Zur Kinetik der Bildung von Arylaminomethylenverbindungen aus Triethoxymethan,Arylaminen und CH2-aciden Verbindungen in einer Dreikomponentenkondensation

Condensation of triethoxymethane and aniline with dimedone gives 2-anilinomethylene dimedone as the main product. An¹H-NMR-spectroscopic investigation of the kinetics in chloroform-d ₁ and methanol-d ₄ shows different rate determining steps in these solvents. There are two predominant rate determining steps in a complicated multistep reaction sequence.The initial one involves condensation of aniline with triethoxymethane to form diphenyl formamidine via ethyl phenyl formimidate. The second step involves reaction of the intermediate diphenyl formamidine with dimedone. The rates are strongly dependent upon the nature of the solvent and the concentration of catalytic acid. In methanol the reaction of dimedone with the intermediate diphenyl formamidine is rate determining. For preparative purposes the isolation of the intermediate diphenyl formamidine and the subsequent use of less polar solvents offer an advantage, because the second step is found to be accelerated.

6. Mitt.:Wolfbeis, O. S., Mh. Chem.112, 369 (1981).     

2-Spiro-indan-1,3-dione

The reaction of 1,3-indandione, formaldehyde and primary amines does not gives doubleMannich bases as described in literature, but the title compounds.

Herrn Professor Dr.F. Bohlmann zum 60. Geburtstag gewidmet.     

Dehydrogenation studies of dihydronicotinamide adenine dinucleotide (NADH) with methylene blue in the presence of the copper hexcyanoferrate(II) complex and light

The effects of copper ferrocyanide and light on the dehydrogenation rate of NADH by methylene blue is studied. The results suggest that the dehydrogenation rate of NADH with methylene blue is enhanced by copper ferrocyanide. Light also affects the reaction rate.     

Darstellung von Organoquecksilber—Stickstoffverbindungen durch Synproportionierung

The exchange reaction ofR ₂Hg and >N–Hg–N< compounds yielding organomercury—nitrogen compounds may be widely applied, as shown here in the synthesis ofN-phenylmercury-amides,-imides,-heterocycles and-triazenes.

     

Degradation of ferric EDTA by Burkhol cepacia

EDTA, the target compound of this study from the effluent of secondary biotreatment units, can be biodegraded by special microorganisms. So far, there are three species of microorganisms—Agrobacterium, Gram-negative BNCI, and DSM9103—that can degrade EDTA and are published in the literature. We have successfully isolated a bacterial strain that can degrade EDTA. It was identified as Burkhol cepacia, an aerobic species, elliptically shaped with a length of 5–15 μm. The growth medium contains 1000 mg/L of ferric-EDTA as carbon source, 750 mg/L of (NH₄)₂SO₄+(NH₂)₂CO as nitrogen source, and 1000 mg/L of KH₂PO₄ as phosphorus source, and mineral factors such as Fe and Mg. Incubated at pH, 7.0, 30°C, and 150 rpm on a shaker for 15 d, the average specific growth rate of this microbe is 0.135 d⁻¹, which shows that the respective degradation efficiency of Fe-EDTA and Cu-EDTA is 90 and 75% individually.     

Detection of nisin expression by Lactococcus lactis using two susceptible bacteria to associate the effects of nisin with EDTA

Nisin, a bacteriocin produced during the exponential growth phase of Lactococcus lactis ATCC 11454, inhibits the growth of a broad range of Grampositive bacteria. Gram-negative bacteria can also be inhibited by nisin with EDTA. In this study, nisin production was assayed by the agar diffusion method using Lactobacillus sake ATCC 15521 and a recombinant Escherichia coli DH5-α expressing the recombinant green fluorescent protein as the nisin-susceptible test organisms. The titers of nisin expressed and released in culture media were quantified and expressed in arbitrary units (AU/mL of medium) and converted to standard nisin concentration (Nisaplin^®, 25 mg of pure nisin with an activity of 1×10⁶ AU/mL). The expression and release of nisin by L. lactis in skimmed milk (9.09% total solids) with Man Rugosa Shepeer-Bacto Lactobacilli broth (1∶1) was monitored in a 5 L New Brunswick fermentor. Combining EDTA with nisin increased the bactericidal effect of nisin on the bacteria examined. The presence of EDTA was necessary to inhibit E. coli growth with nisin. L. sake was shown to be a good indicator for the evaluation of nisin release in the culture media, including with the addition of EDTA.     

