Anwendung thermometrischer Methoden auf die Untersuchung von oxydationsmechanismen aromatischer Amine

Zusammenfassung An Hand von Oxydationsreaktionen einiger aromatischer Amine, deren mechanismus bekannt ist, wurde gezeigt, daß enthalpiometrische Titrationskurven in bedeutenden mass zur Formulierung des Reaktionsmechanismus beitragen und auf diese Weise eine wichtige Ergänzung der spektrophotometrischen, potentiometrischen, chromatographischen und weiteren Methoden bilden. In einigen Fällen ist deren Gebrauch unersetzbar.

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In the oxidation reactions of some aromatic amines with known mechanisms, it was shown that the enthalpimetric titration curves could provide considerable help in the determination of the mechanisms, acting as an important complement for spectrophotometry, potentiometry, chromatography and other methods. In some cases the method proved irreplaceable.

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Kinetics and Mechanism of Monomolecular Heterolysis of Commercial Organohalogen Compounds: XXXVI.1 Solvent Effect on the Activation Parameters of Heterolysis of 1-Methyl-1-chlorocyclohexane. Correlation Analysis of Solvation Effects in Heterolysis of 1-Methyl-1-chlorocyclohexane and 1-Methyl-1-chlorocyclopentane

The kinetics of heterolysis of 1-methyl-1-chlorocyclohexane in six protic and eight aprotic solvents at 25-50°C was studied by the verdazyl method; v = k[RCl], E1 mechanism. The correlation analysis of the solvent effects on the activation free energy G , enthalpy H , and entropy S of heterolysis of 1-methyl-1-chlorocyclohexane and 1-methyl-1-chlorocyclopentane was performed for the same sets of solvents.     

Mechanisms of 5'-O-Benzoyl-2,3'-anhydrothymidine Reactions with Nucleophiles: IV.* Kinetics and Thermodynamics of Azidation with Dimethylammonium Azide in DMF-1,4-Dioxane

The reaction of 5'-O-benzoyl-2,3'-anhydrothymidine with dimethylammonium azide in the system DMF-1,4-dioxane in the temperature range from 80 to 100°C follows the overall second-order kinetics and first-order kinetics with respect to each reactant. The activation parameters in the systems containing 30, 40, and 50 vol % of dioxane are, respectively: H 298 99, 85, and 79 kJ mol^{- 1}; S 298 -46, -83, and -101 J mol^{- 1} K^{- 1}. A refined model of the transition state for the rate-determining stage was proposed, which takes into account specific interaction with 1,4-dioxane.     

Isoparametric kinetic relations for chemical transformations in condensed substances (analytical survey). I

The compensation effect related to isoparametric correlations is analysed within the formal theory, and the statistical and physico-chemical aspects of these correlations are considered.

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Zusammenfassung Der sich auf isoparametrische Korrelationen beziehende Kompensationseffekt wird im Rahmen der formalen Theorie analysiert. Statistische und physikalisch-chemische Aspekte dieser Korrelationen werden erörtert.

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Effect of metal ions forming bromide complexes on the Belousov-Zhabotinskii reaction

Metal ions forming stable complexes with bromide ions greatly influence both the amplitude and frequency of the Belousov-Zhabotinskii reaction. In case of thallium(I), redox reactions involving the metal ion should also be considered beside complex formation.

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Study of thermochemical conversions of alicyclic polyimides

The thermochemical conversions of certain polyimides obtained by the polycondensation of dianhydrides of alicyclic tetracarboxylic acids and 4,4-diaminodiphenyl oxide were studied by different methods of thermal analysis (thermogravimetry, mass-spectrometric evolved gas analysis, and pyrolytic gas chromatography). The thermal dissociation of dianhydride fragments according to the reverse reaction of retrodiene synthesis is the basic reaction that determines the thermal stabilities of the polymers studied. It is shown that the absence of endoethylene bonding or its substitution by oxygen in the dianhydride fragments leads to increases in the thermal stabilities of alicyclic polyimides.

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Zusammenfassung Thermochemische Umwandlungen einiger Polyimide, die durch Polykondensation der Dianhydride alicyclischer Tetracarbonsäuren mit 4,4-Diaminodiphenyloxid dargestellt waren, wurden durch verschiedene thermoanalytische Methoden (TG, massenspektrometrische EGA und Pyrolyse-Gaschromatographie) untersucht. Die thermische Spaltung der Dianhydrid-Komponente nach einer Retro-Diensynthese ist die Hauptreaktion, die die thermische Stabilität der Polymeren bestimmt. Bei Abwesenheit der endo-Ethylen-Bindung in der Dianhydrid-Komponente oder Substitution durch eine Etherbindung wird die thermische Stabilität von Polyimiden mit alicyclischen Baugruppen erhöht.

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The authors would like to thank Yu. A. Sazanov and L. A. Shibaev (IVS AN SSSR, Leningrad) for help in the mass-spectrometric thermal analysis of the polymers.     

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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Discrimination of active sites for ethylene homologation and ethylene metathesis on molybdena silica catalyst

Active sites for ethylene homologation (3C₂H₄2C₃H₆) and ethylene metathesis (C₂H₄–¹²C₂+C₂H₄–¹³C₂2C₂H₄–¹³C₁) were discriminated by adding platinum to a reduced molybdena silica catalyst, and the former was presumed to be composed of several molybdenum species, while the latter was presumed to be composed of one molybdenum species.

