A differential scanning calorimetric study of some phenol derivatives

Differential scanning calorimetry has been applied to derive the fusion enthalpies and entropies of series of mono and dimethylphenols, mono and dichlorophenols, and mono and dinitrophenols.

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Zusammenfassung DSC wurde verwendet zur Ermittlung der Schmelzenthalpie und Entropie der Reihen von Mono- und Dimethylphenolen, Mono- und Dichlorphenolen, Mono- und Dinitrophenolen.

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- , - , - .

     

Study of solid-phase reaction between CsNO3 AND V2O5 in the molar ratio 6:5

Using DTA, DTG and TG methods, the solid-phase reaction between CsNO₃ and V₂O₅ in the molar ratio 65 has been studied in oxygen and air streams in the temperature range 20–550°. The reaction proceeds stepwise and CsV₃O₈ has been identified as an intermediate. A mixture of CsVO₃ and Cs₂V₄O₁₁ is formed as final product of the reaction at 520°. The composition of this mixture does not change up to 1000°.

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Zusammenfassung Unter Anwendung der Methoden DTA, DTG und TG wurde die Festphasenreaktion von CsNO₃ und V₂O₃ im Molverhältnis von 65 im Sauerstoff- und Luftstrom im Temperaturbereich von 20 bis 550° untersucht. Die Reaktion verläuft stufenweise und CsV₃O₃ wurde als Zwischenprodukt identifiziert. Als Endprodukt der Reaktion bei 520° bildete sich ein Gemisch von CsVO₃ und Cs₃V₃O₁₁. Die Zusammensetzung dieses Gemisches ändert sich bis 1000° nicht.

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Resumé On a étudié par ATD, TGD et TG, la réaction en phase solide entre CsNO₃ et V₂O₅ avec le rapport molaire de 65, dans un courant d'oxygène et d'air, dans l'intervalle de températures compris entre 20 et 550°. La réaction s'effectue par étapes et on a identifié CsV₃O₃ comme produit intermédiaire. Lors de la réaction à 520°, un mélange de CsVO₃ et Cs₂V₄O₃ se forme comme produit final. La composition de ce mélange ne varie pas jusqu'à 1000°.

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, , CsNO₃ V₂O₅ 6 5 20–550°. CsV₃O₈. 520° CsVO₃ Cs₂V₄O₁₁, 1000°.

     

Effect of quantization of molecular rotations on the rate of capture in the ion-linear dipole system

The version of transition state theory that accounts for quantization of the rotational energy of a dipole gives ion-dipole capture rate constants in good agreement with the statistical adiabatic channel model and, in the region , gives results more accurate than those obtained by numerical trajectory calculations.

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, , - . , .

     

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. . . .

     

Kinetics and mechanism of the permanganate oxidation of trans-crotonic acid

The kinetics and intermediates of the permanganate oxidation of trans-crotonic acid have been investigated in the pH range of 0.5–5.0 using the stoppedflow technique. The formation of manganese(III) as a short-lived intermediate has been established. The reaction is first order with respect to both MnO ₄ ^– and crotonic acid (crotonate). The resolved rate constants at 25°C are 730 and 410 M^–1 sec^–1 for the acid and the anion, respectively. The reaction mechanism is discussed.

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pH=0,5–5,0, . (III) . MnO ₄ ^– , (). 25°C 730 410 M^{–1 –1} , . .

     

Some kinetic problems of inorganic topochemistry

Some problems of the kinetics and mechanisms of reactions of inorganic solids have been considered: the subject of inorganic topochemistry and its interrelation with adjacent disciplines; localization forms and typical forms of kinetic curves of topochemical reactions; the choice of single-meaning characteristics of the stability of solid compounds; and the employment of rational methods of investigation of decomposition kinetics.

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Zusammenfassung Es werden einige Probleme hinsichtlich der Kinetik und des Mechanismus der Reaktionen von Feststoffen betrachtet: Gegenstand der anorganischen Topochemie und dessen Beziehung zu angrenzenden Wissenschaftszweigen; Lokalisations- und typische Formen der kinetischen Kurven topochemischer Reaktionen; Auswahl eindeutiger Charakteristika für die Stabilität feststoffiger Verbindungen und Entwicklung zweckmäßiger Methoden zur Untersuchung der Kinetik von Zersetzungsvorgängen.

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, : , , .

