Preparation and Microstructural and Textural Characterization of Single-Phase Aluminum Oxides

Conditions for the preparation of single-phase -, -, and -aluminas were determined. The structures of - and -aluminas were characterized. With the use of high-resolution electron microscopy, it was found that -Al₂O₃ particles exhibited the most developed {111} face and consisted of coherently joined domains with a pronounced platelet shape. Planar defects in the (111) plane occurred in the -Al₂O₃ particles. Microstructural differences between single-phase -Al₂O₃ and -Al₂O₃ with a defect spinel structure were revealed. It was found that the -Al₂O₃, -Al₂O₃, and -Al₂O₃ oxides are characterized by uniformly porous structures with average pore diameters of 47, 55, and 110 Å, respectively.     

Phase equilibria in the FeVO4-Fe2(MoO4)3 system

Phase équilibria have been investigated in the FeVO₄-Fe₂(MoO₄)₃ system for the whole concentration range of the components. In this system there is one compound which melts incongruently: Fe₄V₂Mo₃O₂₀. The results are presented in the form of a phase diagram.

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Zusammenfassung Phasengleichgewichte im System FeVO₄-Fe₂(MoO₄)₃ wurden über den ganzen Konzentrationsbereich der Komponenten hinweg untersucht. Eine Verbindung des Systems, Fe₄V₂Mo₃O₂₀, schmilzt inkongruent. Die Ergebnisse sind in Form eines Phasendiagramms angegeben.

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FeVO₄-Fe₂(MoO₄)₃ . Fe₄V₂Mo₃O₂₀, . .

     

Thermal decompositions of (NH4)2WSe4 and (NH4)3VS4 under normal and reduced nitrogen pressures

A method is devised by modification of the author's previous method. Thermoanalytical data are transformed to equivalent isothermal ones, and linear relations are utilized to elucidate the mechanism and the pre-exponential factor, instead of curvefitting. Advantages are illustrated by applying this method to the decomposition of polycaprolactam.

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Zusammenfassung Es wurde eine neue Methode durch Modifizierung der früheren Methode des Autors entwickelt. Bei der neuen Methode werden die thermoanalytischen Daten in isotherme umgewandelt und anstatt der Kurven-Anpassung der vorhergehenden Methode werden lineare Zusammenhänge zur Klärung des Mechanismus und des pre-exponentiellen Faktors eingesetzt. Die Vorteile der neuen Methode werden durch ihre Anwendung bei der Untersuchung der Zersetzung von Polycaprolactan veranschaulicht.

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Résumé La méthode précédemment proposée par l'auteur est modifiée. La nouvelle méthode qui est présentée transforme les données thermoanalytiques en données isothermes équivalentes et utilise des relations linéaires pour établir le mécanisme et le facteur pré-exponentiel au lieu de la méthode antérieure avec ajustement des courbes. Les avantages de cette nouvelle méthode sont illustrés en l'appliquant à la décomposition du polycaprolactane.

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, , , , , . .

     

Effect of substituents at silicon on the oxidative addition of trisubstituted silanes to [RhCl(cod)PPh3]

Summary Trisubstituted silanes, HSiR_3–n X _n (R = Me, Et, Pr or Bu; X = Cl, OEt or Ph; and n = 0–3) readily undergo oxidative addition to complex [RhCl(cod)PPh₃] (where cod = cycloocta-1,5-diene).The quantitative correlation between rate constants, k ₁, of the reaction, followed spectrophotometrically at 20 °C in benzene solutions, and the structure of tri-substituted silanes represented by stereoelectronic parameters , and E of the substituents, was established: logk ₁ = a + b + c + dE. The reaction rate is accelerated by electron-withdrawing substituents at silicon and retarded by the bulk and pd donation of nonalkyl substituents.Author to whom all correspondence should be directed.     

Untersuchungen über die diamagnetische Suszeptibilität einiger Organo (imino-oxy)silane

Diamagnetic susceptibilities of trimethyl(imino-oxy)silanes,Me ₃SiON CMeR, and dimethyldi(imino-oxy)silanes,Me ₂Si(ON CMeR)₂, containing Si–O bonds are reported. _M of these silicon compounds has been calculated theoretically from the method ofBaudet et al. and a good agreement has been obtained between the observed _M values and the corresponding calculated values. _Si in these compounds has been calculated graphically and the lower values have been explained on the basis of back-bonding to the silicon atom from the oxygen lone pair.     

