Kinetics of Cr(VI) and V(V) oxidation of trans-stilbene and indene

Title reactions are acid catalyzed and strongly dependent on the permittivity of the medium. With Cr(VI) indene reacts faster than trans-stilbene, but with V(V), trans-stilbene reacts faster than indene. The mechanism is discussed.

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. Cr(VI) , -, V(V) - , . , .

     

Radiopapierchromatographie der Isomeren des 1.2.3.4.5.6-Hexachlor-cyclohexans (HCH)

Zusammenfassung Für die quantitative Auswertung der Aktivitätsverteilung auf Radiopapierchromatogrammen wurde ein 4-Durchnußzähler gebaut. Der Aufbau und die Betriebsweise dieses Zählers werden beschrieben. Die Anwendung der Radiopapierchromatographie als quantitative Analysenmethode wird am Beispiel des Isomerisierungsgleichgewichtes -HCH -HCH -HCH erläutert.Der Vereinigung von Freunden der Technischen Hochschule Darmstadt und dem Fonds der Chemischen Industrie danken wir für finanzielle Unterstützung.     

Preparation of palladium catalysts via thermal decomposition of supported Pd(O) complexes

Heat treatment of the Pd(O) complex of dibenzylidenacetone on carbon supports was found to afford formation of more uniform Pd particles and an equal or higher activity of samples in hydrogenation of hexene and nitrobenzene compared to conventional methods of catalyst preparation from PdCl₂.

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, Pd(O) Pd , PdCl₂.

     

Effect of CO2 on O2 photo-adsorption on anatase

The presence of CO₂ on TiO₂ affects the process of oxygen photo-adsorption depending on the hydroxylation state of the surface. In dehydroxylated samples CO₂ blocks the formation of O ₃ ^– and O ₂ ^– . On H₂O₂/TiO₂ samples pretreated in the range of 150–200°C it leads to CO₂–O ₂ ^– species.

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, Cu(II). . .

     

Kinetics of decomposition of hydrogen peroxide on Fe(III)?Al(III) hydroxide-oxide systems

The kinetics of decomposition of hydrogen peroxide have been studied on mixed Fe(III)–Al(III) hydroxide and oxide catalysts. While iron hydroxide possesses considerable catalytic activity, aluminium hydroxide has very little activity. The rate of decomposition on mixed hydroxides increases with increasing concentration of aluminium hydroxide up to about 1.5 mol% and decreases thereafter. The mixed oxides possess negligible activity compared to the corresponding hydroxides. The energy of activation, as calculated from the Arrhenius equation, is 10.1 kcal/mol for sample S4, containing 1.52 mol% of alumina. The rate of decomposition of S4 increases with increasing pH up to 6.8 and decreases thereafter. The rate is first order in all these cases. A suitable mechanism is suggested.

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Fe(III)–Al(III). , . , 1,5 , . . , , 10,1 / S4, 1,52 . S4 pH 6,8, . . .

     

Resonance energy transfer from Al2O3 to adsorbed N2O

Radiolysis of adsorbed N₂O is shown to occur due to both the dissociative capture of electrons and direct energy transfer from the excited states of alumina to N₂O. One excited state ensures the decomposition of three N₂O molecules.

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, N₂O , N₂O, N₂O.

     

Ligand exchange between bis-acetylacetonato cobalt(II) and organotin compounds SnR2Cl2 (R=Ph, Et), II. Mechanism of ligand exchange between acetylacetonate complexes of Co(II)

Ligand exchange between the compounds Co(AA)₂Py₂ and Co(AA)Clpy_x (x=1 or 3) formed in the, system, CO(AA)₂–SnR₂Cl₂(R=Ph, Et) in chloroform with pyridine has been established to be catalyzed by SnR₂Cl₂. An interpretation of the catalytic action of SnR₂Cl₂ is suggested.

