A study of the thermal stability of hexaaziridinylcyclotriphosphazene,N3P3(NC2H4)6

Thermal behaviour of N₃P₃Az₆ up to 300 °C was studied by means of TG, DTG and DTA methods. It was found that, when heated in small amounts, N₃P₃Az₆ does not undergo decomposition even up to 300 °C. It rather melts at about 150 °C and then polymerizes at higher temperatures with the formation of an insoluble glassy substance. The proposed polymerization mechanism assumes the opening of aziridine rings and combination of the N₃P₃Az₆ units into a three-dimensional structure. The heating of larger amounts of N₃P₃Az₆ leads to its decomposition, due to the considerable amount of heat evolved during the polymerization.

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Zusammenfassung Mittels TG, DTG and DTA wurde das thermische Verhalten von N₃P₃Az₆ bis 300 °C untersucht. In geringen Mengen erhitzt erleidet N₃P₃Az₆ bis 300 °C keine Zersetzung. Es schmilzt bei etwa 150 °C und polymerisiert bei höheren Temperaturen zu einer unlöslichen glasigen Substanz. Dem angenommenen Mechanismus nach werden die Aziridinringe geöffnet, die N₃P₃Az₆-Einheiten schließen sich unter Bildung einer dreidimensionalen Struktur zusammen. Beim Erhitzen von größeren Mengen an N₃P₃Az₆ wird die Verbindung wegen der bei der Polymerisation entstehenden beträchtlichen Wärme zersetzt.

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, (N₃P₃Az₆) 300°. 300°. 150° , . (N₃P₃Az₆) . (N₃P₃Az₆) , , .

     

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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. , . , . .

     

Thermal characterization of bismaleimide blends

4,4-bismaleimidophenyl methane (BM) and 3,3-bismaleimidophenyl sulfone (BS) were blended in solution using weight ratios 31 (MS31), 21 (MS21), 11 (MS11), 12 (MS12) and 13 (MS13). Chain extended bismaleimide resins were also prepared by treating BS/BM with 4,4-diaminodiphenyl ether in molar ratios of 10.3 (BM-E and BS-E resins). These resins were also blended with bismaleimides and the curing characteristics were evaluated by differential scanning calorimetry. Increase in BM content in BMBS blends or increase in chain extended bismaleimide content in BM-EBS or BS-E BM blends resulted in a reduction of melting and curing temperatures. Indication about the extent of cross-linking was obtained from solubility measurements (in DMF) of isothermally cured resins (180 °C, lh and 220 °C, lh in an air oven). Thermogravimetric analysis of samples isothermally cured at 180 °C and 220 °C (lh each) was carried out in nitrogen atmosphere. Improvement in thermal stability of chain extended bismaleimides was observed on blending.

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Zusammenfassung 4,4-Bismalimidophenyl-methan (BM) und 3,3-Bismalimidophenyl-sulfon (BS) wurden in Lösung in den Gewichtsverhältnissen 31 (MS31), 21 (MS21), 11 (MS11), 12 (MS12) und 13 (MS13) gemischt. Auch kettenpolymerisierten Bismalimid-Harze wurden durch Behandlung von BS/BM mit Diaminodiphenylether im Molverhältnis 10,3 dargestellt (BM-E- und BS-E-Harze). Die Kennwerte der Aushärtung von Mischungen dieser Harze mit den Bismalimiden wurden mittels DSC ermittelt. Eine Erhöhung des BM-Gehaltes in den BM BS-Mischungen oder des Gehaltes der BM-E BS oder BS-E-Mischungen an kettenpolymerisierten Bismalimiden führt zu einer Erniedrigung der Schmelz- und Aushärtetemperaturen. Hinweise über den Vernetzungsgrad wurden aus Löslichkeitsmessungen (in DMF) von Isotherm (je 1 Stunde bei 180 und 220 °C in Luft) gehärteten Harzen erhalten. Die thermogravimetrische Analyse der Isotherm bei 180 bzw. 220 °C 1 Stunde ausgehärteten Proben wurde in Stickstoffatmosphäre ausgeführt. Die thermische Stabilität der Bismalimide wird durch Verschneiden verbessert.

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4,4-- () 3,3-- () 31 (MC 31), 21 (MC 21), 11 (MC 11), 12 (MC 12) 13 (MC13). - / 4,4- 10,3 ( - C-). - . - - - - , . ( 1 180 220°) . . - .

