Correlation between structures and thermal properties of hydrated thallium(I) diborates; H2O-Tl2B4O7 phase diagram

Two synthetic hydrated thallium (I) diborates have been found in the liquidsolid equilibria of the 100° isotherm of the ternary system H₂O-B₂O₃-Tl₂O; they were characterized via the powder diagrams, but classical chemical analysis does not lead to the correct degree of hydration. Through TG of the powders, a complex process is found with no explanation. Structural resolution and TG of the monocrystals allow a correct explanation of the thermal dehydration: these thallium (I) diborates are two distinct compounds, Tl₂B₄O₇ · 3H₂O and Tl₂B₄O₇ · 1.5H₂O, which have their own process of dehydration; they contain infinite chains of polyanions and their structural formulae are Tl₂[B₄O₆ (OH)₂] · 2H₂O and Tl₄[B₈O₁₂ (OH)₄]H₂O; the latter polyanion may be considered as the dimer of the first.The H₂O-Tl₂B₄O₇ phase diagram was established by thermal analysis and solubility experiments, both under pressure; it allows the prediction that another hydrated thallium (I) diborate, Tl₂B₄O₇·H₂O, exists, with possible structural formula Tl₆[B₁₂O₁₈ (OH)₆]. Actually, only monocrystals of Tl₄[B₈O₁₂ (OH)₄]·H₂O have been obtained hydrothermally from Tl₂[B₄O₆ (OH)₂] · 2H₂O.

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Zusammenfassung Im ternären System H₂O-B₂O₃-Tl₂O liegen bei 100° bei Einstellung des Gleichgewichtes flüssig-fest zwei hydratisierte Thallium (I) -diborate vor; diese wurden durch Pulverdiagramme charakterisiert, die klassische chemische Analyse ergab jedoch nicht den richtigen Hydratationsgrad. Bei TGA von Pulvern verläuft ein komplexer Prozeß, für den keine mögliche Erklärung gegeben werden kann. Strukturaufklärung und TGA mit Einkristallen ermöglichen eine korrekte Erklärung der thermischen Dehydratisierung: die hydratisierten Thallium (I) -diborate sind zwei verschiedene Verbindungen der Zusammensetzung Tl₂B₄O₇· 3H₂O und Tl₂B₄O₇· 1.5H₂O mit unterschiedlichem Dehydratisierungsverlauf, die Polyanionketten enthalten und durch die Strukturformeln Tl₂[B₄O₆ (OH)₂] · 2H₂O bzw. Tl₄[B₈O₁₂ (OH)₄] · H₂O zu beschreiben sind. Das Polyanion der zweiten Verbindung kann als Dimeres des der ersten angesehen werden. Das Phasendiagram H₂O-Tl₂B₄O₇ wurde durch unter Druck ausgeführte thermische Analyse und Löslichkeitsexperimente aufgestellt. Aus diesem Phasendiagramm kann die Existenz eines anderen hydratisierten Thallium (I) -diborats, Tl₂B₄O₇ · H₂O, mit der möglichen Strukturformel Tl₆[B₁₂O₁₈ (OH)₆] vorausgesagt werden. In Wirklichkeit wurden aber nur Einkristalle von Tl₄[B₈O₁₂ (OH)₄]·H₂O durch hydrothermale Behandlung von Tl₂[B₄O₆ (OH)₂] · 2H₂O erhalten.

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₂-₂₃-l₂ 100° , . , . : l₂₄₇·₂ l₂₄₇·1.5₂, . l₂[₄₆()₂]· 2₂ l₄[₈₁₂()₄]·₂. . ₂-l₂₄₇. , l₂₄₇·₂ l₆[₁₂₁₈()₆]. , l₄[₈₁₂()₄]·₂ l₂[₄O₆()₂]·2₂O.

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Paper presented at the World Conference on Thermal Analysis Amsterdam, 1984.     

SIMS and XPS studies of Raney nickel catalysts

Chemical composition and structure of surface layers of Raney nickel catalysts prepared from NiAl₃ and Ni₂Al₃ intermetallides and Ni–Al (11) alloy have been studied by SIMS and XPS methods. A model structure of these catalysts is suggested.