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(3C₂H₄2C₃H₆) (C₂H₄–¹²C₂+C₂H₄–¹³C₂2C₂H₄–¹³C₁) . , , .

     

Study of the adsorption properties of a natural Hungarian mordenite and its ion-exchanged derivatives

The texture and adsorption properties of a natural, Hungarian mordenite were investigated by electron microscopy and BET adsorption measurements. The properties of the ion-exchanged adsorbents were characterized by CO₂ and SO₂ isotherms. The measurements were evaluated on the basis of the pore-filling theory of Dubinin. We have found that at 20°C the H⁺-form of mordenite interacts preferably with CO₂, while on the Na⁺- and Ca²⁺-derivatives stronger adsorption of SO₂ takes place. This fact accounts for their applicability as selective adsorbents.

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, . CO₂ SO₂. . , 20°C H⁺- CO₂, Na⁺- Ca²⁺- SO₂ . .

     

51V-NMR spectra of vanadates and oxosulfato-vanadates of alkali metals

A relation between the type of vanadium environment and the chemical shift anisotropy in the⁵¹V-NMR spectra has been established. The results obtained are compared with spectra of real catalysts.

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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.     

Effect of temperature of calcining hydrated aluminium oxides on their sorption properties

The effect of the temperature of calcining hydrated aluminium oxides on their sorption properties was investigated.It was found that the sorption properties and the porous structure of aluminium oxides depend on the type of material calcined and on the conditions under which this process occurs.

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Zusammenfassung Es wurde der Effekt der Kalzinierungstemperatur von hydratiertem Aluminiumoxid auf dessen Sorptionseigenschaften untersucht. Es wurde festgestellt, daß die Sorptionseigenschaften und die Porenstruktur von Aluminiumoxid von Typ des kalzinierten Materials und von den Bedingungen abhängen, unter denen dieser Prozess abläuft.

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Ethylene oxidation by lithium nitrate in the presence of palladium acetate in acetic acid

Data are reported on variations of the gas phase volume and product accumulation in ethylene oxidation by lithium nitrate in acetic acid solutions, catalyzed by palladium acetate. An assumption is made on the routes of nitrate ion reduction.

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Investigation of complete oxidation of organic materials with thermal analytical measurements

The complete oxidation of styrene-divinylbenzene has been examined with complex thermoanalytical methods by derivatograph and thermogastitrimeter. With the combined application of combustion catalyst and postcatalytic method the oxidation of the styrene-divinylbenzene is complete.

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Zusammenfassung Die vollständige Oxydation von Styrol-Divinylbenzol wurde mittels einer komplexen thermoanalytischen Methode unter Verwendung eines mit einem Gastitrimeter kombinierten Derivatographen untersucht. Eine vollständige Oxydation wird bei Anwendung eines Verbrennungskatalysators und der postkatalytischen Methode erreicht.

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High-temperature reduction of SO2 by methane at various CH4/SO2 ratios

The character of the effect of initial reaction mixture and temperature on the selectivity of catalytic reduction of sulfur dioxide by methane in the presence of oxygen has been studied.

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Thermal analysis of thermosetting resins

Applications of thermoanalytical methods for the study of the resinification and curing of phenolic resins are reviewed. Examples are given to illustrate the use of DSC for practical industrial systems such as paper impregnants and saturated papers.

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Zusammenfassung Es wird eine Übersicht über die Anwendungen thermoanalytischer Methoden zur Untersuchung der Harzbildung und der Aushrtung von phenolischen Harzen gegeben. Anhand von Beispielen wird die Verwendung der DSC für praktische industrielle Systeme wie Papierfüllstoffe und gefüllte Papiere aufgezeigt.

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Generation of model reactions leading to limit cycle behavior

The system of differential equations by Feistel and Ebeling has been generalized. Some new formal kinetic reactions with two internal components, which may exhibit limit cycle behavior have been studied. Based upon the numerical integration of the deterministic models of these reactions the oscillatory character of the systems has been confirmed.

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Transformed steroids. 121. Synthesis of the δ-lactone of 3β-acetoxy-16α-hydroxy-6-oxo-24-nor-5α-chol-17(20)-en-23-oic acid

The synthesis of the ¹⁷⁽²⁰⁾-16 analog of natural chiogralactone is described. Attempts to introduce a 6-oxo group directly into the -lactone proved unsuccessful, since the first stage — saponification — took place with the formation of three products: the 3-hydroxy--lactone, the 3-hydroxy-²⁰⁽²²⁾-lactone, and the 15,17(20)-dienoic acid. The synthesis of the desired compound was effected from the ethyl ester of the 5,16-dienoic acid by the scheme 3-acetate3-tosylate6-hydroxy-3,5-cyclosteroid6-oxo-3,5-cyclosteroid6-oxo-5H--lactone. It has been shown that the cyclopropane ring in the 3,5-cyclosteroid -lactone is extremely stable under the conditions of acid treatments.N. D. Zelinskii Institute of Organic Chemistry, Academy of Sciences of the USSR, Moscow. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 184–187, March–April, 1981.