Thermal and some other properties of the complexes crystallizing from the system Ni(II)-en-[Ni(CN)4]2−-H2O

Seven complex compounds exhibiting the compositions Ni(en)₃Ni(CN)₄·H₂O (I), Ni(en)₃Ni(CN)₄ (II),-Ni(en)₂Ni(CN)₄ (III), Ni(en)Ni(CN)₄·2H₂O (IV), Ni(en)Ni(CN)₄ (V), Ni(en)₂Ni(CN)₄ · 2.5H₂O (VI) and-Ni(en)₂Ni(CN)₄ (VII) were prepared from the system Ni-en-[Ni(CN)₄]^2–-H₂O. These compounds were examined by the methods of infrared spectroscopy, X-ray powder diffractometry, UV-VIS reflectance spectroscopy, and also by the measurement of magnetic moments. The thermal stability, the stoichiometry of thermal decomposition and the mutual transformations were investigated with a derivatograph. The reactions proceeding according to the following schemes were observed if the system was heated to appropriate temperature: (I)(II)(III)(V)(IV) and (VI)(VII)(III)(V)(IV) Process (VII)(III) represents isomerization. The reversibility of the process (V)(IV) is due to the high hygroscopicity of the anhydrous complex. The changes in structure in the course of the individual processes are discussed.

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Zusammenfassung Aus einem System Ni-en-[Ni(CN)₄]^2–-H₂O wurden sieben Komplexe der Formeln Ni(en)₃Ni(CN)₄·H₂O (I), Ni(en)₃Ni(CN)₄ (II),-Ni(en)₂Ni(CN)₄ (III), Ni(en)Ni(CN)₄·2H₂O (IV), Ni(en)Ni(CN)₄ (V), Ni(en)₂Ni(CN)₄ · 2.5H₂O (VI) und-Ni(en)₂Ni(CN)₄ (VII) hergestellt. Diese Verbindungen wurden mittels IR-Spektroskopie, Röntgenpulverdiffraktometrie, UV-Reflexionsspektroskopie und durch Messungen des magnetischen Momentes untersucht. Die Wärmestabilität, die Stöchiometrie des thermischen Zerfalles und die gegenseitigen Umwandlungen wurden mittels eines Derivatographen untersucht. Wird das System auf geeignete Temperaturen erhitzt, kann der Reaktionsverlauf durch folgendes Schema dargestellt werden: (I)(II)(III)(V)(IV) und (VI)(VII)(III)(V)(IV).Der Prozeß (VII)(III) verkörpert eine Isomerisierung. Die Umkehrbarkeit von Prozeß (V)(IV) ist auf die ausgeprägten Hygroskopieeigenschaften des wasserfreien Komplexes zurückzuführen. Es werden die im Ablaufe der einzelnen Prozesse vorgehenden Strukturveränderungen besprochen.

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Ni- -[No(N)]² -₂ Ni(en)₃Ni(CN)₄ · ₂ (I), Ni(en)₃Ni(CN)₄ (II),-Ni(en)₂Ni(CN)₄ (III), Ni(en)Ni(CN)₄-2H₂O (IV), Ni(en)Ni(CN)₄ (V), Ni(en)₂Ni(CN)₄ · 2,5H₂O (VI) -Ni(en)₂Ni(CN)₄ (VII). , , - , . , . (I)(II)(III)(V)(IV) (VI)(VII)(III)(V)(IV). (VII)(III) . (V)(IV) . .

     

Catalysts for selective hydrogenation of conjugated dienes into olefins in the presence of PdCl2 complexes

Complexes of PdCl₂ with amines or pyridine reduced by (iso-Bu)₂ AlH are shown to be catalytically active in the selective hydrogenation of conjugated dienes into olefins in aromatic media. The promoting effect of H₂O and O₂ has been established.

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PdCl₂ , (-Bu)₂ AlH, . H₂O O₂.

