Ru(III)-catalyzed oxidation of acetanilide, o-chloroacetanilide, p-chloroacetanilide and p-methylacetanilide by sodium perioda'te at pH 4

The order with respect to [Ru(III)] and [substrate] is unity in each while zero order with respect to [IO ₄ ^– ] has been observed. Variation of solvent composition has no pronounced effect on the rate. A plausible mechanism is suggested.

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[Ru(III)] [] , [IO ₄ ^– ] . . .

     

A new BPO4 catalyst in organic reactions. Dehydration of cycloalkanols

The synthesis of some new and economical BPO₄ catalysts is described. The chemical and textural properties and the thermogravimetric analysis (TGA) of these catalysts is given. The dehydration of cyclohexanol, cycloheptanol and cyclooctanol catalyzed by these new BPO₄ catalysts is studied using the microcatalytic pulse technique.

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BPO₄. , (). , , BPO₄, .

     

Etude thermocinetique des phenomenes de dissolution par calorimetrie Calvet a haute temperature dissolution d'alumines dans la cryolithe

Although the thermal curves given by a Calvet calorimeter can be considered representative of the thermogenesis of slow phenomena, this is not the case for the brief thermal effects of dissolution, for example, which need typically no more than twenty minutes. At high temperatures, a numerical method of deconvolution of the recorded signal was applied in order to obtain the proper thermogenesis of the phenomenon. The time constants of the calorimeter were determined from thermal effects due to the dropping into the bath of small quantities of silver and platinum. The method was applied to the dissolution of a-alumina and industrial aluminas in cryolithic baths at 1290 K. The different kinds of alumina could be classified according to their time of dissolution. The dependence of the alumina concentration of the bath on the dissolution rate was also investigated.

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Zusammenfassung Die mittels eines Calvet-Kalorimeters erhaltenen thermischen Kurven sind zwar repräsentativ für langsame Phänomene der Thermogenese, nicht jedoch für kurzzeitige thermische Effekte wie z. B. ein Inlösunggehen, das im allgemeinen nicht mehr als 20 Minuten dauert. In solchen Fällen wurde für hohe Temperaturen eine numerische Methode zur Zerlegung des registrierten Signals angewandt, um die reine Thermogenese der Phänomens zu erhalten. Zeitkonstanten des Kalorimeters wurden aus den thermischen Effekten bestimmt, die beim Einwerfen kleiner Silber- und Platinmengen in das Bad auftraten. Die Methode wurde zur Untersuchung der Auflösung von -Aluminiumoxid und industriellen Aluminiumoxidproben in Kryolithbädern bei 1290 K herangezogen. Die verschiedenen Aluminiumoxidarten konnten nach der zur Auflösung notwendigen Zeit klassifiziert werden. Die Abhängigkeit der Auflösungsgeschwindigkeit von der Aluminiumoxidkonzentration des Bades wurde ebenfalls untersucht.

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, , . , , , , . , . , . - 1290 K. . .

     

Effect of deuteration on the thermal dehydration of lithium sulfate monohydrate

Effects of deuteration on the thermal stability, enthalpy change and kinetic parameters for the thermal dehydration of Li₂SO₄·H₂O were examined by means of TG and DSC. The enthalpy change for the monohydrate was smaller by 1.63±0.75 kJ/mol than that for the monodeuterate. The rate constant for the monohydrate was a little larger than that for the monodeuterate. However, the thermal stability, activation energy and frequency factor were practically unaffected by deuteration of the hydrate. It is suggested that the activation entropy as well as the activation energy should be considered in explaining the kinetic deuterium isotope effect in the thermal dehydration of Li₂SO₄·H₂O.

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Zusammenfassung Die Wirkung der Deuterisierung auf die Thermostabilität, die Enthalpie-Änderungen und kinetischen Parameter der thermischen Dehydratisierung von Li₂SO₄·H₂O wurden durch TG und DSC untersucht. Die Enthalpie-Änderung für das Monohydrat wurde um 1.63±0.75 kJ/mol niedriger gefunden als für das Monodeuterat. Die Geschwindigkeitskonstante für das Monohydrat war etwas größer als für das Monodeuterat. Die Thermostabilität, die Aktivierungsenergie und der Frequenzfaktor wurden jedoch von der Deuterisierung des Hydrats praktisch nicht beeinflußt. Es wird vorgeschlagen, daß bei der Erklärung des kinetischen Deuterium-Isotop-Effekts bei der thermischen Dehydratisierung von Li₂SO₄·H₂O sowohl die Aktivierungsentropie als auch die Aktivierungsenergie berücksichtigt werden müssen.

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, Li₂SO₄·H₂O. 1.63+0.75 /. , . , , . , Li₂SO₄·H₂O.

     

Electrocatalytic hydroxylation of aniline on metal oxides

Studies of Mn, Cr, Cu, La, Sb, V, Co and W oxides as catalysts for the electrocatalytic oxidation of aniline to p-aminophenol have revealed the electrocatalytic activity of WO₃. A mathematical model for the kinetics of analine oxidation on WO₃ is suggested that agrees fairly well with the experimental data.