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The financial assistance provided by Department of Science and Technology is gratefully acknowledged.     

Catalytic conversion of alcohols, IX. Effect of temperature on the direction of elimination of water from a tertiary alcohol

The amount of 1-alkene formed by the dehydration of 2-methyl-2-butanol with several metal oxide catalysts parallels the temperature dependence of acetate pyrolysis where the amount of 2-methyl-1-butene increases with increasing temperature.

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1-, 2--2- , , 2--1- .

     

X-ray diffraction studies of platinum-alumina catalysts in a high-temperature chamber

X-ray diffraction studies of platinum-alumina catalysts in a high-temperature chamber have revealed that for the catalysts obtained by the reduction of preactivated samples, no complete reduction of platinum takes place.

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, , , .

     

Mechanism of reactions in mixtures of calcium polyphosphate with apatite and accompanying minerals during heating

The thermal interaction of Kovdor apatite, calcite, dolomite and forsterite with calcium polyphosphate up to 1200 °C were studied by chemical, thermal (under dynamic and quasiisothermal and isobaric conditions), X-ray, electronmicroscopic and chromatographic methods. It was found that the accompanying minerals of apatite react with calcium polyphosphate at lower temperature in comparison with apatite, complicating the process of thermal defluorination of papatite.

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Zusammenfassung Die thermische Wechselwirkung von Kovdor-Apatit, Calcit, Dolomit und Forsterit mit Calciumpolyphosphat bei Temperaturen bis 1200 °C wurde durch chemische, thermische (unter dynamischen, quasiisothermen und isobaren Bedingungen), röntgenographische, elektronenmikroskopische und chromatographische Methoden untersucht. Es wurde festgestellt, daß die Begleitminerale des Apatits im Vergleich zum Apatit selbst bei niedrigeren Temperaturen mit Calciumpolyphosphat reagieren und so den Prozeß der thermischen Entfluorierung von Apatit komplizieren.

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, , 1200° , ( ), , - . , , .

     

Photoinduced oxygen adsorption of AgBr crystals at 77 K

Photoinduced adsorption (PIA) of oxygen molecules on AgBr films at 77 K has been experimentally observed and investigated. Lifetimes of PIA centers and desorption activation energies of O₂ molecules have been determined. The process is suggested to compete with the ionic step of AgBr photolysis.

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- () - AgBr 77 K. - O₂. , , - AgBr.

     

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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— . -.

     

A desk computer program for the calculation of rate constants

A desk computer program has been written in BASIC programming language to optimize the values of rate constants determined from kinetic measurements of time and concentration data. The program is capable of the simultaneous refinement of a maximum of 5 rate constants. A FORTRAN version using the Gear method is also available.

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, BASIC , . 5 . FORTRAN .

     

Autocatalysis in the formose reaction

It has been found that carbohydrates naturally present in ppm quantities in paraformaldehyde are the cause of the autocatalysis in the formose reaction of paraformaldehyde solutions. Paraformaldehyde sublimed into Ca(OH)₂ suspension was not transformed to sugars by formose reaction, only to methanol and formate by Cannizzaro reaction. A minute trace of glycolaldehyde — 3 ppm — was sufficient to initiate conventional autocatalysis. A formose reaction scheme in which formaldehyde reacts only with sugars by aldol condensation but not with itself is proposed.

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, , .. . , Ca(OH)₂, , , . — 3 .. — . , , .

     

Thermal decomposition of peroxypropionyl nitrate: Kinetics of the formation of nitrogenous products

The Arrhenius expression for reaction 1, CH₃CH₂COO₂NO₂CH₃CH₂COO₂+NO₂, has been determined to be k=2×10¹⁵ exp (–12800/T)·s^–1. The free radical mechanism is the exclusive thermal decomposition mechanism of PPN. The main nitrogenous decomposition products of pure PPN are ethyl nitrate, nitrogen dioxide and methyl nitrate. In the presence of NO, ethyl nitrite is the major organitrogen product.

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CH₃CH₂COO₂NO₂CH₃CH₂COO₂+NO₂ : k=2·10¹⁵exp (–12800/T) ^–1. () - . , . NO .