Beiträge zur Chemie der Pyrrolpigmente, 78. Mitt.: Die Eigenschaften desb-Nor-bilatrien-abc-b-Nor-biladien-ac-Systems

The redox coupleb-nor-biladiene-ac (2)/b-nor-bilatriene-abc (3) exhibits an oxidative half wave potential of 800 mV in acetonitrile solution. It is demonstrated that it can be used as an extremely efficient electron carrier through bulk membranes. Whereas2 is not suitable as a ligand in carrier mediated cation transport,3 is a medium suited carrier for Cu(II) or Zn(II) ions, however, it is the most efficient one found so far for transport of Hg(II) ions. A 1:1 zinc chelate of3 is isolated and characterized. it is deduced to represent a polymer consisting of about 73 monomer units.

     

1,3-bis(2,4,6-trinitrophenylaminooxy)propane and its 4-cyano-2,6-dinitrophenyl congener: Synthesis and properties

Starting from N-hydroxyphthalimide (5) and 1,3-dibromopropane (6) we obtained 1,3-bis(phthalimidooxy)propane (7) which led to 1,3-bis(aminooxy)propane dihydrochloride (8). From its reaction with picryl chloride or 4-cyano-2,6-dinitrochlorobenzene, the two title compounds (4b, 4a) were obtained. ¹H-NMR and ¹³C-NMR spectra are presented. For comparison with the analogous N-methoxy-2,6-dinitro-4-R-anilines 1a, 1b (R=CN or R=NO₂), wer report the hydrophobic characteristics (by RPTLC), electronic spectra for the neutral compounds and their anions, pK _a values, and the behavior towards oxidizers (DPPH, PbO₂, Pb(CH₃COO)₄, KMnO₄ and Ag₂O); DPPH converts compounds 1a, 1b and 4a, 4b into betainic structures 2a, 2b respectively.     

Physico-chemical properties of Chitosan films

Chitosan films obtained by dry phase inversion were prepared from an aqueous solution of chitosan in acetic acid. The films, of thickness less than 20 μm, were transparent, very flexible and had smooth surfaces. Increasing the film thickness induced an increase of the internal tensions and the consequent formation of a rough surface. Structural investigations by X-ray diffraction and Fourier transform IR analysis, showed that the chitosan films, as prepared, are amorphous. Further annealing to evaporate acetic acid and water traces, changed the amorphous phase into a more ordered phase, characterized by diffraction peaks at 2θ values of 9, 17, 20 and 23 degrees. Thermal investigations by TG, DTG, and DTA revealed that the decomposition of the chitosan films as prepared proceeds in two stages, starting from 180°C and 540°C.     

Zur Reaktion von Hydrazinen mit Fluorsilanen und lithiierten Aminen

Lithium salts of hydrazines react with fluorosilanes under formation of fluorosilylhydrazines and LiF. Five membered rings are obtained in the reaction of bis(fluorosilyl)-hydrazines with lithiated amines. The mass,¹H-and¹⁹F-nmr spectra of the compounds are reported.

     

Kinetische und thermodynamische Untersuchungen im System AgCl-LiCl-NaCl

In the ternary system silver chloride-lithium chloride-sodium chloride the kinetics of the galvanic deposition of silver on graphite electrodes was investigated as well as its dissolution without current in the molten salt saturated with chlorine gas.In addition the emf-values were measured in the temperature range between 923 K and 1,173 K by means of, the formation cell graphite/Ag(s)/AgCl(l)–LiCl(l)–NaCl(l)/Cl₂ graphite From these data the partial molar free excessGibbs energies were calculated. Using the equation for a multicomponent system as suggested byRedlich-Kister ¹ G _AgCl ^E values were obtained by a non-linear fitting process, where the fit was performed for all investigated temperatures and over the entire concentration range in the ternary system. With the parameters obtained the partial and integral excess valuesG _i ^E ,G ^E ,H _i ^E ,H ^E ,S _i ^E andS ^E were calculated.

     

Kinetics and mechanism of oxidation of xylitol and galactitol by hexacyanoferrate(III) ion in aqueous alkaline medium

Kinetics of oxidation of xylitol and galactitol by hexacyanoferrate(III) ion in aqueous alkaline medium is reported. The reaction rate is of first order with respect to hexacyanoferrate(III) in each substrate. The reaction is first order at lower concentrations of xylitol and galactitol and tends towards zero order as the concentration increases. Similarly first order kinetics was obtained with respect to hydroxide ion at lower concentrations and tends to lower order at higher concentration in the oxidation of xylitol; in the oxidation of galactitol the reaction is first order with respect to hydroxide ion even up to manyfold variation. The course of reaction has been considered to proceed through the formation of an activated complex between [K Fe(CN)₆]^2– and substrate anion which decomposes slowly into radical and [K Fe(CN)₆]^3–. A probable reaction mechanism is proposed.

