Thermal properties of the clathrate compounds of binary cyanides

The stoichiometry of thermal decomposition of a particular group of clathrate compounds, of the type Cd(en)Pd(CN)₄·2G, with the same coordination component but different clathrate-enclosed components, was investigated. Irrespective of the experimental conditions, the liberation of the enclosed component G always proceeded in one step. Thermal investigation of the decomposition stoichiometry under identical experimental conditions showed that the temperature intervals in which the enclosed components are given off shift to lower temperatures in the order C₆H₅OH=> C₆H₆ > > C₄H₅N > C₄H₄S. Diffraction measurements indicated a considerable change in the structures of the original clathrate compounds after thermal release of the enclosed componentG.

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Zusammenfassung Die Stöchiometrie der thermischen Zersetzung einer bestimmten Gruppe von Klathratverbindungen vom Typ Cd(en)Pd(CN)₄·2G mit der gleichen Koordinationskomponente und verschiedenen Klathrat-Einschlußkomponenten wurde in dieser Studie untersucht. Ungeachtet der Versuchsbedingungen vollzieht sich die Freisetzung der eingeschlossenen KomponenteG stets in einer Stufe. Die unter gleichen Versuchsbedingungen durchgeführte thermische Untersuchung der Zersetzungsstöchiometrie zeigte, daß die Temperaturbereiche, in denen die eingeschlossenen Komponenten freigesetzt werden in der Reihenfolge C₆H₅OH > C₆H₆ > C₄H₅N > C₄H₄S in Richtung der niedrigeren Temperaturwerte verschoben werden. Die Diffraktionsmessungen weisen darauf hin, daß eine beträchtliche Änderung der Struktur der ursprünglichen Klathratverbindung nach thermischer Freisetzung der eingeschlossenen KomponenteG sichtbar wird.

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Résumé Dans cette étude on a établi la stoechiométrie de la décomposition thermique d'un groupe particulier de clathrates du type Cd(en)Pd(CN)₄·2G, avec le même composant de coordination et différents composants occlus. Indépendamment des conditions d'expériences, la libération du composant occlusG s'effectue toujours en une étape. L'étude thermique de la stoechiométrie de la décomposition effectuée dans les mêmes conditions d'expériences, a montré que les intervalles des températures dans lesquels les composants occlus sont libérés, se déplacent vers les températures plus faibles dans l'ordre suivant: C₆H₅OH > C₆H₆ > > C₄H₅N > C₄H₄S. Les mesures de diffraction indiquent qu'après la libération thermique du composant occlusG, une variation considérable de la structure initiale des clathrates originaux apparaît.

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Cd(en)Pd(CN)₄. 2G . , G . , , , ] ₆₅>₆₆>C₄H₆N>C₄H₄S. - , G.

     

The Stevens rearrangement of methylenedimethyloxonium ylide: A quantum chemical study

The conversion of methylenedimethyloxonium ylide to ethyl methyl ether was investigated by the semiempirical MNDO method. An activation energy of 51 kJ/mol suggests that this rearrangement is a possible elementary reaction in the well-known MTG process.

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. 51 /, , .

     

Developpement de la methode thermique de mesure de la tension superficielle liquide-solide

A thermal method connects the solid-liquid surface tension/s of a substance to its triple point temperature depression. Here a practical process for application of this method is described. A previous determination of the thickness of the condensate layer which does not freeze near the wall of the porous material is no longer necessary. The process is applied to some organic substances and to a metal (indium).

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Zusammenfassung Eine thermische Methode ermöglicht die Oberflächenspannung/s einer Substanz mit der Erniedrigung der Tripelpunkttemperatur in Bezug zu bringen. Eine vorangehende Bestimmung der Dicke der Kondensatschicht, deren Aggregatzustand sich bei Kontakt mit dem porösen Material nicht ändert, ist überflüssig. Die Methode wird auf einige organische Verbindungen und ein Metall (Indium) angewandt.

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, _.,. — . , , . .

     

A study of the surface heterogeneity and catalytic activity of catalysts by means of reaction thermodesorption

Reaction thermodesorption is studied. A generalized wiew is offered regarding the routes along which the transformations take place under the conditions of temperature-programmed desorption.

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. , .

     

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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. - . , . , , , .

     

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 . -, -, - .

     

Hydrogen exchange in intramolecular cycloalkylation of phenylalkanols

Hydrogen exchange in intramolecular cycloalkylation of 2-methyl-4-phenyl-2-butanol (I) and 2-methyl-5-phenyl-2-pentanol (II) in the presence of 85% D₂SO₄ has been studied. The product 1,1-dimethylindane(III) is shown to contain deuterium in both aromatic ring and polymethylene fragment, whereas 1,1-dimethyltetralin (IV) contains deuterium only in the aromatic ring. A probable mechanism of the reaction is discussed.

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2--4--2- (I) 2--5--2- (II) 85% D₂SO₄. , 1,1- (III) , 1,1- (IV) . .

     

The thermometric and enthalpimetric determination of organic compounds

Two main parameters determine the methods for the assay of organic compounds in industrial systems; these are the rates of reaction of the molecular organic and often non-aqueous systems which differ from those in ionic and aqueous systems, and secondly, the fact that in most organic systems an organic functional group is required to be determined by a general method applicable to the functional group in a variety of chemical environments. In pharmaceutical products it is desired to determine the functional groups without prior separation from excipients of various kinds and to obtain rapid assays, often with precision much lower than those normally required in inorganic systems. These methods are discussed with examples taken from the foodstuff industry, the pharmaceutical industry, etc.

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: , . , - , . . , . , , .

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Partly presented at the II. Seminar Thermometric Analysis, Budapest, September 2–7, 1980.     