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, Co(AA₂py₂ Co(AA)Clpy_x (x=1 3) (Co(AA)₂–SnR₂Cl₂ (R=Ph, Et) , SnR₂Cl₂. SnR₂Cl₂.

     

Interaction of PM12?nVnO40?(3+n) (M=Mo, W) heteropoly complexes with nitrogen oxide

In aqueous solution, PM_12–nV_nO₄₀ ^–(3+n) (M=Mo,W) hetero-polyanions provide a much faster oxidation of NO than mononuclear VO ₂ ⁺ ions, yielding HNO₂, NO ₃ ^– and reduced HPA.

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, PM_12–nV_nO₄₀ ^–(3+n) (M=Mo,W) , VO ₂ ⁺ , NO HNO₂ NO ₃ ^– .

     

IR and thermal studies on lithium oxomolybdenum(VI) oxalate

A new molybdenum(VI) complex, Li₂[Mo₂O₆(C₂O₄)] · 2 H₂O (LMO), was prepared and characterized by chemical analysis and IR spectral studies. Its thermal decomposition was studied by using TG and DTA techniques. LMO loses its two moles of water between 75 and 170° to give the anhydrous product, which decomposes in three stages between 240 and 380°. The first two stages occur in the temperature ranges 240–280° and 280–305°, to give intermediates with the tentative compositions Li₆[Mo₆O₁₉(C₂O₄)₂] and Li₆[Mo₆O₂₀(C₂O₄)], respectively. In the third stage, which extends up to 380°, Li₆[Mo₆O₂₀(C₂O₄)] decomposes to give the end-product, Li₂Mo₂O₇.

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Zusammenfassung Ein neuer Molybdän(VI)-Komplex der Formel Li₂[Mo₂O₆(C₂O₄)] · 2 H₂O (LMO) wurde dargestellt und durch chemische Analyse und IR-spektroskopisch charakterisiert. Die thermische Zersetzung dieses Komplexes wurde mittels TG und DTA untersucht. LMO verliert die zwei Wassermoleküle zwischen 75 und 170° unter Bildung des wasserfreien Produktes, das zwischen 240 und 380° in drei Stufen zersetzt wird. Die in den Temperaturbereich von 240–280° und 280–305° verlaufenden ersten zwei Reaktionsschritte ergeben Intermediäre der tentativen Zusammensetzung Li₆[Mo₆O₁₉(C₂O₄)₂] bzw. Li₆[Mo₆O₂₀(C₂O₄)]. In dem sich bis 380° erstreckenden dritten Reaktionsschritt wird Li₆[Mo₆O₂₀(C₂O₄)] unter Bildung des Endproduktes Li₂Mo₂O₇ zersetzt.

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Li₂[MO₂O₆(C₂O₄] · 2 ₂ . . - 70–170° , , 240–380°. 240–280° 280–305° - Li₆[Mo₆O₁₉(C₂O₄)₂] Li₆[Mo₆O₂₀(C₂O₄)]. - 380° Li₂Mo₂O₇.

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The authors are grateful to Prof. S. N. Tandon, Head of the Chemistry Department, for providing the research facilities.     

Differential scanning calorimetry of chloroquine sulphate exposed to sun,heat and ultraviolet radiation

Chloroquine sulphate, like the phosphate, is an antimalarial formulation widely used in the tropics. The stability of such formulations is therefore of interest in the combat against malaria. A DSC study has been made of the effects of exposure to the sun, heat and UV radiation on the stability of chloroquine sulphate, similarly as performed earlier for chloroquine phosphate. When freshly recrystallized from a water-acetone mixture, chloroquine sulphate exhibits two endothermic peaks, at 169.4° and 204.7°, for the expulsion of crystal water (one molecule) and for the melting process, respectively. The exposure of chloroquine sulphate to the sun, heat and UV radiation leads to splitting of the peak for melting.

