Photocatalytic electron transfer across the membranes of lipid vesicles mediated by diglycylamide of mesoporphyrin-IX N-metylglycomate

A peculiarity of the photocatalytic action of porphyrin molecules with different localization inside lipid bilayers of lecithin vesicles has been studied. The influence of an electrostatic field in the lipid membrane on the efficiency of electron photocatalytic transfer across the membrane is discussed.

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, - . . .

     

Studies on the V?Ti?O system obtained by thermal decomposition of vanadyl and titanyl oxalates in argon atmosphere

The V–Ti–O system as a product of thermal decomposition of vanadyl and titanyl oxalates at 873 and 1173 K in argon atmosphere was studied by X-ray diffraction and infrared spectroscopy. The results obtained, the analysis and surface measurement data suggest that a V³⁺–V⁴⁺–Ti⁴⁺–O solid solution is formed. Spectroscopic measurements reveal the presence of a V=O bond in the system obtained at 873 K.

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V–Ti–O, 873 1173 - . , , V⁺³–V⁺⁴–O . V=O , 873 .

     

Ba(OH)2 as catalyst in organic reactions: I. Nature of active sites in the michael addition

In order to determine the nature of active sites that act in the Michael addition of ethyl malonate to chalcone in EtOH, catalyzed by activated barium hydroxide, selective poisoning experiments have been carried out. It has been found that the catalytic activity of the C-200 catalyst is related to the strong basic sites titrated by TBMPHE.

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, - . , C-200 - , TBMPHE.

     

Effect of water on hydrogen desorption from the surface of Rh/C catalysts

An increase in the number of titration cycles results in a considerable decrease in H_T and O_T values, which in turn, brings about a decrease in the amount of desorbed hydrogen. This shows that water, being a product of titration reaction, is adsorbed on the oxidized surface of rhodium and represents a kinetic-diffusive barrier for hydrogen titration.

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, H_T O_T, , , . , , , , , - .

     

On the state of Re in the Pt/Re reforming catalysts

Both Pt/Al₂O₃ and (Pt+Re)/Al₂O₃ industrial catalysts contain, after reduction (at 450 °C) ions, extractable by acetylacetone. However, a substantial part of Re is reduced.

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Pt/Al₂O₃ (Pt+Re)/Al₂O₃ ( 450 °C) , . , .

     

Effects of reactive diluent diepoxidized cardanol and epoxy fortifier on curing kinetics of epoxy resin

Different formulations, composed of the diglycidyl ether of bisphenol-A, diepoxidized cardanol as reactive diluent, an anhydride as curing agent, and a tertiary amine as curing catalyst, with/without the use of an epoxy fortifier, were analysed. The effect of the fortifier on the diluent was also observed. The overall kinetics of curing was observed to follow a simple Arrhenius-type temperaturedependence, with an activation energy in the range 54–120 kJ/mol, with first-order kinetics up to 85% conversion. An increase in activation energy was observed with an increase of diluent content. The curing reaction was found to follow a three-step mechanism, involving a nucleophilic bimolecular displacement reaction, for which an explanation was offered. Incorporation of the fortifier lowers the curing temperature, but does not alter the final degree of reaction.

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Zusammenfassung Es wurden verschiedene Ausgangsgemische, bestehend aus dem Diglyzidyläther von Bisphenol A, diepoxydiertem Kardanol als reaktives Streckmittel, einem Anhydrid als Vernetzungsmittel und einem tertiären Amin als Vernetzungskatalysator mit bzw. ohne Anwendung eines Fortifyers untersucht. Der Einfluss des Fortifyers auf das Streckmittel wurde ebenfalls untersucht. Die Bruttokinetik der Vernetzung zeigt eine Temperaturabhängigkeit einfachen Arrhenius-Types mit einer Aktivierungsenergie im Bereich von 54–120 kJ/mol sowie einen Reaktionstyp erster Ordnung mit einer Konversionsrate von 85%. Ein steigender Streckmittelgehalt bewirkt ein Anwachsen der Aktivierungsenergie. Der Vernetzungsreaktion liegt ein Dreistufenmechanismus zu Grunde, der unter anderem auch eine nukleofile bimolekulare Substitutionsreaktion beinhaltet. Der Einsatz eines Fortifyers senkt zwar die Vernetzungstemperatur, verändert aber nicht die Endkonversionsrate.

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, , , , , , , , . . , 54–120 ·^–1 85% . . , , , . , .

     

Novel multiple methods and results in thermal analysis

The development of the multiple thermal methods and the results obtained with them during the past three years are discussed.

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Zusammenfassung Es wird ein Überblick der vielseitigen thermischen Methoden gegeben und die wesentlichsten in den letzten drei Jahren erzielten Ergebnisse vorgestellt.

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Résumé Mise au point sur le développement des méthodes thermiques associées au cours des trois dernières années et discussion des résultats obtenus.

