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 .

     

Mechanism of hydrogenation of nitric oxide on platinum catalysts in acidic solution

To explain the mechanism of hydrogenation of NO in 2 M H₂SO₄, the kinetics of the hydrogenation of hydroxylamine to ammonia were studied. The rate constant of this reaction was compared with the ratio of rates at which NH₃OH⁺ and NH ₄ ⁺ were generated by the hydrogenation of NO. Both of these products are formed from NO via parallel reactions of a common intermediate. A mechanism for the hydrogenation of NO and the shift of the catalyst of the potential is proposed.

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NO 2M H₂SO₄ . NH₃OH⁺ NH₄ ⁺ NO. NO . . ., NO .

     

Electrochemical model of alkane oxidation by cytochrome P-450

Catalytic oxidation of alkanes to alcohols and ketones was shown to take place in an electrochemical cell with iron porphyrin deposited on a graphite cathode. The oxidation mechanism was assumed to be similar to that of cytochrome P-450 action.

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, . , P-450.

     

Thermal analysis of macromolecular “Haloamines”

The TG, DTG and DTA curves of macromolecular macroporous N-halogeno- and N,N-dihalogenosulfonamides are reported and interpreted. To compare their thermal behaviour with that of their unfunctionalized matrices, analogous studies were performed on the porous styrene-divinylbenzene(20%)copolymer and its sulfonamide derivative.

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Zusammenfassung Die TG-, DTG- und DTA-Kurven makromolekularer makroporöser N-Halogen- und N,N-Dihalogensulfonamide werden beschrieben und gedeutet. Zum Vergleich wurde das thermische Verhalten des unsubstituierten porösen Styren-(20%)Divinylbenzen-Copolymeren und seines Sulfonamids in gleicher Weise untersucht.

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, TA N-- N,N- . , .

     

The UV-VIS spectroscopic study of the interaction between WCl6 and esters of carboxylic acids

The reaction of WCl₆ with methyl 10-undecenoate and methyl palmitate has been studied. The rate constant of the first step of the reaction has been established and compared with that of the WCl₆+(CH₃)₄Sn reaction. On the basis of this comparison the influence of the reaction of WCl₆ + ester on the ester metathesis is discussed.

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WCl₆ -10- -. , WCl₆+(CH₃)₄Sn. WCl₆+ .

     

Dehydrations of Ca(H2PO4)2·H2O and Mg(H2PO4)2·2H2O and their reactions with KCl,examined with simultaneous TG,DTG, DTA and EGA

The dehydrations of Ca(H₂PO₄)₂·H₂O and Mg(H₂PO₄)₂ H₂O were examined with a simultaneous TG, DTG, DTA and EGA method, partly under conventional, and partly under quasi-isothermal and quasi-isobaric conditions. It was found among others that the dehydrations of the examined compounds took place gradually between 100 and 500°, a series of intermediates being formed. The end-products were [Ca(PO₃)₂]₃ and Mg(PO₃)₂. The reactions of these hydrates with KCl were also examined. The many subsequent part reactions could be described by the following overall equation: 3 Ca(H₂PO₄)₂ + 2 KCl=Ca₂P₂O₇ + Ca(PO₃)₂ + 2 KPO₃ + 2 HCl + 5 H₂O It is noteworthy that the reactions do not lead to the formation of orthophosphates, but stop after the liberation of 2 moles of HCl.

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Zusammenfassung Die Autoren untersuchten die Dehydratisierung von Ca(H₂PO₄)₂·H₂O und Mg(H₂PO₄)₂·2H₂O. Zu den Untersuchungen wurde die simultane Methode von TG, DTG, DTA und EGA teils unter konventionellen, teils unter quasi isothermen und quasi isobaren Bedingungen eingesetzt. Die Autoren fanden u.a., daß die Dehydratisierung der untersuchten Verbindungen zwischen 100 und 500 °C stufenweise verlief, während eine Reihe von Zwischenprodukten gebildet wurde. Die Endprodukte waren [Ca(PO₃)₂]₃ bzw. Mg(PO₃)₂. Die Autoren prüften auch die Reaktion der erwähnten Hydrate mit KCl. Sie fanden, daß die zahlreichen aufeinanderfolgenden Teilreaktionen durch folgende Bruttoreaktion beschrieben werden können: 3Ca(H₂PO₄)₂ + 2KCl=Ca₂P₂O₂ + Ca(PO₃)₂ + 2KPO₃ + 2HCl + 5H₂O. Es ist bemerkenswert, daß die Reaktionen nicht zur Bildung von Orthophosphaten führen, sondern daß sie nach Freisetzung zweier Moleküle von HCl zum Stillstand kommen.

