Détermination de la pureté de la sulfapyridine s par analyse thermométrique

Résumé L'étude thermoanalytique de la pureté de deux échantillons de sulfapyridine, médicament (I) et standard (II), a été réalisée par différentes méthodes. Par mesure de la transparence les valeurs moyennes de la température et du domaine de fusion indiquent une teneur en impureté plus faible pour (II) que pour (I). Disposant de deux analyseurs thermiques de conception différente, les auteurs ont montré l'excellente concordance des résultats: 99.790 ± 0.047 % et 99.800 ± 0.045 % (I). Seule l'analyse calorimétrique différentielle permet d'évaluer avec précision le taux de pureté de (II) 99.956 ± 0.028 %, valeur représentant un seuil pour l'analyse calorimétrique différentielle à compensation de puissance (DSC 1B).

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The thermoanalytical purities of two sulfapyridine samples, drug (I) and standard (II), have been studied with different methods. By transparency measurement the fusion temperatures and intervals indicate a lower percentage of impurity for (II) than for (I). By means of two thermal analyzers the authors have shown the good agreement of the results: 99.790±0.047% and 99.800±0.045% (I). Heat-flux differential scanning calorimetry is the only method able to give precisely the degree of purity of (II): 99.956±0.028 %, this value being a limit for the power-compensation differential scanning calorimetry analysis (DSC 1B).

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Zusammenfassung Das Studium der thermoanalytischen Reinheit der beiden Sulfapyridinproben drag(I) und standard(II) wurde durch verschiedene Methoden durchgeführt. Schmelztemperaturen sowie-bereiche zeigen im Falle von Transparenzmessungen einen geringeren Prozentsatz von Verunreinigungen für (II) als für (I). Unter Anwendung zweier Thermoanalyser zeigten die Autoren die gute Übereinstimmung der Ergebnisse: 99.790±0.047% und 99.800 ± 0.045 % für (I). Ein Wärmeströmungs-Differentialabtastkalorimeter bietet die einzige Möglichkeit den Reinheitsgrad von (II) genau zu bestimmen: 99.956 ± 0.028 %, wobei dieser Wert die Grenze für die Kraft-Kompensations-Differentialkalorimetrie (DSC 1B) darstellt.

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: (I) (II). , , II , I. , : 99.790±0.047% 99.800 ± 0.045% I. II: 99.956 ± 0.028% ( 1).

     

Glycosides of marine invertebrates. X. The structure of stichoposides A and B from the holothurianStichopus cloronotus

The structures of two triterpene oligosides from the holothurianStichopus cloronotus (Brandt) have been established; they are: 23-acetoxy-3-[O--D-quinovopyranosyl-(12)--D-xylopyranosyloxy]holost-7(8)-ene and 23-acetoxy-3-[O--D-glucopyranosyl-(12)--D-xylopyranosyloxy]holost-7(8)-ene.Pacific Ocean Institute of Bioorganic Chemistry, Far Eastern Scientific Center, Academy of Sciences of the USSR, Vladivostok. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 181–184, March–April, 1981.     

Intermediates of homogeneous deuterium exchange in alkanes catalyzed by Pt(II)

The rate constants and distribution of deuterated products of the H-D exchange in alkanes (C₁–C₈) have been measured for aqueous solutions of K₂PtCl₄. The reaction involves the intermediate formation of alkyl, 1,1-(carbene). 1,2-(olefin), 1,3-(cyclopropane) and 1,4-(cyclobutane) type hydrocarbon complexes. The selective attack of Pt(II) on the primary, secondary and tertiary C–H bonds in alkanes (110) is due to the predominance of steric over polar effects.

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H-D (C₁–C₈) K₂PtCl₄ , , 1,1-(), 1,2-(), 1,3-() 1,4-() . Pt(II) ., ., . C–H (110) .

