Activation thermodynamic parameters of binary mixtures of propionic acid ando-substituted anilines

Variations of densities and viscosities with temperature and composition are reported for binary liquid mixtures containing propionic acid+aniline (I),+o-toluidine (II),+o-anisidine (III), and+o-chloroaniline (IV). Entropies S _m and enthalpies H _m of activation as functions of the composition of the mixtures, as well as free energies of activation G _m at 10, 20, 30, 40, and 50°C and different compositions were calculated by means of Eyring's equation. The formation of activated complexes between the components of these binary mixtures is postulated and claimed to result from acid-base and hydrogen bonding exchange interactions.     

Surface tension as a function of temperature for some molten metals

Results are given for Sn, In, and Ge from the melting points up to 1700 C, for Pb up to 1400 C, for Tl up to 1100 C, for Bi up to 1300 C, and for Cd up to 600 C. In every case the surface tension is a linear function of temperature. Estimates are made of the critical temperatures of Cd and Ge. It is shown that deductions on the structure of the melts can be drawn from surface-tension data.     

Extended Hückel MO calculations of the conformation of several amino acids

The conformation of the amino acid residues, glycine, alanine, proline, and phenylalanine have been predicted from molecular orbital calculations of appropriate model compounds. Using the current main chain rotation convention (, ) the principle conformations were found to be glycine (0, 0), alanine (240, 240), proline (120, 330) and phenylalanine (30, 330). Several secondary conformations were also found for glycine. A comparison of the predicted conformations is in good agreement with experimental data on comparable residues or model compounds.Supported by National Institutes of Health Grants No. FR 5409-07 and GM 16312-01.Recipient of a Public Health Service Research Career Development Award AM 1159-01.     

Analytische Dichtegradienten-Zentrifugation bei Temperaturen zwischen +4?C und +40?C

Zusammenfassung Es wird gezeigt, da\ die bei der analytischen Dichtegradienten-Zentrifugation benötigten Parameter, die von Hearst u. Mitarb. tabelliert wurden, auch für andere Temperaturen als 25C gültig sind. Das ist von gro\er Wichtigkeit, da hochempfindliche Enzyme nur bei Temperaturen um + 4C lÄnger als 24 h nativ bleiben. Man ist deshalb auf eine Zentrifugation bei dieser Temperatur angewiesen. Weil man oft nur sehr wenig Substanz isolieren kann, bleibt nur die Dichtegradienten-Zentrifugation als Methode der Wahl. Ein Vergleich der gemessenen Molekulargewichte bei 6C und 25C zeigt keine Abweichungen, die über die Me\genauigkeit hinausgehen.

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Analytical density gradient centrifugation at temperatures between +4C and +40 C

It is shown that all the parameters needed for analytical density gradient centrifugation tabulated by Hearst et al. for 25C are valid for other temperatures, too. This will be important in the investigation of highly sensitive enzymes which are only stable at temperatures near +4C over a period of 24 h. Comparison of molecular weights determined at 6C und 25C shows no difference greater than 2%, which will be within the experimental error.

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Das Bundesministerium für Bildung und Wissenschaft hat diese Arbeiten gro\zügig unterstützt.     

Measurement of specific heat and energetic characterization of materials up to high temperatures

A new DSC system has been developed which not only allows quantitative results in the temperature of –160C to 700C, but also allows the quantitative determination of a variety of material properties up to 1500C. For example, the specific heat of materials can be measured to at least 1400C, while enthalpies, etc. can be measured to 1500C.

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Zusammenfassung Ein neuartiges DSC Messystem (Netzsch DSC 404) wurde entwickelt, das sich durch hohe Reproduzierbarkeit der Basislinie, grosse Empfindlichkeit und breiten Temperaturanwendungsbereich (–160C bis 700C resp. bis 1500C) auszeichnet. Die Messanordnung ermöglicht die Verwendung von unterschiedlichen GasatmosphÄren als auch Messungen im Vakuum. Es werden Beispiele der Bestimmung von SchmelzvorgÄngen, der Glasumwandlungstemperatur, der KristallinitÄt und der spezifischen WÄrme, sowohl für Polymere als auch für anorganische Materialien dargestellt und diskutiert.

     

Some mathematical aspects of nonisothermal kinetics

The results of an attempt to derive correct nonisothermal kinetic equations from isothermal ones through the classical nonisothermal change (CNC) of the postulated primary kinetic equations are presented. An alternative possibility through use of the model of infinitesimal isothermal portions (MIIP) is discussed.

