Kinetics of competitive addition of methyldichlorosilane to 1-hexene and to acetone

The competitive addition of methyldichlorosilane (MDChS) to 1-hexene and acetone^** has been studied. The estimated relative constant is effective and depends on acetone concentration and does not obey the Arrhenius temperature equation. A possible explanation is the complexation of methlydichlorosilyl radicals by acetone molecules.

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, 1- , -, . - .

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Initiated by -irradiation of⁶⁰Co.     

Isothermal and isobaric PVT-measurements of anionic polystyrenes

PVT-measurements of anionic polystyrenes on heating have shown that, depending on the mode of operation, specific relaxation zones within the glass transition range are observed. Isothermal PVT curves exhibit always relaxation zones independent whether the pressure is increased or decreased during the scan. The shift of the relaxation zones to higher temperatures is, however, higher for isothermal scans with increasing pressure. These relaxation zones are explained by pressure-dependent changes of the state of the polymeric sample isothermally scanned within the glass transition range. At lower pressures the polymer is actually in the molten state, whereas at higher pressures it may be in the metastable glassy state and the actual state depends on the rate of pressure change. In isobaric PVT curves relaxation zones in heating scans are exhibited only if the pressure applied during glass formation differs from the pressure applied during the heating scan. The observed pressure-dependent shift of the glass temperatures to higher temperatures was higher for the studied polystyrenes of different molecular weight that had a higher glass temperature at normal pressure. But the specific molecular weight influence on the width of the relaxation zone could not be ascertained. An attempt to calculate characteristic volume relaxation times failed because of insufficient precision of the measurements.Dedicated to Professor Bernhard Wunderlich on the occasion of his 65th birthdayAcknowledgement is made to the Deutsche Forschungsgemeinschaft (SFB 60) for financial support of this research.     

Peculiarities in oxidative conversion of methane to C2 hydrocarbons over CaO?CaCl2 catalysts

Experimental data for the oxidative dimerization of methane over CaO–CaCl₂ systems indicate that C₂ hydrocarbons are formed with the participation of chlorine generated by the catalyst surface under the effect of a reaction medium. A heterogeneous-homogeneous scheme for this process is suggested.

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CaO–CaCl₂ , C₂- , . - .

     

Diffusion effects in reversible energy transfer

Back energy transfer reduces the apparent quenching constant, which is an important parameter in the interpretation of energy transfer data. This determination of kinetic results may be erroneous when possible diffusion effects and non-uniform configurational distributions are not taken into account.

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, . , .

     

Infrared spectroscopic study of the interaction between furan and a vanadium oxide catalyst

The results of the infrared spectroscopic study of the interaction between furan and a vanadium oxide catalyst permit to suppose that the intermediates in furan oxidation are surface succinyl oxide and maleates.

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, , , - .

     

Effects of drying conditions on thermal decomposition behaviour of UO3 gel microspheres

The effects of the drying conditions on the thermal behaviour of UO₃ gel microspheres were studied by TG, DTA and X-ray examination. The effects of drying with air, steam or alcohol on the crystal structure and crystallite size were also studied. The results indicate that the thermal decomposition of UO₃ gel microspheres involves five steps: the first two for dehydration, the third for ammonia release, the fourth for ammonia oxidation, and the last one for UO₃ recrystallization. It was also found that the crystal growth varied from 110 Å after air drying to 512 Å and 496 Å after steam and alcohol treatment, respectively.

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Zusammenfassung Die Effekte der Trocknungsbedingungen auf das thermische Verhalten von UO₃-Gelmikrokugeln wurden mittels TG, DTA und Röntgenanalyse untersucht. Ebenfalls wurden die Auswirkungen der Trocknung mit Luft, Dampf und Alkohol auf die Kristallstruktur und die Kristallitgröße untersucht. Die Ergebnisse deuten darauf hin, daß die thermische Zersetzung der UO₃-Gelmikrokugeln in 5 Schritten verläuft: die ersten zwei sind Dehydratisierungsprozessen, der dritte der Freisetzung und der vierte der Oxydation von Ammoniak und der letzte der Rekristallisation des UO₃ zuzuschreiben. Die Kristallitgröße variiert zwischen 110 Å nach Lufttrocknung und 512 bzw. 496 Å nach Trocknung mit Dampf bzw. Alkohol.

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, UO₃ . , UO₃. , UO₃ : — , — , — — UO₃. , 110 Å 512 496 Å , , .

     

Effect of preparation conditions on the properties of carbon-supported nickel catalysts

Carbon-supported Ni catalysts were prepared from nickel nitrate or chloride. Characterization was carried out by H₂ and CO chemisorption, XRD and TEM. Catalysts were further tested in the hydrogenolysis of n-butane.

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, , . H₂ CO, ., -.

