Effect of preliminary mechanical activation on the behaviour of orthorhombic lead dioxide

The thermal behaviour of mechanically activated-PbO₂ was studied. Dry grinding led to the mechanochemical decomposition of this phase into a-PbO₂ and Pb₃O₄ mixture. In contrast, wet grinding prior to the mechanochemical decomposition caused significant changes in the thermal decomposition temperature and an increase in the intensity of the exothermic effect at ca. 200 C, which is associated with structural changes and a partial reduction of Pb(IV) to Pb(II). Throughout the exotherm, the crystallinity of-PbO₂ increased and the cell dimensionb decreased.

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Zusammenfassung Es wurde das thermische Verhalten von mechanisch aktiviertem-PbO₂ untersucht. Trockenmahlen fürt bei der mechanochemischen Zersetzung dieser Phase zu einem Gemisch von Pb₃O₄ und-Pb₃O₄. Im Gegensatz dazu führt ein der mechanochemischen Zersetzung vorangehendes Feuchtmahlen zu Veränderungen der Zersetzungstemperatur und zu einer Verstärkung der Intensität des exothermen Effektes bei ca. 200 C, der von strukturellen Veränderungen und einer teilweisen Reduktion von Pb(IV) zu Pb(II) begleitet wird. Beim Anwachsen der Kristallinität von-PbO₂ verringert sich die Gitterkonstanteb.

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-PbO₂. -PbO_x Pb₃O₄. , , - , 200, . -PbO₂ b.

     

Studies on the characteristics of the isomers of hexachlorocyclohexane (HCCH) by thermogravimetry

A new method of determination of HCCH isomers by thermogravimetry is described. The thermal changes of the isomers, the decomposition characteristics and the parameters for identification are discussed.

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Zusammenfassung Eine neue Methode der Bestimmung von HCCH-Isomeren durch Thermogravimetrie wird beschrieben. Die thermischen Änderungen der Isomere, die Zersetzungscharakteristika und die Identifizierungsparameter werden erörtert.

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Résumé On décrit une nouvelle méthode de détermination des isomères HCCH par thermogravimétrie. On discute les modifications thermiques des isomères, les caractéristiques de décomposition et les paramètres d'identification.

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. , .

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We are grateful to Dr. B. L. Amla, Director of this Institute, for his encoragement, and to Shri Hanumantha Rao Judav for his assistance.     

Gas phase hydrogenation of m-xylene on palladium catalysts

Gas phase hydrogenation of m-xylene on palladium supported catalysts was studied and compared with the hydrogenation of o-xylene. The modification in the stereoselectivity of palladium due to an increase in the acidity of the support is explained in terms of an increased residence time of the reactive species on the active surface, leading to a product composition closer to that predicted by thermodynamics.

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- -. , , .

     

Cobalt(III) dicarboxylato bis-ethylenediamine nitrates: Preparation and characterization by thermal analysis and other analytical methods

Compounds with the general formulacis ortrans-[Coen ₂ (RCOO)₂]NO₃ were prepared by modifications of known procedures; R was H, CH₃, C₂H₅ or C₃H₇, anden was ethylenediamine. The compounds were characterized by TLC and UV-Vis spectrophotometry, and their thermal behaviour was examined via TG and DTA, and via IR spectra on heated samples.The thermal stabilities are discussed in terms of the strengths of the bonds in the solids [1] and steric hindrance; the thermal decompositions are described with the aid of hypothesized intermediates and IR spectra.Reaction steps are identified and the thermal stability sequence is discussed: thecis compounds are less stable than the correspondingtrans compounds, due to the lower reticulation effect; the sequence of thecis compounds is the reverse of the sequence of carboxylate ion basicity, while the sequence displalyed by thetrans compounds can be interpreted in terms of solid lattice stabilization.

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Zusammenfassung Unter Durchführung einiger Abänderungen des bekannten Verfahrens wurden Verbindungen der allgemeinen Formel conf-Co[en₂(RCOO)₂]NO₃ hergestellt. Der AlkylrestR war H, CH₃, C₂H₅, C₃H₇ unden war Ethylendiamin. Die Verbidungen mitconf=cis odertrans wurden mittels TLC und UV-Spektrophotometrie charakterisiert. Ihr thermisches Verhalten wurdeanhand von TG, DTA und IR-Spektren von erhitzten Proben untersucht. Die thermische Stabilität wurde untersucht und in Abhängigkeit von Bindungsstärke und sterischer Behinderung diskutirt; weiterhin wurden die thermischen Zersetzungen mit Hilfe angenommener Intermediäre und deren IR-Spektren beschrieben. Die Reaktionsschritte wurden identifiziert und eine Stabilitätsreihe aufgestellt und diskutiert: cis-Verbindungen erwiesen sich als instabiler als die entsprechenden trans-Verbindungen, was einem geringeren Vernetzungseffekt zuzuschreiben ist; Die Reihenfolge folgt im Falle voncis dem Reziproken der Carboxylationenbasizität, während die Reihenfolge im Falle vontrans mittels der Gitterstabilisierung erklärt werden kann.