     

Vibrational isotope effect of linear and planar molecules: Deuterated bromoethenes

Linear (planar) molecules A and B which are identical except for isotopic substitutions at the atomic sites are considered. Stretching (bending, out-of-plane) frequencies _k and normal modes _k of the isotopically perturbed molecule B are expressed in terms of stretching (bending, out-of-plane) frequencies _i and the corresponding normal modes _i of the unperturbed molecule A. Complete specification of the unperturbed normal modes is not required. All that is needed are stretching (bending, out-of-plane) amplitudes | _i of the normal modes _i at those sites that are affected by isotopic substitution. The rule which interlaces frequencies _k of molecule A with frequencies _i of molecule B is derived. Given two isotopic molecules A and B that differ by a single isotopic substitution at site , the inversion relation is derived. This relation expresses unperturbed stretching (bending, out-of-plane) amplitudes at the site in terms of stretching (bending, out-of-plane) frequencies of molecules A and B . As an example, out-of-plane vibrations of deuterated bromoethene were considered. In the simplest method 12 out-of-plane frequencies of four polydeuterated bromoethenes were calculated from 12 out-of-plane frequencies of bromoethene and three monodeuterated bromoethenes. Standard deviation of thus calculated frequencies from experimental frequencies is =2.74 cm^–1. In another method, 15 out-of-plane frequencies of four polydeuterated bromoethenes and selected monodeuterated bromoethene are calculated from 9 out-of-plane frequencies of bromoethene and the remaining two monodeuterated bromoethenes. Depending on which monodeuterated bromoethene is selected (1-, cis- or trans-), standard deviation of thus obtained frequencies from experimental frequencies is 1=2.84 cm^–1, c=2.96 cm^–1 and t=2.72 cm^–1.     

Rearrangement ofα -trifluoromethyl-β-dialkylamino-β-fluoroacrylic acid N.N-dialkylamides

Conclusions When heated in the presence of a catalytic amount of BF₃ etherate,-trifluoromethyl--diethylamino--fluoroacrylic acid N, N-dimethylamide is reversibly isomerized to-trifluoromethyl--dimethylamino--fluoroacrylic acid N, N-diethylamide. The methyl esters of-trifluoromethyl--diethylammo--fluoroacrylic acid and-trifluoromethyl--phenoxy--fluoroacrylic acid N,N-dimethylamide are not isomerized under the same conditions.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No.1, pp.137–141, January, 1976.     

Dehydration-dehydrogenation of 1- and 2-butanols on lanthanide oxide catalysts

Catalytic decomposition of 1- and 2-butanols on the rare earth oxides CeO₂, Pr₆O₁₁, and Me₂O₃ (Me=La, Sm, Eu, Dy, Ho and Yb) has been studied. Dehydration-dehydrogenation selectivity of these oxides was analyzed from the point of view of the fractional selectivity (S_F). For the decomposition of 2-butanol and the product distribution on the lanthanide oxides, preferential orientation to Hofmann olefin as well as a cis/trans ratio slightly higher than that of the equilibrium value is observed.

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1- 2- CeO₂, Pr₆O₁₁ Me₂O₃ (Me=La, Sm, Eu, Dy, Ho Yb). - (S_F). 2- , , / .

     

Influence of substituents on rate constants for recombination of tertiary peroxy radicals

A linear correlation between the logarithm of rate constant (2k_t) for recombination of tertiary peroxy radicals (ROO)^* and ^* constants of substituents R was found to be 1g 2k_t=lg 2k _t ^° . The calculated values are 1g 2k _t ^° =4.59±0.08 and ^*=5.56±0.35.