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Zusammenfassung Die Autoren stellen die Ergebnisse eines Versuchs vor, korrekte Gleichungen für die nicht-isotherme Kinetik durch den klassischen nichtisothermen Übergang aus den als primär postulierten isothermen kinetischen Gleichungen abzuleiten. Als alternative Möglichkeit wird das Modell der infinitesimalen isothermen Abschnitte diskutiert.

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. .

     

Activation of magnesia by hydrogen spillover

Magnesia aerogel activated by hydrogen spillover at 430 °C or at 200 °C becomes a catalyst for the hydrogenation of ethylene. This catalytic activity, observed already at 50 °C, is further enhanced by a treatment in oxygen at 430 °C.

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, 430 200°C, . 50°C 430°C.

     

Kinetic analysis of thermogravimetric data. XI thermal decomposition of some metal dithionates

A thermal analytical study of Li, Na, K, Rb, Cs, NH₄, Mg, Ca, Sr, Ba and Zn dithionates is reported. The decomposition of the dithionate ion is endothermic in the case of the Na, K, Rb, Cs and NH₄ salts, but exothermic with Li, Mg, Sr, Ba and Zn. Kinetic parameters have been derived from the TG curves by means of the Coats-Redfern method. The validity of a linear kinetic compensation law is reported for the loss of crystal water and separately for the decomposition of the dithionate ion.

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Zusammenfassung Es wird über eine thermoanalytische Untersuchung der Dithionate von Li, Na, K, Rb, Cs, NH₄, Mg, Ca, Sr, Ba und Zn berichtet. Die Zersetzung des DithionatIons ist im Falle von Na, K, Rb, Cs und NH₄-Salzen endotherm, im Falle von Li, Mg, Sr, Ba und Zn hingegen exotherm. Die kinetischen Parameter wurden aus den TG-Kurven mittels der Coats-Redfern-Methode abgeleitet. Es wird über die Gültigkeit eines linearen kinetischen Kompensationsgesetzes für den Verlust von Kristallwasser berichtet und gesondert für die Zersetzung des Dithionat-Ions.

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Résumé On présente les résultats d'une étude par analyse thermique des dithionates de Li, Na, K, Rb, Cs, NH₄, Mg, Ca, Sr, Ba et Zn. La décomposition est endothermique dans le cas des sels de Na, K, Rb, Cs et ammonium tandis qu'elle est exothermique dans le cas des sels de Li, Mg, Sr, Ba et Zn. Les paramètres cinétiques sont déduits des courbes TG par la méthode de Coats-Redfern. La validité d'une loi de compensation cinétique linéaire est étudiée pour la perte de l'eau d'hydratation ainsi que pour la décomposition de l'ion dithionate.

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Li, Na, K, Rb, Cs,. NH₄, Mg, Ca, Sr, Ba Zn. [ Na, K, Rb, Cs NH₄ , Li, Mg, Sr, Ba Zn . - . .

     

Solvent effects on the kinetics of solvolysis of trans-dichlorobis (N-methylethylenediamine)cobalt(III) ion in water–propan-2-ol and water–acetonitrile mixtures

First order solvolysis rates of the trans-dichlorobis (N-methylethylenediamine) cobalt(III) ion have been measured over a wide range of solvent compositions and temperatures in water–propan-2-ol and water–acetonitrile mixtures. The rate of solvolysis is faster in the former mixtures rather than the latter. Plots of log(rate constant) versus the reciprocal of the dielectric constant of the co-solvent, and also versus the Grunwald–Winstein Y-values are non-linear for both co-solvents; this non-linearity is derived from a large differential effect of solvent structure between the initial and transition states. However, extrema in the variation of enthalpy H and entropy S of activation correlate well with the extrema in physical properties of the mixtures which are related to changes in solvent structure. Linear plots of H versus S were obtained and the isokinetic temperature indicates that the reaction is entropy controlled. The application of a free-energy cycle shows that changes in solvent structure affect the pentacoordinated cobalt(III) ion in the transition state more than the hexacoordinated cobalt(III) ion in the initial state. In addition, the stabilizing influence of changes in solvent structure is greater in propan-2-ol–water mixtures than in acetonitrile–water mixtures, and the difference becomes greater as the mole fraction, x2 of the organic co-solvent increases.     

