Cyclohexane photooxygenation by air oxygen in CH2Cl2 in the presence of chromium oxocomplex-iodosylbenzene system

Cyclohexane is oxidized by air oxygen in CH₂Cl₂ solution to yield cyclohexanol, cyclohexanone and cyclohexyl chloride when irradiated by light (>310 nm) in the presence of (Bu₄N)₂CrO₄ or (Bu₃SnO)₂CrO₂. The addition of PhIO greatly accelerates the reaction and increases the yield of products. The reaction mixture contains neither cyclohexanol nor cyclohexanone when the photoreaction in the presence of the Cr(VI)–PhIO system is carried out in argon atmosphere. Hence neither iodosylbenzene nor oxochromium compounds can be oxygen atom donors in alkane oxygenation. The accelerating effect of iodosylbenzene may be due to the enhanced oxidizing power of photo-excited oxochromium species when coordinated to iodosylbenzene.

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CH₂Cl₂ , , (>310 ) (Bu₄N)₂CrO₄ (Bu₃SnO)₂CrO₂. PhIO . Cr(VI)–PhIO , , . , ( ) . .

     

Effect of surfactants on the cleavage of the N?O bond in O-(2,4-dinitrophenyl)-cyclohexanone oxime

Kinetics of cleavage of N–O bond in O-(2,4-dinitrophenyl)-cyclohexanone oxime with hydroxide ions both in the presence and absence of surfactants has been studied. The reaction is accelerated by cationic micelles, slightly by non-ionic micelles and there is no effect of anionic micelles. A plot of the rate constant vs. [surfactant] shows a maximum corresponding to the CMC of surfactant.

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NO O-(2,4-) - , - (). , , - . , .

     

Interaction of super-finely dispersed Al powders with water

Interaction of super-finely dispersed Al powders (SFDP) with water is characterized by the presence of a considerable section on the kinetic curves, where the conversion rate is maximum and its degree is as high as =0.5–0.7. It is suggested that the essential factor accounting for the conversion kinetics and the phase composition of its products is the self-heating of Al particles.

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() , , () 0,5–0,7. , .

     

Effect of carbon dioxide on the catalytic oxidation of ethylene over silver. Kinetic reaction model accounting for the modification of catalyst surface by carbonate groups

Changes in the character of catalytic oxidation of ethylene over silver upon increasing pressure of reaction mixture, reflected in increased ethylene oxide selectivity, are due to the modifying effect of suface carbonate groups. A kinetic reaction model is suggested based on the individual investigations of reaction steps.

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, , . , .

     

On the selection of the optimal plasticizer for calix[n]arene-based ion-selective electrodes: Possible correlation between the ion selectivity and the ‘softness’ of the plasticizer

A criterion for the selection of a suitable plasticizer for calix[n]arene-based ion-selective electrodes is discussed. The cation selectivity of plasticized membranes without the ligand was first measured as a reference. The membranes can be roughly classified into two groups. The first group shows cation selectivity in the order Cs⁺+>K⁺>Na⁺>Li⁺. The membranes in the second group are made of phosphorus plasticizers, which show a selectivity in the reverse order. The plasticizers in the first group featured a linear relationship between the dipole moment of the plasticizer (calculated by a PM3 method) and the ratio of cesium selectivity to lithium selectivity. The linear relationship supports the view that the polar membrane which includes a soft plasticizer with a large dipole moment shows selectivity for Cs⁺, whereas the nonpolar membrane including the soft plasticizer with the small dipole moment shows much lower selectivity for Cs⁺. Next, 2-fluorphenyl-2-nitrophenyl ether (FPNPE) which showed the highest Cs⁺ selectivity and tris(2-ethylhexyl)phosphate (TEHP) which showed the highest Li⁺ selectivity were mixed in an appropriate ratio to make membranes with a different affinity for hard ions. The metal selectivities of several crown-based and calixarene-based ionophores were examined in these membranes. Although a few exceptions exist, the polar soft membrane is favorable when the interfering metal ion is hard, whereas the hard membrane is favorable when the interfering metal ion is soft.     

Thermal decomposition of 10-molybdo-2-vanadosilicic heteropolyacid:29Si and51V-NMR study

Thermal decomposition of 10-molybdo-2-vanadosilicic heteropolyacid has been studied by²⁹Si and⁵¹V-NMR method.²⁹Si-NMR MAS spectra of solid samples indicate that the HPA begins to decompose at T<300°C and the decomposition is complete at 300–400°C.

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²⁹Si ⁵¹V Si–Mo-V () 12- . ²⁹Si MAS , 300°C 300–400°C.