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, .

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The author wishes to express her thanks to Miss Beata Androsits for her valuable help in assembling the material.     

Measurement of the rate constant of hydrogen atoms with carbon monoxide in tubular and jet stirred open reactors

The reaction of hydrogen atoms with carbon monoxide has been studied in discharge flow systems with a new method of detection of atoms. The results obtained with tubular and jet stirred open reactors agree with those of other authors working in transient conditions and with more sophisticated techniques.

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. , , , .

     

Thermal decomposition of ammonium nitrate dispersed in a multicomponent nitrate system

To obtain the kinetic curves of thermal decomposition of ammonium nitrate occurring together with decomposition of metal nitrates contained in a mixture, the ammonia contents evolved from samples heated under thermoanalytical conditions were determined by the Kjeldahl method.

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Zusammenfassung Der aus unter thermoanalytischen -Bedingungen erhitzten Proben freigesetzte Ammoniakgehalt wird durch das Kjeldahlverfahren bestimmt, um die kinetischen Kurven der thermischen Zersetzung von Ammoniumnitrat zusammen mit der Zersetzung von Metallnitraten in Gemischen zu erhalten.

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, , , .

     

Differential-thermal and thermogravimetric analysis of some gagates from Bulgaria

The thermal behaviour of three gagates (Bulgaria) was investigated by DTA and TG. The characteristic endo- and exoeffects and the sequence of the thermal stabilities are established.

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Zusammenfassung Das thermochemische Verhalten von drei Gagaten (Bulgarien) wurde mittels DTA und TG untersucht. Die charakteristischen endo- und exothermen Effekte und die Reihenfolge der thermischen Stabilitäten wurden ermittelt.

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(). - .

     

Usefulness of kinetic parameters in investigations of thermal decompositions of solids

The theoretical curves in the coordinates a vs. time for isothermal, and avs. temperature for non-isothermal experiments are calculated as functions of three kinetic parameters: activation energyE, pre-exponentical factorA and theg() function describing the mechanism of thermal decomposition of solids. The results show that conclusions not taking into consideration all three parameters can lead to information of little value concerning the mechanism of the decomposition and kinetic calculations. A correlation between non-isothermal and isothermal experiments, important for determination of the thermal stabilities of the compounds, is impossible without a knowledge of theg() function.

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Zusammenfassung Theoretische Umsatzkurven gegent für isotherme bzw gegen Temperatur für nichtisotherme Versuchsführung wurden berechnet in Abhängigkeit von den drei kinetischen Parametern AktivierungsenergieE, PräexponentialfaktorA und derg()-Funktion, die den Mechanismus der Zersetzung von Festkörpern beschreibt. Die Ergebnisse zeigen, dass Schlussfolgerungen, die nicht alle drei Parameter berücksichtigen, zu, Ergebnissen von geringer Aussagekraft bezüglich des Zersetzungsmechanismus und der kinetischen Interpretation führen. Eine Korrelation nicht-isothermer und isothermer Experimente, die für die Bestimmung der thermischen Stabilität der Verbindungen wichtig ist, ist ohne Kenntnis der Funktiong() unmöglich.

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- - : , - g(), . , , , . , g().

     

Interrelation of addition reactions of hexachlorocyclopentadiene and bromine to N-arylimides of endo-and exo-bicyclo[2,2,1]hept-5-ene-2,3-dicarboxylic acids

A comparative analysis of the relative reactivities of N-arylimides of endo-and exobicyclo[2,2,1]hept-5-ene-2,3-dicarboxylic acids for the addition reactions of hexachlorocyclopentadiene and bromine has been carried out. According to different correlations the transition states of these two processes are shown to be similar.

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N- - - [2,2,1] -5--2,3- . .

     

Numerical solution of direct kinetic problems

An algorithm is proposed to construct the righthand sides and the Jacobian matrix for a set of differential equations and a heat balance equation in terms of a given kinetic mechanism of a chemical reaction in a non-isothermal, constant-volume reactor. Its application is illustrated by the calculation of the dependence of the carbon monoxide explosion limit on the concentration of hydrogen added.

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. .

     

Cyclohexene skeletal isomerization activity of sepiolites modified with B3+ or Al3+ ions

The effect of sepiolite modification by B³⁺ and Al³⁺ ions on catalytic performance were investigated in cyclohexene skeletal isomerization (CSI) reaction. Catalytic activity to 1- and 3-methylcyclopentenes (1- and 3-MCP) fit the Bassett-Habgood kinetic model for first order processes. These ions induced strong acidity in the sepiolite and the best results (greater activity and selectivity to 1-MCP) were found when the sepiolite was exchanged with an BF₃/methanol solution which contained 3 wt.% of the B³⁺ ion.

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B³⁺ Al³⁺ . 1- 3- - . . - 1-- , BF₃/, 3 . % B³⁺.

