural and functional models for the intradiol-cleaving catechol 1,2-dioxygenases (CTD). The complexes [Fe(L1)Cl] (1), [Fe(L2)(H2O)Cl] (2), [Fe(L3)Cl] (3), and [Fe(L4)(H2O)Cl] (4) have been characterized using absorption spectral and electrochemical techniques. The single-crystal X-ray structures of the ligand H2(L1) and the complexes 1 and 2 have been successfully determined. The tripodal ligand H2(L1) containing a N2O2 donor set represents the metal-binding region of the iron proteins. Complex 1 contains an FeN2O2Cl chromophore with a novel trigonal bipyramidal coordination geometry. While two phenolate oxygens and an amine nitrogen constitute the trigonal plane, the other amine nitrogen and chloride ion are located in the axial positions. In contrast, 2 exhibits a rhombically distorted octahedral coordination geometry for the FeN2O3Cl chromophore. Two phenolate oxygen atoms, an amine nitrogen atom, and a water molecule are located on the corners of a square plane with the axial positions being occupied by the other nitrogen atom and chloride ion. The interaction of the complexes with a few monodentate bases and phenolates and differently substituted catechols have been investigated using absorption spectral and electrochemical methods. The effect of substituents on the phenolate rings on the electronic spectral features and FeIII/FeII redox potentials of the complexes are discussed. The interaction of the complexes with catecholate anions reveals changes in the phenolate to iron(III) charge-transfer band and also the appearance of a low-energy catecholate to iron(III) charge-transfer band similar to catechol dioxygenase-substrate complexes. The redox behavior of the 1:1 adducts of the complexes with 3,5-di-tert-butylcatechol (H2DBC) has been also studied. The reactivities of the present complexes with H2DBC have been studied and illustrated. Interestingly, only 2 and 4 catalyze the intradiol-cleavage of H2DBC, the rate of oxygenation being much faster for 4. Also 2, but not 4, yields an extradiol cleavage product. The reactivity of the complexes could be illustrated not on the basis of the Lewis acidity of the complexes alone but by assuming that the product release is the rate-determining phase of the catalytic reaction.     

Alkaloids ofGlaucium fimbrilligerum. II

The alkaloids of the epigeal part and roots of the plantGlaucium fimbrilligerum have been studied. A total of 18 alkaloids has been isolated, of which epiglaufidine proved to be new, and its structure has been established. Columbamine has been isolated from the genusGlaucium for the first time, and magnoflorine and stilopine -hydroxymethylate from this species of plant for the first time.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Purkinje University, Brno, Czechoslovakia. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 493–496, July–August, 1983.     

4-Hydroxylindole-acetic acid — The microbiological transformation product of indole-3-acetic acid

Conclusions The isolation of an unknown intermediary in the microbiological transformation of indole-3-acetic acid to 4-hydroxyindole-3-acetic acid may help us to determine the structure of 4-hydroxyindole-3-acetic acid.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 5, pp. 1155–1158, May, 1975.The authors express their gratitude to G. K. Skryabin and M. N. Kolosov for assistance in carrying out the present work.     

Composition of the coats and kernels of the seeds ofNepeta pannonica andLavandula vera

The lipid compositions of the coats and kernels of the seeds ofNepeta pannonica andLavandula vera have been studied. It has been established that the lipids of the seed coats of the two species of plants differ substantially in their composition. The lipids of the kernels ofNepeta have been found to contain free fatty acids with chain lengths of from C₂₀ to C₃₅. Ursolic acid and its acetate have been isolated from extracts of the seed coats ofLavandula, and dimethyladipic acid from the seed oil of this species. Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 614–620, September–October, 1980.