Arjunolic acid derivative glycoside from the stems of <Emphasis Type="Italic">Hedera colchica</Emphasis>

Five triterpenoid saponins were isolated from the stems of Hedera colchica K. Koch, Araliaceae. Two of them are new natural substances. HCSt-A (1): 3-O--D-arabinopyranoside; 28-O--L-rhamnopyranosyl-(1 4)-O--D-glucopyranosyl-(16)-O--D-glucopyranosyl-arjunolic acid. HCSt-B (2): 3-O--D-xylopyranoside; 28-O--L-rhamnopyranosyl-(14)-O--D-glucopyranosyl-(16)-O--D-glucopyranosyl-hederagenin. The derivative of arjunolic acid is described for the first time in Araliaceae family. The chemical structures of isolated compounds were established on the base of chemical and 1D and 2D NMR experiments.Published in Khimiya Prirodnykh Soedinenii, No. 6, pp. 461–463, November–December, 2004.This revised version was published online in April 2005 with a corrected cover date.     

Comparative selectivities of two copper-based catalysts: Mixed Cu?Cr and Cu?Al oxides for allylic alcohol reactions in the presence of molecular hydrogen

In the presence of mixed copper-chromium (aluminium) oxide, allylic alcohols react with molecular hydrogen and lead to several primary products. This is due to the simultaneous presence of two active sites in the mixed oxides. Copper species (Cu⁺) are responsible for hydrogenation (HYD) and the chromium (Cr³⁺) (aluminium [Al³⁺]) species for the isomerization (I) and the hydrodeoxygenation (HDO) reactions. However, the stronger acidic character of Al³⁺, compared with Cr³⁺, entails some differences evidenced by the HYD/(I+HDO) and HDO/I ratios.

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- () , . . (Cu⁺ (), (Cr³⁺) ( Al³⁺) (), (). , Al³⁺ Cr³⁺ , /(+) /.

     

Thermal properties of 5-(subst)-amino-1,2,3,4-thiatriazoles

The thermal properties of 5-(subst)-amino-1,2,3,4-thiatriazoles were studied using TG and DTA. 5-amino-1,2,3,4-thiatriazole was actively decomposed at the melting temperature. The active thermal decomposition proceeds at a very fast rate, being accompanied by exothermic reactions of recombination. In comparison with this, the different-5-(subst)-amino-1,2,3,4-thiatriazoles are decomposed at slower rates in several degradative steps. The effects of some substituents on the total course of thermal degradation are discussed.

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Zusammenfassung Die thermischen Eigenschaften von 5-(subst)-Amino-1,2,3,4,-Thiatriazolen wurden mittels der Methoden TG und DTA untersucht. Das 5-Amino-1,2,3,4-Thiatriazol wurde bei der Schmelztemperatur aktiv zersetzt. Die aktive thermische Zersetzung verläuft mit einer sehr großen Geschwindigkeit und wird von den exothermen Reaktionen der Rekombination begleitet. Im Vergleich hierzu werden die verschiedenen 5-(subst)-Amino-1,2,3,4-Thiatriazole mit einer geringeren Geschwindigkeit, in mehreren Zersetzungsstufen abgebaut. Die Wirkung einiger Substituenten auf den Gesamtablauf der thermischen Zersetzung wird erörtert.

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Résumé On a étudié par TG et ATD les propriétés thermiques des 5-(subst)-amino-1,2,3,4-thiatriazoles. Le 5-amino-1,2,3,4-thiatriazole se décompose activement à la température de fusion. La décomposition thermique active s'effectue avec une très grande vitesse et s'accompagne de réactions exothermiques de recombinaison. Par contre, les divers 5-(subst)-amino-1,2,3,4-thiatriazoles se décomposent avec une vitesse plus faible et en plusieurs étapes. On discute l'effet de quelques substituants sur le processus complet de la dégradation thermique.

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, , 5-()--1,2,3,4-. 5--1,2,3,4- . , . , 5-()--1,2,3,4- . .

     

Ru(III) catalyzed oxidation of some aliphatic alcohols by N-bromosuccinimide (NBS). A kinetic study

Kinetics of Ru(III) catalyzed oxidation of methanol, ethanol, n-propanol, n-butanol, isopropanol and iso-butanol by N-bromosuccinimide (NBS) in the presence of Hg(II) acetate have been studied in acid medium. The oxidation exhibits a fractional order in [alcohol] and first order in [NBS]. The applicability of Taft's equation was tested. The probable mechanism is discussed.

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, , -, -, - () Hg(II), Ru(III), . . . .

     

Kinetic study of the thermally initiated cyclocondensation of some 1,3-dimethyl-4-alkylamino-5-nitrosouracils

The isothermal and non-isothermal DSC method was used to investigate the influence of changes in structure of 1,3-dimethyl-4-alkylamino-5-nitrosouracils on the 8-substituted theophyllines originating in the cyclocondensation reaction. The evaluation of the optimum reaction mechanism obtained on the basis of the corresponding model functions by using the integral method of Coats and Redfern is discussed. Significant differences, depending on the nature of the substituents, were observed in the course of the reaction.

