Setting the boundary conditions by the potential shift in the self-consistent field (Xα-scattered wave) cluster calculations

Potential shifts given by the Madelung potentials in different regions of a molecular cluster are determined in the MT approximation. Nickel and zinc oxides are employed to consider the interrelation between the approaches to the calculation of the boundary conditions in terms of the Watson sphere and the potential shift in the cluster calculations of perfect and imperfect ionic crystals using the self-consistent field (Xα-scattered wave) method. Translated fromZhurnal Strukturnoi Khimii, Vol. 38, No. 1, pp. 23–31, January–February, 1997. Original article submitted February 12, 1996.     

Alkylierung ambidenter Heterocyclen-Anionen, 1. Mitt.: Über die Benzylierung des 4-Hydroxy-carbostyrils

Zusammenfassung 4-Hydroxy-carbostyrile (1a–c) werden mit Benzylchlorid inDMF bevorzugt zu den 4-Benzyloxy-carbostyrilen (2a–c) alkyliert. In wäßr. NaOH dagegen erhält man aus1a und1c als Hauptprodukt das 3,3-Dibenzyl-2,4-dioxo-1,2,3,4-tetrahydrochinolin (3).

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Alkylation of 4-hydroxy-quinol-2-ones (1a–c) with benzyl chloride inDMF in the presence of K₂CO₃ mainly gives the 4-benzylethers2a–c. However, carbon dialkylation takes place in aqueous NaOH and the main product of the reaction between benzylchloride and1a is 3.3-dibenzyl-2.4-dioxo-1.2.3.4-tetrahydro-quinoline3.

     

Determination of moisture on thorium dioxide by a coulometric electrolytic measurement with electronic integration

The coulometric electrolytic principle is utilized for the measurement of moisture sorbed on sintered thorium dioxide. Moisture is removed from the sample by heating and is swept by dry argon gas through a hygrometer. The resulting hygrometer output is converted into frequency pulses and counted cumulatively. The instrument is calibrated by use of standard hydrated chemicals. The number of counts/mu;g of water obtained from standards compares favourably with the theoretical number of counts/mu;g calculated from performance specifications of the components employed. The error is <5% for 1-350mu;g of water. A high sensitivity and low operating blank recommends application of this method to materials other than thorium dioxide, having very low moisture contents.     

Formation constants of zinc(II) complexes with Semi-Xylenol Orange

A potentiometric and spectrophotometric investigation on the formation of zinc(II) complexes with Semi-Xylenol Orange (SXO or H(4)L) is reported. In an aqueous solution (mu = 0.1), three 1:1 complex species, MH(2)L, MHL(-), ML(2-), and a 1:2 complex, ML(6-)(2), seem to exist. In a strongly alkaline medium (above pH 12.5) the complexes may dissociate to give zinc hydroxide and L(4-). The formation of a hydroxy complex is not observed. The absorption maxima are at 445 nm (MH(2)L), 466 nm (MHL(-)) and 561 nm (ML(2-)), the molar absorptivities being 2.34 x 10(4), 2.42 x 10(4) and 3.14 x 10(4) 1.mole(-1) .cm(-1) respectively. The formation constants are (at 25 +/- 0.1 degrees ) log K(M)(ML) = 11.84, log K(M)(MHL) = 7.13, log K(M)(MH(2)L) = 2.70, log K(M)(ML(2)) = 16.60.     

Oxidation of the [Rh(CO)2Cl2] anion in aqueous solution

The reaction of rhodium(I) carbonyl chloride, [Rh(CO)₂Cl]₂, with dichromate, cerium(IV) sulfate, hexachloroplatinic acid or p-benzoquinone in aqueous hydrochloric acid proceeds by consumption of 4 equivalents of oxidizing agent per mole or rhodium(I) in accordance with the equation Rh^I(CO)₂  4e + H₂O → Rh^III(CO) + 2H⁺ + CO₂A “cyclic” oxidation mechanism is suggested.     

Preparation of isomeric 1,3- and 1,5- (o-phenylene)-hexamethylcyclotetrasiloxanes and investigation of their spectral characteristics

Workup of the mixture of products of pyrolysis of cyclotetrasiloxane (Me₂SiO)₂(MePhSiO)₂ yielded 1,3- (I) and 1,5-(o-phenylene)cyclosiloxane (II), the structures of which were established on the basis of data from their IR, PMR, and mass spectra.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 24–25, January, 1978.     