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Zusammenfassung Chloroquine-Sulfat ist ebenso wie das entsprechende Phosphatderivat ein in den Tropen weitverbreitet angewandtes Antimalaria-Präparat. Die Stabilität dieses Präparates hat damit Bedeutung für die Malariabekämpfung. Die vorliegende Arbeit ist eine Erweiterung einer Untersuchung über den Effekt der Einwirkung.von Sonne, Hitze und UV-Strahlen auf die Stabilität von Chloroquine-Phosphat auf Chloroquine-Sulfat. Aus Wasser-Aceton-Mischungen frisch kristallisiertes Chloroquine-Sulfat zeigt zwei endotherme Peaks bei 169,4 und 204,7 °C, die durch Abgabe von Kristallwasser (ein Molekül) bzw. durch den Schmelzvorgang bedingt sind. Wird Chloroquine-Sulfat der Sonne, Wärme oder UV-Licht ausgesetzt, so wird der dem Schmelzvorgang zuzuscheibende Peak aufgespalten.

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, -, , . . , . , , 169,4 204,7°, , , . , .

     

Dispersity of oxidized and reduced palladium on Al2O3

The amount of PdO not dissolving in dilute HCl as a function of its content in palladium catalysts calcined in air has been determined. Mean size of Pd particles in the same samples has been evaluated from oxygen chemisorption. A comparison of these data indicates their correlation, which permits to determine Pd dispersity variations according to the solubility of supported PdO before reduction.

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. . , .

     

Catalytic epoxidation of propylene with tert-butyl peroxide in presence of molybdenum complexes on polymer carriers

A polymer catalyst has been synthesized on the basis of Amberlite IRA-45 anion-exchange resin modified with molybdenum hexacarbonyl. Its catalytic activity in the epoxidation of propylene with tert-butyl hydroperoxide is similar to the activity of Mo(CO)₆ used under homogeneous conditions.

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, - Amberlite IRA-45, . - Mo(CO)₆, .

     

Acidity and oxidation activity of MoO3?UO3/SiO2 catalysts

The effect of UO₃ on the acidity of MoO₃–UO₃/SiO₂ catalysts has been studied by means of infrared spectroscopy of adsorbed pyridine. The surface acidity exhibited a maximum for the same U/(U+Mo) atomic ratio (=0.11) that yielded a maximum in total conversion for isobutene oxidation. The catalytic properties for oxidation are discussed in terms of the acidic properties of the samples.

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UO₃ MoO₃–UO₃/SiO₂ . U/(U+Mo)=0,11, . , .

     

Hydrogenolysis of n-butane on Ni-Pd/SiO2 catalysts

Supported Ni-Pd/SiO₂ catalysts of different Ni and Pd composition were studied in n-butane hydrogenolysis. The reaction rate, selectivity towards methane, ethane and propane were determined. On the basis of these data the relationship between the size and composition of the active center and the possibility of surface segregation of one of the components is discussed.

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Ni-Pd/SiO₂ Ni Pd -. , . .

     

NO adsorption on tin(IV) oxide

The adsorption of NO on SnO₂ has been studied in the temperature range from 0 to 86°C, at pressures from 0.4 to 3.5 Torr. The adsorption isotherms are described by the Freundlich equation. The rate of adsorption obeys the Roginskii-Zeldovitch equation and decreases with increasing temperature. The reduction of SnO₂ with carbon monoxide results in a drop in the adsorption rate and in the amount of adsorbed NO.

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NO SnO₂ 0°–86°C 0,4–3,5 . . - . SnO₂ NO.

     

Effect of free phosphine on the reactivity of phosphine-containing rhodium(I) complexes

The photolysis products of SO₂-pentane-NO mixtures are N₂O, H₂O and a compound designated as RNO. Kinetic data obtained by OC method confirm the previously proposed scheme of photolysis. Also studied was the photolysis of SO₂, NO and cyclohexane mixtures. From comparison of spectral characteristics of RNO and its analog 2-methyl-2-nitrosopropane, the probable structure of RNO is suggested.

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SO₂--NO N₂O, H₂O , RNO. , , . SO₂ NO . RNO 2--2- RNO.