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Zusammenfassung Der Einflu\ von VerÄnderungen in der Struktur von 1,3-Dimethyl-4-alkylamino-5-nitrosouracilen auf die in einer Zyklokondensationsreaktion gebildeten, 8-substituierten Theophylline wurde mittels isothermer und nicht-isothermer DSC untersucht. Die optimalen, basierend auf entsprechenden Modellfunktionen bei Anwendung der Integralmethode von Coats und Redfern erhaltenen Reaktionsmechanismen werden diskutiert. Im Verlaufe der Reaktion wurden signifikante, von der Natur der Substituenten abhÄngende Unterschiede festgestellt.

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1,3--4--5- 8- , . , , - . .

     

Superacid alumina catalysts II

The acidity and catalytic activity of alumina doped with AlCl₃, CH₃AlCl₂, PCl₅, PCl₃, I₂, Cl₂ and H₂PO₃F were studied. Vapors of AlCl₃ and CH₃AlCl₂ induce superacid sites in alumina, whereas PCl₃ and PCl₅ produce less acidic systems, which nevertheless catalyze the skeletal isomerization of alkenes. The modification of Al₂O₃ with other specified compounds affects only slightly the acidity and catalytic activity of alumina.

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AlCl₃, CH₃AlCl₂, PCl₅, PCl₃, I₂, Cl₂ H₃PO₃F. AlCl₃ CH₃AlCl₂ - . PCl₃ PCl₅ - , . Al₂O₃ - .

     

Thermal and some other properties of the complexes crystallizing from the system Ni(II)-en-[Ni(CN)4]2−-H2O

Seven complex compounds exhibiting the compositions Ni(en)₃Ni(CN)₄·H₂O (I), Ni(en)₃Ni(CN)₄ (II),-Ni(en)₂Ni(CN)₄ (III), Ni(en)Ni(CN)₄·2H₂O (IV), Ni(en)Ni(CN)₄ (V), Ni(en)₂Ni(CN)₄ · 2.5H₂O (VI) and-Ni(en)₂Ni(CN)₄ (VII) were prepared from the system Ni-en-[Ni(CN)₄]^2–-H₂O. These compounds were examined by the methods of infrared spectroscopy, X-ray powder diffractometry, UV-VIS reflectance spectroscopy, and also by the measurement of magnetic moments. The thermal stability, the stoichiometry of thermal decomposition and the mutual transformations were investigated with a derivatograph. The reactions proceeding according to the following schemes were observed if the system was heated to appropriate temperature: (I)(II)(III)(V)(IV) and (VI)(VII)(III)(V)(IV) Process (VII)(III) represents isomerization. The reversibility of the process (V)(IV) is due to the high hygroscopicity of the anhydrous complex. The changes in structure in the course of the individual processes are discussed.

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Zusammenfassung Aus einem System Ni-en-[Ni(CN)₄]^2–-H₂O wurden sieben Komplexe der Formeln Ni(en)₃Ni(CN)₄·H₂O (I), Ni(en)₃Ni(CN)₄ (II),-Ni(en)₂Ni(CN)₄ (III), Ni(en)Ni(CN)₄·2H₂O (IV), Ni(en)Ni(CN)₄ (V), Ni(en)₂Ni(CN)₄ · 2.5H₂O (VI) und-Ni(en)₂Ni(CN)₄ (VII) hergestellt. Diese Verbindungen wurden mittels IR-Spektroskopie, Röntgenpulverdiffraktometrie, UV-Reflexionsspektroskopie und durch Messungen des magnetischen Momentes untersucht. Die Wärmestabilität, die Stöchiometrie des thermischen Zerfalles und die gegenseitigen Umwandlungen wurden mittels eines Derivatographen untersucht. Wird das System auf geeignete Temperaturen erhitzt, kann der Reaktionsverlauf durch folgendes Schema dargestellt werden: (I)(II)(III)(V)(IV) und (VI)(VII)(III)(V)(IV).Der Prozeß (VII)(III) verkörpert eine Isomerisierung. Die Umkehrbarkeit von Prozeß (V)(IV) ist auf die ausgeprägten Hygroskopieeigenschaften des wasserfreien Komplexes zurückzuführen. Es werden die im Ablaufe der einzelnen Prozesse vorgehenden Strukturveränderungen besprochen.

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Ni- -[No(N)]² -₂ Ni(en)₃Ni(CN)₄ · ₂ (I), Ni(en)₃Ni(CN)₄ (II),-Ni(en)₂Ni(CN)₄ (III), Ni(en)Ni(CN)₄-2H₂O (IV), Ni(en)Ni(CN)₄ (V), Ni(en)₂Ni(CN)₄ · 2,5H₂O (VI) -Ni(en)₂Ni(CN)₄ (VII). , , - , . , . (I)(II)(III)(V)(IV) (VI)(VII)(III)(V)(IV). (VII)(III) . (V)(IV) . .

     

Coadsorption of ethylene and oxygen on an iridium surface

It is established that the hydrocarbon coverage (0<1) formed at T<400 K on the Ir surface is oxidized upon oxygen exposures to CO and H₂O by an adsorption mechanism. Complete oxidation to CO₂ and H₂O is achieved at T350 K after C₂H₄ exposures of the oxygen coverage.

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, (<1), T<400 K Ir, CO H₂O . CO₂ H₂O T350 K C₂H₄ .