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Kinetik und Mechanismus der Oxidation von Xylit und Galaktit mit Hexacyanoferrat(III) in wäßriger, alkalischer Lösung

Zusammenfassung Das Geschwindigkeitsgesetz der Titelreaktion ist in beiden Fällen erster Ordnung bezüglich Hexacyanoferrat(III). Die Oxidation ist erster Ordnung bei niedrigen Konzentrationen von Xylit und Galaktit und geht bei Erhöhung der Konzentration gegen null. In gleicher Weise wurde eine Kinetik erster Ordnung bezüglich Hydroxyl bei niedrigen Konzentrationen und eine erniedrigte Ordnung bei höheren Konzentrationen für die Oxidation von Xylit beobachtet; bei Galaktit bleibt die Oxidation auch bei höheren Hydroxyl-Konzentrationen erster Ordnung. Es wird angenommen, daß die Reaktion über einen aktivierten Komplex zwischen [KFe(CN)₆]^2– und dem Substrat-Anion verläuft; dieser Komplex zerfällt in [KFe(CN)₆]^3– und ein Substrat-Radikal. Ein möglicher Reaktionsmechanismus wird vorgeschlagen.

     

Validation of methodology for determination of the mercury methylation potential in sediments using radiotracers

Experiments to determine the mercury methylation potential were performed on sediments from two locations on the river Idrijca (Slovenia), differing in ambient mercury concentrations. The tracer used was the radioactive isotope ¹⁹⁷Hg. The benefit of using this tracer is its high specific activity, which enables spikes as low as 0.02 ng Hg²⁺ g⁻¹ of sample to be used. It was therefore possible to compare the efficiency of the methylation potential experiments over a range of spike concentrations from picogram to microgram levels. The first part of the work aimed to validate the experimental blanks and the second part consisted of several series of incubation experiments on two different river sediments using a range of tracer additions. The results showed high variability in the obtained methylation potentials. Increasing Hg²⁺ additions gave a decrease in the percentage of the tracer methylated during incubation; in absolute terms, the spikes that spanned four orders of magnitude (0.019–190 pg g⁻¹ of sediment slurry) resulted in MeHg formation between 0.01 and 0.1 ng MeHg g⁻¹ in Podroteja and Kozarska Grapa. Higher spikes resulted in slightly elevated MeHg production (up to a maximum of 0.27 ng g⁻¹). The values of methylation potential were similar in both sediments. The results imply that the experimental determination of mercury methylation potential strongly depends on the experimental setup itself and the amount of tracer added to the system under study. It is therefore recommended to use different concentrations of tracer and perform the experiments in several replicates. The amount of mercury available for methylation in nature is usually very small. Therefore, adding very low amounts of tracer in the methylation potential studies probably gives results that have a higher environmental relevance. It is also suggested to express the results obtained in absolute amounts of MeHg produced and not just as the percentage of the added tracer.     

The dual role of cytochrome c2 in the facultative phototrophic bacteriumRhodopseudomonas capsulata

Succinate oxidation is stimulated by addition of cytochrome c₂ in cytochrome c₂-deficient spheroplasts from the M6-mutant and from the wild type strain ofRhodopseudomonas capsulata. Inhibition of the alternative oxidase in the wild type by CO facilitates this observation. The finding confirms a dual role of cytochrome c₂, in photosynthetic and in respiratory electron transport.

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Die doppelte Rolle von Cytochrome c₂ in Rhodopseudomonas capsulata

Zusammenfassung Die Oxidation von Succinat wird durch Zugabe von Cytochrom c₂ zu Cytochrom c₂-defizienten Sphäroplasten der Mutante M6 und des Wildtyps vonRhodopseudomonas capsulata stimuliert. Die Hemmung der alternativen Oxidase durch CO im Wildtyp erleichtert diese Beobachtung. Der Befund bestätigt die Doppelrolle von Cytochrom c₂ im photosynthetischen und respiratorischen Elektronentransport.

