On the mechanism of n-butane conversion on H-mordenite

It is suggested that n-butane isomerization on H-mordenite takes place via a step of disproportionation due to the increased acidity of the latter. This suggestion is confirmed by a comparison between the product distribution of n-butane and C₈ hydrocarbons (n-octane and isooctane) in the presence of dealuminated mordenite containing no Pt group metals.

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, - - , . - C₈ (-qo ) , , .

     

Infrared spectra of nitric oxide adsorbed on photoreduced V/SiO2 catalyst

Studies of the IR spectra of surface species produced via NO adsorption on selectively photoreduced V/SiO₂ catalysts indicate that at low coverages NO is adsorbed on V³⁺ ions to form strongly bonded mononitrosyl species V³⁺...... NO. With increasing NO coverage, V³⁺ is oxidized to V⁴⁺, which is accompanied by the appearance of gaseous N₂O and weak adsorption of NO on V⁴⁺.

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- , NO V/SiO₂ . , V³⁺ NO V³⁺... NO. V³⁺ V⁴⁺, N₂O NO V⁴⁺.

     

A differential scanning calorimetric study of some phenol derivatives

Differential scanning calorimetry has been applied to derive the fusion enthalpies and entropies of series of mono and dimethylphenols, mono and dichlorophenols, and mono and dinitrophenols.

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Zusammenfassung DSC wurde verwendet zur Ermittlung der Schmelzenthalpie und Entropie der Reihen von Mono- und Dimethylphenolen, Mono- und Dichlorphenolen, Mono- und Dinitrophenolen.

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- , - , - .

     

The thermal decomposition of thaumasite from Mothae kimberlite pipe,Lesotho, Southern Africa

The endothermic decomposition of thaumasite from Mothae which has been investigated by DTA and TG shows a peak temperature of 138–203°, and reaction orders of 0.45–1.00, depending on the heating rate employed. The activation energy of the reaction was found to be about 19 kcal/mole; the enthalpy is 246 cal/g.The decomposition seems to be divided into one reaction withn=0.90, immediately followed by one withn=1.59. The first reaction is attributed to the loss of H₂O, the second one to the (partial) release of OH and CO₂.

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Zusammenfassung Die durch DTA und TG überprüfte endothermische Zersetzung von Thaumasit aus Mothae zeigt in Abhängigkeit der angewandten Aufheizgeschwindigkeiten Spitzentemperaturen zwischen 138 und 203° C, sowie Reaktionsordnungen von 0.45 bis 1.00. Die Aktivierungsenergie der Reaktion ergab sich zu 19 Kcal/Mol, die Enthalpie zu 246 cal/g.Die Zersetzung scheint in eine Reaktion vonn=0.90 und eine sofort darauffolgende vonn=1.59 geteilt zu sein. Die erste Reaktion wird dem Verlust von H₂O, die zweite der (teilweisen) Freisetzung von OH und CO₂ zugeschrieben.

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Résumé La décomposition endothermique de la thaumasite de Mothae a été étudiée par ATD et TG. Suivant la vitesse de chauffage utilisée la température au sommet du pic varie de 138 à 203° C et l'ordre de réaction de 0.45 à 1.00. On a trouvé que l'énergie d'activation s'élevait à 19 kcal, mol^–1 et l'enthalpie à 246 cal. g^–1.Il semble que la décomposition s'effectue suivant une réaction d'ordren=0.90, immédiatement suivie par une autre oùn=1.59. On attribue la première réaction à la perte d'eau et la seconde à la libération (partielle) d'hydroxyles OH et d'anhydride carbonique CO₂.

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, , 138–203° 0,45–1,00 . , 19 /, - 246 /. , n=0,90, n=1,59. , - OH CO₂.

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The material used for this study has been kindly supplied by Dr. P. H. Nixon, former chief geologist, Department of Mines, Maseru, Lesotho.     

Effect of catalyst surface modification on pentachlorobutene-1 oxidation to dichloromaleic anhydride

Modification of V–P–O catalyst surface by reaction products changes the reaction course and increases its catalytic activity in pentachlorobutene-1 oxidation to dichloromaleic anhydride.

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V–P–O . -1 .

     

Effect of the medium on the oxidation of aliphatic monocarboxylic acids

Oxidation rates and k₂/k₆ ratios are given for some acids from propionic to lauric. The k₂/k₆ ratio is shown to be influenced by the electrostatic effect of the solvent. A linear dependence between the isodielectric values of k₂/k₆ and the number of methylene groups in the acid molecules is described.

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k₂/k₆ . k₂/k₆ k₂/k₆ .

     

The compound Rh[HN((CH2)3P(C6H5)2)2]Cl in a hydrogenation reaction

The tridentate chelate ligand bis(diphenylphosphinopropyl) amine and its title complex were prepared and characterized by³¹P n.m.r. and other spectroscopic data. Its activation energy E_A for hydrogenation of cyclohexene is 52.3 kJ mol^–1.