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SIMS , NiAl₃, Ni₂Al₃ Ni–Al (11). .

     

Temperature effects on the fluorescence kinetics of excited cyclohexane

In agreement with the results reported by Lipsky, emission from cyclohexane depends on the temperature T and on the nature of the phase (liquid or solid). Determination of the lifetimes of the fluorescent state with a single photon counting apparatus gives similar results. Our experimental work shows that the rate constant of fluorescence for the solid phase I (face-centered cubic cell) practically does not depend on temperature. Variations of lifetime vs. T cannot easily be interpreted only with the classical theory of non-radiative transitions.

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, , ( ). , , . , I ( ) . .

     

Rate constants for the reaction of singlet oxygen with diazocompounds

Rate constants for the reaction of singlet oxygen with a series of diazocompounds and diazoketones have been measured. Diazoketones were found to possess lower reactivity than diazocompounds.

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- . , .

     

FT-Raman Spectra of o-, m-, and p-Nitrophenol Included in Cyclodextrins

FT-Raman spectra of o-, m-, and p-nitrophenol included in -cyclodextrin (CD), -CD, hydroxypropyl (HP) -CD, andsulfated -CD were recorded. The phenyl (C=C) band of o- and p-nitrophenol in the CD inclusion complexes was shifted to higher wavenumber thanthat of pure o- and p-nitrophenol,whereas the phenyl (C=C) band of m-nitrophenol in the CD inclusion complexes was shifted to lower wavenumber than that of pure m-nitrophenol. The ring CH peak of o-nitrophenol in the CD complexes was shifted to higher wavenumber than that of pure o-nitrophenol, whereas the ring CH peak of m- and p-nitrophenol in the CD complexes was shifted to lower wavenumber than that of pure m- and p-nitrophenol.     

Preparation and characterization of iron(II) complexes of ethylene glycol

Nine iron(II) ethylene glycol sulphate complexes were prepared. Their compositions were determined by standard analytical methods. They were characterized by means of temperature-dependent magnetic susceptibility and Mössbauer spectroscopic measurements. On the basis of the patterns of their thermal decompositions, the complexes could be classified into three groups.

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Zusammenfassung Neun Eisen(II)-ethylenglykol-sulfat-Komplexe wurden dargestellt. Die Zusammensetzung dieser Komplexe wurde nach analytischen Standardmethoden bestimmt. Die Verbindungen wurden durch Messungen der temperaturabhängigen magnetischen Susceptibilität sowie mittels Mössbauer-Spektroskopie charakterisiert. Nach dem Verhalten bei der thermischen Zersetzung konnten diese Komplexe in drei Gruppen klassifiziert werden.

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, . . , .

     

Kinetics and mechanism of piperidine carbonylation in the presence of Cu(I) and Cu(II) complexes

The kinetics of piperidine carbonylation to bispentamethylenurea in the presence of Cu(I) and Cu(II) complexes has been studied. An adequate mechanism of the process is proposed and the constant of the rate-determining step has been calculated.

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(I, II) -. .

     

Cyclic transition states in the cleavage of C?H bonds in alkanes by solutions of metal complexes and oxidants

The oxidative cleavage of C–H bonds in alkanes in solutions is suggested to proceed via cyclic transition states (CTS). Probable CTS structures have been analyzed for various reagents.

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C–H (). .

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A contracted text of the paper for the 1st All-Union Symposium on Homogeneous Catalysis New Methods to Transform Saturated Hydrocarbons, Donetsk, May 12–14, 1982.     

Kinetic studies on the aminolysis of O-(2,4-dinitrophenyl)-cyclopentanone oxime in benzene

The reaction of O-(2,4-dinitrophenyl) cyclopentanone oxime with four primary alkylamines and a secondary arylamine, pyrrolidine, in benzene has been investigated. In pyrrolidinolysis, a third order dependence on [amine] has been observed, which has been explained on the basis of a cyclic transition state. The aminolysis with primary alkyl amines shows a normal dependence of second order on [amine].

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O-(2,4-) - . , . .