     

Zur Reaktivität des neuen Codimeren aus Malonitril und Cyanessigester bzw. dimeren Cyanessigester gegenüber Benzilen

Condensation of benzils with 3-amino-2,4-dicyano-crotonic-ester (2a, b) and dimer cyanoacetate (2c, d) resp. leads to 4,5-diaryl-3-pyrroline-2-ylidenecyanoacetates3a-m. It can be shown by¹³C-spectroscopy that in the monosubstituted benzil1c the carbonyl function adjacent to the unsubstituted phenyl reacts with the methylene group of2a orb. With aqueous alkaline the pyrrolines3 rearrange to pyrrolidinones4a-i.¹H-NMR-CIDNP experiments support the assumption of a partial radical character of this rearrangement.

     

Comparative study of structural stability in [NH4−n (CH3) n ]2HgCl4 and in related compounds

The structural instability of the [NH_4−n (CH₃) _n ]₂HgCl₄ group has been investigated. Consideration of different crystals of this family shows that the H-bonds, obviously, hinder the appearance of incommensurate modulation. The dependence of phase transition sequence on the sizes of cation and anion may be obtained only for crystals with simple cation. The appearance of H-bonds complicates the situation and, leads to gradual disappearance of IC phase in the A₂BX₄ family.     

Über Erdalkalimetalloxogallate. VIII Synthese und Aufbau eines neuen Calciumoxogallats: Ca3Ga4O9

The hitherto unknown compound Ca₃Ga₄O₉ was prepared and investigated by X-ray single crystal methods. Ca₃Ga₄O₉ has orthorhombic symmetry:a=1435.8;b=1682.5;c=532.1 pm; space group C _2v ¹¹ –Cmm2,Z=6. The tetrahedra network (circles of 4 and 5 GaO₄-tetrahedra) and the surrounding of Ca²⁺ are described and discussed with respect to other oxogallates.

     

Characterization and sorption properties of Aspergillus niger waste biomass

The structure and the biosorption properties of fungal biomass of Aspergillus niger originated from citric acid fermentation industry was investigated. This waste biomass, produced in high quantity in carefully controlled industrial processes, has certain favourable characteristics that may be improved for its usefulness. In environmental chemistry, it is known for the removal of heavy metals cations. In this work, different alkaline treatments (1M NaOH/20°C/24 h and 10M NaOH/107°C/6 h) were used to evaluate the dependence of sorption properties of biomass on the cell wall composition. The biosorption was studied by the batch method, with the biomass concentration of 1 g/l, at pH 6. The adsorption of lead was more effective than that of cadmium. The biosorption capacity was evaluated using the biosorption isotherm derived from the equilibrium data. At pH 6, the maximmum lead biosorption capacity estimated with the Langmuir model was 93 mg/g dry biomass.     

A comparison of sequential extraction procedures for fractionation of arsenic,cadmium, lead,and zinc in soil

Twelve soil samples differing in physicochemical properties and total element contents were extracted by three sequential extraction procedures to determine As, Cd, Pb, and Zn bound to individual soil fractions and are defined by individual operational procedures. In the case of arsenic, two additional sequential extraction schemes were designed entirely for fractionation of soil containing arsenic were tested. The results confirmed that determination of element proportions bound to individual soil fractions is strongly dependent on the extracting agent and/or procedure applied within individual extracting schemes. As expected, absolute values of the elements released among the individual extracting procedures are weakly comparable. More reliable results were determined for the more mobile soil elements i.e. cadmium and zinc, in the fractions characterizing the most mobile proportions of investigated elements where significant correlations with basic soil characteristics were observed. In contrast, ambiguous results were observed for As and Pb, for both the individual extraction procedures and the effect of the soil characteristics. Regardless of the studied element, the poorest results were determined for reducible and oxidizable soil fractions. The application of at least two independent procedures or modification of the extraction scheme according to element investigated and/or particular soil characteristics can also be helpful in definition of element pattern in soils in further research.     

Segregated network polymer/carbon nanotubes composites

In this work we present the preparation of conductive polyethylene/carbon nanotube composites based on the segregated network concept. Attention has been focused on the effect of decreasing the amount of filler necessary to achieve low resistivity. Using high- and low-grade single-walled carbon nanotube materials we obtained conductive composites with a low percolation threshold of 0.5 wt.% for high-grade nanotubes, about 1 wt% for commercial nanotubes and 1.5 wt% for low-grade material. The higher percolation threshold for low-grade material is related to low effectiveness of other carbon fractions in the network formation. The electrical conductivity was measured as a function of the single-walled carbon nanotubes content in the polymer matrix and as a function of temperature. It was also found that processing parameters significantly influenced the electrical conductivity of the composites. Raman spectroscopy was applied to study single wall nanotubes in the conductive composites.