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I (2k_t) (ROO) R: 1g 2k_t=lg 2k _t ^° . , 1g 1g 2k _t ^° =4,59±0,08 =5,56±0,35

     

Propos sur l'interpretation de l'energie d'activation experimentale

Résumé Les résultats de divers travaux montrent que la valeurE _e de l'énergie activation expérimentale tirée des diagrammes d'Arrhénius varie avec la pression, dans le cas de réactions de décompositions endothermiques.L'analyse de divers modèles permet d'expliquer cette constatation en montrant que la grandeurE _e n'a pas le sens d'une énergie d'activation mais est une fonction de nombreux paramètres. Deux d'entre eux ont été retenus dans le cadre de cette étude: le terme d'écart à l'équilibre et le terme de gradient thermique, provoqué par l'endothermicité du phénomène.Cette analyse permet d'établir une prévision de la fonctionE _e (P) conforme aux résultats expérimentaux.

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The results from various investigations show that the experimental activation energy valueE _e derived from the Arrhenius diagrams varies with pressure for endothermic decomposition reactions.The analysis of various models allows this fact to be accounted for by showing thatE _e should be regarded not in its fundamental formulation, but as being a function of numerous parameters. Two of these were taken into account in the present study, i.e. deviation from equilibrium and a thermal gradient due to the fact that the phenomenon is endothermic.FunctionE _e (P) fitting the experimental results may be predicted by such an analysis.

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Zusammenfassung Die Ergebnisse verschiedener Untersuchungen zeigen, dass die aus den Arrhenius-Diagrammen abgeleiteten experimentellen Werte der AktivierungsenergieE _e bei endothermen Zersetzungsreaktionen mit dem Druck variieren.Die Analyse verschiedener Modelle ermöglicht eine Erklärung dieser Tatsache, indem gezeigt wird, dassE _e nicht in ihrer grundliegenden Formulierung betrachtet werden darf, sondern als Funktion einer Anzahl von Parametern. Zwei dieser Parameter wurden in der vorliegenden Untersuchung berücksichtigt d.h. die Abweichung von dem Gleichgewicht und der thermische Gradient, welcher infolge der endothermen Beschaffenheit der Erscheinung auftritt.Eine den Versuchsergebnissen entsprechende FunktionE _e (P) kann mittels einer solchen Analyse vorausgesagt werden.

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, _e, , . , _ee , . , : , , . _e (), , .

     

Mass spectral and thermogravimetric studies of some iron(III) binuclear complexes with bridging thiuram disulfide ligands

Mass spectral and thermal studies by TG and DTG of some iron(III) binuclear complexes of the general type Fe₂(R₂dtc)₂(tds)X₂X/ have been carried out to determine their modes of decomposition. Fragmentation patterns are given and possible mechanisms are discussed.

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Zusammenfassung Massenspektrometrische und thermische Untersuchungen (TG und DTG) einiger zweikerniger Eisen(III)-Komplexe des allgemeinen Typs (R₂dtc)₂(tds)X₂X₂ wurden ausgeführt, um deren Zersetzungsmechanismus zu ermitteln. Fragmentspektren werden angegeben und mögliche Mechanismen diskutiert.

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- ( ) Fe₂(R₂dtc)₂(tds)X₂X₂ . .

     

Preparation et proprietes physico-chimiques de l'hydrure d'aluminium AlH3γ

Résumé AlH₃ a été synthétisé. La décomposition thermique de cet hydrure ainsi que la désolvatation de Al(AlH₄)₃, (C₂H₅)₂O ont été étudiés par analyse thermogravimétrique. L'analyse thermique différentielle effectuée sur AlH₃ montre un effet exothermique dû au passage à la forme AlH₃ puis endothermique correspondant à la décomposition de la phase formée. Une structure type alanate est proposée pour AlH₃ .

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Aluminium hydride has been synthetised. Thermogravimetry has been used to investigate the thermal decomposition of this phase and the desolvation of A1(AlH₄)₃· (C₂H₅)₂O. Differential thermal analysis of-AlH₃ shows an exothermic effect due to transformation to -A1H₃, followed by the endotherm of -AlH₃ decomposition. A structure of alanate type is proposed for -AlH₃.