     

Investigations on the ternary system Ag-P-S and thermal behaviour of the compounds

Parts of the ternary system Ag-P-S were investigated by DTA- and X-ray measurements. The quasibinary section of Ag₂S-P₄ S₁₀ is described. The thermal behaviour and X-ray diffraction patterns of Ag₇PS₆, Ag₃PS₄, Ag₇P₃S₁₁, Ag₄P₂S₇ and Ag₂P₂S₆ were studied. DTA-diagrams and X-ray powder data are given.

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Zusammenfassung Mittels DIA- und Röntgendiffraktionsmessungen wurden Teile des Dreikomponentensystemes Ag-p-s untersucht. Es wird der quasibinäre Schnitt von Ag₂S-P₄ S₁₀ beschrieben. Weiterhin wurden das thermische Verhalten und die Röntgenbeugungsbilder von Ag₇PS₆, Ag₃PS₄, Ag₇P₃S₁₁, Ag₄P₂S₇ und Ag₂P₂S₆ untersucht. DTA-Diagramme und Röntgen-Pulverdaten werden gegeben.

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Ag-P-S. Ag₂S-P₄S_IO. $ Ag₇PS₆, Ag₃Ps₄, Ag₇P₃S_II, Ag₄P₂S₇ Ag₂P₂S₆. .

     

High activity of MgO catalyst prepared from magnesium oxalate for the hydrogenation of butadiene

High activity of magnesium oxide prepared by thermal decomposition of magnesium oxalate for the hydrogenation of 1,3-butadiene has been examined by XPS and IR, together with the isomerization of 1-butene. XPS spectra of MgO differed from those of two other MgO catalysts. With Ar etching, the binding energies of Mg2p and 01s shift, which is related to the surface basicity. Both basic and acidic sites are responsible for hydrogenation, but isomerization proceeds only on basic sites.

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, 1,3- 1-, . MgO ; Ar 2p 1s Mg, . , , , - .

     

Effect of supports on the energetics of CO chemisorption on rhodium catalysts

The kinetics of adsorption-desorption processes were measured using Frequency Response Chemisorption for CO on supported Rh catalysts. Measurements on Rh/SiO₂ failed to give a signal, most likely due to the strong natures of the CO sorption on the metal. CO on Rh/TiO₂ measurements indicated the existence of one molecularly adsorbed state. The rate constants for adsorption state were derived.

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- CO Rh . Rh/SiO₂ , - CO . Rh/TiO₂ . .

     

Frequencies and integral intenstities of the lactone and ester carbonyls of natural guaianolides

The frequencies and integral intensities of the IR bands of the stretching vibrations of lactone and acyclic ester carbonyls at C-8 of ten natural guaianolides and their derivatives, and of three model compounds have been studied. The most probable interpretation of the change in the value of A_C=O and _C=O of the lactone carbonyl have been suggested. In elegin and some of its derivatives, acroptilin, chlorohyssopifolin B, and eleganin, a lowering of the values of A_C=0 and _C=0 in comparison with dihydroelegin, hexahydroelegin, and the hydroxylactone of cynaropicrin is caused by nonvalent interactions of the lactone carbonyl with the -exocyclic double bond. The increase in A_C=O and _C=O in dihydroelegin, hexahydroelegen, and the hydroxylactone of cynaropicrin is due to the angular strain of the -lactone ring. It has been shown that in an acyclic side chain at C-8 an increase in the integral intensity and in the frequency of the ,-unsaturated ester carbonyl relative to guaianolides in which the terminal vinyl group at C-17 is absent is due to a conjugation effect.Institute of the Chemistry of Plant Substances, Uzbek SSR Academy of Sciences, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 805–811, November–December, 1987.     

The apparatus function of quantitative differential thermal analysis,including heat convection and radiation

The apparatus function, i.e. the response of the equipment to a heat pulse, is derived for DTA instruments where, besides heat conduction, convection and radiation are considered. The solution of the heat-balance equation is described by a superposition of two exponential functions, which leads to the dependences of the calibration factor and the time constants on the heat capacity, the heating rate and the temperature. For the experimental determination, the relations are transformed into expressions which can easily be obtained from the calibration measurements.