     

Activity of tungstate catalysts in the synthesis of metylmercaptane from methanol and hydrogen sulfide

Catalysis obtained by impregnation of Al₂O₃ with solutions of hepta-, dodeca-, meta- and normal alkaline metal tungstates showed approximately the same activity. Most selective towards methylmercaptane were catalysts with an alkaline metal to tungsten atomic ratio equal to 21.

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, Al₂O₃ -, -, -, . , : 21.

     

Kinetics and mechanism of OsO4 catalyzed oxidation of chalcones by Ce4 in aqueous acetic sulfuric acid media

Kinetics of OsO₄ catalyzed oxidation of chalcones by Ce⁴⁺ has been studied in aqueous acetic-sulfuric acid medium in the temperature range 313 to 338 K. The order in [oxidant] is zero while the order with respect to [substrate] and [catalyst] are each fractional. The rate of the reaction decreased with increase in percentage of acetic acid while [H⁺] had practically no effect on the rate The rates of various substituted chalcones (with substituents in the phenyl. ring attached to the moiety) are in the orderp-CH₃>m-CH₃>H>p-Cl>m-Cl>m-NO₂>p-NO₂. A mechanism in which formation of a cyclic ester between chalcone and OsO₄ in a fast step followed by its decomposition in a rate-determining step is envisaged.

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Ce⁴⁺, OsO₄, - 313–338 . —, —. , [H⁺] . ( , : -CH₃>-CH₃>H>-Cl>-NO₂>-NO₂. , OsO₄ , , .

     

Kamlet-Taft solvatochromic parameters of aqueous binary mixtures oftert-butyl alcohol and ethyleneglycol

The , , and * Kamlet-Taft solvatochromic parameters have been determined for aqueous mixtures of tert-butanol and ethyleneglycol from spectroscopic data.     

Thermal characterization of bismaleimide blends

4,4-bismaleimidophenyl methane (BM) and 3,3-bismaleimidophenyl sulfone (BS) were blended in solution using weight ratios 31 (MS31), 21 (MS21), 11 (MS11), 12 (MS12) and 13 (MS13). Chain extended bismaleimide resins were also prepared by treating BS/BM with 4,4-diaminodiphenyl ether in molar ratios of 10.3 (BM-E and BS-E resins). These resins were also blended with bismaleimides and the curing characteristics were evaluated by differential scanning calorimetry. Increase in BM content in BMBS blends or increase in chain extended bismaleimide content in BM-EBS or BS-E BM blends resulted in a reduction of melting and curing temperatures. Indication about the extent of cross-linking was obtained from solubility measurements (in DMF) of isothermally cured resins (180 °C, lh and 220 °C, lh in an air oven). Thermogravimetric analysis of samples isothermally cured at 180 °C and 220 °C (lh each) was carried out in nitrogen atmosphere. Improvement in thermal stability of chain extended bismaleimides was observed on blending.

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Zusammenfassung 4,4-Bismalimidophenyl-methan (BM) und 3,3-Bismalimidophenyl-sulfon (BS) wurden in Lösung in den Gewichtsverhältnissen 31 (MS31), 21 (MS21), 11 (MS11), 12 (MS12) und 13 (MS13) gemischt. Auch kettenpolymerisierten Bismalimid-Harze wurden durch Behandlung von BS/BM mit Diaminodiphenylether im Molverhältnis 10,3 dargestellt (BM-E- und BS-E-Harze). Die Kennwerte der Aushärtung von Mischungen dieser Harze mit den Bismalimiden wurden mittels DSC ermittelt. Eine Erhöhung des BM-Gehaltes in den BM BS-Mischungen oder des Gehaltes der BM-E BS oder BS-E-Mischungen an kettenpolymerisierten Bismalimiden führt zu einer Erniedrigung der Schmelz- und Aushärtetemperaturen. Hinweise über den Vernetzungsgrad wurden aus Löslichkeitsmessungen (in DMF) von Isotherm (je 1 Stunde bei 180 und 220 °C in Luft) gehärteten Harzen erhalten. Die thermogravimetrische Analyse der Isotherm bei 180 bzw. 220 °C 1 Stunde ausgehärteten Proben wurde in Stickstoffatmosphäre ausgeführt. Die thermische Stabilität der Bismalimide wird durch Verschneiden verbessert.

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4,4-- () 3,3-- () 31 (MC 31), 21 (MC 21), 11 (MC 11), 12 (MC 12) 13 (MC13). - / 4,4- 10,3 ( - C-). - . - - - - , . ( 1 180 220°) . . - .

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The financial assistance provided by Department of Science and Technology is gratefully acknowledged.     