     

Changes in the acid-strength distribution and the catalytic selectivity of H,Na?MOR

Acidities of synthetic H,Na–MOR samples decationized to different degrees have been characterized by differential adsorption heat distribution of ammonia. A fairly good correlation has been found between the number of acid sites of different strengths and the catalytic activity as well as the selectivity for xylene isomerization and disproportionation. The results are correlated with the mechanism of these reactions.

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H,Na–MOR, , - . , . .

     

Synthesis and thermal stability of the adducts of rare earth element β-diketonates with macrocyclic polyethers

Synthesis methods for the adducts of lanthanoid pivaloyltrifluoroacetonates with 1,4,7,10,13,16-hexaoxacyclooctadecane are described. The applicability of thermal analysis at quasi-equilibrium conditions for coordination compounds of this type is demonstrated for the first time. Based on experimental results the effect of the starting reactants on the structure of the adducts, on their volatility and thermal stability is established.

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Zusammenfassung Methoden zur Synthese von Addukten von Lanthanoidpivaloyltrifluoracetonaten mit 1,4,7,10,13,16-Hexaoxacyclooctadekan werden beschrieben. Die Anwendbarkeit der thermischen Analyse unter Quasi-Gleichgewichtsbedingungen zur Untersuchung von Koordinationsverbindungen wird erstmals aufgezeigt. Basierend auf die Versuchsergebnisse wird die Beziehung zwischen der Natur der Reaktanten und der Struktur, der Flüchtigkeit und der thermischen Stabilität der Addukte aufgezeigt.

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1,4,7,10,13,16- . , .

     

Crystallite size effect of Pd/charcoal catalysts for benzene hydrogenation

The dispersity, calculated from the particle size distribution functions obtained by Small Angle X-ray Scattering (SAXS) measurements, when related to the chemical behavior of Pd/charcoal catalysts in benzene hydrogenation, points out that this reaction is mildly structure-sensitive below the range of 40 Å, whereas no dependence on particle size is observed above this limit.

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, , (SAXS), Pd/ , , 40 Å .

     

M?ssbauer spectroscopic studies of passivated layers of iron-containing catalysts for ammonia synthesis

Combined conversion electron (CEMS) and transmission -ray (MS) Mössbauer spectroscopy was used to study the structure of passivated layers of promoted and unpromoted iron-containing catalysts. In both catalysts the oxide-coated films were found to consist of small paramagnetic (at 300 K) clusters of ferric oxide.

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. , ( 300 ) .

     

On the relationship between the structures of Cu(II) complexes and their chemical transformations IX

The Stoichiometry and the kinetics of thermal decomposition of the title compounds were studied. The results were correlated with the structures of the Cu(II) coordination polyhedra, which have in general a 4+2 type of coordination. It was shown that the equatorial Cu-H₂O bond distances are important for the found decomposition stoichiometries. As an intermediate of thermal decomposition, Cu(H₂O)₅(CH₃C₆H₄SO₃)₂ was prepared and characterized via its IR and electronic spectra and powder X-ray diffractogram. The experimental activation energies increase with increasing degree of tetragonality of the Cu(II) coordination polyhedron forX ^–=C₆H₅SO₃ and D-C₁₀ H ₁₅OSO₃, but decrease forX ^–=4-CH₃C₆H₄SO₃. TheE ^* value found for the decomposition of the latter compound can not be attributed to the chemical reaction.

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Zusammenfassung Die Stöchiometrie und Kinetik der thermischen Zersetzung der Titelverbidungen wurde untersucht. Die Ergebnissen wurden auf die Strukturen der Cu(II) Koordinationspolyeder bezogen, die im allgemeinen eine 4+2 Koordination aufweisen. Die Länge der äquatorialen Cu-H₂O Bindung erwies sich als bedeutungsvoll für die ermittelte Stöchiometrie der Zersetzung. Das Zwischenprodukt Cu(H₂O)₅(CH₃C₆H₄SO₃)₂ der thermischen Zersetzung wurde dargestellt und mittels IR- und Elektronenspektren sowie Röntgenpulveraufnahmen beschrieben. Mit ansteigendem Tetragonalitätscharakter der Cu(II) Koordinationspolyeder wachsen die experimentell ermittelten Aktivierungsenergien fürX ^–=C₆H₅SO₃ und D-C₁₀H₁₅OSO₃ an, nehmen aber fürX ^–= 4-CH₃C₆H₄SO₃ ab. Der für letztere Verbindung ermittelteE ^* Wert kann der chemischen Reaktion nicht zugeschrieben werden.

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. , 4 + 2. , Cu-H₂O . Cu(H₂O)₅(CH₃C₆H₄SO₃)₂ , -. X ^–=C₆H₅SO₃ -C₁₀H₁₅OSO₃, X ^–= 4-CH₃C₆H₄SO₃. .