15N-NMR spectroscopy. III. Neighboring residue effects in sequence polymers containing glycylglycine units

The tripeptides Phe-Gly-Gly, β-Ala-Gly-Gly, and ?-Aca-Gly-Gly as well as the peptide derivatives δ-isothiocyanatovaleroyl-Gly-Gly and ?-isothiocyanatocaproyl-Gly-Gly were synthesized by using known methods so that the peptide nitrogen between the two glycyl residues was isotopically enriched in ¹⁵N to a level of 0.8–0.9%. These monomer units were then used to produce the sequence polymers (Phe-Gly-Gly)_n, (β-Ala-Gly-Gly)_n, (δ-Ava-Gly-Gly)_n, and (?-Aca-Gly-Gly)_n. The 18.24 MHz ¹⁵N-NMR spectra of the oligo- and polypeptides were obtained by using trifluoroacetic acid as solvent, since the solutions have relatively low viscosity and exhibit a strong negative nuclear Overhauser enhancement of the ¹⁵N signals. For comparison, ¹⁵N-NMR spectra of the homopolymers (Gly)_n, (β-Ala)_n, (γ-Abu)_n, (δ-Ava)_n, and (?-Aca)_n were also recorded. The ¹⁵N signals from the ω-aminoacyl residues in the sequence polymers appear up to 11 ppm upfield of the signals observed for the homopolyamides. The ¹⁵N signals from the two glycyl residues are separated by 3–7 ppm. Comparison with the ¹³C-NMR spectra of the same polymers indicates that ¹⁵N-NMR is better suited for the characterization and sequence analysis of these types of polymers.     

Thermal density fluctuations in amorphous polymers as revealed by small angle X-ray diffraction

Summary Thermal density fluctuations in amorphous polymethyl methacrylate, polycarbonate and polyethylene terephthalate were studied by means of small angle X-ray scattering. The measurements were performed in a temperature range from 20 °C up to about 50 °C above the glass transition temperatureT _g of the individual sample.AboveT _g the experimental values of the fluctuations are proportional to the isothermal compressibility and the temperature of the sample as predicted by the fluctuation theory for a system in thermodynamic equilibrium.At temperatures belowT _g this relation is no longer correct. The experimentally determined fluctuations are now proportional to the compressibility of the sample in the equilibrium state atT _g and to the actual temperature of the glassy sample. By considering a statistical ensemble with exchange of energy, particles and order between the systems of the ensemble an equation can be derived for the fluctuations of the number of particles per given volume which predicts the observed behaviour. The order parameter takes into account the fact that the properties of the glassy state depend on the way by which the state was produced.

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Zusammenfassung Es wurden thermische Dichtefluktuationen in amorphem Polymethylmethacrylat, Polycarbonat und Polyäthylenterephthalat mit Hilfe der Röntgenkleinwinkelstreuung untersucht. Die Messungen erstrecken sich über einen Temperaturbereich von 20 °C bis zu etwa 50 °C oberhalb der GlastemperaturT _g der jeweiligen Probe.In Übereinstimmung mit den Ergebnissen der Fluktuationstheorie sind die Fluktuationen oberhalb vonT _g proportional zur isothermen Kompressibilität und zur Temperatur der Probe.Unterhalb der Glastemperatur ist diese Beziehung nicht mehr erfüllt. Hier ist die Fluktuation proportional zur Kompressibilität der Probe im Gleichgewichtszustand beiT _g und zur Temperatur. Auf der Basis einer statistischen Gesamtheit mit der Austauschmöglichkeit von Energie, Partikel und Ordnung zwischen den Systemen der Gesamtheit kann eine Beziehung für die Dichtefluktuation abgeleitet werden, die mit den experimentellen Ergebnissen übereinstimmt. Der zusätzliche Ordnungsparameter berücksichtigt die Tatsache, daß die Eigenschaften im Glaszustand wegabhängig sind.

     

Structure of 6-β-[(hexahydro-1H-azepin-1-yl)methyleneamino]penicillanic acid sulfoxide

The oxidation of 6--[(hexahydro-1H-azepin-1-yl)methyleneamino]penicillanic acid with potassium periodate or m-chloroperbenzoic acid leads to the corresponding sulfoxide. Its structure was proved by alternative synthesis by splitting out the N-phenylacetyl group from the benzylpenicillin sulfoxide and condensation of the 6-aminopenicillanic acid sulfoxide with N-formylhexamethyleneimine dibutylacetal.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 649–651, May, 1982.     

Spectrophotometric investigation of the reaction of eriochrome cyanin RC and magnesium and aluminium

The reaction of magnesium or aluminium ions with Eriochrome Cyanin RC in alkaline medium leads to formation of a complex of type ML. The molar absorptivities of the complexes are 1.90 +/- 0.14 x 10(3)1. mole(-1).cm(-1) at 570 nm for the magnesium complex and 3.87 +/- 0.04 x 10(4) at 555 nm for the aluminium complex. The conditional stability constants of the complexes were determined at various pH values, and hence the overall formation constants, which were found to be log beta(111) = 8.65 +/- 0.06 for MgOHL, log beta(121) = 22.29 +/- 0.05 for AlH(2)L, log beta(111) = 18.25 +/- 0.14 for AlHL, and log beta(101) = 13.66 +/- 0.01 for AlL.