ESR spin-trapping study of radicals produced by donor-acceptor interactions

Nitroso compounds, well known as spin traps, have not been applied for scavenging free radicals formed in reactions with the contribution of chloranil, so far. In our studies we show that spin traps such as nitrosodurene (ND), 2,6-dichloronitrosobenzene (Cl₂NB) react with radicals formed in the reaction between chloranil and durene, yielding stable spin adducts.

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, , . , 2,6-, , , , . , , , , .

     

Kinetics of isotope exchange of dioxygen with a powdered high-temperature superconducting material Ba2YCu3O7?x

It has been found that the rate of isotope exchange in Ba₂YCu₃O_7–x–O₂ system is high. Its kinetics is exponential, first order with respect to dioxygen and the exchange is of the mixed first/third type.

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Ba₂YCu₃O_7–x–O₂ . -, -, - .

     

Thermal degradation of epoxidized polydienes III. Thermal behaviour of some cross-linked epoxidized polydienes

DTA and TG has been used to study the thermal stability of cross-linked epoxidized polydienes. Cross-linking has been achieved using some derivatives of hydroxycarbostyrils, triazines and phthalimide. The new properties of the polymers after curing are interpreted on the basis of the results of DTA and TG.

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Zusammenfassung DTA und TG wurden zur Untersuchung der Thermostabilität von quervernetzten epoxidierten Polydienen eingesetzt. Die Quervernetzung wurde unter Verwendung einiger Derivate von Hydroxycarbostyrilen, Triazinen und Phtalimid durchgeführt. Die neuen Eigenschaften der Polymere nach einer Wärmebehandlung wurden aufgrund der Ergebnisse der DTA und TG gedeutet.

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. , . , .

     

Routes of catalytic oxidation of o-xylene to phthalic anhydride

Relative reactivity of o-xylene, o-tolualdehyde, phthalide, and phthalane and the rate of phthalic anhydride formation from them have been determined. The main route of o-xylene oxidation to phthalic anhydride is due to the o-arrangement of methyl groups, proceeding through bicyclic products, such as dihydrobenzofuran (phthalane) and 3,4-benzofuran.

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-, - , , . - - : () 3,4-.

     

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]. . .

     

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.

     

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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, , .

     

Non-isothermal thermogravimetry of polymer

A Model of polymer decomposition is proposed which formally involves the termination of active centres. It yields reasonable activation energies for the decompositions of polypropylene, polyethylene, polystyrene and polymethyl methacrylate investigated by non-isothermal thermogravimetry. In the value of a formal reaction orders the model reflects the reaction conditions, such as initial sample weight, atmosphere, ventilation conditions, sample holder nature and shape, etc.

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Zusammenfassung Ein Modell für Zersetzungsreaktionen von Polymeren wurde entworfen, das auf dem Abbau von aktiven Zentren basiert. Es liefert richtige Aktivierungsenergien für die Zersetzung von Polypropylen, Polyäthylen, Polystyren und Polymethylmethakrylat (bestimmt durch nichtisotherme Thermogravimetrie) und macht es ausserdem möglich, die äusseren Reaktionsbedingungen, wie Einwaage, Atmosphäre, Ventillationsbedingungen, Art und Form des Probenhalters usw. zu berücksichtigen.

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, . , , , . «» , , , , . .

     

Etude des melanges binaires khelline-cafeine et khelline-sulfapyridine

Résumé Après avoir étudié le comportement thermique des principes actifs les auteurs ont établi les diagrammes de phase des mélanges binaires khelline(I)-caféine(I) et khelline(I)-sulfapyridine(I) par thermomicroscopie, analyse thermique et calorimétrique différentielles. Les compositions des eutectiques, du péritectique et du composé défini khelline(I)-caféine(I) ont été déterminées en vue d'une étude physico-chimique, plus particulièrement de solubilité en relation avec la biodisponibilité.

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After studying the thermal behaviours of the drugs, the authors established the state diagrams of the binary systems khellin(I)-caffeine(I) and khellin(I)-sulfapyridine(I) by thermomicroscopy, differential scanning calorimetry and differential thermal analysis.Eutectic, peritectic and molecular compound khellin(I)-caffeine(I) compositions were determined for a physico-chemical study, particularly of solubility, in relation with bioavailability.

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Zusammenfassung Nach der Untersuchung des thermischen Verhaltens von Wirkstoffen (Drogen) bestimmten die Autoren die Phasendiagramme der BinÄrsysteme Khellin(I)-Koffein(I) und Khellin(I)-Sulfapyridin(I) durch Thermomikroskopie, Thermoanalyse und Differentialkalorimetrie. Die Zusammensetzung der Eutektika, des Peritektikums und der Molekularverbindung Khellin(I)-Koffein(I) wurden zu physikalisch-chemischen Untersuchungen, insbesondere der Löslichkeit im Zusammenhang mit der BiodisponibilitÄt, bestimmt.

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, , (II) —(II) (II)- (II). , - - , .

     

Kinetics of autocatalytic hydrolysis of tetraethyl orthosilicate in the presence of aluminium nitrate

Kinetics of autocatalytic hydrolysis of tetraethyl orthosilicate in the presence of aluminium nitrate has been studied experimentally. According to the suggested reaction mechanism and the proposed mathematical model, kinetic constants have been determined.

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. , .

     

Catalytic oxidation of monosubstituted phenols by hydrogen peroxide

Studies of kinetic peculiarities in hydroxylation of phenols by H₂O₂ in the presence of ferric sulfate have revealed general regularities of this process. A scheme of this process is suggested accounting for the stepwise conversion of Fe³⁺ into various complex forms. The reaction is suggested to take place in the coordination sphere of Fe³⁺.

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H₂O₂ . . , Fe³⁺ .