     

Effect of the medium on the oxidation of aliphatic monocarboxylic acids

Oxidation rates and k₂/k₆ ratios are given for some acids from propionic to lauric. The k₂/k₆ ratio is shown to be influenced by the electrostatic effect of the solvent. A linear dependence between the isodielectric values of k₂/k₆ and the number of methylene groups in the acid molecules is described.

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k₂/k₆ . k₂/k₆ k₂/k₆ .

     

The thermal decomposition of thaumasite from Mothae kimberlite pipe,Lesotho, Southern Africa

The endothermic decomposition of thaumasite from Mothae which has been investigated by DTA and TG shows a peak temperature of 138–203°, and reaction orders of 0.45–1.00, depending on the heating rate employed. The activation energy of the reaction was found to be about 19 kcal/mole; the enthalpy is 246 cal/g.The decomposition seems to be divided into one reaction withn=0.90, immediately followed by one withn=1.59. The first reaction is attributed to the loss of H₂O, the second one to the (partial) release of OH and CO₂.

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Zusammenfassung Die durch DTA und TG überprüfte endothermische Zersetzung von Thaumasit aus Mothae zeigt in Abhängigkeit der angewandten Aufheizgeschwindigkeiten Spitzentemperaturen zwischen 138 und 203° C, sowie Reaktionsordnungen von 0.45 bis 1.00. Die Aktivierungsenergie der Reaktion ergab sich zu 19 Kcal/Mol, die Enthalpie zu 246 cal/g.Die Zersetzung scheint in eine Reaktion vonn=0.90 und eine sofort darauffolgende vonn=1.59 geteilt zu sein. Die erste Reaktion wird dem Verlust von H₂O, die zweite der (teilweisen) Freisetzung von OH und CO₂ zugeschrieben.

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Résumé La décomposition endothermique de la thaumasite de Mothae a été étudiée par ATD et TG. Suivant la vitesse de chauffage utilisée la température au sommet du pic varie de 138 à 203° C et l'ordre de réaction de 0.45 à 1.00. On a trouvé que l'énergie d'activation s'élevait à 19 kcal, mol^–1 et l'enthalpie à 246 cal. g^–1.Il semble que la décomposition s'effectue suivant une réaction d'ordren=0.90, immédiatement suivie par une autre oùn=1.59. On attribue la première réaction à la perte d'eau et la seconde à la libération (partielle) d'hydroxyles OH et d'anhydride carbonique CO₂.

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, , 138–203° 0,45–1,00 . , 19 /, - 246 /. , n=0,90, n=1,59. , - OH CO₂.

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The material used for this study has been kindly supplied by Dr. P. H. Nixon, former chief geologist, Department of Mines, Maseru, Lesotho.     

Thermodynamics and thermochemistry of kinetic (real) phase diagrams involving solids

A theoretical analysis of the formation of materials with metastable microstructures under non-ideal and highly non-equilibrium conditions is presented.

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Zusammenfassung Es wird eine theoretische Untersuchung der Bildung von Stoffen mit metastabilen MikroStrukturen unter nichtidealen Bedingungen weitab vom Gleichgewicht dargelegt.

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.

     

The kinetics of Ln2O3 Hydration under mild conditions

The kinetics of Ln₂O₃ hydration (Ln=Sm, Ho, Yb, Lu) have been studied at room temperature and atmospheric pressure, as have the influence of the activation temperature and the method of preparation of the oxides.The best correlation coefficients are obtained for a diffusion mechanism. If a structural relationship between the C-Ln₂O₃ and their precursors is considered, the possibility arises of the existence of defect planes in the oxides prepared from the hydroxide and carbonate. This facilitates the hydration process through a diffusion mechanism in the case of the rare earth sesquioxides prepared from the above precursors.

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Zusammenfassung Die Kinetik der Hydratisierung von Ln₂O₃ (Ln=Sm, Ho, Yb, Lu) wurde bei Raumtemperatur und atmosphärischem Druck bezüglich des Einflusses der Aktivierungstemperatur und der Art der Darstellung der Oxide untersucht. Die besten Korrelationskoeffizienten werden für einen Diffusionsmechanismus erhalten. Wenn die strukturelle Beziehung zwischen den C-Ln₂O₃ in Betracht gezogen wird, so ergibt sich die Möglichkeit der Existenz von defekten Gitterebenen in den aus Hydroxiden und Carbonaten hergestellten Oxiden. Dies erleichtert den Hydratisierungsprozeß durch einen Diffusionsmechanismus im Falle von aus den oben genannten Vorstufen hergestellten Sesquioxiden der Seltenen Erdmetalle.