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³¹P. 52,3 /.

     

A surface potential study of adsorbed oxygen species on a Bi2Mo3O12 catalyst

Bi₂Mo₃O₁₂ is a selective oxidation catalyst of propylene into acrolein. Surface potential measurements proved the presence of an equilibrium between gaseous oxygen and the O^2– species adsorbed on the surface of the catalyst, under oxygen atmosphere, in the range 538K–673K. This is in accordance with the fact that O^2– is a selective oxidation species. An oxygen adsorption mechanism is also discussed.

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Bi₂Mo₃O₁₂ . O^–2, , 538–613 . , O^–2 . .

     

A novel method for the preparation of extensively dealuminated faujasites

Open structure faujasites may be dealuminated with retention of crystallinity using phosgene (or similar reactants) provided the sample has been made ultrastable in a previous procedure.

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( ) . .

     

On the relationship between the structures of Cu(II) complexes and their chemical transformations

The paper deals with the relationship between the crystal and molecular structures of CuSO₄.5 H₂O, CuSO₄.3 H₂O and CuSO₄.H₂O on the one hand, and the stoichiometries of their thermal decompositions on the other. With the use of methods of X ray powder diffractograms, i.r. and electronic spectra, evidence is provided that the intermediates of the thermal decomposition of CuSO₄.5 H₂O have the same crystal and molecular structures as CuSO₄.3 H₂O and CuSO₄.H₂O prepared by other procedures. It is also shown that at temperatures near that of the thermal decomposition, certain, not further identified structural changes take place in CuSO₄.5 H₂O.

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Zusammenfassung Es wird einerseits der Zusammenhang der Kristall- und Molekularstruktur von CuSO₄ · 5H₂O, CuSO₄ · 3H₂O und CuSO₄ · H₂O behandelt und andererseits die Stöchiometrie ihrer thermischen Zersetzung. Mit der Auswertung der Röntgen-Pulverdiffraktogramme, der IR- und Elektronenspektren wurde der Beweis erbacht, da\ die Zwischen-produkte der thermischen Zersetzung von CuSO₄ · 5H₂O dieselben Kristall- und Molekül-strukturen besitzen, wie auf anderen Wegen hergestelltes CuSO₄ · 3H₂O bzw. CuSO₄ · H₂O. Ferner wurde gezeigt, da\ bei Temperaturen in der NÄhe der thermischen Zersetzungstemperatur gewisse, jedoch noch nicht identifizierte StrukturÄnderungen in dem CuSO₄ · 5H₂O stattfinden.

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Résumé L'article examine la corrélation entre les structures cristallines et moléculaires de CuSO₄.5 H₂O, CuSO₄.3 H₂O et CuSO₄.H₂O d'une part et la stoechiométrie de leur décomposition thermique de l'autre. En se servant des méthodes des diffraction des rayons X sur poudre et des spectres infra-rouges et électroniques on montre que les produits intermédiaires de la décomposition thermique de CuSO₄.5 H₂O ont les mÊmes structures cristallines et moléculaires que celles de CuSO₄.3 H₂O et de CuSO₄.H₂O préparées par d'autres procédés. On montre également qu'à des températures proches de celle de la décomposition thermique de CuSO₄. 5H₂O des changements structuraux non encore identifiés ont lieu.

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uSO₄ · 5₂, uSO₄ · ₂ uSO₄ · ₂, — . , , , uSO₄ · 5₂ uSO₄ · ₂ uSO₄ · ₂, . , , uSO₄, · 5₂ , .

     

Acid-base properties of Al2O3/MgO oxides, II. Infrared study of adsorption of pyridine

Mixed oxides of alumina and magnesia were characterized by an IR study of pyridine adsorption. Three different Lewis acid sites, but no Brönsted acid sites were detected. The strongest adsorption sites are attributed to Al³⁺ cations of the alumina phase (1455 cm^–1), the weaker Lewis acid sites were assumed to be due to cations of the MgAl₂O₄ phase (1449–1443 cm^–1) and the MgO phase (1440–1438 cm^–1).

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. , , . Al⁺³ (1455 ^–1), MgAl₂O₄ (1443 ^–1) MgO (1438 ^–1).

     

Decomposition of hydrotrioxides catalyzed by carboxylic acids

Carboxylic acids (HCOOH, CH₃COOH, CH₂ClCOOH, CCl₃COOH, CF₃COOH and C₄H₉COOH) are shown to increase the firstorder effective rate constant of chemiluminescence quenching (k_q) in the decomposition of hydroxides Me₂C(OH)OOOH and Me₂CHOC(OOOH)Me₂. With decreasing pK_a of an acid, its catalytic effect on k_q grows.