     

DTA-controlled reactions and phase relations in the ternary system Sn-Te-I

The system Sn-Te-I was investigated by DTA and X-ray powder methods. No intermediate ternary phase exists in the respective phase diagram. Reactions of the components on pseudobinary joins are easily explained by the phase relations. Liquidus isotherms of the ternary system are given.

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Zusammenfassung Das System Sn-Te-I wurde durch DTA- und Röntgenmethoden untersucht. In dem Phasendiagramm existiert keine intermediäre Ternärphase. Die Reaktionen der Komponenten der pseudobinären Koppelungen können durch die Phasenverhältnisse leicht erklärt werden. Flüssigkeitsisothermen des Ternärsystems werden gegeben.

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Résumé Le système Sn-Te-I a été étudié pa ATD et rayons X sur poudre. Il n'existe pas de phase ternaire intermédiaire dans le diagramme de phases correspondant. Les réactions des composants en systèmes pseudobinaires s'expliquent facilement par les relations de phases. Les isothermes des liquidus du système ternaire sont données.

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Sn--I. . . .

     

The use of copper(III) complex compounds for the thermochemical analysis (DIE) of different organic substances

Potassium diperiodatocuprate(III), K₇[Cu(IO₆)₂], was tested as a reagent for the determination of mono- and disaccharides by means of direct injection enthalpimetry. The reagent reacted readily with acyclic polyhydroxy compounds, the reaction proceeding the better, the more hydroxy groups there were in the substance and the closer the hydroxy groups were one to the other. It also reacted readily with phenols, the polyhydric ones in particular. Carbonyl and amino compounds mostly didn't react or did so slowly, but reacted readily in the presence of some other reactive group such as hydroxy, sulphhydryl or thioxo group. Semicarbazide reacted readily, presumably due to the presence of the reactive-CO-NH-group. It is concluded that carboxy groups in the proximity of hydroxy groups exercise a positive effect on the reaction. The presence of a nitro or sulphonic acid group has a negative effect on the course of the reaction with the copper(III) compound.

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Zusammenfassung Kalium-diperiodatocuprat(III), K₇[Cu(JO₆)₂], wird als Reagenz für die Bestimmung von Mono- und Disacchariden durch direkte Injektionsenthalpimetrie vorgeschlagen. Es wurde festgestellt, daß das Reagenz leicht mit azyklischen Polyhydroxy-Verbindungen reagiert, und zwar umso besser, je mehr Hydroxylgruppen die Substanz enthält und je näher diese beieinander liegen. Das Reagenz reagiert leicht mit Phenolen, insbesondere wenn diese mehrere Hydroxylgruppen enthalten. Carbonyl- und Aminoverbindungen reagieren meistens nicht oder nur langsam, aber leicht in Gegenwart einiger anderer reaktiver Gruppen, wie Hydroxy-, Sulfhydryl- oder Thioxogruppen. Semicarbazid reagiert leicht, wahrscheinlich wegen der reaktiven Gruppe-CO-NH₂-. Es wird der Schluß gezogen, daß Carboxylgruppen in der Nachbarschaft von Hydroxylgruppen eine positive Wirkung auf die Reaktion ausüben. Die Anwesenheit der Nitro- oder Sulfonsäuregruppe wirkt sich negativ auf den Verlauf der Reaktion mit Kupfer(III)-Verbindungen aus.

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- K₇[u(IO₆)₂] — - . , . , . , , . . , -, - , . , , , -NH-. , , , , - .

     

Kinetics of thermal decomposition of diacyl peroxides in the presence of aerosil

In the presence of aerosil the thermal decomposition of the polymeric peroxide of sebacic acid is enhanced proportionally to the filler weight fraction in the reaction system. This is attributed to the interaction of peroxide groups with acidic groups on the aerosil surface and their decomposition according to a nonradical mechanism unlike the homolytic radical decomposition in solution.

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, , . .