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Mn, Cr, Cu, La, Sb, V, Co, W -. , . , , .

     

Thermal and mechanical behavior of polyethylene film obtained by orientational crystallization

The thermal and mechanical behaviour was measured in the U. S.for a polyethylene that had been prepared and highly drawn in the U. S. S. R. The melting point and percent crystallinity were evaluated in this studies as a function of heating rate and recrystallization. The Young's modulus and tensile stress to break in the orientation direction were 4.1 and 0.15 GPa, respectively.The tensile strain to break was about 8%.

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Zusammenfassung Das thermische und mechanische Verhalten eines in der UdssR hergestellten und stark gezogenen Polyäthylens wurde in den U. S. A. gemessen. Schmelzpunkt und Prozentsatz der Kristallinität wurden als Funktion der Aufheizgeschwindigkeit und Rekristallisation in den Untersuchungen ausgewertet. Der Young-sche Modulus und die Zugspannung zum Reissen in der Orientierungsrichtung betrugen 4.1, bzw. 0.15 GPa. Die Dehnung bis zum Bruch betrug etwa 8 %.

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Résumé On a effectué, aux Etats Unis, l'étude du comportement thermique et mécanique d'un polyéthylène préparé et fortement étiré en URSS. Le point de fusion et le pourcentage de cristallinité ont été évalués en fonction de la vitesse de chauffage et de la recristallisation. Lesvaleurs respectives du module d'Young et de la limite de rupture dans la direction d'orientation s'élèvent respectivement à 4.1 et 0.15 GPa. L'allongement à la rupture est d'environ 8%.

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, . . . 4.1 0.15 . 8%.

     

Changes in activity, selectivity and surface area along an iron-molybdenum catalyst bed after its industrial application

After the industrial use in a combined reactor the surface area of catalysts continuously decreases along the tube. Activity and selectivity of the samples show an extremum as a function of the height (minimum activity corresponds to maximum temperature in the layer). Above and below the hot point, the activities are almost the same but are lower than the initial value. Selectivity is a maximum for samples taken below the hot point. Upwards and downwards from this point the selectivity slightly decreases but remains significantly higher than for the initial catalyst.

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. , , . , . , . , . , , .

     

Comparative studies of the behavior of unsaturated acids and their salts in hydrogenation over platinum

Hydrogenation of unsaturated aliphqtic acids in water and of their unsaturated salts in aqueous metal hydroxide solutions over Pt black has been studied. Kinetic measurements are compared with quantum-chemical calculations.

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Pt-. .

     

Properties of some catalysts used for the decarbonylation of furfural

Three catalysts containing Mn, Zn, Cd, Sr and K oxides supported on alumina and used for the decarbonylation of furfural are described in this work. The properties of these catalysts such as coefficient and heat of adsorption, specific surface and pore distribution and volume are reported in this work.

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, Mn, Zn, Cd, Sr K, , . , , , .

     

Catalytic effect of hydroxy groups on reaction of polyamine with tert-butyl acrylate

The reaction of N-cyclohexyl-1,3-propanediamine with tert-butyl acrylate and the catalytic effect of hydroxy groups on the reaction course was investigated by Near Infrared spectroscopy. The reaction was found to be bimolecular and of second order. The dependence of rate constant on catalyst concentration (diols) is linear and the structure of diol used has no effect.

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N--1,3- -. . . () , .

     

Catalytic reduction of NO with CO over CuxCo3?xO4 spinels

The interaction between NO and CO over Cu_xCo_3–xO₄ spinels (0x1) has been studied. It has been found that the two reactions of NO reduction, to N₂O and N₂, respectively, are accelerated by the increase of Cu content (x). With the second reaction acceleration occurs only at x>0.5. This is attributed to the presence of different centers on which N₂O and N₂ are formed.

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NO CO Cu_xCo_3–xO₄ (0x1). , NO N₂O N₂ Cu (x). x>0,5. , N₂O N₂.

     

Quantitative parameters by thermoanalytical methods

The conditions and premises of the kinetic evaluation of thermoanalytical curves on the basis of chemical kinetics are demonstrated, and the limits of their availability are pointed out. For reactions with an unclear structural and chemical course, some appropriate definitions of terms are proposed.The possibilities of the use of the inflection points of the reaction rate versus time curve are presented. New methods of determination of kinetic parameters are described, including the ratio of the degrees of reactionx, the ratio of the reaction ratesx and the ratio of the tangent slopesx at these points.

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Zusammenfassung Bedingungen und Voraussetzungen der kinetischen Auswertung thermoanalytischer Meßkurven auf der Basis der chemischen Kinetik werden dargestellt, gleichzeitig wird auf die Grenzen ihrer Gültigkeit hingewiesen. Für Reaktionen mit unklarem chemischem oder strukturellem Ablauf werden geeignete neue Bezeichnungen definiert.Die Möglichkeit zur Verwendung der Wendepunkte der Kurve Reaktionsgeschwindigkeit gegen Zeit vorgestellt. Neue Methoden werden beschrieben, die zur Bestimmung kinetischer Parameter das Verhältnis der Umsätzex ₁ x ₂, das Verhältnis der Reaktionsgeschwindigkeitenx ₁/x ₂, und das Verhältnis der Tangentensteigungenx ₁/x ₂ an den Wendepunkten verwenden.