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Zusammenfassung -AlH₃ wurde synthetisiert. Die thermische Zersetzung dieses Hydrids sowie die Desolvatation von Al(AlH₄)₃·(C₂H₅)₂O wurden mittels Thermogravimetrie untersucht. Die Differentialthermoanalyse von-AlH₃ zeigt einen dem Übergang in die AlH₃ -Form entsprechenden exothermen und mit nachfolgenden endothermen Effekt, welcher der Zersetzung der gebildeten Phase entspricht. Eine Struktur von solvatfreien Alanat-Typ wird für-AlH₃ vorgeschlagen.

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- . l(l₄)₃. (C₂H₅)₂O . l₃ , l₃. lH₃ .

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Ce travail a été effectué dans le cadre d'un contrat de recherches passé par le Laboratoire de Chimie Minérale avec la Direction des Recherches et Moyen d'Essai. Nous remercions bien vivement cet organisme ainsi que le Centre de Recherches ELF ERAP de Solaize de l'aide qu'ils nous ont apportée.     

Thermogravimetric and kinetic study of a clodronic acid complex formed with sodium

Thermal stability of the clodronic acid complex formed with sodium (Na₂CCl₂(HPO₃)₂ ·4H₂O) was studied using both dynamic and isothermal thermogravimetric analyses as well as mass spectra. The thermal decomposition has two stages: dehydration and loss of two molecules of hydrogen chloride. Using the isothermal TG data the first step was found to be a phase-boundary reaction while the second step obviously cannot be described with just one reaction mechanism. The final residue of the dynamic TG analyses above 810 K was found to be sodium metaphosphate.

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Zusammenfassung Sowohl mittels dynamischer und thermogravimetrischer Untersuchungen als auch and Hand von Massenspektren wurde die thermische Stabilität des mit Natrium gebildeten Säurekomplexes Na₂CCl₂(HPO₃)₂·4H₂O untersucht. Die thermische Zersetzung vollzieht sich in zwei Schritten: Dehydratation und Verlust von zwei Molekülen HCl. Auf Grund der isothermen TG Angaben ist der erste Schritt eine Phasengrenzreaktion, während der zweite Schritt mit einem einzigen Reaktionsmechanismus nicht eindeutig beschrieben werden kann. Das Endprodukt der DTG Analyse oberhalb 810 K erwies sich als Natriummethaphosphat.

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-Na₂CCl₂/HPO_3/2·4H₂O — , - . , , , . , , . 810 .

     

Thermal decomposition of some homobinuclear dihalide-bridged iron(III) complexes

Thermal studies by TG and DTG on some homobinuclear dihalide-bridged iron(III) complexes of the general type [Fe(S₂CNR₂)₂X]₂(}-X ₂) were carried out in air and nitrogen atmospheres. The apparent activation energies were determined by graphical methods and the TIN temperatures were calculated from the TG profiles. Finally, a possible mechanism of the decomposition is suggested on the basis of the pyrolysis and mass spectral data.

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Zusammenfassung Einige homobinukleare Eisen(III)-Komplexe mit Dihalidbrücken der allgemeinen Formel [Fe(S₂CNR₂)₂X]₂(–X₂) wurden mittels TG und DTG in Luft und Stickstoffatmosphäre untersucht. Die scheinbaren Aktivierungsenergien wurden nach graphischen Methoden aus den TG-Profilen bestimmt. Ein möglicher, auf pyrolytischen und massenspektrometrischen Daten basierender Zersetzungsmechanismus wird vorgeschlagen.

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[Fe(S₂CNR₂)₂X]₂ (-₂) . , . - .

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Thanks are due to Dr. G. Karagiannidis, Laboratory of Organic Chemical Technology, Aristotelian University, for technical assistance.     

Reactivity of electronically excited Br(2P1/2) atoms towards CH3F

The rate constants for Br(²P_1/2) and Br(²P_3/2) atoms in the reaction Br+CH₃FHBr+CH₂F in photobromination of CH₃F have been determined. Their ratio is 10^{–(2.6±0.5)} exp(10100±1000/RT) in the temperature range of 60–200 °C.