Acid — Base properties of 3(5)-azido-1,2,4-triazoles

The pK_a and values of a series of 3(5)-azido-1,2,4-triazoles are correlated with the _I and _C constants according to the equation pK =_II + _CC + pK_o. The high _I values in both cases are due to the closeness of the substituent to the reaction center. The _C/_I ratio attests to different contributions of the inductive and mesomeric effects of a substituent during transmission of its effect from the 5-position to the N₁ and N₄ heteroatoms.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1288–1291, September, 1974.     

Molecular orbital calculations on the conformation of polypeptides and proteins

The conformational energy maps are computed for the lysyl and the arginyl residues with the help of the quantum-mechanical method PCILO. Because of the relatively very large number of the possible combinations of the side chain rotational angles, sub-maps are constructed only for the most common such combinations as indicated from the X-rays study of ten globular proteins. These submaps are then combined for the construction of the general conformational energy map. The comparison of the theoretically allowed and experimentally observed values of backbone dihedral angles and for the lysyl and arginyl residues in the globular proteins indicates a very satisfactory agreement among the two. These results confirm that the contour of the stable zone on the conformational energy map depends primarily on ¹ but indicate also that its fine structure is sensitive to the remaining 's in particular to ².

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Zusammenfassung Diagramme der Konformationsenergie werden für den Lysyl- sowie den Arginylrest mit Hilfe der quantenmechanischen PCILO-Methode berechnet. Wegen der großen Zahl möglicher Kombinationen der Rotationswinkel der Seitenketten werden Teildiagramme nur für die wichtigsten derartigen Kombinationen, die bei Untersuchungen nach der Röntgenstrahlmethode an zehn globulären Proteinen gefunden wurden, konstruiert. Diese Teildiagramme werden dann zum Gesamtdiagramm der Konformationsenergie kombiniert. Die Übereinstimmung zwischen experimentellen und theoretisch erlaubten Winkeln und der Hauptkette und den Lysyl- und Arginylresten ist sehr zufriedenstellend. Diese Ergebnisse bestätigen, daß der stabile Bereich des Diagramms der Konformationsenergie hauptsächlich von ¹ abhängt; sie zeigen aber auch, daß seine genaue Struktur von den übrigen -Werten beeinflußt wird, insbesondere von ².

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Résumé Les cartes d'énergie conformationelle des résidus lysyle et arginyle sont construites à l'aide de la méthode PCILO de la Chimie Quantique. A cause du nombre très élevé des combinaisons possibles des angles rotationnels de la chaîne latérale, des sous-cartes sont construites pour les plus fréquentes seulement de ces combinaisons (selon les indications de l'étude aux rayons X de dix protéines globulaires). Ces sous-cartes sont ensuite combinées pour la construction de la carte générale d'énergie conformationnelle. La comparaison des valeurs théoriques et expérimentales des angles et de la chaîne principale pour les résidus lysyle et arginyle des protéines indique un accord très satisfaisant entre les deux. Ces résultats confirment que le contour de la zone stable sur la carte d'énergie conformationnelle est déterminé principalement par la valeur de ₁ mais indiquent aussi que la structure fine de cette zone est sensible aux valeurs des supérieurs, en particulier de ².

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This work was supported by grant n 67-00-532 of the Délégation Générale à la Recherche Scientifique et Technique (Comité de Biologie Moléculaire).     

Properties of χ-alumina as related to catalysis

-Alumina was synthesized by thermal decomposition of aluminium(III) isopropoxide, and its properties were investigated. The change in its surface area with increasing calcination temperature resembled that of -alumina. Both aluminas had the same acid strength, and their activities in isomerization of 1-butene were the same. -Alumina as a support for molybdenum catalyst in the epoxidation of allyl alcohol also behavedin the same manner as -alumina. Thus -alumina has almost the same catalytic properties as -alumina.     

Upper limits of magnetic anisotropy of molecule with closed electron shell

Two simple upper limits have been established for the anisotropy of magnetic susceptibility of linear molecules with closed electron shells; these can be used to estimate the top limit on magnetic anisotropy of a molecule = – if its mean magnetic susceptibility is known, without any information whatever on the electronic wave function. The first of these limits is valid for the magnetic anisotropy of the ground electronic state X¹, and the second is valid for any ¹ state, including the excited state. The application of these limits to the evaluation of magnetic anisotropy is illustrated in the examples of the molecules of CO₂, FCCF, HCCF, FCN, LiH, and the excited state of the H₂ molecule. It is shown that these limits are useful for revealing cases of internal contradictions (or error) in individual values of magnetic anisotropy, including very rough values obtained in calculations of the magnetic properties of molecules in a limited basis set.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 24, No. 2, pp. 143–149, March–April, 1988.     