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, -[Coen₂(RCOO)₂]NO₃, R=H, CH₃, C₂H₅, C₃H₇, aen= . - - - . , . . , . : - , , . - -, - .

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This work was carried out with the financial support of the Consiglio Nazionale delle Ricerche (C.N.R.), which also gave a grant to one of us (A.M.G.).     

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.     

Interaction of atomic fluorine with XeF2 and Xe at 77 K

The probabilities of the decay of atomic fluorine on solid xenon and xenon difluoride at 77 K have been determined.

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77 .

     

Kinetic model and mechanism for selective hydrogenation of acetylene alcohols

A complex approach to the development of kinetic models in terms of the joint kinetic and physicochemical methods is suggested. To establish kinetic models for the hydrogenation of C₅, C₁₅ and C₂₀ acetylene alcohols on a modified Pd/Al₂O₃ (0.5% Pd) catalyst, the kinetics of their selective hydrogenation and the adsorption of their components have been studied.

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- . C₅, C₁₅, C₂₀ Pd/Al₂O₃ (0,5% Pd), .

     

Study of propylene adsorption and conversion on a gallium-molybdenum catalyst by IR spectroscopy and thermodesorption techniques

A study of propylene adsorption on gallium molybdate by IR spectroscopy and thermodesorption techniques has shown that propylene is adsorbed in reversible (-allyl) and irreversible (carboxyl, carbonate and formate) forms. The analysis of the spectra observed is supported by deuterated propylene adsorption. The conversion of the surface -allyl complexes into an Me–O–CH₂–CH=CH₂ type compound is followed.

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- , - : , . , . - Me–O–CH₂–CH=CH₂.

     

Colour changes in the uncatalyzed and Ag+ catalyzed oxidation of aromatic amines by persulphate ion

Summary A scheme has been proposed for the identification of some of the aromatic amines, viz., aniline, ethyl and methyl aniline, diethyl and dimethyl aniline, - and -naphthylamine, o-, m- and p-toluidine, o-, m- and p-anisidine, m- and p-phenetidine, o-, m- and p-phenylenediamine, carbazole, benzidine, o-tolidine, quinoline and iso-quinoline, p-xylidine and diphenylamine. It is based on the reaction of an aqueous persulphate solution with an alcoholic solution of the amine.

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Zusammenfassung Eine systematische Identifizierung einiger aromatischer Amine aufgrund der Oxydation mit Persulfatlösung wird beschrieben. Folgende Verbindungen werden dabei berücksichtigt: Anilin, Äthyl- und Methylanilin, Diäthyl- und Dimethylanilin, - und -Naphthylamin, o-, m- und p-Toluidin, o-, m- und p-Anisidin, m- und p-Phenetidin, o-, m- und p-Phenylendiamin, Carbazol, Benzidin, o-Tolidin, Chinolin und Isochinolin, p-Xylidin und Diphenylamin.

     

Über den Einfluß der Mesomerie auf IR- und NMR-Spektren α,β-ungesättigter Carbonylverbindungen

Zusammenfassung An Grundzuständen ,-ungesättigter Carbonylverbindungen sind polare Grenzstrukturen stark beteiligt, vgl. z. B.1011. Die bathochrome Verschiebung der Carbonylabsorption in IR- und der Einfluß auf chemische Verschiebungen und Kopplungskonstanten in NMR-Spektren wird untersucht.

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The influence of mesomerism in IR and NMR spectra of ,-unsaturated carbonyl compounds

Polar resonance structures have a great share in the ground level of ,-unsaturated carbonyl compounds, compare1011. The bathochrome displacement of carbonyl absorption in IR spectra and the influence on shift and coupling constants in NMR spectra are investigated.

     

Influence of substituents on hydrogenation of nitro groups in aromatic hydrocarbons catalyzed by rhenium thiocomplexes

Homogeneous hydrogenation studies of (NO₂)_1–2–C₆H_3–4–L nitro compounds (where L=–H,–NH₂,–COOH,–CHO,–OH,–CH₃ and –CH=CH–COOH) catalyzed by Re₂S₆TThio₃Cl₂ in dimethylformamide solutions at and T=343 K, have revealed that the reaction is enhanced by electron-acceptor substitutents and hindered by electron-donor ones.

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(NO₂)_1–2–C₆H_3–4–L, L=–H,–NH₂,–COOH,–CHO,–OH,–CH₃,–CH=CH–COOH, Re₂S₆Thio₃Cl₂ 343 . , .