Influence of the essential features of the potential energy surface on the temperature dependence of the H+CH3→CH4 reaction

Microcanonical statistical adiabatic channel model calculations show that the temperature dependence of the limiting high pressure rate coefficients of the title reaction becomes less positive (or more negative) when the attractiveness of the radial or the attenuation of anisotropic parts of the potential energy surface increases.

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, ( ) .

     

Composition and properties of the cobalt-molybdenum oxide system

The physico-chemical and catalytic properties of the Co–Mo oxide system have been studied in a wide range of various molybdenum to cobalt ratios. The activity increase at 1.21Mo:Co?11 is assumed to be due to the formation of solid solutions.

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- Co–Mo- . , - 1,21Mo:Co>11 .

     

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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. , .

     

Influence of substituents on rate constants for recombination of tertiary peroxy radicals

A linear correlation between the logarithm of rate constant (2k_t) for recombination of tertiary peroxy radicals (ROO)^* and ^* constants of substituents R was found to be 1g 2k_t=lg 2k _t ^° . The calculated values are 1g 2k _t ^° =4.59±0.08 and ^*=5.56±0.35.

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I (2k_t) (ROO) R: 1g 2k_t=lg 2k _t ^° . , 1g 1g 2k _t ^° =4,59±0,08 =5,56±0,35

     

Oxidation of [Co(en)2(SOCH2CO2)]+ by S2O82− and by IO4− in binary aqueous solvent mixtures at pressures up to 1.25 kbar

Second order rate constants and activation parameters H, S, and V have been measured for the oxidation of [Co(en)2(SOCH2CO2)]+ by S2O82– and by IO4– in highly aqueous H2O – t-BuOH mixtures. The changes in solvation on going from the initial to the transition state are discussed on the basis of the transfer functions Gto, Hto and Sto. Whereas Gt changes smoothly as the proportion of t-BuOH increases, the plots of Ht and TSt exhibit mirror behaviour and pass through extrema located around x2(t- BuOH)=0.038. Information on the role of solvation is complemented by the determination of activation volumes. These are discussed in terms of intrinsic and solvational contributions. It is proposed that changes in hydrophobic hydration are of principal importance in determining the response of H, S, and V to changes in solvent composition in H2O – t-BuOH mixtures.     

Continuum composition models to describe multicomponent reaction kinetics

Some principles of the construction of kinetic models for multicomponent processes of oil-refining and petrochemistry are suggested in terms of the continuum mixture composition concepts. The results of computer simulation of industrial gasoline fraction hydrocracking processes are presented.

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Study of the thermal decomposition of solids in a fluidized bed,II

In order to eliminate the errors of the TG method with a static layer, and to determine the influence of the heating rate, the composition of the carrier gas and the particle size of the solids, a method of thermal gas evolution from a fluidized bed (FTGE) with continuous and linear increase of temperature was worked out and the thermal decomposition of diammonium hydrogen phosphate was followed. This method gives reproducible results and makes possible the determination of the apparent activation energies and kinetic parameters.

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Zusammenfassung Um die Fehler der TG Methode unter fixierten Verhältnissen zu eliminieren, den Einfluß der Temperaturerhöhung, der Zusammensetzung des Trägergases und des Ausmaßes der Festkörper zu klären, wurde eine thermogasanalytische Methode im fluidisierten Bett (FTGE) mit kontinuierlichem und linearem Temperaturanstieg entwickelt und die thermische Zersetzung des Diammonium-biphosphates verfolgt. Man erhielt mit dieser Methode reproduzierbare Ergebnisse. Sie ist zur Bestimmung der scheinbaren Aktivierungsenergien und kinetischer Parameter geeignet.

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Résumé Dans le but d'éliminer les erreurs des procédés thermogravimétriques avec couches fixes, et de mettre en évidence l'influence de la vitesse d'échauffement de la composition du gaz porteur et de la dimension des solides, on a développé une méthode d'analyse des gaz dégagés, avec lit fluidifié et élévation de la température continue et linéaire. On a suivi ainsi la décomposition thermique de (NH₄)₂HPO₄. Cette méthode donne des résultats reproductibles et rend possible la détermination des énergies d'activation apparentes et des paramètres cinétiques.

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, , . . , .

