Oxidative Deprotection of Cyclic Acetals and Trimethylsilyl Ethers by γγ-Picolinium Chlorochromate Under Nonaqueous Conditions

Deprotection of cyclic acetals and oxidative desilylation of trimethylsilyl ethers into the corresponding carbonyl compounds with -picolinium chlorochromate (-PCC) under nonaqueous conditions at room temperature is described. Oxidation of aldehydes to carboxylic acids was not observed in any case.     

Reaction of scandium trifluoride with hydrazine

ScF₃ reacts with anhydrous hydrazine yielding ScF₃·N₂H₄; upon heating the compound in inert atmosphere ScF₃ is regained. With hydrazine hydrate N₂H₅Sc(OH)F₃ is obtained with solid ScF₃; it decomposes to ScF₃ in two steps.     

The catalytic reactions of triethyl- and triethoxy-silane with unsaturated sulphides

The hydrosilylation of mono- and di-alkenyl sulphides of the type RS(CH₂)_nCH=CH₂ (R = C₂H₅, CH₂=CH, CH₂=CHCH₂, C₃H₇, n = 0, 1 and 4) by triethyl- and triethoxy-silane, catalyzed by H₂PtCl₆·6 H₂O, (Ph₃P)₃RhCl and (PhCN)₂PdCl₂·Ph₃P, has been studied. The addition of hydrosilane to the double bond of alkenyl sulphide leads to a mixture of two isomeric monoadducts. The hydrosilane can cleave the C---S bond of the initial sulphides giving the corresponding derivatives of thiosilanes, X₃SiS(CH₂)_nCH=CH₂ (X = C₂H₅, C₂H₅O). Hydrosilylation of alkenyl sulphides is accompanied by some side reactions such as dehydrocondensation, reduction and polymerization. The effect of the catalyst nature, the structure of hydrosilane and alkenyl sulphide on the reaction route has been investigated.     

The lipids of microalgae II. Lipids of the dry biomass ofMonochrysis lutheri

Institute of the Chemistry of Plant Substances, Uzbekistan Academy of Sciences, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 899–900, November–December, 1993.     

Zircon SHRIMP age of Mesoarchaean meta-argilloarenaceous rock in the Anshan area and its geological significance

In order to better understand the early continental evolution of the Anshan area, one ofthe typical Precambrian distribution areas of the North China Craton, the geochronology and REEcomposition of the zircons from the meta-argillo-arenaceous rock occurred as enclave in 3.1 GaLishan trondhjemite are studied by using SHRIMP ll ion microprobe. It is indicated that the Pa-leoarchaean is a very important continental formation period in the Anshan area and 3.2 Ga can beregarded as the boundary between the Paleoarchaean and Mesoarchaean.     

Effect of hydrothermal treatment on catalytic properties of superhigh-silica zeolites

The effect of hydrothermal treatment of decationized superhigh-silica zeolite on the mechanism of n-hexane conversion has been studied. It has been established that thermosteam modification sharply decreases the cracking activity and increases the selectivity to aromatization reactions. Zeolite acidity markedly decreases, but its crystal structure does not become amorphous.

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Spectroscopic and thermoanalytical characterization of standard substances for the identification of reaction products on iron electrodes

The in situ spectroscopic investigation of electrochemical, and especially corrosion processes in iron requires well-characterized reference substances. It has been found that the application of spectroscopic methods alone is not sufficient for the detection of impurities in certain phases. Thermoanalytical methods have therefore additionally been used to detect impurities and to optimize the preparation methods. Infrared and Raman spectra and thermoanalytical data on-FeOOH,-FeOOH,-FeOOH,-FeOOH and on amorphous iron(III) hydroxide sol are reported.

