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+ .

     

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 .

     

Ruthenium clusters containing the [2.2] paracyclophane ligand: Recent developments in arene-cluster chemistry

In this article we review the synthesis, reactivity, and characterization of a number of clusters bearing the [2.2] paracyclophane ligand with nuclearities ranging from two to eight. Particular attention is focused on the different coordination modes that paracyclophane adopts; these being µ₁- ⁶, µ₂- ³ : ³, µ₃- ¹ : ² : ², and µ₃- ² : ² : ². Structural modifications which take place within the ring system on bonding in these various modes are also discussed.     

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. - .

     

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 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- . , .

     

Properties of a multiple bond conjugated with the pyridine ring

The products of the addition of diazomethane to the double bond of -, -, and -vinyl-pyridines, 2-propenyl-, 2-styryl-, and 2-(p-nitrostyryl)pyridines, and -(2-pyridyl)acrylic acid were obtained. When a hydrogen atom or alkyl or phenyl group is present in the -position of the vinyl group, 3-pyridyl-²-pyrazolines are formed (they are isolated as the acetyl derivatives). Electron-acceptor substituents (COOCH₃ and C₆H₄NO₂) in this position disrupt the polarization, and this leads to the formation of a mixture of two isomeric pyrazolines. The primary formation of ¹-pyrazolines was proved by means of IR and UV spectroscopy.See [1] for communication IX.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 64–69, January, 1973.     

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.     

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.

     

Laser Sintering of SnO2 : Sb Sol-Gel Coatings

Sb doped sol-gel SnO2 single layers (thickness 100 nm) were prepared from alcoholic solution and deposited via a dip coating process on fused silica substrates. The coatings have been sintered at a typical rate of 10–15 cm2/s by CO2 laser irradiation. The laser spot was scanned in one direction at a speed of 15,000 cm/s and the sample was moved in a perpendicular one at a speed up to 250 mm/s. The temperature of the topmost 10 m layer was monitored by a fast pyrometer (s resolution). The following properties of the coatings have been determined: the electrical resistivity , the carrier density n, and mobility , the structure, the thickness, the mesoscopic and micromorphology and the density. The sintering by CO2 laser radiation is mainly a thermal driven process. At T 500°C it allows to obtain coatings with a smaller resistivity (6.8×10–3 cm) than those produced by conventional furnace firing (el2.9×10–2 cm). The results are discussed in terms of particle size and packing density.     

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. , .

     

A Simple Sensitive Spectrophotometric Method for the Determination of Ce4+ Using Variamine Blue as a Chromogenic Reagent

A rapid and sensitive spectrophotometric method is described for the determination of trace amounts of cerium using Variamine Blue (VB) as a chromogenic reagent. The proposed method is based on the reaction of cerium with potassium iodide in acidic medium to liberate iodine, which oxidizes Variamine Blue to give a violet colored species with an absorption maximum at 560nm. Beers law was obeyed in the range 2–10µg mL^–1 of cerium. The molar absorptivity and Sandells sensitivity are found to be 1.65×10⁴L mol^–1cm^–1 and 8.48×10^–3µgcm^–2, respectively. The proposed method has been successfully applied to the determination of cerium in alloy and synthetic mixtures.     

Optical and electrical measurements on CO2 covered copper films

Thin polycrystalline copper films are deposited in a special UHV cell on glass substrates and are covered step by step with CO₂. The optical and electrical properties of the films are studied in-situ by means of ellipsometry and resistivity measurements. The properties of the clean films correspond to literature data. In the case of monolayer adsorption of CO₂, the changes in the ellipsometrical angles are +1° and +0.1°, similar to the Cu/O and Cu/CO systems. Three-dimensional island growth leads to a drastical increase of and by several orders of magnitude. The resistivity first quickly decreases and then slowly reapproaches the initial value. This marked kinetics is quantitatively interpreted on the basis of a diffusion model.     

Aqueous solubilities and octanol-water partition coefficients of binary liquid mixtures of organic compounds at 25°C

From thermodynamics and certain assumptions it is shown that, under the usual experimental conditions, the octanol-water partition coefficient (K_o/w) of a given organic liquid should be the same whether the substance is partitioned neat or as part of a mixture. Measurements of several mixtures of n-propylbenzene (log K_o/w=3.71±0.04)+ethylbenzene (log K_o/w=3.16±0.01) clearly confirm this. It is also shown that the aqueous solubility (S_w) of a neat organic liquid can be related to its aqueous solubility (S _w ), when it is present at volume fraction in an organic liquid mixture, by S _w =S_w, where is its activity coefficient in the organic mixture. The measured S _w values for n-propylbenzene + ethylbenzene (1), n-hexane + nitrobenzene (>1) and di-isopropyl ether + chloroform (<1) are found to be in good agreement with the predicted values (average differences of, respectively, <2%, 8% and 6%). In general, the bounds on S _w are expected to be 0w w.     

The Radiation Resistance of Films Obtained by Plasma Deposition of Polypropylene Electric-Discharge and Thermal Degradation Products

By means of the ESR technique, it was shown that paramagnetic species with polyconjugated carbon–carbon bonds are stabilized in the films produced in a plasma from polypropylene (PP) electric-discharge and thermal degradation products. A high radiation resistance of the film material was revealed, which was manifested as a 160-fold lower radiation-chemical yield of radicals relative to that from parent polypropylene (G _R 0.4 for precursor PP and G _R 0.0025 for the plasma-deposited film). The obtained films were insoluble in common organic solvents and resistant to acid and alkali solutions. The film density was 1.4 g/cm³.     

Separation of Cs and Sr using polyoxonium compounds

Extraction separation and concentration of Cs and Sr from aqueous solutions, containing macroconcentrations of competitive ions (Li⁺, Na⁺, K⁺, Mg²⁺, Ca²⁺, Al³⁺, Fe³⁺) by the nitrobenzene solutions of bis-1,2-dicarbollylcobaltate in the presence of linear and cyclic polyoxonium compounds (POC) has been investigated. It has been found, that the addition of DB18C6 increases the distribution ratio of cesium (D_cs) but the addition of other crowns and PEG decreases D_Cs value and selectivity of D_Sr and the selectivity of Sr/Ca separation. Separation factors of Sr/Ca increase from (Sr/Ca)2 (found in the absence of POD) to (Sr/Ca)50 (for DB18C6), (Sr/Ca)100 (for 18C6 and DCH18C6) and (Sr/Ca)1000 for 15C5.     

Phenyliodonium Derivatives of N-Heterocycles and CH-Acids, Their Synthesis, and Their Use in the Chemistry of Heterocycles. (Review)

The reactions of iodosylbenzene with CH-acids, including -dicarbonyl and N-heterocyclic compounds in the presence of alkali, which lead to the aryliodonium ylides (betaines) used in the synthesis of new derivatives of heterocycles, are examined. Both -dicarbonyl compounds and the anions of various heterocyclic compounds (pyrrole, indole, pyrazolidinedione, hydroxypyrones, hydroxypyridones, oxo- and dioxopyrimidines) and -keto sulfones, -disulfones, cyclopentadienes, and malononitrile enter into the reaction.