High-Sensitivity Determination of Hydrocarbon Impurities in Arsine by Reaction Gas Chromatography

It is shown that the results of determining methane in high-purity arsine by reaction gas chromatography can be overestimated by more than two orders of magnitude. This overestimation is caused by the formation of methane as a side product of the reaction. Cryogenic preconcentration at the injection stage is proposed to improve the accuracy of determination of methane, and the cryofocusing of impurity hydrocarbons is proposed to improve separation. Detection limits of (3–10) × 10^–6 vol % are achieved for C₁–C₅ hydrocarbons.     

Thermochemistry of Dissolution of Glucose in Binary Systems N-Methylmorpholine N-Oxide Monohydrate-Aprotic Solvent

Glucose enthalpies of solution in binary systems N-methylmorpholine N-oxide monohydrateaprotic solvent at 75°C are measured.     

Effect of Mechanochemical Activation on the Catalytic Properties of Ferrites with the Spinel Structure

It was found experimentally that stacking defects formed in the mechanochemical activation of zinc ferrite enhanced the specific catalytic activity in the reaction of CO oxidation. The specific rate of CO oxidation was a linear function of defect concentration, which was determined using Mössbauer spectroscopy and X-ray diffraction. A conclusion was drawn that the same centers are responsible for an increase in the catalytic activity, the sorption capacity for hydrogen sulfide, and the reactivity of zinc ferrite in the interaction with hydrochloric acid. It was assumed that analogous factors caused an increase in the catalytic activity and reactivity of magnesium ferrite.     

Composition and Physicochemical Properties of Schungite Sorbent as Influenced by Thermal Treatment

The chemical composition, specific surface area, and pore structure of a schungite sorbent were studied as influenced by the conditions of thermal treatment.     

Synthesis of Aryl Ethers by Nonactivated Aromatic Nucleophilic Substitution Reactions

The results of a kinetic study of model reactions between substituted phenols and bromobenzene in the presence of potassium carbonate and the copper(I) chloride–8-hydroxyquinoline catalytic complex in N,N-dimethylformamide are presented. The reactions were found to obey a first-order rate law. Both orbital and charge interactions should be taken into account in a consideration of the effect of the structural characteristics of reactants on the rate of reaction. The kinetics of substitution of the phenoxide anion for an aromatically bound halogen atom in activated and nonactivated systems with the formation of practically valuable aryl ethers were comparatively studied. The results presented provide an opportunity to distinguish the common features and regularities of activated and nonactivated aromatic substitution in the test systems.     

Indirect laser photoacoustic detection for trace samples on membranes

An indirect laser photoacoustic technique is described. The basic principle, the experimental set-up and the influencing factors are discussed in detail. This method was used to quantify phenylamine, arginine and methylene blue on membranes. The linear ranges of the calibration curve are up to two orders of magnitude. With 1 microliter of sample solution, the detection limits are 0.25, 1.52 and 0.14 pmol for phenylamine, arginine and methylene blue, respectively.     

Asymmetry and magnetism in bis(oximato)-bridged heterobimetallic compounds: a computational approach

A density functional study of exchange coupling was carried out for a series of heterobinuclear oximato-bridged transition metal complexes. Model calculations were used to examine the influence of the electronic configuration of the metal atoms on the coupling constants. This analysis was complemented by a study of the variation of the coupling constant with the most usual structural distortions within this family of compounds. The influence of the nature of the terminal ligands as well as that of the symmetry on the bridge were also investigated.     

Action of nucleophilic agents on the pyrimidine ring

It is shown that 2-alkylpyrimidine methiodides in which the alkyl group is activated by electron-acceptor substituents undergo recyclization to the corresponding 2-methylaminopyridines in an alcohol solution of methylamine. Similar recyclization also takes place without quaternization of the pyrimidine ring when there is a strong electron-acceptor substituent (a nitro group) in the ring.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1400–1405, October, 1978.