Calculations of van der Waals interaction energies for Al, Cr, Fe, and Ir acetylacetonate crystals

Experimental data have been analyzed and interpreted for four volatile acetylacetonates of trivalent metals Al, Cr, Fe, and Ir. The crystal lattice energies were calculated by the atom-atom potential method. The lattice energies obtained by using the Buckingham potential are in better agreement with the sublimation heats of these metal complexes than those calculated from the Lennard-Jones potential. The experimental dependences of vapor pressure for the complexes are in satisfactory agreement with the values obtained from the calculated lattice energies and entropies of crystal-gas transitions.     

Detection and separation of two forms of cotton-plant pyrophosphatase

Two pyrophosphatase isoenzymes with identical molecular weights but differing in the pH optima of their action and also in their senstivity to some bivalent metal ions have been isolated from extracts of the cotyledons of three-day cotton-plant shoots by gel filtration and ion-exchange chromatography.V. I. Lenin Tashkent State University. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 375–378, May–June, 1985.     

Analytical Application of Silica Gel Modified with Didecylaminoethyl-beta-Tridecylammonium Iodide

Sorption of a high molecular weight quaternary ammonium salt, didecylaminoethyl-β-tridecylammonium iodide (DDATD) on different types of sorbents was investigated. The nature of reagent adsorption on silica gel was examined by spectroscopic and computer methods. The sorption of anionic metal complexes of cobalt, copper, zinc and manganese on silica gel modified with DDATD was studied. The possibility of recovery of cobalt and copper thiocyanate complexes and their further atomic absorption determination is shown. Modified sorbent was applied to cobalt chemiluminescence and determined in natural water and a nickel preparation (detection limit, 2 μg/l.).     

Structure of phenolic stabilizers for polymers VIII. Crystal structure of 2,2′-methylenebis(4-methyl-6-ter-butylphenol) monoacrylate

L. Ya. Karpov Scientific-Research Physicochemical Institute. Scientific-Research Institute of Rubber and Latex Goods. Translated from Zhurnal Strukturnoi Khimii, Vol. 32, No. 5, pp. 162–164, September–October, 1991.     

Nature of intermolecular interactions and conductance in a system consisting of alkali metal ions,crown ether,anion radicals,and a polar solvent

The methods of²³Na and⁷Li NMR, EPR and conductimetry have been used to investigate the intermolecular interactions in systems consisting of the anion-radical salt of an alkali metal and a crown ether, dissolved in acetonitrile. Relations have been established between the structure of the complexes formed in solution, their magnetic resonance characteristics, and their limiting conductance. For solutions of anionradical salts in the presence of an excess of crown ether additional routes for conductance have been identified, connected with electron exchange reactions between the molecules of organic -acids in different charge states.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 25, No. 2, pp. 173–182, March–April, 1989.     

pH-Metric determination of acid numbers in petroleum oils without titration

A new pH-metric method without titration has been developed for determination of acid numbers lower than 0.1 mg (KOH) g(-1) (oil) in petroleum oils such as White, Transformer and Basic oils. The method is based on rapid and complete extraction of acids from an oil test portion into the novel reagent and measurement of the conditional pH in the ;oil-reagent' mixture by a glass electrode. The method has a quantitation limit equal to 1x10(-3) mg (KOH) g(-1) (oil), uses non-toxic reagents, is not time and labor consuming, and is cheap and simple for automation.     

Micellar enhanced cyanide ion determination in samples from synthetic organic processes

A method was developed for the recovery and determination of cyanide ion in organic sample matrices. To facilitate the solubilization of cyanide ions, cetyltrimethylammonium bromide (CTAB) was added at concentrations above the critical micelle concentration. Sample cyanation reaction products consisted of solvent mixtures of a hydroxynitrile in DMF-toluene or DMF-isopropylacetate (IPAC). Spectrophotometric determination of cyanide ion at 578 nm by the pyridine-barbituric acid method was automated by flow injection analysis. Recovery of cyanide ion from spiked samples was 93.2% in DMF-IPAC solvent matrix and 93.9% in DMF-toluene. Low alkali concentration was observed to favor solubilization of cyanide ion in the micellar solution.     

On the mechanism of hydrogen evolution at GaAs electrodes

The hydrogen evolution reaction at n- and p-GaAs electrodes has been reinvestigated. As in the case of metal electrodes, hydrogen evolution can occur in two ways: at ?0.5 V (SCE) hydronium ions are reduced, at ?1.25 V (SCE) reduction of water molecules takes place. It is confirmed that in both cases conduction band electrons are responsible for the two reduction steps, forming adsorbed hydrogen atoms in the first and hydrogen molecules in the second step. Hole injection can occur only to a negligible extent, although it appears energetically feasible.     

Methylation analysis in glycoprotein chemistry. General procedure for quantification of the products of solvolysis of permethylated glycopeptides and glycoproteins

A technique for the gas chromatographic analysis of the products of solvolysis of permethylated glycopeptides and glycoproteins has been developed. It involves methanolysis of a permethylated compound, quantitative transformation of methyl ethers of methyl glycosides into the corresponding O-trimethylsilyl(TMS)-O-methylalditols [2-deoxy-2-(N-methyl)acetamido-O-TMS-O-methylalditols in the case of hexosamine derivatives] and gas chromatographic quantification using a single column packed with 0.4% OV-225 on surface-modified Chromosorb.     

Configurational inversion and hexachloroethane chlorination of α-sulfonylcarbanions

The cis fused bicyclic sulfones 1a, 1c and 3a are lithiated in benzene with n-butyllithium under concomitant cis/trans isomerization of the ring fusion, involving intramolecular proton transfer. H/D exchange of the three α-hydrogens in protic solvents proceeds with retention of configuration. The lithiated sulfones are chlorinated with hexachloroethane (HCE) and show a strong preference for introduction of halogen at an equatorial α-position.