Kinetics of p-cumylphenol alkylation by isobutylene in the presence of p-toluenesulfonic acid

Kinetics of p-cumylphenol alkylation by isobutylene in the presence of 0.1–2 wt.% p-toluenesulfonic acid has been studied and a reaction scheme is suggested. The rate constants have been determined.

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- 0,1–2 % . -. .

     

Studies of n-octane transformations on zeolites under hydrocracking conditions in a two-reactor flow-circulation system

Transformations of n-octane under hydrocracking conditions in a two-reactor flow-circulation system have been studied. It has been established that at high hydro-dehydrogenation activity of zeolite catalysts the reaction mechanism involves an initial step of paraffin dehydrogenation on a metal component and subsequent steps of cracking, isomerization and disproportionation of intermediate olefins on an acid component. Sodium content in zeolite determines the paraffin hydrocracking selectivity.

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- - . , - , . .

     

Basic properties of alkaline earth metal oxides and their catalytic activity in the decomposition of diacetone alcohol

The effect of CO₂ adsorption on the catalytic activity of alkaline earth metal oxides in the title reaction reveals that the number of active (basic) sites follows the order MgO>CaO>SrO>BaO, and the order of base strength is MgO

CO₂ , () : MgO>CaO>SrO>BaO, : MgO     

Mechanism of isotope exchange of dihydrogen with liquid ammonia catalyzed, by amide ions

The interacting bonds method (IBM) has been used for the analysis of hydrogen bonds in liquid ammonia, including estimates of the resonance components of the H=bonds of ammonia molecules with ammonium and amide ions. According to the E_a estimates for the interaction of a hydrogen molecule with an amide-ammonia solution (AAS) and the data on liquid ammonia structure, a kinetic mechanism for isotope exchange (IE) of hydrogen with liquid ammonia is formulated.

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(MBC) , -, - -. E_a - (AAP). () .

     

A rapid method for catalyst testing. Zeolite catalysts for methanol conversion to hydrocarbon

A rapid method for testing catalysts is suggested, which permits a 30-fold reduction in the time of their examination. The method is recommended for studying catalytic processes taking place with either evolution or absorption of heat.

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- , Qj 30 . , .

     

Methods for finding steady-state solutions of mathematical models for chemico-technological schemes

Gradient and Newton methods are suggested for searching for steady-state solutions of chemico-technological schemes to obtain synthetic fuels.

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- .

     

Temperature effects on the fluorescence kinetics of excited cyclohexane

In agreement with the results reported by Lipsky, emission from cyclohexane depends on the temperature T and on the nature of the phase (liquid or solid). Determination of the lifetimes of the fluorescent state with a single photon counting apparatus gives similar results. Our experimental work shows that the rate constant of fluorescence for the solid phase I (face-centered cubic cell) practically does not depend on temperature. Variations of lifetime vs. T cannot easily be interpreted only with the classical theory of non-radiative transitions.

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, , ( ). , , . , I ( ) . .

     

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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, , , . ( -) . .

     

Computation in kinetics, IV. Regression estimation of Arrhenius equation parameters from non-isothermal kinetic data

Computer method for evaluation of Arrhenius equation parameters from non-isothermal kinetic data is offered in KILET program. Changes of temperature can be linear, hyperbolic or of any smooth function which could be expressed by a polynomial of up to 4th degree. The method is demonstrated on examples of linear and hyperbolic changes for simulated and experimental data. The advantage of non-isothermal experiment over isothermal one for evaluation of kinetic solution data is stressed.

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KILET. , , 4- . . .

     

Mass-spectrometric detection of an unstable product in silver-methanol interaction

The low pressure interaction of methanol vapors with a silver catalyst was studied by mass spectrometry. An unstable product contributing to m/e-15 was detected in this reaction. While yield of formaldehyde increased with addition of oxygen, the unstable product showed towards oxygen a reversed, decreasing trend.

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- , m/e=15. , .

     

Silane-silanol condensation catalyzed by organotin compounds

The rate of condensation of H–SiR₂–(OSiR₂)_n–H (n=2, 3 or 4 and R=CH₃) and HO-SiRR–(OSiRR)₃–OH (R=C₆H₅) in xylene at 100 °C, catalyzed by dibutyltin diacetate, dilaurate and di-(2-ethyl)hexanoate, has been studied by infrared spectroscopy. The kinetic law is first order in each reactant and the reaction is accompanied by autocondensation of the silanol. The mecha nism involves complexation of the silanol with the catalyst, followed by the attack of a silane or silanol molecule.

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H–SiR₂–(OSiR₂)_n–H ( n=2,3 4 R=CH₃) HO–SiRR–(OSiRR)₃–OH ( R=C₆H₅) 100° C, , -(2-) , . . .

     

Review of some metallurgical problems suitable for quantitative calorimetric treatment

A review is given of various metallurgical problems treated in the author's laboratory, for which quantitative calorimetry gave very valuable information. Measurements of thermodynamic data for phase diagram calculations, vacancies in ordered alloys, annealing of steels, and the recovery and crystallization of amorphous alloys are successively examined.

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Zusammenfassung Es wird eine Übersicht über verschiedene, in unserem Laboratorium bearbeitete metallurgische Probleme gegeben, für die durch quantitative Kalorimetrie sehr genaue Informationen erhalten werden. Es wird auf Messungen thermodynamischer Daten für Phasendiagrammberechnungen, auf Fehlstellen in geordneten Legierungen, auf das Tempern von Stahl sowie auf Aufarbeitung und Kristallisation von amorphen Legierungen eingegangen.

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, . , , .

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Dedicated to Professor Dr Kurt Komarek on his 60th birthday.