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Zusammenfassung Die Apparatefunktion, das ist die Reaktion der Anordnung auf einen Heizimpuls, wird für eine Differential-Thermo-Anlage abgeleitet, wobei neben Wärmemeitung auch -Konvektion und-Strahlung zugelassen sind. Die Lösung der Wärmebilanzgleichung wird durch die Überlagerung zweier Exponentialfunktionen beschrieben, wobei sich die Anhängigkeiten des Gerätefaktors und der Zeitkonstanten von der Wärmekapazität, der Heizrate und der Temperatur ergeben. Zur experimentellen Bestimmung werden die Ausdrücke zu leicht aus den Kalibrierungsmessungen zugänglichen Größen aufbereitet.

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— , , , . , , . , .

     

On the complexity of linear reaction mechanisms

A complexity index is proposed, based on the structure of kinetic equations as well as on the formulas derived for the number of maximal trees.

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, , .

     

Multiple reaction scheme modelling

Analyses of the kinetics of the effective reactions, resulting from linear combinations of a wide range ofn ^th order single reactions in a multiple set with variously chosen energies of activation and pre-exponential factors, generated under simulated non-isothermal conditions, have been carried out. The global kinetics parameters of the several mode's were obtained by subjecting extent and rate of reaction data, generated at a number of different linear heating rates, to Arrhenius, Kissinger and Friedman isoconversional analyses. Multiple sets, comprising from five to fifty individual members, with order varying from 0.25 to 5 have been considered. The effects of model design on the overall reaction kinetics parameters are discussed. Criteria applicable to experimental thermoanalytical data for recognition of multiple reactions are presented.

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Zusammenfassung Es wurde eine Analyse der Kinetik von Effektivreaktionen durchgeführt, die sich unter Annahme simulierter nicht-isothermischer Bedingungen mit einem Multipel von unterschiedlich gewählten Aktivierungsenergien und präexponentiellen Faktoren aus der Linearkombination von Einzelreaktionen mit einem breiten Bereich der Reaktionsordnungn ergaben. Die globalen kinetischen Parameter der einzelnen Modelle wurden unter Anwendung der isokonversiven Friedman-, der Arrhenius- und Kissingeranalysen aus Größe und Quotient der Reaktionsdaten ermittelt, die für eine Anzahl verschiedener Aufheizgeschwindigkeiten generiert wurden. Multiple mit fünf bis fünfzig Elementen mit Werten zwischen 0,25 und 5 wurden betrachtet. Es wird die Abhängigkeit der kinetischen Reaktionsbruttoparameter von der Gestaltung des Modelles besprochen. Es werden Kriterien gegeben, die an experimentellen thermoanalytischen Daten zur Erkennung von Mehrfachreaktionen angewendet werden können.

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, n- , . , , . , 5 50 , 0,25 5. . , .

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The continuing support of this work by the management of Merck and Co. is gratefully acknowledged.     

Thermal stability of poly(β-bromostyrene) and copolymers of β-bromostyrene with methyl methacrylate

The thermal stabilities of poly(-bromostyrene), poly-(methyl methacrylate) homopolymers and copolymers of-bromostyrene-methyl methacrylate covering the entire composition range were studied using TG analysis. At each extreme of the composition range, incorporation of comonomer units results in a copolymer more stable than the brominated homopolymer. Maximum stability occurs for compositions of approximately 62 mole percent-bromostyrene. The formation of the anhydride structure among the degradation products leads to the stability of the copolymers.

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Zusammenfassung Die thermische Stabilität von-Bromstyrol- und Methylmethacrylat-Homopolymeren sowie von sich über den ganzen Zusammensetzungsbereich erstreckenden-Bromstyrol/Methylmethacrylat-Kopolymeren wurde thermogravimetrisch untersucht. An beiden Enden des Zusammensetzungsbereichs führt der Einbau von Komonomereinheiten zu einem Kopolymer, das stabiler als das bromierte Homopolymer ist. Maximale Stabilität wird bei einem Gehalt von etwa 62 Mol-%-Bromstyrol erreicht. Die Bildung der Anhydridstruktur führt zur Stabilität des Kopolymers.

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/-, - . , . - 62%. .