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Ln₂O₃, Ln=Sm, Ho, Yb, Lu, . . , , . .

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We thank the CAICYT (Project No. 1377/82) for financial support.     

Catalytic properties of V?Mo?O systems in acrolein oxidation

Catalytic properties of V–Mo–O systems have been studied in acrolein oxidation. When catalysts are activated in reaction mixtures at 673 K, then a solid solution of molybdenum oxides in reduced vanadium oxides is formed, which is responsible for deep oxidation. Also, several compounds are produced, which by their activity and selectivity to acrylic acid formation are arranged in the sequences VMo₃O₁₁VMo₂O_8+x>V₆Mo₄O₂₅, and VMo₃O₁₁>VMo₂O_8+xV₆Mo₄O₂₅, respectively.

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V–Mo–O . 673 K , , , : VMo₃O₁₁VMo₂O_8+x>V₆Mo₄O₂₅, : VMo₃O₁₁>VMo₂O_8+xV₆Mo₄O₂₅.

     

Effect of carbon support on the hydrogen sorption of platinum

The hydrogen sorption of carbon-supported platinum catalysts, studied by the potentiodynamic method, differs significantly from that of unsupported platinum. The difference depends on the preparation method and on the nature of the support. Possible explanations are suggested as (i) some kind of interaction between metal and support atoms during impregnation, (ii) high dispersity (amorphous structure) and (iii) hydrogen spillover onto the carbon support.

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Pt/C, . . (I) , (II) ( ), (III) .

     

Chemical,dehydration, differential thermal and X-ray analysis of Salal bauxite deposits

Chemical, dehydration, differential thermal and X-ray analysis data on four samples of mineral deposits from the Salal region (J & K) have been determined to assess their mineral compositions. All the samples appear to be kaolinitic in character, though in association with other mineral impurities, such as boehmite, diaspore and dickite, in varying proportions.

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Zusammenfassung Vier Proben von Minerallagerstätten der Salal-Region (J & K) wurden chemisch sowie mittels DTA und röntgenographischer Analyse untersucht, um ihre Mineralzusammensetzung zu ermitteln. Alle Proben sind dem Charakter nach kaolinitisch, allerdings in unterschiedlichen Verhältnissen mit anderem mineralischem Material wie Boehmit, Diaspor und Dickit verunreinigt.

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, , , . , - , .

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The authors are grateful to the Head of the Department of Physics, Jammu University, for his interest in the research programme.     

Synthesis of esters of the furan series

Five new esters of the furan series have been synthesized by the reaction of-(5-methyl-2-furyl)propionyl chloride with 2-(3-hydroxypropyl)-furan, 2-(3-hydroxybutyl)tetrahydrofuran, and furfuryl, tetrahydrofurfuryl, and allyl alcohols in the presence of pyridine.     

Heats of adsorption of CO2 and NH3 on natural mordenites

The heats of adsorption of CO₂ and NH₃ were studied for sodium, lithium, calcium and decationized forms of natural mordenites. The exchange of Na⁺ for Ca²⁺ leads to increasing adsorption heats at low coverages. For CO₂ the region of elevated heats corresponds to the formation of Ca²⁺ ... CO₂ adsorption complexes. Two molecules of NH₃ probably interact with each Ca²⁺ ion (or with the Li⁺ ions in Li-mordenite). The heats of adsorption of NH₃ on decationized mordenite are much higher than those on calcium mordenite.

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Zusammenfassung Adsorptionswärmen von CO₂ und NH₃ an der Na-, Li-, Ca- und dekationisierten Form von natürlichem Mordenit wurden bestimmt. Der Austausch von Na⁺ gegen Ca²⁺ führt zu einer Erhöhung der Adsorptionswärmen bei geringen Bedeckungen. Bei CO₂ erfolgt im Bereich hoher Adsorptionswärmen die Bildung des Adsorptionskomplexes Ca²⁺ ...CO₂. Mit jedem Ca²⁺-Ion (bzw. Li⁺-Ion im Li-Mordenit) treten wahrscheinlich zwei NH₃-Moleküle in Wechselwirkung. An dekationisiertem Mordenit sind die Adsorptionswärmen von NH₃ höher als an Ca-Mordenit.

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, , . . Ca²⁺ ... CO₂. B , , ( -). , -.

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The authors would like to thank Dr. I. A. Belitsky for supplying the sample of natural mordenite. They also thank Professor S. P. Zhdanov for his interest and encouragement of this work.