Microcalorimetric and FT-IR spectroscopic study of benzene adsorption on α-Fe2O3 and γ-Al2O3

The adsorption of benzene at room temperature on-Fe₂O₃ and on-Al₂O₃ powders was investigated by heat-flow microcalorimetry and FT-IR spectroscopy.On iron oxide a chemisorption-combustion step is followed by a highly exothermic adsorption step, reversible at r.t.Few combustion centres exist on alumina if reducing pretreatment is not carried out. Two reversible adsorption steps are subsequently observed and were interpreted as due to interaction with two different types of surface hydroxy groups.

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Zusammenfassung Die Adsorption von Benzol an-Fe₂O₃- und-Al₂O₃-Pulvern bei Raumtemperatur wurde mittels Wärmefluß-Kalorimetrie und FT-IR-Spektroskopie untersucht. Beim Eisenoxid folgt auf dem Chemisorptions-Verbrennungs-Schritt ein bei Raumtemperatur reversibler, stark exothermer Adsorptionsschritt. Aluminiumoxid besitzt einige Oxydationszentren, sofern keine reduzierende Vorbehandlung erfolgt. Zwei aufeinanderfolgende reversible Adsorptionsschritte treten auf und werden der Wechselwirkung mit zwei verschiedenen Typen von Oberflächenhydroxylgruppen zugeschrieben.

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-Fe₂O₃ -l₂₃. - , . , , . , .

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This work was supported by the CNR Progetto Finalizzato Chimica Fine e Secondaria. Prof. Vincenzo Lorenzelli is gratefully thanked for the kind loan of instrumental facilities and helpful discussions.     

Isomerization of unsaturated compounds on Pd/Al2O3 in the presence of additives

Studies of the effect of zinc chloride and aluminium additives on the activity of a Pd/Al₂O₃ catalyst (5 wt.%Pd) in the isomerization of heptene-1, allylbenzene,p-allylphenol and 4-allyl-2-methoxyphenol (eugenol) indicate that the rate and selectivity of isomerization depend on the sequence of addition of salts and reagent to the catalytic system. The simultaneous addition of ZnCl₂ or AlCl₃ with olefin, produces a 2–3 fold increase in the isomer yield compared to ethanol.

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Pd/Al₂O₃- (5 .% Pd) -1, , -, 4--2- (). , . ZnCl₂ AlCl₃ 2–3 .

     

Order and disorder in mixed metal linear chains: The homo and heterobimetallic EDTA (M(H2O)4OIOII)[M′(EDTA)] · 6H2O complexes (M = Mg,Mn, Co,Zn and Ni; M′ = Co,Ni, Cu and Zn)

Summary Polymetallic solid solutions of the ethylenediaminetetracetic acid (EDTA) and six divalent metal ions exist in the range: MgMnCoZnNiCu(EDTA) · 6H₂O where + + + + + =2, 01, 0,,2, 0, 1.This type of structure is characterized by the presence of two different octahedral carboxylate-bridged coordination sites forming infinite zig-zag chains. Visible and i.r. spectra and t.g.a. analysis show that there is occupational preference for the two coordination sites in the crystalline structure.Due to this preference, and also to the structural features, the heterobimetallic MM(EDTA) · 6H₂O compounds constitute a structurally new class of materials which can be described as ordered alternating-heterobimetallic polymeric coordination complexes.     

Triterpene glycosides from Pulsatilla chinensis

Four triterpene glycosides were isolated from the roots of Pulsatilla chinensis (Bunge) Regel (Ranunculaceae). Two new glycosides, chinensiosides A (1a) and B (2), were identified as 3-O-[-L-rhamnopyranosyl-(12)--L-arabinopyranosyl]-28-O-[-L-rhamnopyranosyl-(14)--D-glucopyranosyl-(16)--D-glucopyranosyl]-3,23-dihydroxylup-20(29)-en-28-oic acid and 3-O-{-L-rhamnopyranosyl-(12)-[-D-glucopyranosyl-(14)]--L-arabinopyranosyl}-28-O-[-L-rhamnopyranosyl-(14)--D-glucopyranosyl-(16)--D-glucopyranosyl]-3,23-dihydroxylup-20(29)-en-28-oic acid. The other two glycosides were identified as previously known hederasaponin C (3) from Hedera helix and glycoside III (4) from Pulsatilla cernua.     