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Presented at the World Conference of Thermal Analysis, held in Bad Hofgastein (Austria), 1985.     

Microwave Spectrum and Hindered Pseudorotation of Tetrahydrofuran

The microwave spectrum of the tetrahydrofuran (C₄H₈O) molecule in the ground state and eight excited states of hindered pseudorotation has been studied. A strong perturbation of rotational spectra has been found for three pairs of pseudorotational states, which is due to the vibrational-rotational interaction. To analyze the nonrigid spectra of these states we used the double resonance technique. Two hundred and sixty nine rotational and vibrational-rotational transitions corresponding to the _a and _c components of the dipole moment have been identified. The rotational constants have been determined along with the quartic constants of centrifugal distortion and the spectroscopic parameters of the interaction between the overall rotation and hindered pseudorotation. The splittings of three pairs of quasidegenerate vibrational levels have been calculated: ₀₁ = 21,308.17 MHz, ₂₃ = 61,205.28 MHz, ₅₆ = 68,183 MHz. The potential function of hindered pseudorotation V()=- 7.84(1-cos2)/2+36.10(1-cos4)/2 (cm^–1) was found from the splittings. It is concluded that the molecule has a twisted conformation (C₂ symmetry) in the states =0 and =1 of hindered pseudorotation and a bent conformation (C_s symmetry) in the states = 2 and = 3. The component of the dipole moment of the transition ‹ = 2 |_c | = 3› = 0.57± 0.01D was determined from the Stark effect of the rotational transitions in the = 2, = 3 states.     

Solvation corrections to the Br?nsted equation for general base catalysis

A quantitative allowance for the solvation corrections f^solv eliminates deviations from the Brönsted lines for the bases OH^–, H₂O, and primary and secondary amines and straightens these lines for known base-catalysed reactions.

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f^solv OH^–, H₂O, .

     

Kalorische Exzeßcharakteristik flüssiger Nichtelektrolyt-systeme

Zusammenfassung Die mittleren molaren Exzeßenthalpien der ternären Systeme Benzol /n-Heptan/n-Tetradecan, Benzol/n-Decan/n-Tetradecan und Benzol/Toluol/n-Tetradecan sowie die der korrespondierenden binären Systeme wurden titrationskalorimetrisch bei 298.15 K über den gesamten Molenbruchbereich bestimmt. Auf der Grundlage dieser experimentellen Ergebnisse sollte die Anwendbarkeit des Gruppenlösungsmodells von Ratcliff u.a. zur Vorausberechnung mittlerer molarer Exzeßenthalpien an ternären Gemischkombinationen getestet werden. Die Abweichung zwischen den gemessenen und inkrementell berechneten Mischungsenthapien lag bei den hier untersuchten Systemen im Bereich von 0 bis 12%.

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Via a titration calorimetric method the molar enthalpies of mixing for the three ternary systems benzene/n-heptane/n-tetradecane, benzene/n-decane/n-tetradecane and benzene/toluene/n-tetradecane, as well as for all of the corresponding binary systems, were measured over the whole range of mole fractions at 298.15 K. On the basis of the experimental results the applicability of the Group Solution Model, proposed by Ratcliff et al. for predictive calculations of heats of mixing, was tested for the treatment of ternary systems mentioned above.The differences between the measured and incrementally calculated heats of mixing were found to range from 0 to 12 %.

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Résumé Les enthalpies de mélange des trois systèmes ternaires benzène/n-heptane/n-tétradécane, benzène/n-décane/n-tétradécane et benzène/toluène/n-tétradécane ont été mesurées ainsi que celles des systèmes binaires correspondants, à 298.15 K dans le domaine complet des fractions molaires, par une méthode de titrage calorimétrique. En se fondant sur les résultats expérimentaux, on examine la possibilité d'appliquer aux systèmes ternaires, tels que ceux mentionnés ci-dessus, le modèle proposé par Ratcliff et al. pour prévoir les chaleurs de mélange. L'écart entre les chaleurs de mélanges mesurées et celles calculées par incréments varie de 0 à 12%.

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, /-/- , /-/- //- , 298,15 . , , . . 0 12%.