     

Catalytic activity of high-silicon TsVK and Y type zeolites

Conversion of paraffins on TsVK and Y zeolites follow a similar mechanism yielding the same intermediates. Low selectivity of Y zeolites with respect to aromatic hydrocarbons is attributed to the strong adsorption of these hydrocarbons on zeolites. It is assumed that the centers of strong adsorption are Al³⁺ ions in cationic positions in zeolite.

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, . . , Al³⁺ .

     

Thermische Zersetzung des Kaliumhexacyanoferrats (II)

Zusammenfassung Es wurde festgestellt, daß unter Luftzutritt die Grenze der thermischen Beständigkeit des K₄[Fe(CN)₆] bei 200° liegt. Die Zersetzung des Komplexes führt im Temperaturbereich von 200° bis 350° zu ferromagnetischen Intermediären. Der Ferromagnetismus der erwärmten Präparate konnte mit der Bildung von-Fe₂O₃ erklärt werden. Bei 250° besteht die vorherrschende kristalline Phase aus Kaliumkarbonat.

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It has been found that the limit of thermal stability of K₄[Fe(CN)₆] in air is 200°. The decomposition of the complex in the temperature range of 200°–350° leads to ferromagnetic intermediates. The ferromagnetism of these products could be explained by the formation of-Fe₂O₃. At 250° the crystalline phase consists mainly of potassium carbonate.

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Résumé On a établi que la limite de la stabilité thermique de K₄[Fe(CN)₆] en présence d'air s'élève à 200°. Entre 200 et 350°, la décomposition du complexe donne des produits intermédiaires ferromagnétiques. Ce ferromagnétisme s'explique par la formation de-Fe₂O₃. A 250°, la phase cristalline dominante est constituée par du carbonate de potassium.

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, K₄[Fe(CN)₆] , 200°. 200°–350° . -Fe₂O₃. 250° .

     

Kinetic studies of thiolane synthesis from tetrahydrofurane and H2S

Kinetic studies of tetrahydrofuran reaction with H₂S were carried out in a flow-circulation reactor. Presumably, the reaction takes place through dissociative chemisorption of reactants and the interaction of surface structures formed to produce thiolane and water. A kinetic equation that agrees with the suggested mechanism has been derived.

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- H₂S. , . , .

     

Hysteresis of thermogravimetric curves of nickel catalysts for methane conversion in CH4+CO2 mixture

Characteristic peculiarities of the supercarbonization peak, i. e. the effect of carbon accumulation on the catalyst surface and its subsequent removal under heating in the CH₄+CO₂ mixture have been studied. Hysteresis of thermogravimetric curves in the heating/cooling cycle has been established.

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— . -.

     

Reactivity of coordinated O2?, ion-radicals towards one-electron reductants

Using the flow ESR method, the rates of the reaction between the radical complex Ti(IV)(O ₂ ^– ) and one-electron reductants in aqueous solution have been measured. The redox potential for the Ti(IV) (O ₂ ^– )/Ti(IV) (O ₂ ^2– ) couple is about 1.7 V.

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Ti(IV)(O ₂ ^– ) . - Ti(IV)(O ₂ ^– )/Ti(IV)(O ₂ ^2– ) 1,7 .

     

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.     

General equation for dissociative heterolytic reaction rates and corrections to the Br?nsted relationship

A general equation is proposed for the rates of halide and H⁺ ion transfer. A relay-type participation of H₂O in the transfer of H⁺ in aqueous solutions is substantiated.

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: - H⁺. H₂O H⁺ .

     

Kinetic analysis of thermal dehydration and hydrolysis of MgCl2·6H2O by DTA and TG

The thermal decomposition of MgCl₂·6H₂O (non-dried and partly dried) and the kinetics of the process were studied by DTA, TG, DTG, IR, X-ray diffraction and chemical analysis of Mg and Cl. The reactions which occurred in the course of the thermal analysis were identified as dehydration (in steps), thermal hydrolysis of MgCl₂·H₂O and dehydrochloridization of magnesium hydroxy chlorides. Melting of the phases MgCl₂·6H₂O, MgCl₂·4H₂O and MgCl₂ was also identified in the thermal curves. Thermal weight loss continued up to 800 °C in flowing air or nitrogen, but only up to 700 °C in static air. MgO was the end-product of thermal treatment in both cases.The kinetic parameters of the reaction, the activation energyE, pre-exponential factorA and apparent order of reactionb, were computed by several methods. The activation energy and the apparent reaction order of dehydration were found to increase with decreasing hydration number of the Mg. The dehydrochloridization process had the highest activation energy.