     

Reaction routes for hydrogenation of acetylene-ethylene mixtures using a double labelling method

Hydrogenation of C₂H₂:C₂H₄ mixtures using a double labelling method has been studied. Both in the presence and absence of ethylene the rate of acetylene hydrogenation on its partial pressure proceeds through a maximum and the rate is higher when ethylene is added. Using¹⁴C–C₂H₂ it was demonstrated that at low acetylene partial pressures the main route of acetylene hydrogenation was the formation of ethane and C₄ hydrocarbons. Using¹⁴C–C₂H₄ it was also shown that at certain acetylene partial pressures the formation of ethane from ethylene completely ceased. Different surface species are suggested and a reaction mechanism is proposed.

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C₂H₂:C₂H₄, . , , . C¹⁴–C₂H₂, , C₄. C¹⁴–C₂H₄, , . .

     

Rapid analysis of dosage forms of some pharmaceuticals by nonaqueous thermometric titrimetry

The use of the technique of solution thermochemistry is proposed for the rapid assay for quality control and quality assurance of dosage amounts of some ethical formulations of some antimalarial drugs. The active ingredients are chloroquine, hydroxychloroquine, dapsone, proguanil hydrochloride, and pyrimethamine.Assay is done without the separation of the excipients and without isolation or derivatisation of the analytes. The titrations are done in glacial acetic acid and utilise the catalysed hydrolysis of acetic anhydride by perchloric acid to indicate the endpoint of the reactions.The time taken for a typical assay, of a typical dosage amount is about 3–5 minutes. The reproducibility is of the order of 1% for the milligramme amounts of analyte present in the dosage amounts of the drugs.

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Zusammenfassung Es wird die Anwendung eines lösungsthermochemischen Verfahrens zu Schnellbestimmungen bei der Qualitätskontrolle und — sicherung von Wirkstoffeinsatzmengen einiger rezeptpflichtiger Präparate von einigen antimalarischen Arzneimitteln empfohlen. Die aktiven Bestandteile sind Chloroquin, Hydroxychloroquin, Dapson, Proguanilhydrochlorid und Pyrimethamin.Die Bestimmungen werden ohne jegliche Abtrennung der Bindestoffe und ohne Isolierung oder Derivatisierung der zu bestimmenden Substanzen durchgeführt. Die Titrierungen werden in Eisessig durchgeführt und bedienen sich der katalytischen Hydrolyse von Essigsäureanhydrid durch Perchlorsäure als Endpunktindikation der Reaktion.Die Dauer für eine typische Probe bei einer typischen Wirkstoffmenge beträgt etwa 3–5 Minuten. Die Reproduzierbarkeit liegt in der Größenordnung von 1% für Milligrammengen der zu analysierenden Stoffe im Arzneimittel.

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. , , , . - . . 3–5 . 1% , .

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We acknowledge the Nigerian Government for the provision of a grant to one of us (S.I.A.). We acknowledge the following for the gifts of samples of the authentic drugs and the tablets assayed in this work: Imperial Chemical Industries plc; May and Baker plc; Winthrop Laboratories plc; Wellcome Foundation (Medical Division).     

Possibilities of applying the piloyan method of determination of decomposition activation energies in the differential thermal analysis of polynitroaromatic compounds and their derivatives

Piloyan activation energiesE as well as initals of exothermT _D of sevenN-monoalkyl and fiveN,N-dialkyl-2,4-dinitroanilines were determined. Relationships were found between the T_D values and R_f factors as well asE values and those R_M functions and also theET _D ^–1 term and R_M functions.

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Zusammenfassung Die AktivierungsenergienE nach Piloyan sowie die Anfangswerte der ExothermenT _D wurden für siebenN-Monoalkyl- und fünfN,N-Dialkyl-2,4-dinitroaniline bestimmt. Die Zusammenhänge zwischen denT _D-Werten und den papierchromatographischenR _f-Faktoren der gemessenen Dinitroaniline wurden abgeleitet und erörtert. Desgleichen wurden auch die Zusammenhänge zwischen denE-Werten und denR _M-Funktionen der Papierchromatographie abgeleitet und erörtert. Auch zwischen dem AusdruckE ·T _D ^–1 und denR _M-Funktionen wurde ein Zusammenhang gefunden.

