Study of solid-phase reaction of RbNO3 with V2O5

Using DTA, TG and DTG methods, the reaction between RbNO₃ and V₂O₅ in the molar ratio 65 in air atmosphere was studied. The reaction proceeds stepwise. In individual steps of the reaction the formation of RbV₃O₈, RbVO₃ and Rb₃V₅O₁₄ was observed. Rubidium pentavanadate is thermally unstable. At 1000°, RbVO₃ and Rb₂V₄O₁₁ were identified as products of its thermal decomposition. Rubidium tetravanadate was also prepared by the isothermal reaction of RbNO₃ with V₂O₅ in the molar ratio 11.

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Zusammenfassung Unter Anwendung der DTA-, TG- und DTG-Methoden wurde die Reaktion RbNO₃-V₂O₆ bei dem Molverhältnis von 65 in Luft untersucht. Die Reaktion verläuft stufenweise. Bei den einzelnen Stufen der Reaktion wurde die Bildung von RbV₃O₈, RbVO₃ und Rb₃V₅O₁₄ beobachtet. Rubidiumpentavanadat ist thermisch instabil. Bei 1000° wurden RbVO₃ und Rb₂V₄O₁₁ als Produkte seiner thermischen Zersetzung beobachtet. Rubidiumtetravanadat wurde auch durch die isotherme Reaktion von RbNO₃-V₂O₅ bei dem Molverhältnis von 11 hergestellt.

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Résumé On a étudié par ATD, TG et TGD dans l'air, la réaction RbNO₃-V₂O₅ (rapport molaire 65). La réaction s'effectue par étapes, avec formation de RbV₃O₈, RbVO₃ et Rb₃V₅O₁₄. Le pentavanadate de rubidium est thermiquement instable. A 1000°, RbVO₃ et Rb₂V₄O₁₁ ont été identifiés comme produits de la décomposition thermique. Le tétravanadate de rubidium a également été préparé par voie isotherme en faisant réagir RbNO₃-V₂O₅ (rapport molaire 11).

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, , RbNO₃-V₂O₅ 6 5. . RbV₃O₈, RbVO₃ Rb₃V₅O₁₄. 1000° RbVO₃ Rb₂V₄O₁₁, . RbVO₃-V₂O₅ 11.

     

C-Deuteration and cyclization of 2-hydroxypropiophenones

For planning of the conditions of Claisen condensation the relationship between CH-acidity and reactivity of 2-hydroxypropiophenones was investigated. It was found that there is a linear correlation between the acidity of the -methylene group of these compounds and the rate of base-catalyzed Claisen condensation in the synthesis of chromones.

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CH- 2-- . - , .

     

Catalytic hydrogenation of olefins with the VCl4?Mg?H2 system in tetrahydrofuran

The hydrogenation of olefins with the VCl₄–Mg–H₂ system in tetrahydrofuran was examined. The yield was found to depend on the Mg: VCl₄ mole ratio. The maximum yield of cyclohexene hydrogenation is achieved at C₆H₁₀/VCl₄=4. Addition of AlCl₃ or triphenylphosphine increases the yield of hydrogenation to a mole ratio C₆H₁₂/VCl₄=7.

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: VCl₄–Mg–H₂ . , Mg:VCl₄. C₆H₁₀/VCl₄=4. AlCl₃ C₆H₁₂/VCl₄=7.

     

Thermal research of montmorillonite synthetized from the oxides SiO2-Al2O3-MgO-CaO

The thermal behaviour of synthetic montmorillonite of relatively simple chemical composition has been studied and interpreted. Montmorillonite was prepared by hydrothermal synthesis at 300° and 8.8 MPa during 165 hours. With the methods of DTA, DTG, TG, X-ray diffraction analysis, infrared spectroscopy and electron microscopy it was proved that the synthetic montmorillonite is a monomineral sample and no differences from natural montmorillonite were observed.

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Zusammenfassung Das thermische Verhalten synthetischer Montmorillonite verhältnismässig einfacher chemischer Zusammensetzung wurde untersucht und gedeutet. Montmorillonit wurde durch hydrothermische Synthese bei 300°C und 8.8 MPa in 165 Stunden hergestellt. Durch die Methoden der DTA, DTG, TG, Röntgendiffraktionsanalyse, Infrarotspektroskopie und Elektronenmikroskopie wurde erwiesen, daß synthetische Montmorillonit eine monominerale Probe ist und keine Abweichungen von natürlichem Montmorillonit beobachtet werden konnten.

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. 165 300° 8.8 . , , , , , .

     

Kinetic data on the interaction between triplet anthraquinone and 2-naphthol in oxygen

During the photooxidation of ethylbenzene in the presence of 2-naphthol a new interaction has been found between the sensitizer anthraquinone and the inhibitor. The quantum yield and the kinetics of this interaction have been investigated in the temperature interval of 28–98°C.