     

α,β-Butenolides

,-Dibromo--('-carbethoxyacetony)-^,-butenolide (I) reacts with amines in diethyl ether solution to give -bromo-amino--('-carbethoxyacetony)-^,-butenolides. Compounds n are converted to -bromo-amino--('-carbethoxyacetony)-^,-butenolides on reaction with amines. The corresponding arylhydrazones (VI and VII) are obtained by the reaction of I and II with p-nitro- and 2,4-dinitrophenylhydrazines. Compound I reacts with phenylhydrazine to give furopyridazine VIII.See [1] for communication IV.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 867–871, July, 1972.     

Experimental setup to study catalysts by combined pulse microcatalytic and ESR spectroscopic methods

A setup consisting of an ESR spectrometer and a pulse microcatalytic installation is suggested for simultaneous kinetic and spectral measurements directly in catalytic processes.

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- , , .

     

DSC and vapour pressure investigation of some β-diketonates

DSC and vapour pressure measurements are presented on some Be, Al and Cr complexes with 2,4-pentanedione tetramethyl-3,5-heptanedione, 1,1,1-trifluoro-2,4-pentanedione and hexafluoro-2,4-pentanedione. Thermodynamic functions are given for the sublimation, vaporization and melting processes of the substances.

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Zusammenfassung Die Ergebnisse von DSC- und Dampfdruckmessungen einiger Komplexe von Beryllium, Aluminium und Chrom mit 2,4-Pentandion (HAA), Tetramethyl-3,5-heptandion (HTHD), 1,1,1-Trifluoro-2,4-pentandion (HATA) und Hexafluoro-2,4-pentandion (HHFA) werden beschrieben. Die berechneten thermodynamischen Funktionen für Sublimation, Verdampfung und Schmelzen der Komplexverbindungen sind tabelliert.

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, 2,4- , 1,1,1-- -2,4- -3,5- . , .

     

Die Ultraviolettabsorption von organischen Peroxyden und verwandten Verbindungen

Zusammenfassung Es wird die Ultraviolettabsorption (in Benzinlösung im Bereich bis ungefähr 2200 ) von Benzoylperoxyd, o- und p-Toluylperoxyd, o-, o- und p-, p-Dichlorbenzoylperoxyd, Cinnamoylperoxyd, Tetralinhydroperoxyd, Benzoesäureanhydrid, o- und p-Toluylsäureanhydrid, Zimtsäureanhydrid gemessen.In dem untersuchten Bereich liefert die –O–O-Gruppe praktisch keinen Beitrag zur Lichtabsorption.Mit 5 Abbildungen.     

O-acylated flavonoid glycosides of the needles ofPinus sylvestris II. 3“-O-p-coumaroylisoquercitrin

Summary A new acylated flavonoid glycoside has been isolated from Scotch pine needles and the structure of 3,4,5,7-tetrahydroxyflavone 3-O--D-(3-O-p-coumaroylglucopyranoside) has been established for it.Irkutsk Institute of Organic Chemistry, Siberian Branch of the Academy of Sciences of the USSR. All-Union Scientific-Research Institute of Medicinal Plants, Moscow. I. M. Sechenov I Moscow Institute. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 196–200, March–April, 1978.     

Kinetics of perborate oxidation of quinol

The perborate oxidation of quinol in aqueous acetic acid is first order with respect to perborate, zero order with respect to quinol, and first order with respect to H⁺. The oxidation is faster than H₂O₂ oxidation. Breakdown of protonated perboric acid is suggested as the rate-limiting step.

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, H⁺. . , , , .

     

Isoparametric kinetic relations for chemical transformations in condensed substances (Analytical survey). II. Reactions involving the participation of solid substances

Various manifestations of the kinetic compensation effect are considered in reactions involving the participation of solid substances under isothermal and nonisothermal conditions, as well as manifestations of other isoparametric correlations. It is shown that isoparametric correlations can be used for the analysis of solid-phase reactions and the exclusion of artefacts in nonisothermal kinetics.

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Zusammenfassung Verschiedene Erscheinungen des kinetischen Kompensationseffektes bei unter Beteiligung von festen Substanzen unter isothermen und nichtisothermen Bedingungen verlaufenden Reaktionen werden erörtert, ebenso Erscheinungen anderer isoparametrischer Korrelationen. Es wird gezeigt, daß isoparametrische Korrelationen zur Analyse von Festphasenreaktionen und zum Ausschluß von Artifakten in der nicht-isothermen Kinetik herangezogen werden können.

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, , . .

     

In situ X-ray diffraction studies of structural transformations in V-P-O catalysts

Structural transformations of V-P-O catalysts have been studied in situ in oxidative, inert and reducing atmosphere by the high-temperature X-ray diffraction method. Formation of vanadyl phosphates is shown to depend on the P/V ratio in the initial sample. It has been established that transformations in the phase composition of catalysts is independent of the reaction media at P/V=2. The effect of catalyst composition on catalytic properties is discussed.

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V-P-O , . , P/V . P/V=2. V-P-O .