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. . . — . , (x), () () .

     

X-ray and thermal studies of ferroelectric Dy2(MoO4)3

Dysprosium molybdate, Dy₂(MoO₄)₃, displays a ferroelectric phase transition at 145 °C. The X-ray and thermal (DTA, TG and DSC) properties of this compound have been studied. The X-ray study confirmed the ferroelectric phase in the orthorhombic space group Pba2. Thermal analysis demonstrated the existence of a ferroelectric and another phase transition in this compound.

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Zusammenfassung Dysprosiummolybdat, Dy₂(MoO₄)₃ (Abk.: DMO), ein Vertreter der Seltener-denmolybdatreihe zeigt bei 145 °C einen ferroelektrischen Phasenübergang. Röntgendiffraktion und thermische Eigenschaften (DTA, TG, DSC) der genannten Verbindung wurden untersucht. Auf Grund der Röntgendiffraktionsuntersuchung gehört die ferroelektrische Phase in die orthorhombische Raumgruppe Pba2. Mittels Thermoanalyse konnte bei dieser Verbindung die Existenz ferroelektrischer und anderer Phasenübergänge nachgewiesen werden.

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145 °C. (, ) . , Pba2. .

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The authors wish to thank Prof. A. Paul and Mr. R. Bhatnagar for their kind help in some of the experimental work. One of us (MR) gratefully acknowledges a Fellowship from DST, Government of India.     

Regioselective synthesis of α- and α'-sulfur-containing ethyl esters of dehydrodesthiobiotin

Conclusions The ethyl esters of- and'-oxodehydrodesthiobiotin when reacted with thioacetic acid in the presence of BF₃ etherate respectively give the ethyl esters of-thiooxo- and, -diacetytmercaptodehydrodesthiobiotin.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 4, pp. 954–956, April, 1978.     

Effect of ion exchange and regeneration conditions on the catalytic activity of H-ZSM-5 zeolites

The effect of Na⁺ H⁺ ion-exchange conditions on catalytic properties of the resulting H-ZSM-5 zeolites has been investigated. The concentration and mode of addition of the reactant to the exchange medium affect the degree of exchange achieved. During low-temperature conversion of olefins, the H-ZSM-5 zeolites have become rapidly deactivated. Thermal regeneration fully restores their original catalytic properties.

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Na⁺H⁺ --5. . - --5 . .

     

Contribution of adsorption to retention data in glass capillary gas chromatography part. I. Polar stationary phases

Summary The influence of the film thickness of Carbowax 20M coated onto glass surfaces (series of columns with different mode of surface treatment) upon the retention indices of solutes which exhibit tendency to hydrogen bonding has been investigated. Limiting values of Kovats indices, I, are calculated for all the columns examined.Presented at the 14th International Symposium on Chromatography London, September, 1982     

An approach to describe relaxation rates in heterogeneous catalytic reactions

A system of equations allowing for the most essential properties of catalytic surfaces is suggested to describe the rate of chemical conversion.

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, .

     

X-ray spectral investigation by synchrotron radiation of supported Re/SiO2 and (Re+Pt)/SiO2 catalysts prepared via triethoxyrhenium

Using synchrotron radiation L_III absorption spectra of rhenium in Re/SiO₂ and (Re+Pt)/SiO₂ catalysts prepared via triethoxyrhenium have been studied. The conclusion has been drawn that reduced catalysts contain lowvalent rhenium ions and their composition is more uniform than that of the previously examined catalysts Re/Al₂O₃ and (Re+Pt)/Al₂O₃ prepared by a conventional impregnation technique.

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L_III- Re/SiO₂ (Re+Pt)/SiO₂, . , , Re/Al₂O₃ (Re+Pt)/Al₂O₃, .

     

Withasteroids ofPhysalis. V. A study of the1H and13C NMR spectra of the withasteroids visconolide and 28-hydroxywithaperuvin C

The PMR and¹³C NMR spectra of new withasteroids — visconolide and 28-hydroxywithaperuvin C, isolated fromPhysalis viscosa L. — have been investigated. A detailed analysis of the spectral characteristics obtained is given. For visconolide is proposed the structure of 4,12,17,28-pentahydroxy-1-oxo-5, 6-epoxy-22R-witha-2,24-dienolide, and for 28-hydroxywithaperuvin C that of 6,14,17,20R, 28-pentahydroxy-l-oxo-22R-witha-2, 4, 24-trienolide.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 657–663, September–October, 1985.     

Reactivation of Cu-promoted lanthanum phosphate

Cu-promoted lanthanum phosphate is a catalyst for chlorobenzene hydrolysis. A decrease in catalytic activity is observed during reaction. The deactivation is partly due to coke deposition, which is eliminated by periodic regenerations. There is also a deactivation due to the loss of Cu. A method is described to keep constant the Cu content of the catalysts by placing prior to the catalyst bed a layer of copper metal chips.

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. . , . . , .