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-, , 28–98°C , .

     

On the deactivation of Fe2O3?MoO3/SiO2 catalysts in the oxidation of methanol to formaldehyde

The deactivation behavior of Fe₂O₃–MoO₃/SiO₂ catalysts with different Fe₂O₃+MoO₃ content in the oxidation of methanol to formaldehyde is investigated. A simplified reaction-deactivation kinetic model is presented and used to compare and discuss the different behaviors.

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Fe₂O₃–MoO₃/SiO₂ Fe₂O₃+MoO₃ . : -.

     

The thermal dehydration of Sr(HCOO)2·2(H,D)2O. Influence of the isotopic substitution on the kinetics

The kinetics of thermal dehydration of Sr(HCOO)₂·2(H, D)₂O were investigated using a dynamic thermogravimetric technique. Differences were found when the hydrogen was partially substituted by deuterium. These differences were explained by means of a microscopic approach based on the static and dynamic microscopic properties.

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Zusammenfassung Die Kinetik der thermischen Dehydratisierung von Sr(HCOO)₂·2(H, D)₂O wurde mittels dynamischer Thermogravimetrie untersucht. Bei partieller Substitution von Wasserstoff durch Deuterium wurden Unterschiede gefunden, die durch eine auf den statischen und dynamischen mikroskopischen Eigenschaften beruhende Betrachtungsweise erklärt werden.

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Sr(HCOO)₂ · 2(H, D)₂O. , .

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The authors whish to thank Dr. J. M. Pastor for valuable discussions, and Prof. O. Garcia of the Instituto de Quimica Inorgánica Elhuyar (C.S.I.C.) for the use of the experimental devices.     

Ba(OH)2 as catalyst in organic reactions, part XIV. Michael addition catalyzed by barium complex salts in the homogeneous phase

Michael addition to chalcone is catalyzed by barium complex salts in the homogeneous phase under various conditions. The nature of these intermediates is analyzed. These complex salts are described for the first time. The Michael adduct of malonodinitrile to chalcone is described for the first time.

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, , . . . . .

     

Catalytic desulfurization of ethanethiol over zinc-forms of NaX zeolites

Zinc exchanged zeolite X was found to catalyze effectively the dehydrosulfurization of ethanethiol. The catalytic activity correlated linearly with the degree of ion exchange and increased with the reaction temperature. The role of zinc cations in the reaction examined is discussed and suggestions concerning the reaction mechanism are put forward.

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X, Zn, . . .

     

Thermal conductivity of cemented carbides

The hypothetical salts Li₄SiN₂O and Li₇SiN₃O were sought in the course of studies on the reactions of Li₂SiN₂ and Li₅SiN₃ with lithium oxide, and of LiSiNO with lithium nitride.

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Zusammenfassung In einer Reihe von Studien der Reaktionen von Li₂SiN₂ und Li₅SiN₃ mit Lithiumoxid bzw. LiSiNO mit Lithiumnitrid wurde nach den hypothetischen Salzen Li₄SiN₂O und Li₇SiN₃O gesucht.

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Li₂SiN₂ Li₅SiN₃ LiSiNO Li₄SiN₂O Li₇SiN₃O.

     

n-Hexane dehydrocyclization on modified L-zeolite

Platinum dispersity and catalytic activity of L-zeolite-metal catalysts at 773 K have been studied depending on the nature of a modifying agent. The mean size of Pt particles is shown to decrease by a factor of 1.5–2 upon adding Re or W. No relation between Pt dispersity and activity in n-hexane dehydrocyclization has been revealed.

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773 L . 1, 5–2 Re W. -.

     

Sensitization of the photoadsorption of O2 and NO on SnO2

Photoadsorption activity of SnO₂ with respect to O₂ and NO after CO chemisorption has been revealed to be drastically increased. Photoadsorption is suggested to be sensitized by surface carbonates formed due to CO chemisorption.

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. , .

     

Calculation of the rate of SO2 oxidation to SO3

Approximate equation to calculate the effectiveness factor of catalyst for SO₂ oxidation to SO₃ has been derived. Calculated data agree well with those predicted by a quasi-homogeneous model.

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. .

     

Experimental study of the bifurcation diagram in the Belousov-Zhabotinskii reaction

In the citric acid-Mn²⁺–H₂SO₄–KBrO₃ system a hysteresis phenomenon in the switching on and off of the oscillations has been observed. The possible bifurcation diagrams of the system are discussed.

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-Mn⁺²–H₂SO₄–KBrO₃ . .

     

Kinetics of oxidation of vanadium(III) by hydroxylamine in acid medium

The kinetics of oxidation of vanadium(III) by hydroxylamine have been investigated at high acidities in the temperature range 25–30 °C. Rates decreased with increasing acidity of the medium. Both NH₂OH and NH₃OH⁺ are capable of oxidizing V(III) in parallel reactions, the order being unity each in oxidant and reductant.