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Résumé On a déterminé les températures initialesT _D de l'effet exothermique ainsi que les énergies d'activationE d'après la méthode de Piloyan, de sept N-mono alcoyl et cinqN,N-dialcoyl-2, 4-dinitroanilines. Une corrélation entre les valeursT _D et les facteursR _f de la Chromatographie sur papier des dinitroanilines étudiées a été trouvée et discutée, ainsi qu'entre les valeursE et les fonctionsR _M de la Chromatographie sur papier. Une relation entre le termeE ·T _D ^–1 et les fonctionsR _M a également été trouvée.

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E T _D N- N,N- -2,4- . _D R _f , E R _M. E. _D ^–1 R _M.

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The authors would like to thank Mrs. Anna Collàkovà for careful DTA measurements, and Dr. Ladislav Smolka for help in treatment of the measured results with the Wang 600 computer.     

Mechanism of catalysis and factors responsible for oxide catalyst activity in deep oxidation reactions

A general scheme for the deep oxidation mechanism on oxide catalysts including stepwise and concerted mechanisms as well as their mutual transformations is suggested. The principal factor responsible for the activity in the concerted mechanism region is the rate of oxygen binding. For the stepwise mechanism the main factor is the rate of catalyst interaction with oxidizable reactant.

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, . , . .

     

Mechanism of NO adsorption and decomposition on ruthenium catalysts

Thermal desorption and IR spectroscopic studies of NO adsorption on disperse Ru-black and Ru/Al₂O₃ catalysts have revealed that NO is adsorbed as a surface nitrosyl, nitrite and nitrate complex, the stability of which depends on the temperature. A mechanism for the interaction of adsorbed NO with Ru catalysts is suggested.

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NO Ru Ru/Al₂O₃ , NO , , . (II) .

     

Ba(OH)2 as catalyst in organic reactions, III. The structure of adsorbed ylids

The nature of adsorbed sulfonium and phosphonate ylids on a new barium hydroxide catalyst (C-200) is analyzed by IR. The catalytic activity of C-200 in solid-liquid phase transfer conditions is explained by these IR studies.

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(C-200) . C-200 - .

     

Catalytic reaction of methane with carbon dioxide

High activities and selectivities of Ni on SiO₂ catalysts producing CO in the reaction of CH₄ with CO₂, have been obtained at relatively low temperatures. These aspects are considerably different from the activities or selectivities of other catalysts, and have been explained by assuming that the Ni on SiO₂ catalyst markedly suppresses carbon deposition.

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CO Ni SiO₂ CH₄ CO₂. , Ni SiO₂.

     

Oxidative dehydrogenation of n-butane IV. Kinetic and catalytic activity of copper oxide

Copper oxide is moderately active and selective in the oxidative dehydrogenation of n-butane. Selectivity to C₄ olefin is almost constant in the range of 200–520°C. The apparent activation energy determined between 200 and 360°C was 18.8 kcal/mol, and 9.2 kcal/mol at higher temperatures.

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-. C₄ 200–520°C. 200–360°C 18,8 /, 9,2 /.

     

Systemes metaux alcalins-oxygene

Résumé Le comportement thermique du monooxyde de césium Cs₂O a été déterminé par analyse thermique différentielle, thermogravimétrie et diffraction X. L'utilisation de différents matériaux pour contenir ce produit a été nécessaire pour cerner les phénomènes propres à cet oxyde. On trouve la température de fusion de Cs₂O=495±5° et sa pression de vapeur égale à 10^–4 Torr à 240°. Aucune transformation allotropique n'est mise en évidence.

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The thermal behaviour of cesium monoxide (Cs₂O) was determined by differential thermal analysis, thermogravimetry and X-ray diffraction. The use of several materials as sample holders was necessary to clarify the properties of this oxide. The melting point of Cs₂O was found to be 495±5°, and its vapour pressure equal to 10^–4 torr at 240°. No allotropic transformation was observed.

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Zusammenfassung Es wird über die DTA, TG und röntgenographische Untersuchung des Caesium monoxyds berichtet. Verschiedene Materien als Probenbehälter wurden herangezogen damit die dem Oxyd eigene Eigenschaften klar festgelegt werden können. Der Schmelzpunkt von Cs₂O liegt bei 495±5°, der Dampfdruck beträgt 10^–4 Torr bei 240°. Es fand keine allotrope Umwandlung statt.

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Cs₂O , . , , . , 495±5 °C, 10^–4 240 °. .