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Zusammenfassung Die thermische Zersetzung von MgCl₂·6H₂O (nicht und teilweise getrocknet) und die Kinetik dieses Prozesses wurden mittels DTA, TG, DTG, IR, Röntgendiffraktometrie und chemischer Analyse von Mg und Cl untersucht. Die im Verlaufe der thermischen Analyse vor sich gehenden Reaktionen sind Dehydratisierung (in Schritten), thermische Hydrolyse von MgCl₂·H₂O und Chlorwasserstoffaustritt aus Magnesiumhydroxychloriden. Das Schmelzen der Phasen MgCl₂·6H₂O, MgCl₂·4H₂O und MgCl₂ ist in den thermischen Kurven ebenfalls zu erkennen. Im Luft- und Stickstoffstrom erfolgt ein Gewichtsverlust bis 800 °C, in statischer Luftatmosphäre dagegen nur bis 700 °C. MgO war in beiden Fällen Endprodukt der thermischen Behandlung. Die kinetischen Parameter der Reaktion (AktivierungsenergieE, präexponentieller FaktorA, scheinbare Reaktionsordnungb) wurden nach verschiedenen Methoden berechnet. Aktivierungsenergie und scheinbare Reaktionsordnung der Dehydratisierung nehmen mit abnehmendem Hydratationsgrad des Mg zu. Die Chlorwasserstoffabspaltung erfordert die höchste Aktivierungsenergie.

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, , , , ( ) . : ( ), . , . 800 °C, - 700 °C. B . , . , . .

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The authors express their appreciation to Dr. Jacob Nathan and Mr. Yoetz Deutch from th Geological Survey, Jerusalem, for the use of the thermal analysis instrument and for useful discussion, and to Mrs. Sarah Erlich from the same institute, for the chemical analysis. The financial support by Everyman's University, Tel-Aviv, and by the Hebrew University of Jerusalem is acknowledged.     

Synthetic investigations in the field of the curare alkaloids

It has been shown that the compounds obtained previously corresponding in comparison to the -[4-(5-carboxymethyl-2-hydroxyphenoxy)3-methoxyphenyl]ethylamide of 4-benzyloxyphenylacetic acid have practically the same spectra and on further condensation with 3-bromo-4-hydroxy-5-methoxyphenylethylamine give an equilibrium mixture of diamide compounds. The difference in the physicochemical properties of the diphenyl esters and the diamides can be explained by steric differences. On cyclization, the diamides are converted into bis-dihydroisoquinoline compounds of the same elementary composition. The hydrochloride of 7-[2-acetoxy-5-(7-acetoxy-8-bromo-6methoxy-3, 4dihydroisoquinol-1-ylmethyl)phenoxyl)-1-(4-benzyloxybenzyl)-6-methoxy-3,4-dihydroisoquinoline, with mp 180–181° C, after saponification, intramolecular Ullman condensation, reduction, and stepwise methylation, was converted into isomeric tubocurarin iodides with mp 189–190.5° C, 164–166.5° C, 257–260.5° C, and 210–212° C, which were separated on the basis of their different solubilities in organic solvents and water.For part XII, see [1].     

Structure and M-cholinoblocking activity of chlorine derivatives of imperialine

Characteristics of the M-cholinoblocking activities of the alkaloid imperialine, three of its chlorine derivatives, and atropine have been shown. -Chloroimperialine is a highly active central mixed M_2,4-cholinoblocker, while its -isomer is predominantly a peripheral mixed M_2,4-cholinoblocker; a mixture of the - and -isomers is a central selective, and imperialine a peripheral selective, M₂-cholinoblocker.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Republic of Uzbekistan, Tashkent, fax (3712) 40 64 75. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 613–616, July–August, 1997.     