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Zusammenfassung Die in situ-Untersuchung von elektrochemischen und speziell von Korrosionsprozessen an Eisen mit spektroskopischen Methoden erfordert gut charakterisierte Standardsubstanzen. Es zeigte sich, daß die spektroskopische Charakterisierung allein nicht ausreicht, um Verunreinigungen in definierten Phasen zu erkennen. Deshalb wurden zusätzlich thermoanalytische Untersuchungsmethoden zur Auffindung von unreinen Substanzen und zur Optimierung der Präparationsmethoden angewandt. Es werden IR- und Ramanspektroskopische sowie thermoanalytische Daten von-, -, - und-FeOOH sowie eines amorphen Eisen(III) hydroxidsols berichtet.

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in situ , , , . , . , , . , -FeOOH,-FeOOH,-FeOOH,-FeOOH .

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We gratefully acknowledge the financial support given by the Fonds zur Förderung der wissenschaftlichen Forschung of Austria. We also thank Prof. A. Otto (Düsseldorf) and Prof. H. Kuzmany (Wien) for measuring the Raman spectra; thanks are also due to Prof. R. Kellner (Wien) for his kind permission to use the FTIR equipment.     

The electrocapillarity of polyacrylates

Summary The electrocapillary properties of polyacrylic acid have been studied by two methods. Exploratory measurements have been made of the effect of the polymer on the differential capacity of a mercury drop in 0.1 m sodium perchlorate. They showed that the polymer was strongly adsorbed over a wide range of potentials but that it did not appear to form a monolayer. The surface excess of polymer obtained from drop weight data showed a maximum at very low concentrations and then a decline at higher concentrations. The bulk of the work was carried out by making surface tension measurements, using a sessile mercury drop, in solutions of a fraction of polyacrylic acid (mol. wt. 7.02×10⁴) in potassium chloride at 0.01, 0.1, 0.2, and 0.5 m at 25°C.The data have been used to evaluate the surface excesses of the polymer and of the inorganic ions. The distribution of K⁺ and Cl^– in the electrical double layer and the contact adsorption of Cl^– on the mercury were very little affected by the presence of the polymer. The surface excess of polymer was always found to be greatest at low concentrations, to decrease steeply at first as the concentration was increased and then to decrease more slowly at higher concentrations.Possible explanations of this behaviour are discussed and it is concluded that the rapid decrease is a consequence of molecular weight dispersion and the stronger adsorption of high molecular weight polymer. The slow decrease in surface excess at higher concentrations may be a result of configurational changes of the polymer molecules.Surface pressure data show that, despite this decrease in the surface excess, the surface coverage reaches a high level at very low polymer concentrations and then continues to increase slowly as the concentration of polymer is increased. This apparent contradiction is due to changes in configuration of the adsorbed polymer molecules. At higher bulk concentrations the chain configurations are more compact and each adsorbed molecule makes more contacts with and so occupies a greater area of the mercury surface than at low concentrations.The conclusion is reached that the surface excess of polymer is mostly contained in a layer probably more than 1000 Å thick. It consists of a concentrated and entangled mass of polymer chains. Relatively few of these chains are in contact with the mercury at any istant. The concentration in this surface layer decreases steadily with increasing distance from the mercury surface and it merges without discontinuity into the bulk solution.With 10 figures in 22 details     

Synthesis and conversions of metallocycles. 7. A novel approach to the synthesis of 3,4-dialkyl-substituted aluminacyclopentanes in the presence of Cp2ZrCl2

A novel approach was developed for the stereoselective synthesis of trans-3,4-dialkyl-substituted aluminacyclopentanes from -olefins, metallic magnesium, and EtAlCl₂ in the presence of catalytic amounts of Cp₂ZrCl₂. The hydrolysis and deuterolysis products of the 3,4-dialkyl-substituted aluminacyclopentanes obtained are only in the trans configuration.For previous communication, see [1].Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 7, pp. 1607–1609, July, 1991.     

Catalytic properties of iron tetracarbonyl π-complexes of vinylsilanes in the addition of polyhalomethanes and hydrosilanes to vinylsilanes

Conclusions The high catalytic activity of (CH₂=CHSiR₃)·Fe(CO)₄ complexes was demonstrated in the reaction of vinylsilanes with polyhalomethanes and hydrosilanes.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 4, pp. 914–920, April, 1982.