Structure and Magnetic Properties of Solid Solutions of Molecular Magnetics Based on Ni(II) and Co(II) Complexes with Nitroxyl Radicals

Ni(II) and Co(II) complexes with deprotonated paramagnetic enaminoketones 4(3,3,3trifluorine2oxopropylidene) 2,2,5,5tetramethyl3imidazolidine1oxyl (L) and 4(3,3,3trifluorine1chlorine2oxopropylidene)2,2,5,5tetramethyl3imidazolidine1oxyl (L¹) and alcohols are shown to form continuous solid solutions Ni_xCo_1-xL₂(C₂H₅OH)₂ and Ni_xCo_1-xL₂ ¹(CH₃OH)₂. Single crystal Xray diffraction analysis showed that concentration variation practically does not affect the structural characteristics of the solid solutions. Distinguishing features if the magnetic behavior of Ni_xCo_1-xL₂ · (C₂H₅OH)₂ and Ni_xCo_1-xL₂ ¹(CH₃OH)₂ are the antiferromagnetic interaction of the moments of the nickel and cobalt sublattices inside the polymeric layers and the antiferromagnetic nature of interlayer interaction of the magnetic moments.     

Catalysts for metathesis of olefins obtained through [Mo3O4(C2O4)3 (H2O)3]2? coordinated to γ-Al2O3

New highly active catalysts for the metathesis of olefins have been obtained through the interaction of [Mo₃O₄ (C₂O₄)₃ (H₂O)₃]^2– anion with Al₂O₃ surface and further activation in H₂ or CO atmosphere.

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[Mo₃O₄ (C₂O₄)₃ (H₂O)₃]^2– Al₂O₃ H₂ CO .

     

Kinetics of carbonyl triplet reactions in water

The presence of urea during the gelling of AlPO₄–Al₂O₃ catalysts (AlPO₄/Al₂O₃ weight ratio =3) has been studied with respect to its effect on the porous texture and surface acidity of the resulting gels. An increase in pore volume and mean pore radius with no modification in surface acidity is found when the AlPO₄–Al₂O₃ catalyst is modified by the addition of 5 mol% urea in the AlPO₄ solution.

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, AlPO₄/Al₂O₃ ( AlPO₄/Al₂O₃=3) . , AlPO₄/Al₂O₃ 5 .% AlPO₄ - .

     

Etude cinetique de la decomposition thermique de l'anhydride chromique depose sur alumine

Résumé On présente les résultats obtenus dans l'évaluation des paramètres cinétiques de la réaction de décomposition thermique de l'anhydride chromique déposé sur de l'alumine. Grâce aux données sur l'influence de la teneur en anhydride chromique et de la vitesse de chauffage sur les paramètres cinétiques, on obtient des conclusions sur les conditions d'obtention du catalyseur Cr₂O₃/Al₂O₃.

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Results obtained in the determination of the kinetic parameters of the thermal decomposition of CrO₃ on alumina are presented. The experimental data on the effects of CrO₃ concentration and heating rate on the kinetic parameters are used to draw conclusions on the conditions of preparation of Cr₂O₃/Al₂O₃ catalysts.

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Zusammenfassung Die bei der Bestimmung der kinetischen Parameter der thermischen Zersetzungsreaktion von CrO₃ auf Aluminiumoxid-Träger erhaltenen Ergebnisse werden erörtert. Aus den Versuchsangaben über den Einfluß der Cr₂O₃-Konzentration und die Aufheizgeschwindigkeit auf die kinetischen Parameter werden Schlüsse bezüglich der Herstellungsbedingungen der Cr₂O₃/Al₂O₃-Katalysatoren gezogen.

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, Cr₃ . Cr₂O₃ , Cr₂O₃/l₂O₃.

     

PVT properties of concentrated electrolytes. VI. The speed of sound and apparent molal compressibilities of NaCl,Na2SO4, MgCl2, and MgSO4 solutions from 0 to 100°C

The sound velocities of aqueous NaCl, Na₂SO₄, MgCl₂, and MgSO₄ solutions were measured from 25 to 95°C in 10^o intervals from dilute to saturated solutions. The results were combined with our earlier data and fitted to functions of molality and temperature to within ±0.4 m-sec^–1. The adiabatic compressibilities _S were calculated from sound speeds and used to calculate the adiabatic apparent molal compressibilities . Isothermal compressibilities and isothermal apparent molal compressibilities were calculated from _S using literature values for the expansibilities and heat capacities. The values of were extrapolated to infinite dilution using the Debye-Huckel limiting law to determine partial molal compressibilities. The apparent molal compressibilities were fitted to Pitzer's equations. The Pitzer parameters for the concentration dependence of were determined as a function of temperature. Correlations of and V at various temperatures were found for the electrolytes.     