     

Kinetics of photochemically induced benzaldehyde-cumene cooxidation

Benzaldehyde-cumene co-oxidation was carried out using biacetyl as a photosensitizer. A co-oxidation mechanism is proposed and the kinetic study allows us to show a higher reactivity towards oxidizable substances of the peroxybenzoyl radicals than that of peroxy-,-dimethylbenzyl radicals, thus explaining the quenching effect of cumene.

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- . . , , ,- , .

     

Formation of methyl platinum complex in the reaction of methane with chloroplatinic acid

The¹HNMR method and chemical analysis indicate that a complex of Pt(IV) containing a CH₃–Pt fragment is formed in the reaction of H₂PtCl₆+H₂PtCl₄ with methane at 120 °C in aqueous CF₃CO₂H. The complex was isolated from the solution as an adduct of Ph₃P.

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, H₂PtCl₆ H₂PtCl₄ CF₃COOH 120°C (IV), Pt–CH₃. Ph₃P , .

     

IR spectra of oxygen adsorbed on SnO2

IR spectra of oxygen adsorbed on SnO₂ with and without lattice defects have been studied. At low temperatures oxygen is adsorbed on defect SnO₂ in two forms of O ₂ ^– . This supports the earlier results obtained by ESR. The low-temperature forms of adsorbed oxygen (unrevealed in ESR spectra) were detected on defectless SnO₂. High-temperature forms of adsorbed oxygen appear in the IR-spectra as bands due to vibrations of the cation-oxygen bond.

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- SnO₂. , O ₂ ^– , . SnO₂ .

     

Thermal decomposition of Y,La and light lanthanide complexes of hippuric acid

The conditions of thermal decomposition of the hippurates of Y, La and the light lanthanides from Ce(III) to Gd have been studied. When heated, the Y, Ce(III), Pr and Gd complexes decomposed in two stages, those of La, Sm and Eu in three stages, and that of Nd in four stages, the oxides finally being formed. The complexes lost crystallization water to form anhydrous (Nd) or hydrated salts, and then decomposed to oxides directly (Y, Ce(III), Pr(III) and Gd) or with intermediate formation of Ln₂O₂CO₃ (La, Nd, Sm and Eu). The temperature of oxide formation varied periodically with the ionic potential in the lanthanide series.

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Zusammenfassung Die Bedingungen der thermischen Zersetzung der Hippurate von Y, La und der leichten Lanthanide von Ce(III) bis Gd wurden untersucht. Beim Aufheizen zersetzen sich die Komplexe von Y, Ce(III), Pr und Gd in zwei Schritten, die von Sm und Eu in drei Schritten und der von Nd in vier Schritten zu den Oxiden. Die Komplexe verlieren Kristallwasser unter Bildung wasserfreier (Nd) oder hydratisierter Salze und zersetzen sich dann direkt (Y, Ce(III), Pr(III), Gd) oder über Ln₂O₂CO₃ (Ln, Nd, Sm, Eu) zu den Oxiden. Die Temperatur der Oxidbildung verändert sich periodisch mit abnehmenden Ionenpotential in der Lanthanidenreihe.

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, . , , , , — , — , . , , (, , ) Ln₂O₂CO₃ (, , ). .

     

Kinetic analysis of thermogravimetric data. XXVI

Ten metal and ammonium salts of the acid H₂[ReCl₆] were obtained by double decomposition reactions, and their pyrolyses in air atmosphere were studied by means of DSC measurements. The kinetic parameters of these reactions were derived and are discussed.

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Zusammenfassung 10 Metall- und Ammoniumsalze der Säure H₂[ReCl₆] wurden durch Doppelzersetzungsreaktionen erhalten. Die Pyrolyse dieser Salze in Luft wurde mittels DSC untersucht. Die kinetischen Parameter dieser Reaktionen wurden ermittelt und diskutiert.

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H₂[ReCl₆]. . .

     

Investigation of kinetics and mechanism of maleic anhydride interaction with pentachlorinated phosphorus

Kinetics and mechanism of the interaction of maleic anhydride with pentachlorinated phosphorus have been studied. Kinetic parameters of a model making it possible to control this reaction have been calculated.

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, , .