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Résumé Les auteurs ont étudié la déshydratation de Ca(H₂PO₄)₂·H₂O et Mg(H₂PO₄)₂·2 H₂O. Les méthodes de TG, TGD, ATD et AGE on été utilisées simultanément en partie dans les conditions conventionelles et en partie dans les conditions quasi isothermes et quasi isobares. Les auteurs ont trouvé, entre autres, que la déshydratation de ces composés a eu lieu de façon graduelle entre 100 et 500 °C, avec formation d'une série de produits intermédiaires. Les produits finaux sont respectivement [Ca(PO₃)₂]₃ et Mg(PO₃)₂. Les auteurs ont également examiné la réaction des hydrates mentionnés avec KCl. Ils ont trouvé qu'un grand nombre de réactions partielles consécutives peut être décrit par la réaction brute suivante: 3 Ca(H₂PO₄)₂ + 2 KCl=Ca₂P₂O₇ + Ca(PO₃)₂ + 2 KPO₃ + 2 HCl + 5 H₂O. Il est remarquable que les réactions n'entraînent pas la formation d'orthophosphates mais qu'elles s'arrêtent après l'élimination de 2 moles de HCl.

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(₂₄)₂ ·₂ Mg(H₂PO₄)₂ 2H₂O. , , . , 100–500° . , , [(₃)₂]₃ Mg(PO₃)₂. l. , : 3(₂₄)₂ + 2KCl=₂₂₇ + (₃)₂ + 2₃ + 2l + 5₂ , , l.

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The authors wish to thank Prof. E. Pungor for his interest in this work.     

Contribution a l'etude de l'oxyde de cadmium en milieu alcalin

Résumé L'étude de la réaction de NaOH sur CdO ou Cd(OH)₂ a nécessité de reprendre celle des courbes ATG et ATD de NaOH à différents stades de pureté. Ceci a permis, en particulier, de préciser l'existence de l'eutectique ternaire NaOH-Na₂O-Na₂CO₃ dans les mélanges réactionnels traités, d'exclure la possibilité de la présence de peroxyde. Le produit de la réaction, obtenu avant 130°, est plus stable à la chaleur que NaOH. Son spectre IR est compatible avec l'existence d'un hydroxocadmiate de sodium.

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The investigation of the reaction of sodium hydroxide with CdO or Cd(OH)₂ made necessary some studies on the DTA and TG curves of sodium hydroxide samples of different purities. These studies have evidenced the formation of a ternary eutectic NaOH-Na₂O-Na₂CO₃ in the heat-treated reaction mixtures, and have also shown that no peroxide is present. The product of reaction obtained below 130° had a greater thermal stability than NaOH. On the basis of the infrared spectrum the existence of a sodium hydroxocadmiat can be assumed.

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Zusammenfassung Die Untersuchung der Reaktion von Natriumhydroxyd mit CdO oder Cd(OH)₂ erforderte eine neue Untersuchung der DTA und TG Kurven des NaOH von verschiedenem Reinheitsgrad. Dies bewies das Vorhandensein eines ternären Eutektikums NaOH-Na₂O-Na₂CO₃ in den behandelten Reaktionsgemischen, weiterhin, daß kein Peroxyd gegenwärtig ist. Das vor 130° erhaltene Reaktionsprodukt besitzt höhere thermische Stabilität als NaOH. Aufgrund der infraroten Spektren darf die Existenz eines Natriumhydroxocadmiats angenommen werden.

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NaOH CdO Cd(OH)₂ . NaOH-Na₂O-Na₂CO₃ . , 130°, , NaOH. - .

     

Cardiac glycosides of Cheiranthus allioni. X

Summary Another two cardiac glycosides have been isolated from the seeds ofCheiranthus allioni hort. One of them has been identified as bipinogulomethyloside. The second, which we have called glucobipindogulomethyloside is new and is bipindogenin 3-O-[O--D-glucopyranosyl-(14)--D-gulomethylopyranoside].The glycoside M-64 isolated previously from this plant, which is uzarigenen 3-O-[O--D-glucopyranosyl-(14)--D-glucopyranoside] is also new and has been called neouzarin.Khar'kov Scientific-Research Institute of Pharmaceutical Chemistry. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 738–741, November–December, 1974.     

Determination of the kinetic parameters of the multi-stage thermal decomposition of solids under non-isothermal conditions by the non-linear estimation approach

The activation energy of decomposition of aluminium hydroxidevs. weight loss was estimated from thermogravimetric data collected over a wide range of heating rates, without resorting to the model of the reaction mechanism.These activation energy values were subsequently used to distinguish individual dehydration stages and to determine the best models of the reaction kinetics for these stages.Finally, the overall decomposition model was formulated, and its parameters were determined by the non-linear estimation approach.