Thermal studies of lead(II) salts,VI

The kinetics and mechanisms of the thermal decomposition of lead(II) carbonate and lead(II) hydroxide carbonate have been studied over a range of temperatures and partial pressures of carbon dioxide using both isothermal and programmed heating. All stages in each decomposition are diffusion controlled and Arrhenius parameters have been determined. These values for loss of carbon dioxide are all extremely high for a diffusion process, but show a compensation effect, following the equation: logA=–5.02+0.067E The compensation effect is discussed and comparisons with other systems showing such effects are made.

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Zusammenfassung Kinetik und Mechanismus der thermischen Zersetzung von Blei(II)carbonat und Blei(II)hydroxycarbonat wurden bei verschiedenen Temperaturen und CO₂-Partialdrücken sowohl isotherm als auch unter den Bedingungen der programmierten Aufheizung untersucht. Bei allen Zersetzungsschritten ist die Diffusion der geschwindingkeitsbestimmende Schritt; die Arrhenius-Parameter wurden bestimmt. Für einen Diffusionsprozess sind diese Werte extrem hoch, sie zeigen aber einen durch die Gleichung logA=–5.02+0.067E zu beschreibenden Kompensationseffekt, der diskutiert wird. Durch Vergleich mit anderen Systemen wird gezeigt, wie solche Effekte zustande kommen.

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- - , . - - . , , - : log=– 5.02 + 0.067. K .

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We wish to record our thanks to Dr. A. K. Galwey for his interest and the considerable time he has spent discussing the general and particular problems of the compensation effect.     

Thermal decompositions of Y,La and light lanthanide thiodiglycolates

The conditions of thermal decomposition of the thiodiglycolates of Y, La and light lanthanides from Ce to Gd have been studied. On heating, these complexes decompose in various ways. Hydrated thiodiglycolates of La,Ce(III), Pr(III) and Gd lose crystallization water in one step, while those of Y, Nd, Sm and Eu(III) do so in two steps. The anhydrous complexes subsequently decompose in several steps to the oxysulfates Ln₂O_3–x((SO₄)_x.

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Zusammenfassung Bedingungen der thermischen Zersetzung der Thiodiglycolate von Y, La und den leichten Lanthaniden von Ce bis Gd wurden untersucht. Beim Erhitzen zersetzen sich diese Komplexe auf verschiedene Weise. Hydratisierte Thiodiglycolate von La, Ce(III), Pr(III) und Gd verlieren das Kristallwasser in einem Schritt, die von Y, Nd, Sm, und Eu(III) dagegen in zwei Schritten. Die wasserfreien Komplexe zersetzen sich in mehreren Schritten zu den Oxysulfaten Ln₂O_3–x(SO₄)_x.

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. . . , , , , , . Ln₂O_3–x(SO₄)_x.

     

Study of the thermal dissociation of processes of nickel(II) and cobalt(II) β-diketonate adducts

Thermal dissociation processes of-diketonate adducts with the composition ML₂ · 2B (L = acetylacetone and its substituted derivatives;M = Ni, Co;B = H₂O, BuNH₂CH₃OH, Py, NH₃) were investigated. Kinetics of dissociation were studied in a flow reactor. For dehydration processes a compensation relationship is observed (lgA=E+b), demonstrating analogous mechanisms.A semi-quantitative series of the thermodynamic stabilities of the dihydrates is obtained from experimental data at quasi-equilibrium conditions (Q-derivatograph).

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Zusammenfassung Es wurden die thermischen Dissoziationsprozesse von-Diketonataddukten der Zusammensetzung ML₂ · 2B (L=Azetylazeton und dessen substituierte Abkömmlinge;M=Ni, Co;B=H₂O, BuNH₂, CH₃OH, Py, NH₃) untersucht. Die Kinetik der Dissoziation wurde in einem Flowreaktor untersucht. Als Beweis für die Ähnlichkeit der Mechanismen der Dehydrierungsprozesse konnte eine lgA=aE+b Beziehung festgestellt werden. Von unter Quasi-Gleichgewichtsbedingungen gewonnenen Daten konnte eine semiquantitative Serie der thermodynamischen Stabilitäten der Dihydrate abgeleitet werden (Q-Derivatograph).

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- ML₂·2B (L = ;M= Ni, Co;B=H₂O, BuNH₂, CH₃OH, Py, NH₃). ; (lgA=aEs+b) . (Q- ).

     

Solid state reaction between dichromates and oxalates

The thermal investigation of the reaction taking place between dichromates and oxalates in the solid state has been done taking two systems of potassium dichromate-potassium oxalate and sodium dichromate-sodium oxalate. The techniques employed include thermogravimetry, differential thermal analysis, infrared spectroscopy and X-ray diffraction studies. The results indicate a stoichiometric reaction of dichromate and oxalate in 11 ratio to give the corresponding chromate as the sole product.

