Determination of copper impurities in nickel and cobalt salts by atomic absorption spectroscopy

Summary A method is described for the rapid determination of traces of copper in the ppm range in cobalt and nickel salts. The % standard deviation for the analysis is reported as 3.4 to 3.7 for aequous solutions and 4.8 to 5.0 for carbon tetrachloride sprayed directly into the flame after extraction.

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Zusammenfassung Ein Verfahren zur raschen Bestimmung von Kupferspuren im ppm-Bereich in Kobalt- und Nickelsalzen wurde beschrieben. Die Standardabweichung in wäßrigen Lösungen beträgt 3,4 bis 3,7%, bei unmittelbarem Versprühen der Tetrachlorkohlenstoffextrakte in die Flamme 4,8 bis 5,0%.

     

Nitration of pentaerythritol by HNO3-H2SO4-H2O system

Conclusions It was shown experimentally that the nitrating agent in the O-nitration of pentaerythritol by HNO₃-H₂SO₄-H₂O nitrating mixtures is not the nitronium cation but evidently the free unionized nitric acid molecule.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 1, pp. 134–140, January, 1970.     

Applications of benzotriazole methodology in heterocycle ring synthesis and substituent introduction and modification

Applications of benzotriazole methodology for the preparation of heterocyclic compounds are reviewed. The characteristic advantages of benzotriazole as a synthetic auxiliary are first briefly considered. This is followed by a summary of its use in ring synthesis in which the construction of small; five-membered; six-membered; and larger heterocyclic rings using benzotriazole methodology are each examined separately. Finally, consideration of the use of benzotriazole in the ring annulation - particularly benzannulation - of heterocycles. Subsequent sections deal with the introduction of substituents into aromatic heterocycles; the ring substitution of saturated heterocycles; and benzotriazole assisted modification of heterocyclic substituents. The present review supplements a recent comprehensive review of benzotriazole chemistry [1] which covers the literature through 1996.     

Isothermal degradation of poly-2,2′-(m-phenylene)-5,5′-bibenzimidazole

The isothermal degradation of poly-2,2′-(m-phenylene)-5,5′-bibenzimidazole in vacuo has been studied. Measurement of the increase in pressure with time, coupled with infrared analysis, was used to determine the distribution of the degradation products. Processes A and B with different second-order rate laws were determined to be significant in the temperature range of 550–700°C. Process A leads to the formation of equimolar quantities of hydrogen and ammonia and has an activation energy of 68 kcal/mole. Process B leads to the production of HCN, NH₃, and H₂ in the ratio of 1:1:2.5 and has an activation energy of 77 kcal/mole. The activation energies and the rate laws are consistent with a mechanism in which the initial degradation step is the bimolecular reaction of two aromatic rings.     

Overlapping spheres multiple scattering Xα calculations of the ionization potentials and electron affinities of nitrogen oxides

The ionization potentials and electron affinities of a series of nitrogen oxygen compounds have been calculated by the overlapping spheres MS Xα method to assess its applicability on a series for which good experimental data is available. The results for the ionization potentials were satisfactory although a straightforward matching of calculated and experimental IP's without consideration of other criterion would have led to some misassignments. The results for the electron affinities are in excellent agreement with experiment.     

On the synthesis of the N2F+5 cation. A critical comment on the paper by Toy and Stringham.

Toy and Stringham recently reported [1] the synthesis of N₂F⁺₅ (CF₃)₃CO^-, a salt containing the novel pentafluorohydrazinium cation. This cation would be of significant academic and practical interest [2] since it would constitute the first known example of a substituted NF⁺₄ cation, i.e. an NF⁺₄ cation in which a fluorine ligand is replaced by an NF₂ group. According to the authors of [1], N₂F⁺₅(CF₃)₃CO^- was formed in a very unusual reaction involving the transfer of a fluorine cation from (CF₃)₃COF to N₂F₄ according to:

     

Direct detection of the biradicals generated in the Norrish type II reaction

The biradicals generated in the Norrish type II reaction from the triplet manifold have been observed using laser flash photolysis techniques. The spectra and extinction coefficients closely resemble those of typical ketyl radicals. Typical lifetimes are in the 40–100 ns range depending on the solvent. Their interaction with oxygen is essentially diffusion controlled.     

Zum thermischen Verhalten von Li3MnO4. II [1, 2]. Über α- und β- Li2MnO3

Thermal Behaviour of Li₃MnO₄. II. α- and β-Li₂MnO₃ By thermal decomposition of Li₃MnO₄ we obtained two new forms of Li₂MnO₃: α-Li₂MnO₃ crystallizes due to Guinier-Simon photographs cubic face-centered with a = 4.09₂ Å, β-Li₂MnO₃ hexagonal with a = 4,93, c = 14.24 Å, c/a = 2.89. α-Li₂MnO₃ is paramagnetic with μ = 3,82 B.M. Below the Neel temperature (≈? 50 K) β-Li₂MnO₃ is antiferromagnetic. Effective Coordination Numbers, ECoN, are calculated and discussed.