Thermal decomposition of Cu(II) Malonate

The isothermal decomposition of anhydrous Cu(II) malonate of uniform particle size has been studied at 170, 180 and 190°. Decomposition to cupric oxide takes place via the intermediate formation of 2CuCO₃.Cu(OH)₂. X-ray diffraction has been employed to identify the decomposition products. The experimental kinetic data for Cu(II) malonate decomposition are best fitted by two stages: (i) a linear process and (ii) a first-order expression. The activation energies for the two kinetic stages have been found to be 45.7 and 57.2 kcal/mole, respectively. A DTA study of Cu(II) malonate decomposition has also been made. Activation energies have been determined via analysis of the DTA curve using the Borchardt and Piloyan equations.

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Zusammenfassung Die isotherme Zersetzung von wasserfreiem Cu(II)-malonat einheitlicher Partikelgröße wurde bei Temperaturen von 170°, 180° und 190° untersucht. Die Zersetzung von Cu(II)-malonat zu Kupfer(II)-oxid erfolgt über die intermediäre Bildung von 2CuCO₃.Cu(OH)₂. Die Röntgendiffraktionstechnik wurde zur Identifizierung der Zersetzungsprodukte eingesetzt. Die Versuchsergebnisse von Cu(II)-malonat können am besten zwei kinetischen Zuständen angepaßt werden: (1) einem linearen Prozeß und (2) einem Ausdruck erster Ordnung. Die entsprechenden Aktivierungsenergien für die zwei kinetischen Zustände waren 45.7 Kcal/Mol bzw. 57.2 Kcal/Mol. Eine DTA-Untersuchung von Cu(II)-malonat wurde ebenfalls durchgeführt. Die Aktivierungsenergien wurden aus der Analyse der DTA-Kurve mittels der Gleichungen von Borchardt und Piloyan bestimmt.

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Résumé On a étudié la décomposition thermique du malonate de cuivre(II) anhydre à 170, 180 et 190°. La décomposition du malonate en CuO se produit avec formation intermédiaire de 2CuCO₃.Cu(OH)₂. Les produits de décomposition ont été identifiés par diffraction des rayons X. Les données expérimentales correspondent à deux étapes de cinétique différente: (i) un processus linéaire et (ii) une expression du premier ordre. Les énergies d'activation respectives des deux étapes cinétiques s'élèvent à 45.7 et 57.2 kcal.mol^/s-1. Le malonate de cuivre(II) a aussi été étudié par ATD. Les énergies d'activation ont été déterminées à partir de la courbe ATD en appliquant les équations de Borchardt et de Piloyan.

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(II) 170°, 180° 190°. (II) 2CuCO₃. Cu(H)₂. . (II) : (1) (2) . , , , 45,7 / 57,2 /. (II). , , .

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One of the authors (P.C.K.) is grateful to the University Grants Comission, New Delhi, for the award of a junior research fellowship. The authors are grateful to Dr. K. N. Goswami of the Physics Department, University of Jammu, for his help in the X-ray studies of the products.     

The structure of ulopterol

Conclusions A new coumarin C₁₅H₁₈O₅ with mp 141.5–142.5° C (from benzene) has been isolated from the roots and fruit ofPrangos uloptera D. C., and it has been called ulopterol. On the basis of UV, IR, NMR, and mass spectra it has been found to have the structure of 6-(2,3-dihydroxy-3-methylbutyl)-7-methoxy-coumarin and is a geometrical isomer of meranzin hydrate.Khimiya Prirodnykh Soedinenii, Vol. 6, No. 3, pp. 300–304, 1970     

Physical properties of the catalyst used for partial oxidation of anthracene to anthraquinone. II. Electron paramagnetic resonance study

Electron paramagnetic resonance studies on intermediates and final active catalyst material used for partial oxidation of anthracene to anthraquinone are reported.