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Some parts presented at the IIIrd Analytical Conference, Budapest, 1970     

Propos sur l'interpretation de l'energie d'activation experimentale

Résumé Les résultats de divers travaux montrent que la valeurE _e de l'énergie activation expérimentale tirée des diagrammes d'Arrhénius varie avec la pression, dans le cas de réactions de décompositions endothermiques.L'analyse de divers modèles permet d'expliquer cette constatation en montrant que la grandeurE _e n'a pas le sens d'une énergie d'activation mais est une fonction de nombreux paramètres. Deux d'entre eux ont été retenus dans le cadre de cette étude: le terme d'écart à l'équilibre et le terme de gradient thermique, provoqué par l'endothermicité du phénomène.Cette analyse permet d'établir une prévision de la fonctionE _e (P) conforme aux résultats expérimentaux.

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The results from various investigations show that the experimental activation energy valueE _e derived from the Arrhenius diagrams varies with pressure for endothermic decomposition reactions.The analysis of various models allows this fact to be accounted for by showing thatE _e should be regarded not in its fundamental formulation, but as being a function of numerous parameters. Two of these were taken into account in the present study, i.e. deviation from equilibrium and a thermal gradient due to the fact that the phenomenon is endothermic.FunctionE _e (P) fitting the experimental results may be predicted by such an analysis.

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Zusammenfassung Die Ergebnisse verschiedener Untersuchungen zeigen, dass die aus den Arrhenius-Diagrammen abgeleiteten experimentellen Werte der AktivierungsenergieE _e bei endothermen Zersetzungsreaktionen mit dem Druck variieren.Die Analyse verschiedener Modelle ermöglicht eine Erklärung dieser Tatsache, indem gezeigt wird, dassE _e nicht in ihrer grundliegenden Formulierung betrachtet werden darf, sondern als Funktion einer Anzahl von Parametern. Zwei dieser Parameter wurden in der vorliegenden Untersuchung berücksichtigt d.h. die Abweichung von dem Gleichgewicht und der thermische Gradient, welcher infolge der endothermen Beschaffenheit der Erscheinung auftritt.Eine den Versuchsergebnissen entsprechende FunktionE _e (P) kann mittels einer solchen Analyse vorausgesagt werden.

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, _e, , . , _ee , . , : , , . _e (), , .

     

Chemical oscillations in the uncatalyzed bromate oxidation of hydroquinone and nitrophenols

Chemical oscillatory behavior in the uncatalyzed bromate oxidation of hydroquinone and nitrophenols is reported. The reaction is strongly inhibited by stirring. Effect of one-electron redox couples (EZ catalysts) on the system is described.

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. . - ( EZ) .

     

Non-catalyzed oscillation reaction in the aniline-KBrO3?H2SO4 system. II. Reaction products and their oscillating behavior

By means of thin-layer and gas chromatography the reaction products have been determined in the oscillation system of aniline, KBrO₃ and H₂SO₄. These products include: 2-bromoaniline, 4-bromoaniline, 2,4-dibromoaniline, 2,4,6-tribromoaniline, 1,4-benzoquinone, 2-bromo-1,4-benzoquinone, 2,6-dibromo-1,4-benzoquinone and a brominated oxidation product. The brominated aniline derivatives do not exhibit an oscillating behavior, and the addition of these substances to an oscillating mixture damps the course of other oscillations.

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, KBrO₃ H₂SO₄. : 2-, 4-, 2,4-, 2,4,6-, 1,4-, 2--1,4-, 2,6--1,4- . , , , .

     

Thermal and spectroscopic study of the solid complexes of furan-2-hydroxamic acid and several divalent metallic cations

Solid crystalline complexes of furan-2-hydroxamic acid (FHA) and six metallic divalent cations (Ca(II), Ba(II), Co(II), Ni(II), Cu(II), and Cd(II)) were prepared. In all cases the stoichiometry was 2(FHA)1 (cation). The solids were characterized by elemental analysis, TG, DSC and IR techniques.

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Zusammenfassung Es wurden feste, kristalline Komplexe von Furan-2-hydroxamsäure (FHA) und sechs verschiedenen bivalenten Metallkationen hergestellt: Ca(II), Ba(II), Co(II), Ni(II), Cu(II) und Cd(II). Die stöchiometrische Zusammensetzung betrug in allen Fällen 2(FHA)1(Kation). Die Feststoffe wurden mittels Elementaranalyse, TG-, DSC- und IR-Techniken charackterisiert.

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-2- , , , , . : 21. , , .