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(III) 25–30 °C. . NH₂OH NH₃OH⁺ V(III) , , .

     

Study of CO oxidation on the (111) face of nickel during Ni?NiO phase transition

CO oxidation on the (111) face of Ni has been studied over a wide temperature range and reactant ratio in CO+O₂ reaction mixtures. A significant nonstationary increase in the reaction rate due to the formation of a two-dimensional surface oxide has been found. Subsequent formation of threedimensional NiO(111) phase sharply decreases the CO oxidation rate.

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CO (111) Ni (CO+O₂). , . , NiO(111) CO.

     

Depolymerization kinetics of the polymer formed in the reaction of 1-bromobutane on unmodified alumina

The slow processes accompanying the reaction of 1-bromobutane on unmodified alumina have been studied. Butenes and octane are formed via depolymerization of a low polymeric complex formed from the reaction product. The activation energy for the formation of products from the polymer has been determined.

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, 1- . , , , , . .

     

Thermal properties of elastin-fatty acid complexes

Differential scanning calorimetry has been applied to study the interaction of fibrous or of soluble elastin with fatty acids and their trialanine derivatives. The DSC curves of elastin-fatty acid preparations exhibited an endothermic transition in the temperature range - 10° to + 50°. The peak temperatures and the enthalpy changes were independent of the chain length and of the saturation of the fatty acid. The interaction with the trialanine derivatives was similar to that with the fatty acids.Such interactions between elastin and lipids might take place in vivo as well, resutling in the loss of elasticity of elastin fibres and consequently in the development of arteriosclerotic lesions.

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Zusammenfassung Zur Untersuchung der Wechselwirkung zwischen dem fibrösen oder lösbaren Elastin, und den Fettsäuren und ihren Trialanin-Derivaten wurde die DSC-Methode angewandt. Die DSC-Kurven der Elastin-Fettsäure-Präparate zeigten in dem Temperaturbereich von - 10° bis + 50° einen endothermischen Übergang. Die Peak-Temperaturen und die Änderungen der Enthalpie waren von der Kettenlänge und der Sättigung der Fettsäure unabhängig. Die Wechselwirkung mit den Trialanin-Derivaten war der mit den Fettsäuren ähnlich.Solche Wechselwirkungen zwischen Elastin und den Lipiden können auch in vivo stattfinden, und die Abnahme der Elastizität der Elastin-Fibern, und folglich die Entfaltung der arteriosklerotischen Schädigungen resultieren.

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. - — — 10° - + 50°. , . , . , , .

     

The preparation and thermal analysis studies on some first row transition metal complexes of 2-aminopyrimidine

Complexes of 2-aminopyrimidine with the chlorides, bromides and iodides of cobalt(II), zinc(II) and also with the chlorides and bromides of manganese(II), nickel(II) and copper(II) have been prepared. The chloride complex of iron(II) was also obtained. The stereochemical configurations of the complexes were deduced using spectral and magnetic properties. The decomposition of the complexes was studied by thermogravimetry and differential thermal analysis.

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Zusammenfassung Komplexe von 2-Aminopyrimidinen mit den Chloriden, Bromiden und Jodiden von Kobalt(II), Zink(II) und den Chloriden und Bromiden von Mangan(II), Nickel(II) und Kupfer(II) wurden hergestellt. Der Chloridkomplex von Eisen(II) wurde ebenfalls erhalten. Die stereochemischen Konfigurationen der Komplexe wurden aus spektralen und magnetischen Eigenschaften abgeleitet. Die Zersetzung der Komplexe wurde durch Thermogravimetrie und Differentialthermoanalyse untersucht.

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Résumé Les complexes de l'amino-2 pyrimidine avec les chlorures, bromures et iodures de cobalt(II), zinc(II) ainsi qu'avec les chlorures et bromures de manganèse(II), nickel(II) et cuivre(II) ont été préparés. Le complexe formé avec le chlorure de fer(II) a aussi été obtenu. Les configurations stéréochimiques des complexes ont été déduites des propriétés spectrales et magnétiques. La décomposition thermique des complexes a été étudiée par thermogravimétrie et analyse thermique différentielle.

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2- , (II) (II), (II), (II) (II). (II). . .

     

Permanganate oxidations in strongly basic solutions

In strongly basic solutions the permanganate ion oxidation of C₁ and C₂ alcohols, aldehydes and acids obeys a second-order kinetic law of the type rate=k_o [S]_o [MnO ₄ ^– ], where S is the substrate. The rate constant k for both alcohols and aldeydes is proportional to the OH^– ion concentration. This behavior is interpreted in terms of a deprotonation equilibrium followed by rate-determining hydride ion transfer to MnO ₄ ^– .

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, C₁ C₂ W=k_o [S]_o [MnO ₄ ^– , S — . OH^–. MnO ₄ ^– , .