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, .

     

Steady conduction of heat in prolate spheroidal systems

The steady local temperature distribution has been determined for arbitrary prolate spheroidal systems with various boundary conditions. The temperature was derived for all possible systems, such as when the temperature was kept constant on the hyperbolic surfaces and variable on the prolate spheroidal surfaces, and vice versa. In'the latter case, roots with respect to the degree of the associated Legendre function for arguments larger than unity had to be determined. Some of the presented solutions have been evaluated numerically, and the isothermal surfaces have been presented.

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Zusammenfassung Für beliebig ausgedehnte sphäroide Systeme wurde mit verschiedenen Randbedingungen eine stationäre lokale Temperaturverteilung ermittelt. Die Temperatur wurde für alle möglichen Fälle ermittelt, so auch für den Fall, in dem die Temperatur an der Hyperbeloberfläche konstant gehalten und an den ausgedehnten sphäroiden Flächen veränderlich ist bzw. umgekehrt. Für letzteren Fall mußten für Argumente größer als eins Wurzeln betreffs des Grades der zugehörigen Legendre Funktion ermittelt werden. Einige der dargestellten Lösungen wurden numerisch ermittelt und die isothermen Flächen dargestellt.

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. , . , . .

     

Thermochemistry of hydrated rare earth orthophosphates

The hydrated rare earth orthophosphates LnPO₄ ·xH₂O (Ln=La-Dy) contain zeolitic water in the structural channels, which is released reversibly up to 300°. The thermal stabilities of the hydrates depend upon the nature of the Ln atom. The dehydration temperature decreases with decreasing ionic radiusr of Ln³⁺, according to the general equation=(r–a)/b (where is the DSC and/or DTG dehydration peak temperature, anda andb are empirical constants depending on the experimental conditions).The contracting-area rate equation was valid for linearization of the isothermal vs. time plots in the range 0; 0.65. Kinetic values ofE, A, H ⁺ and S⁺ were calculated and the kinetic stabilities of the hydrates are discussed.

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Zusammenfassung Die hydratisierten Seltenerdiphosphate LnPO₄·xH₂O (Ln=La bis Dy) enthalten in Kanälen ihrer Struktur zeolithisches Wasser, das reversibel bis 300 °C abgegeben wird. Die thermische Stabilität der Hydrate hängt von der Natur des Ln ab. Die Entwässerungstemperatur sinkt mit abnehmendem Ionenradiusr der Ln3+-Ionen gemäss:=(r–a)/b (a undb sind empirische Konstanten, die von den experimentellen Bedingungen abhängen). Die isotherme Entwässerung lässt sich im Umsatzbereich 0 0,65 mit der Gleichung für kontrahierende Fläche (zweidimensionale Phasengrenzreaktion) beschreiben. Die kinetischen Grössen AktivierungsenergieE, -enthalpieH ^*, und -entropieS ^* wurden berechnet und die kinetische Stabilität der Hydrate wird diskutiert.

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LnPO4·xH2O (Ln=La-Dy) , 300°. . r =(r-)/b, 9 — , a b — , . — <0; 0,65>. , , ^* S ^* .

     

Competitive hydrogenation of binary olefin mixtures in the liquid phase

The effect of a series of alcohol solvents on the selectivity of the competitive catalytic hydrogenation of 1-hexene and 2-methyl-3-butene-2-ol on Pt/SiO₂ catalyst has been investigated. With increasing molecular mass of the alcohol, the rate of hydrogenation of 1-hexene becomes relatively preferred; the same was observed also with branched alcohols compared with those having a straight chain. Systems were found in which the degree of coating of the platinum catalyst with copper affected (or did not affect) the selectivity of the competitive hydrogenation of pairs of olefinic substrates.

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— — 1- 2--3--2- Pt/SiO₂ . 1-, . , ( ) .