Chromium (III) trihalide complexes of 4-aminobenzophenone

Summary The following chromium(III) complexes of 4-aminobenzophenone have been prepared and investigated by infrared and electronic spectra and magnetic susceptibility measurements: CrCl₃L, CrCl₃L₂ (pink and brown), CrCl₃L₃, CrCl₃L₆, CrBr₃L₂, CrBr₃L₃, CrBr₃L₄, CrBr₃L₆, CrBr₃L₇ and CrBr₃L₈. The CrBr₃ complexes were each isolated in a yellow and a red form. In the red CrBr₃ and in the yellow CrBr₃L₂ the ligand is bonded through the amine nitrogen. The CrCl₃ complexes are probably molecular complexes.     

A TG/DTA/MS study of the oxidation of nickel sulphide

The oxidative behaviour of synthetic millerite (Ni_0.994S) has been studied by TG and DTA in a dynamic oxygen atmosphere (0.2 l min^–1) over the temperature range 20–1000° (heating rate 10° min^–1). EGA was carried out by a coupled mass spectrometer. The reaction products at various intermediate temperatures were characterized by X-ray powder diffractometry. A reaction sequence has been deduced, in which in the temperature range 550–700° complete oxidation of Ni_0.994S had occurred with the formation of NiSO₄, Ni₃S₂, NiO and possibly-Ni₇S₆. Between 700–800°, NiSO₄ continued to be formed, whilst Ni₃S₂ and-Ni₇S₆ were oxidised. Above 800°, NiSO₄ decomposed to NiO, the latter being the only species evident above 800°.

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Zusammenfassung Das oxidative Verhalten von synthetischem Millerit (Ni_0.994S) wurde mittels TG und DTA in einer dynamischen Sauerstoffatmosphäre (0.2 l min^–1) im Temperaturbereich von 20 bis 1000° (Aufheizgeschwindigkeit 10° min^–1) untersucht. EGA wurde mit einem gekoppelten Massenspektrometer durchgeführt. Die Reaktionsprodukte bei verschiedenen Zwischentemperaturen wurden mittels Röntgen-Pulver-Diffraktometrie charakterisiert. Eine Reaktionssequenz wurde abgeleitet, nach welcher im Temperaturbereich von 550 bis 700° die vollständige Oxidierung von Ni_0.994S unter Bildung von NiSO₄, Ni₃S₂, NiO und wahrscheinlich-Ni₇S₆ vor sich geht. Zwischen 700 und 800° wird NiSO₄ auch weiterhin gebildet, während Ni₇S₂ und-Ni₇S₆ oxidiert wurden. Oberhalb von 800° wurde NiSO₄ zu NiO zersetzt, das einzig nachweisbare Produkt oberhalb von 800°.

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Résumé On a étudié l'oxydation de la millérite synthétique (Ni_0.994S) par TG et ATD en atmosphère dynamique d'oxygène (0,2 1· min^–1) et dans l'intervalle de températures allant de 20 à 1000° (vitesse de chauffage 10°· min^–1). L'analyse des gaz émis s'est effectuée avec un spectromètre de masse couplé. Les produits de réaction ont été caractérisés à diverses températures intermédiaires par diffractométrie de poudre aux rayons X. On a déduit une séquence de réactions, selon laquelle, dans l'intervalle compris entre 550 et 700°, l'oxydation complète de Ni_0.994S a lieu avec formation de NiSO₄, Ni₃S₂, NiO et probablement-Ni₇S₆. Entre 700 et 800°, la formation de NiSO₄ se poursuit tandis que Ni₃S₂ et-Ni₇S₆ sont oxydés. Au-dessus de 800°, NiSO₄ se décompose en NiO qui constitue l'unique composé qui puisse être décelé au-dessus de 800°.

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(Ni_0.994S) (0,2 . ^–1) 20–1000° 10° ^–1. - . . 550–700° Ni_0.994S NiSO₄, Ni₃S₂, NiO -Ni₇S₆. 700–800° , Ni₃S₂ -Ni₇S₆ . 800° NiO, 800°.

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We wish to thank Dr. T. Kennedy for useful discussions and Messrs. B. Sturman, I. Twaddle, K. Oliver and W. Thomas for technical assistance.