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Zusammenfassung Die Aktivierungsenergie der Zersetzung von Aluminiumhydroxid wurde in Abhängigkeit vom Gewichtsverlust aus einen weiten Bereich von Aufheizgeschwindigkeiten umfassenden thermogravimetrischen Daten gesammelt, ohne auf das Modell des Reaktionsmechanismus einzugehen.Diese Werte der Aktivierungsenergien wurden daraufhin zur Unterscheidung einzelner Dehydratisierungsstufen und zur Bestimmung der besten Modelle der Reaktionskinetik dieser Stufen eingesetzt.Schließlich wurde ein allgemeines Zersetzungsmodell formuliert und seine Parameter durch nichtlineare Schätzungsnäherung bestimmt.

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Résumé On a estimé l'énergie d'activation de la décomposition de l'oxyde d'aluminium en fonction de la perte de poids à partir de données thermogravimétriques obtenues avec un large intervalle de vitesses de chauffage, sans avoir recours au modèle du mécanisme de la réaction. On a utilisé ensuite ces valeurs de l'énergie d'activation pour distinguer les étapés individuelles de la déshydratation et pour déterminer les meilleurs modèles de cinétique réactionnelle correspondant à celles-ci.Enfin, on a formulé un modèle général de décomposition et déterminé ces paramètres par approximations non linéaires.

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, , . . .

     

Thermal decomposition kinetics of iron(III), cobalt(II), nickel(II) and copper(II) complexes of a Schiff base derived from quinoxaline-2-carboxaldehyde and glycine

Quinoxaline-2-carboxalideneglycine complexes of iron(III), cobalt(II), nickel(II) and copper(II) complexes were subjected to a systematic TG/DTG analysis. The decomposition process consists of two stages for all these complexes. Kinetic parameters were evaluated for each of these stages using the Coats-Redfern equation. The rate of decomposition at the second stage seems to have a bearing on the catalytic effect of the metal oxides formed during this stage.

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-2- (III) (II), (II) (II) /. . - . , -, , .

     

Orientation towards alcohols in CO, H2 reactions on some iron catalysts

Adding rare earths like dysprosium or lanthanum to silica-supported iron or iron-copper catalysts enhances the formation of C₁ to C₅ alcohols and the total conversion in CO–H₂ reactions. Copper rises the alcohol orientation and also the reactivity.

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, - SiO₂ C₁ C₅, CO–H₂. , .

     

Liquid-phase catalytic oxidation of methyl derivatives of biphenyl

Liquid-phase catalytic oxidation into acids by air was studied for the following hydrocarbons: isomers of cyclohexyltoluenes and cyclohexyl derivatives of para-xylene, mesitylene, pseudocumene, cyclopentyltoluene, cyclohexyladamantane, 4-methylbiphenyl, 2,4-, 2,5- and 3,4-dimethylbiphenyls, hydroxymethylbiphenyls, and hydroxymethylbenzenes. The oxidation of cyclohexyltoluenes involves a methyl group and proceeds without participation of the -CH bond of the cyclohexyl fragment in the oxidative conversions. The reactivity of the hydrocarbons increases in the order ortho < meta < para. Consecutive conversions of the methyl groups to carboxyls occur during the oxidation of dimethylbiphenyls. In 3,4- and 2,5-dimethylbiphenyls, the methyl groups in the para and ortho positions, respectively, are first oxidized, whereas the reactivity of both of the methyl groups in 2,4-dimethylbiphenyl is virtually the same. The mechanism of the oxidation of hydroxymethylbiphenyls and hydroxymethylbenzenes involves the formation of an unstable cation radical, which is then stabilized by emitting a proton, giving hydroxybenzyl, a more stable radical.Translated from Kinetika i Kataliz, Vol. 45, No. 6, 2004, pp. 872–876.Original Russian Text Copyright © 2004 by G. Koshel, S. Koshel, Postnova, Lebedeva, Kuznetsova, Belysheva, Yunkova.     

AlPO4-supported rhodium catalysts. VIII. Gas-phase adsorption of arenes by gas-chromatography

The adsorption of normal and -methylated series arenes on rhodium supported on two kinds of AlPO₄ has been studied by using a gas-solid chromatographic technique. The adsorption process was exothermic (H_ads<0) and non spontaneous (G_ads>0) the relative adsorption constants being fitted to the Pavelich-Taft equation in which the electrical effect of the alkyl substituent is the main influence.

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- , AlPO₄, - . (H_ads>0) (G_ads<0). -, .