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Br(²P_1/2) Br(²P_3/2) Br+CH₃FHBr+CH₂F CH₃F. 60–200 °C 10^{–(2,6±0,5)} exp (10100±1000/RT).

     

Capacité calorifique molaire du composé Bi.4 Te.6 dans les états solide et liquide

The heat capacities of Bi.4Te. 6 in the solid and liquid states are calculated from the results of the experimental drop calorimetric method, and the heat of fusion of the compound is deduced.

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Zusammenfassung Die Wärmekapazitäten von Bi.4Te. 6 in fester und flüssiger Phase werden aus experimentellen Daten berechnet, die mit der tropfenkalorimetrischen Methode erhalten wurden. Die Schmelzwärme der Verbindung wird abgeleitet.

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« » Bi₄Te₆ , .

     

Isoprene hydrogenation in the presence of cobalt pohosphine complexes

The influence of the type of phosphine on the yield of methylbutenes in isoprene hydrogenation with complex cobalt catalysts has been studied. The complex H₃Co[P(n-C₄H₉)₃]₃ has been identified by the NMR method in the catalytic system Co(C₅H₇O₂)₂+P(n-C₄H₉)₃+Al(C₂H₅)₃. A mechanism of isoprene hydrogenation is suggested.

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. Co(C₅H₇O₂)₂+P(n-C₄H₉)₃+Al(C₂H₅)₃ H₃Co[P(n-C₄H₉)₃]₃. .

     

Kinetics of cerium(IV) oxidation of propionic acid in perchloric acid: Role of solvent

The oxidation rate of propionic acid (PROA) by cerium(IV) in aqueous perchloric acid (1.0–6.0 mol/dm³) is proportional to the PROA concentration, the total order of the reaction being two. It was found that the rate is related to the values of Hammett's acidity function (H₀) in agreement with both Zucker-Hammett's hypothesis and Bunnett-Olsen's criterion, the water acting as a proton transfer agent. A mechanism consistent with the findings is proposed.

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() (IV) (1,0–6,0 /³) . (H₀) -, -. . .

     

Application of emissionless infrared diffuse reflectance spectrometry for following reactions of adsorbed alcohols on an alumina catalyst

IR spectra of adsorbed alcohols on alumina were measured under the reaction conditions at elevated temperatures. The transient response of IR absorption intensity indicates that alkoxides are reactive adsorbed species but carboxylates are not. The rate constants of surface reactions were calculated from the transient response.

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, . , , , —, .

     

Monolayer vanadia on titania systems from alkoxide precursors. Part III. Activity in secondary alcohol oxidation

The activity of V⁵⁺ ion monolayer supported on anatase, rutile, and anatase-rutile mixed carrier and of bulk V₂O₅ was examined in isopropyl alcohol and cyclohexanol oxidation. Catalysts exhibited remarkable activity in ketone formation. At higher temperatures benzene was the predominant product of cyclohexanol reaction.

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V⁵⁺, , - V₂O₅, . . .

     

Kinetic analysis of thermogravimetric data. XI thermal decomposition of some metal dithionates

A thermal analytical study of Li, Na, K, Rb, Cs, NH₄, Mg, Ca, Sr, Ba and Zn dithionates is reported. The decomposition of the dithionate ion is endothermic in the case of the Na, K, Rb, Cs and NH₄ salts, but exothermic with Li, Mg, Sr, Ba and Zn. Kinetic parameters have been derived from the TG curves by means of the Coats-Redfern method. The validity of a linear kinetic compensation law is reported for the loss of crystal water and separately for the decomposition of the dithionate ion.