     

Thermal and photochemical stability of polystyrene and its blends with polyvinyl chloride

The influence of some irregularities in polystyrene (PS) and polyvinyl chloride (PVC) chains on their thermal stability was investigated. UV irradiation caused an increase in the content of these irregularities in the polymers. It was found that the presence of carbonyl groups and crosslinking of the polymer chains hamper the thermal dehydrochlorination of PVC and the total decomposition of both polymers. On the other hand, weak peroxy linkages (which facilitate degradation processes) and conjugated double bonds decrease the temperature of total decomposition of PS and PVC blends.

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Zusammenfassung Es wurde der Einfluß von Unregmlmäßigkeiten in Polystyrol (PS)- und Polyvinylchlorid (PVC)-Ketten auf deren thermische Stabilität untersucht. UV-Bestrahlung verursacht ein Ansteigen des Gehaltes an Unregelmäßigkeiten in den Polymeren. Es wurde festgestellt, daß die Gegenwart von Carbonylgruppen und Querverbindungen der Polymerketten die thermische Dehydrochlorierung von PVC und eine vollständige Zersetzung beider Polymere verhindern. Andererseits senken Peroxidverknüpfungen (die die Degradierungsvorgänge erleichtern) und konjugierte Doppelbindungen die Temperatur für eine vollständige Zersetzung von PS und PVC Gemischen.

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. - . , . , , , .

     

Reactivity of hydrocarbons on Fe?Cr?O catalysts

Generalized experimental data for deep and complete oxidation of hydrocarbons on Fe–Cr–O catalysts are presented with calculated kinetic parameters and reactivity of hydrocarbons.

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. .

     

Specific activity of ruthenium for hydrogenation and hydrogenolysis of benzene in relation to metal dispersity

The specific activity V_sp of ruthenium supported on -alumina (0.084–0.84 wt.%, average particle size 1=1–7 nm) has been investigated for hydrogenation and hydrogenolysis of benzene at 80–320°C and compared with that of Ru powder of 1>1400 nm. A decrease of V_sp with increasing Ru dispersity was found for both reactions, the decrease having been more pronounced for hydrogenolysis. The effect is considered to be due mainly to an influence of dispersity of supported metal on the mode and extent of benze chemisorption.

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(V_Sp) , - (0,084–0,84 .%, 1=1–7 ), 80–320°C - 1>1400 . V_Sp , . , -, - .

     

Gradient systems are cross-catalytic

If the kinetic differential equation of a chemical mechanism is a gradient system, the mechanism is essentially cross-catalytic. Consequently, rather few conservative (in the Horn-Jackson sense) mechanisms have a kinetic differential equation of the gradient type. Relations with thermodynamics are only briefly mentioned.

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, , , . ( -) . .

     

On the catalytic system MgO?Na

Acid-base and radical properties of two sets of MgO–Na catalysts have been studied. The catalysts were prepared (I) by impregnation of MgO with NaOH in aqueous solution, and (II) by evaporation of metallic sodium onto a MgO surface. The catalyst prepared by the second method was much more basic than pure MgO (H_o=35) and showed a high activity in olefin isomerization.

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- MgO–Na. 1) MgO (NaOH) 2) MgO. , , , MgO(H₀=35), .

     

The consistency of repeated H2?O2 titration cycles on supported Pt catalysts

H₂ and O₂ uptakes at 296 K on a Pt/Al₂O₃ catalyst remained constant during repeated H₂–O₂ titration cycles conducted in a high vacuum adsorption system. Previously reported variations in these uptakes are attributed to adsorption of contaminants during desorption conditions. Also, it was found that nearly 40% of the H₂ adsorbed could be removed by degassing at 296 K for 1 hr.

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H₂ O₂ 296 Pt/Al/₂O₃ H₂–O₂, . . , 40% H₂ 1 296 .

     

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 , .

     

Influence of pressure reduction on the shapes of thermoanalytical curves of red muds

The effect of reduction of pressure on the shapes of the TG, DTG and DTA curves and the mass-spectra of hydroxide and carbonate phases was investigated in some typical Hungarian red muds. The pressure change caused different decomposition rates of the phases and resulted in better separation of the overlapping thermal curves; this led to advantages as regards phase analysis. For phase analysis the red muds were extracted with water, and the extracts and solid residues were identified by IR- and X-ray methods.

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Zusammenfassung Die Wirkung der Druckänderung auf die Form der TG-, DTG- und DTA-Kurven, sowie der MS-Spektra der Hydroxid- und Carbonatphasen in einigen typischen ungarischen Rotschlamm-Sorten wurde geprüft. Die Druckänderung verursachte verschiedene Zersetzungsgeschwindigkeiten der Phasen, führte zur besseren Auftrennung der sich überlappenden thermischen Kurven, und war ausserdem auch hinsichtlich der Phasenanalyse vom Vorteil. Zur Phasenanalyse wurden die Rotschlämme mit Wasser extrahiert und die Extrakte und festen Rückstände mittels IR- und Röntgenmethoden identifiziert.

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Résumé On a étudié dans quelques espèces typiques de boues rouges de Hongrie l'effet des variations de pression sur la forme des courbes TG, TGD et ATD ainsi que les spectres de masse des phases hydroxyde et carbonate. La variation de la pression entraîne des vitesses de décomposition différentes. Il en résulte une meilleure séparation des phénomènes dans le cas où ceux-ci se chevauchent ainsi que des avantages du point de vue de l'analyse des phases. L'analyse des phases présentes dans les boues rouges a été effectuée par extraction à l'eau. Les extraits et les résidus solides ont été identifiés par spectrométrie infrarouge et par diffraction des rayons X.

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, - . , , . .

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Paper presented at the Scientific Session on Thermal Analysis held at Balatonfüred, Hungary, on 14–16 October 1976.