     

Errors in the determination of activation energies of solid-state reactions by the Piloyan method,as a function of the reaction mechanism

The errors in the activation energies of solid-state reactions determined with the Piloyan method are more larger than those previously assumed in the literature. On the other hand, the errors in the kinetic parameters are strongly dependent on the kinetic law obeyed by the reaction. A theoretical explanation of this behaviour is given.

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Zusammenfassung Die Fehler der nach der Piloyan-Methode bestimmten Aktivierungsenergien von Festkörperreaktionen sind grö\er als bisher in der Literatur angenommen und stark abhÄngig von der Reaktionsordnung. Eine theoretische ErklÄrung dieses Verhaltens wird gegeben.

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, , . , , , . .

     

Catalytic mechanism of the reaction between N(4S) nitrogen atoms and sodium azide

Catalytic effect of transition metal oxides on the reaction of monatomic nitrogen with sodium azide has been experimentally established. The maximum effect is exerted by metal oxides with d³ configuration. Absorption of nitrogen atoms by reactive mixtures is accompanied by the complete compensation for the spins of unpaired d-electrons. A catalytic mechanism accounting for the formation of intermediate between d-metal ion and nitrogen atom is suggested.

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. —d³. d-. , d- .

     

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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, , , - .

     

Benzene hydrogenation on platinum-tin bimetallic catalysts

Various catalysts were prepared by impregnating a commercial alumina with solutions containing the complex dichlorobis(trichlorostannato)platinate (II). [Pt Cl₂ (SnCl₃)₂]^2–. After reduction, 1–20 fold variations in the catalytic activity in benzene hydrogenation were observed in direct proportion to the stability of the complex in the impregnating solution.

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, — - ( ()-(II) [PtCl₂(SnCl₃)₂]^–2. , 1–20 . .

     

Topics in calixarene chemistry

Several facets of calixarene chemistry have been investigated including the mechanism of their formation by the base-induced condensation of phenols and formaldehyde, procedures for introducing functional groups onto the upper rim and lower rim of calixarenes, the conformational behavior of calixarene oxyanions, the formation of complexes in aqueous and nonaqueous systems, and the application of calixarenes as catalysts.     

Thermogravimetric characterization of Quayarah heavy crude oils

Five heavy crude oil samples from the Quayarah field were thermally evaluated using two modes of thermogravimetry (TG): dynamic and programmed TG with heating and hold-up periods at 350 and 550°. The light and medium volatility fraction (L+M) appeared directly proportional to the metal content. In contrast, the heavy fraction (H) (350–550°) was inversely proportional to the metal content. This contradiction was attributed to the autocatalytic degradation of some of the heavy fraction into lighter species, which upgrades the crude with respect to the (L+M) fraction at the expense of the heavy fraction. The crudes were identical with regard to the ratio (L+M) to (H+R), whereR=residue, as a consequence of their identical API gravity and sulphur contents.The rate of degradative volatilization of the heavy fraction was measured by DTG, which indicated a direct correlation with the vanadium content as regards the onset temperatures and the DTG peak maximum.

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Zusammenfassung Fünf vom Quayarah-Feld stammende schwere Rohöle wurden mittels dynamischer und programmierter TG mit konstanten Perioden bei 350 und 550 °C charakterisiert. Der Anteil der leicht- und mittelflüchtigen Fraktion (L+M) schien proportional, der der schwerflüchtigen Fraktion (H) (350 550°) dagegen umgekehrt proportional dem Metallgehalt zu sein. Dieser Widerspruch wurde dem autokatalytischen Abbau einiger der schwerflüchtigen Komponenten zu leichteren Spezies zugeschrieben, der zu einer Erhöhung des Anteils der (L+M)-Fraktion auf Kosten der schwerflüchtigen Fraktion führt. Die Rohöle waren wegen der gleichen API-Schwere und gleicher Schwcfclgehalle hinsichtlich des Verhältnisses von (L+M) zu (H+R) identisch (R=Rückstand). Die Geschwindigkeit der degradaliven Verflüchtigung der schweren Fraktion wurde mittels DTG gemessen, wobei sich eine direkte Korrelation zwischen dem Vanadingehalt einerseits und der Einsatztemperatur bzw. dem DTG-Peakmaximum andererseits ergab.

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350 550°. (+ ) , () (350–550°) — . , . + +, — , . . , , .

     

Specificity of hydrogen adsorption on chromia-supported platinum group metal catalysts

Hydrogen adsorption on chromia supported Pd, Rh and Pt was studied under various pretreatment conditions. The reduction temperature influences strongly the hydrogen uptake for all these metals. Platinum supported on chromia shows an unusually high hydrogen adsorption stoichiometry.

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Pd, Rh Pt, Cr₂O₃, . , . Cr₂O₃ .