NMR Study of Structural Changes in Humic Acids of Meadow Soddy Soils

Quantitative and qualitative changes in humic acids of meadow soddy soils, occurring under the action of various fertilizer systems, were studied by ¹³C and ³¹P NMR.     

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.     

Stabilization of Graphite Nitrate by Intercalation of Organic Compounds

New thermally stable intercalation compounds of graphite were obtained by the further intercalation of a series of organic compounds into graphite nitrate. The stabilization is explained by the formation of hydrogen bonds between the protonated form of the modifying substance and neutral surrounding molecules.     

A facile entry to l-aryl-4,5-dihydro[1,4]oxazepino-[5,4-a]isoindole-2,7-diones

The titled compounds were prepared by reacting N-(2-bromoethyl)phthalimide with enolates of phenylacetic acid esters. 2,3-Dihydrooxazolo[2,3-a]isoindolones are believed to be intermediates in the process. An X-ray crystallographic analysis was conducted on one of the compounds.     

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.