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Zusammenfassung Anhand der Systeme Kaliumdichromat-Kaliumoxalat bzw. Natriumdichromat-Natriumoxalat wurde eine thermische Untersuchung der Festkörperreaktion zwischen Dichromaten und Oxalaten durchgeführt. Dazu wurden thermogravimetrische, dififerentialthermoanalytische, IR-spektroskopische und Röntgendiffraktionsverfahren angewendet. Im Ergebnis zeigte sich eine stöchiometrische Reaktion von Dichromat und Oxalat im Verhältnis 11, die das entsprechende Chromat als einziges Produkt liefert.

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, , — — . , 11 .

     

Inhibiting action of divalent copper compounds on microsomal oxidative demethylation of N,N-dimethylaniline

CuCl₂ is a non-competitive inhibitor whereas CuTyr₂ and CuLys₂ complexes are characterized by mixed-type inhibition. The inhibition action mechanism is discussed.

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CuCl₂ , . .

     

Zur thermoanalytischen charakterisierung von amorphen synthetischen,organisch nachbehandelten Kieselsäureprodukten

Zusammenfassung Für eine anwendungstechnische Beurteilung von amorphen synthetischen Kieselsäuren sind neben der Dispersität und Morphologie insbesondere auch strukturelle Eigenschaften bedeutsam. Die vorliegende Veröffentlichung zeigt, daß auf der Basis von thermoanalytischen Untersuchungen eine Unterscheidung unterschiedlicher Kieselsäuretypen möglich ist. Aus den TG- und DTA-Ergebnissen sind dabei Aussagen über die Art und Menge des adsorptiv bzw. chemisch gebundenen Wassers, sowie die oxydative Zersetzung des organischen Beschichtungsmittels abzuleiten.

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Besides dispersity and morphology, structural characteristics are of importance for the estimation of amorphous synthetic silicic acids with regard to their application. The present publication shows that it is possible to identify the different silicic acid types on the basis of thermoanalytical studies. The TG and DTA results provide information on the type and quantity of adsorbed or chemically bound water, and on the oxidative decomposition of the organic coating agent.

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, . . , .

     

Mössbauer studies of thermal decomposition of metal(III) hexacyanoferrates(II)

The thermal decomposition of metal(III) hexacyanoferrates(II) (Al, As, Sb, Bi) was studied up to 700° in air by employing Mössbauer, infrared spectroscopy and thermal analysis techniques. With the exception of the bismuth compound, the isomer shift of these hexacyanoferrates(II) increases on dehydration at 200°. Dehydration is complete at 200°, decomposition into the ferrite at 300°, and formation of-Fe₂O₃ from aluminium and bismuth hexacyanoferrates(II) and Fe₃O₄ from antimony and arsenic hexacyanoferrates(II) at 700°.

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Zusammenfassung Die thermische Zersetzung von Metall(III)ferrocyaniden (Al, As, Sb, Bi) wurde bis zu 700° in Luft unter Anwendung der Mössbauer und Infrarotspektroskopie, sowie thermoanalytischer Techniken untersucht. Die Isomerverschiebung dieser Ferrocyanide nimmt mit der Dehydratisierung bei 200° zu, mit Ausnahme des Wismuts. Die Dehydratisierung ist bei 200° abgeschlossen, die Zersetzung zum Ferrit bei 300° und die Bildung von-Fe₂O₃ aus Aluminium- und Wismutferrocyanid, von Fe₃O₄ aus Antimon- und Arsenferrocyanid bei 700°.

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Résumé On a étudié dans l'air jusqu'à 700°, la décomposition thermique des ferrocyanures de métaux trivalents (Al, As, Sb, Bi), par spectroscopies Mössbauer et infrarouge, ainsi que par les techniques d'analyse thermique. Le déplacement des isomères de ces ferrocyanures augmente lors de la déshydratation à 200°, à l'exception du bismuth. La déshydratation est complète à 200°, la décomposition en ferrite à 300°, la formation d'-Fe₂O₃ à partir des ferrocyanures d'aluminium et de bismuth ainsi que du Fe₃O₄ à partir des ferrocyanures de l'antimoine et de l'arsenic à 700°

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-, , — Al, As, Sb, Bi- 700° . , , 200°. 200°, 300° -Fe₂O₃. 700° Fe₃O₄.

     

Calorimetric study of dinitrogen adsorption at 310 K on a chromia/silica catalyst

The energetics of dinitrogen adsorption on 310 K on a chromia catalyst has been investigated by adsorption calorimetry. Two types of heats have been detected and assigned to a least two different interactions with Cr^II sites of the catalyst.

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310 . , , - , Cr^II .

     

Hydrolysis kinetics of the acid and base species of oxacillin in aqueous solution

Using the method of initial rates, a study has been carried out on the different kinetic behavior of the acid and base forms of oxacillin. The acid catalytic constants of both species are determined. The acid form is much more stable with respect to hydrolysis.

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, . . , .