     

IR and thermal studies on lanthanum zirconyl oxalate

Lanthanum zirconyl oxalate hydrate (LaZO) was prepared and characterized by chemical analysis and i.r. spectral studies. Its thermal decomposition was investigated by using DTA, TG, X-ray diffraction and i.r. spectral studies. On the basis of the TG and`isothermal results, a tentative decomposition scheme was proposed. In the first step the dehydration of LaZO takes place in two steps between room temperature and 498 K, to give the anhydrous compound. The anhydrous oxalate decomposes in a series of steps (498–548 K, 548–673 K and 673–773 K). Finally the decomposition of the carbonate takes place (773–1073 K) to give lanthanum zirconate (La₂Zr₂O₇).

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Zusammenfassung Lanthanzirkonyloxalathydrat (LaZO) wurde hergestellt und durch chemische Analyse sowie durch Infrarotspektroskopie charakterisiert. Seine thermische Zersetzung wurde unter Einsatz von DTA, TG, Röntgendiffraktion und Infrarotspektroskopie untersucht. Aufgrund der TG und isothermen Ergebnisse wurde ein Zersetzungsschema vorgeschlagen. In der ersten Stufe erfolgt die Dehydratisierung von LaZO in zwei Schritten zwischen (RT-498 K) um die Anhydroverbindung zu ergeben. Das wasserfreie Oxalat wird in einer Serie von Stufen zersetzt und verschiedene Zwischenprodukte enthalten sowohl Oxalat als auch Carbonat (498–548 K, 548–673 K und 673–773 K). Abschließend findet die Zersetzung des Carbonats statt (773–1073 K) unter Bildung von Lanthazirkonat (La₂Zr₂O₇).

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Résumé L'oxalate hydraté de lanthane-zirconyle (LaZO) a été préparé et caractérisé par analyse chimique et spectrométrie infrarouge. La décomposition thermique de ce composé a été examinée par ATD, TG, diffraction des rayons X et spectrométrie infrarouge. Un mécanisme de décomposition est proposé, d'après les résultats TG, obtenus en régimes dynamique et isotherme. Dans un premier temps la déshydratation de LaZO a lieu en deux étapes (température ambiante —498 K) pour fournir le composé anhydre. L'oxalate anhydre se décompose en plusieurs étapes et plusieurs composés intermédiaires contenant l'oxalate ainsi que du carbonate (498–548 K, 548–673 K, 673–773 K). Finalement, la décomposition du carbonate (773–1073 K) fournit du zirconate de lanthane (La₂Zr₂O₇).

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, . , , . , . , 498 . , , 498–548 , 548–673 673– 773 . 773–1073 -La₂Zr₂O₇.

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The authors are grateful to Dr. W. U. Malik, Prof. & Head of Chemistry Department, Roorkee University, for providing the research facilities. V. B. R. is also grateful to the CSIR (India) for the award of a senior research fellowship.     

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 ^– .

     

Acid properties and stability of operation of vanadium catalysts in benzene oxidation to phenol

Catalytic properties of V₂O₅/SiO₂ in benzene oxidation by N₂O were examined. Sodium additive was shown to affect the catalyst operation stability.

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V₂O₅/SiO₂ N₂O. .

     

Evaluation of triplet repulsion energies

The equation is suggested for predicting triplet repulsion energies. X=R–R^o, while R^o and¹V^o are the equilibrium bond length and the spectroscopic dissociation energy, respectively. Parameters and may be estimated from known bond properties.

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( X=R–R^o, a R^{o 1}V^o , . , .

     

Formation of the active component of a vanadium complex catalyst for the oxidation of anthracene to anthraquinone

The phase composition in various stages of preparation of the active material coating the catalyst for the partial oxidation of anthracene to anthraquinone was studied. The presence of an active phase was evidenced in the final active material as well in a precursor.

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, . , .

     

Kinetics of the gas-phase pyrolysis of some secondary acetates

The rates of the gas-phase thermal decomposition of three secondary acetates have been measured in a static system over the temperature range 290–350°C and pressure range 54–250 Torr. The reactions in seasoned vessels are homogeneous, follow a first order-law, and are unimolecular. The effect of -substituents in acetates is discussed.

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290–350°C 54–250 . , , , . - .

     

Effect of hydrogen pressure on the selectivity of 2-butene-1-al hydrogenation

The effect of hydrogen pressure on the selectivity of hydrogenation of 2-butene-1-al at the carbonyl group in the presence of Ru and Ru–ZnO catalysts indicates that the selectivity on the modified ruthenium catalyst in the pressure range of 0.51–8.08 MPa is a maximum at .

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-2--І Ru Ru–ZnO-. , 0,51–8,08 , .