Structural equilibrium (S=0) ⇄ (S=1)and inversion of the configuration of the seven-membered saturated metal-containing ring in four-coordinate pyrazolealdiminate metal chelates of nickel(II) based on tetradentate ligands

¹H and¹³C NMR, x-ray structural analysis, and magnetic moment measurements have shown that in 5-thio(seleno)pyrazolealdiminate complexes of nickel(II) based on tetradentate ligands containing the fragment, with n=2, flattening of the chelate unit takes place in solution and in the solid state. A similar structure in which the diamine metal-containing ring has the twist-chair conformation is observed for the crystals of the complexes with n=4. For the complexes with n=4 in solution at a temperature below –50°C, rapid (on the NMR time scale) interconversion of the flattened (P) (S=0) and pseudotetrahedral (T) (S=1) structures is observed, not accompanied by inversion of the tetrahedral configuration of the metal atom. At temperatures above –50°C, in addition to the low-barrier reactions (T) (P), conversion of the seven-membered saturated metal-containing ring and inversion of the tetrahedral configuration of the Ni atom with activation barriers of 48–51 kJ/mole are observed.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 2, pp. 327–335, February, 1990.     

The RS-.HSR Hydrogen Bond: acidities of alpha,omega-dithiols and electron affinities of their monoradicals

Gas-phase acidities (deltaGo(acid)) have been measured for 1,2-ethanedithiol, 1,3-propanedithiol, and 1,4-butanedithiol, using a Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometer. Adiabatic electron affinities (EAs) of the thiolate monoradicals of these compounds were assigned from electron photodetachment spectra of their corresponding thiolate monoanions, acquired using a cw-ICR. The dithiols exhibit enhanced acidities (up to 8.7 kcal/mol in deltaGo(acid)) and greater EAs (up to 6.7 kcal/mol) than analogous monothiol species. These differences are attributed to an intramolecular RS-.HSR hydrogen bond in the thiolate anion. Considerations of the RO-.HOR hydrogen bond in monoanions of alpha,omega-diols and in the [CH(3)O-.HOCH(3)] complex anion suggest that the RS-.HSR hydrogen bond provides up to 9 kcal/mol extra stabilization.     

Composition of lipids of the grain of opaque-2 maize

It has been established that the change in the composition of the total lipids and the fall in the fatty acid content depend on the initial maize genotype. A decrease in the amount of unsaponifiable substances in the grain of mutants is accompanied by qualitative changes in the composition regardless of the nature of the genotype.Scientific-Research Institute of Biology Dnepropetrovsk State university. Translated from Khimiya Prirodnykh Soedinenii. No. 3. pp. 360–363. May–June, 1988.     

Cyclization of n-alkylazinium cations with bisnucleophiles. 4. Regio- and stereospecificity of the reactions of β-diketones with quinoxalinium salts and their aza and benzo analogs

The reactions of substituted quinoxalinium, benzo[g]- and benzo[f]quinoxalinium, and pyrido[2,3-b]pyrazinium salts with anions of -dicarbonyl compounds give furo[2,3-b]-annelated systems with strictly determined regio- and stereoorientations.See [1] for Communication 3.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1543–1548, November, 1981.     

Degradation of aromatic compounds in ground-water, and methods of sample preservation

The degradation of acenaphthylene, acenaphthene, 2-methylnaphthalene, 2-methylindene, 3-methylindene and indene in water solutions was studied. These compounds at the 25-150 mug/l. level were almost totally degraded at ambient temperature within three days. The microbial population responsible for the degradation occurs naturally in ground-water taken from an aquifer in Ames, Iowa, which is contaminated with coal-tar products. These unidentified micro-organisms adapt readily to other waters when used as an inoculant for the degradation of aromatic compounds. The preservation of water to prevent such degradation was also investigated. Filtration through a 0.45-mum filter was found the most effective procedure for preserving the hydrocarbons in these waters.     

Chemistry of heteroanalogs of isoflavones

Condensation of 2-pyridylacetonitrile with polyphenols gave the corresponding -(2-pyridyl)-acetophenones, which were converted to the pyridine analogs of natural isoflavones and to 3-pyridylchromones with methyl, trifluoromethyl, and ethoxycarbonyl groups in the 2 position. The antimicrobial activity of 3-pyridylchromones and their reaction with alkylating and acylating agents and phosphorus pentasulfide were investigated.See [1] for communication V.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1180–1185, September, 1977.     

Chemische Vitamin D<Subscript>3</Subscript>-Bestimmung in Lebertran

The different aspects of Vitamin D₃ determination and the data reported in the literature are discussed. The spectrophotometric determination of Vitamin D₃ in cod-liver oil is carried out after the alkaline saponification, extraction of unsaponified parts, precipitation of accompanying sterols and the column- and thin-layer chromatographic purification and separation of vitamin D₃ on 40 cm plates from other vitamins. The dyestuff α-naphtholbenzein is suited well as standard substance for the better location and identification of vitamin D₃ zone on the thin-layer plate. The results obtained from the chemical method were checked through the simultaneous biological determination.     

The polarized ion model and the bending force constants of the group IIB halides

The applicability of the polarized ion model to the bending force constants of the group II metal dihalides is examined. Calculations are carried out for zinc, cadmium and mercury halides and show that the force constant values obtained are insensitive to the anion polarizability values used, but are quite sensitive to the metal ion polarizability values. It is shown that available polarizability values are not applicable to the group II dihalides. Therefore, force constant calculations with the metal ion polarizability as a variable parameter are carried out. Results agreeing with experimental values of the bending force constants are obtained for reasonable polarizability values, except for the case of the mercury halides. This discrepancy is discussed.

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Zusammenfassung Die Anwendbarkeit des polarisierten Ionenmodels zur Berechnung der Kraftkonstanten der Beugungsschwingung bei Metalldihalogeniden der Gruppe II wird untersucht. Berechnungen für Zink-, Cadmium- und Quecksilberhalogeniden werden durchgeführt und zeigen, daß die Werte für die Kraftkonstanten nur schwach von der Polarisierbarkeit der Anionen, dagegen ziemlich stark von der Polarisierbarkeit der Metallionen abhängen. Weiter wird gezeigt, daß die in Betracht kommenden Polarisierbarkeiten für die Dihalogenide der Gruppe II zu keinen sinnvollen Ergebnissen führen. Deshalb wurden die Berechnungen mit der Metallionen-Polarisierbarkeit als variablem Parameter ausgeführt. Resultate, die mit den experimentellen Werten übereinstimmen, wurden für vernünftige Polarisierbarkeiten erhalten. Die Quecksilberhalogenide bilden eine Ausnahme, die diskutiert wird.

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Résumé Examen de l'applicabilité du modèle de l'ion polarisé pour le calcul des constantes de force de déformation des dihalogénures des métaux du groupe II. Des calculs sont effectués pour les halogènures de zinc, cadmium et mercure, montrant que les valeurs obtenues pour les constantes de force sont insensibles aux valeurs des polarisabilités de l'anion, mais sont assez sensibles à celles de l'ion métallique. On montre que les polarisabilités disponibles ne sont pas applicables aux dihalogènures du groupe II. De ce fait les calculs de constante de force sont menés avec la polarisabilité variable pour l'ion métallique. Des résultats en accord avec les valeurs expérimentales des constantes de force de déformation sont obtenues pour des valeurs raisonnables de la polarisabilité, sauf dans le cas des halogènures de mercure. Cette discordance est discutée.