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Zusammenfassung Es wird über eine thermoanalytische Untersuchung der Dithionate von Li, Na, K, Rb, Cs, NH₄, Mg, Ca, Sr, Ba und Zn berichtet. Die Zersetzung des DithionatIons ist im Falle von Na, K, Rb, Cs und NH₄-Salzen endotherm, im Falle von Li, Mg, Sr, Ba und Zn hingegen exotherm. Die kinetischen Parameter wurden aus den TG-Kurven mittels der Coats-Redfern-Methode abgeleitet. Es wird über die Gültigkeit eines linearen kinetischen Kompensationsgesetzes für den Verlust von Kristallwasser berichtet und gesondert für die Zersetzung des Dithionat-Ions.

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Résumé On présente les résultats d'une étude par analyse thermique des dithionates de Li, Na, K, Rb, Cs, NH₄, Mg, Ca, Sr, Ba et Zn. La décomposition est endothermique dans le cas des sels de Na, K, Rb, Cs et ammonium tandis qu'elle est exothermique dans le cas des sels de Li, Mg, Sr, Ba et Zn. Les paramètres cinétiques sont déduits des courbes TG par la méthode de Coats-Redfern. La validité d'une loi de compensation cinétique linéaire est étudiée pour la perte de l'eau d'hydratation ainsi que pour la décomposition de l'ion dithionate.

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Li, Na, K, Rb, Cs,. NH₄, Mg, Ca, Sr, Ba Zn. [ Na, K, Rb, Cs NH₄ , Li, Mg, Sr, Ba Zn . - . .

     

Degradation of rocket insulator at high temperature

The degradation of a rocket insulator compound based on ethylene propylene diene rubber (EPDM) containing asbestor, cork and iron oxide (Fe₂O₃) as fillers has been studied at high temperature (up to 600°) by using differential thermal analysis (DTA) and thermogravimetry (TG). The changes in physical properties on high-temperature aging are also reported. EPDM gum vulcanizates involving different types of diene, namely ethylidene norbornene (ENB), dicyclopentadiene (DCPD) and 1,4-hexadiene (HD), were used. In each case, the kinetic parameters for degradation have been evaluated. From these data, the lifetime of the rocket insulator compound has been found.

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Zusammenfassung Die Zersetzung einer Raketenisolator-Verbindung auf Äthylen-Propylen-Dien-Gummibasis (EPDM) mit Asbest, Kork und Eisenoxid (Fe₂O₃) als Füllstoffe wurden bei hohen Temperaturen (bis 600°) mittels Differentialthermalanalyse (DTA) und Thermogravimetrie (TG) untersucht. Die bei Hochtemperaturen eintretenden Veränderungen der physikalischen Eigenschaften sind ebenfalls angegeben. Verschiedene Typen von Dienen, nämlich Äthyliden-norbornen (ENB), Dicyclopentadien (DCPD) und 1,4-Hexadien (HD) enthaltenden EPDM-Gummivulkanisate waren Gegenstand der Untersuchung. In allen Fällen wurden die kinetischen Parameter der Zersetzung ermittelt. Aus diesen Daten wurde die Lebensdauer der Raketenisolator-Verbindung bestimmt.

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600° (), , . , . , , 1,4- . . .

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The authors are grateful to the Indian Space Research Organization for funding, and acknowledge the help and suggestions from Mr. T. S. Ram and Mr. Baby John, R.P.P., V.S.S.C., Trivandrum. The authors are also grateful to Prof. S. K. De, Rubber Technology Centre, and Prof. R. Ghosh, Chemistry Department, I.I.T., Kharagpur.

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The authors thank Mr. Asutosh Ghosh, Indian Association for the Cultivation of Science, for experimental assistance.     

Coke deposits on Pt/Al2O3 catalysts of varying dispersities

Coke deposition during cyclopentane reaction was investigated on Pt/Al₂O₃ catalysts of varying dispersity. For all working pressures the higher the metallic accessibility, the higher the amount of coke deposited on the catalyst. Nevertheless, coke deposited on the less dispersed catalysts is more toxic for the metallic function. An increasing metal accessibility improves the graphitization of coke on the support and so, prevent the deactivation of the metal of a bifunctional catalyst.

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Pt/Al₂O₃ . , , , . , , , . , .