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, HCOOH, CH₃COOH, CH₂ClCOOH, CCl₃COOH, CF₃COOH, C₄H₉COOH () Me₂C(OH)OOOH Me₂CHOC(OOOH)Me₂. .

     

Studies of adsorption-desorption processes in SO2 oxidation on the active component of vanadium catalysts

Diffusion and solubility coefficients of O₂, SO₂ and SO₃ in the active component of vanadium catalysts have been determined by a high-speed relaxation method. Processes of their dissolution are shown to be quasi-equilibrium with respect to catalytic reactions.

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O₂, SO₂ SO₃ ,

     

Various dynamic behavior of Ag+-induced oscillations in uncatalyzed bromate oscillators

Silver ion induces the uncatalyzed bromate oscillators /aromatics-bromate-acid/on a variety of dynamic behavior, including high frequency and complex oscillations. The behavior of a reacting system depends on the chemical composition of the armatics, the time of addition of Ag⁺, and the concentration of Ag⁺. The chemistry underlying the phenomena is discussed.

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(--) , . , Ag⁺ Ag⁺. .

     

Asymmetric hydrogenation in the presence of bicyclic chiral phosphines

Both enantiomers of trans-2,3-diphenylphosphinomethyl-norbornene-(5), prepared by two independent synthetic routes, were used as ligands in the asymmetric hydrogenation of -acetamidocinnamic acid in the presence of rhodium(I). Small variations in the ligand structure have a remarkable influence on the activity of the catalytic system.

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-2,3----(5), , - (I). .

     

Structure of vanadium phosphate anion in solutions from17O,51V and31P NMR data

¹⁷O,⁵¹V and³¹P NMR studies indicate that the anion structure of sodium vanadophosphate in an aqueous solution is close to that in crystals of the (CN₃H₆)₈HPV₁₄O₄₂ 7H₂O salt.

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¹⁷O,⁵¹V,³¹P , (CN₃H₆)₈HPV₁₄O₄₂ 7H₂O.

     

Steroid compounds of marine sponges. VII. Preparation of derivatives of sokotrasterol and halistanol sulfates and structure-activity interrelationships among these compounds

Five new sulfated derivatives of sokotrasterol and halistanol have been obtained: 24-nor-5-cholane-2,3,6,23-tetraol 2,3,6-tri(sodium sulfate); 24-nor-5-cholane-2,3,6,23-tetraol 2,3,6-tri(sodium sulfate) 23-palmitate; 24,25-dimethyl-5-cholestane-2,3,6-triol 3-(sodium sulfate); 24,25-dimethyl-5-cholestane-2,3,6-triol 6-(sodium sulfate); and 24,25-dimethyl-5-cholestane-2,3,6-triol 2,6-di(sodium sulfate). The inhibiting and membranolytic properties of the polysulfated steroids from sponges and their derivatives have been studied. It has been shown that physiological activity in this series of compounds depends on biphilicity.Pacific Ocean Institute of Bioorganic Chemistry, Far Eastern Scientific Center, Academy of Sciences of the USSR, Vladivostok. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 441–445, July–August, 1986.     

Kinetics of Cu(II)-ion catalyzed oxacillin hydrolysis

The kinetics of Cu(II)-ion catalyzed oxacillin hydrolysis have been studied. The applicability of a reaction scheme is tested together with the influence of several factors and the kinetic and thermodynamic parameters of the reaction are determined.

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CO₂ TiO₂ , . CO₂ O ₃ ^– O ₂ ^– . H₂O₂/TiO₂, 150–200°C, CO₂–O ₂ ^– .

     

An investigation of some homo- and heterobinuclear complexes of copper(II) and nickel(II) with pyridine-2-aldoxime

The reactions between copper(II) or nickel(II) with thecis-pyridine-2-aldoxime complexes of the same metal ions have been investigated by spectrophotometric measurements. The homo and heterobinuclear chelates involved have been isolated as the chlorides and characterized by spectroscopic and thermoanalytical techniques. The first decomposition step is not dependent on the furnace atmosphere (N₂ or O₂) and is accompanied by a large exothermic effect (DSC curves in N₂). TG curves show that binuclear complexes are generally slightly less stable than the respective mononuclear complexes but, in the case of [Cu(NiL₂)Cl₂(H₂O)₂], the complexation of copper(II) gives rise a drastic decrease of its thermal stability.

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Zusammenfassung Die Reaktionen zwischen Kupfer(II) und Nickel(II) mit den cis-Pyridin-2-aldoxim-Komplexen der gleichen Metallionen wurden spektrophotometrisch untersucht. Die homo- und heterobinuklearen Chelate wurden als Chloride isoliert und durch spektroskopische und thermoanalytische Methoden charakterisiert. Der erste Zersetzungsschritt ist unabhängig von der Ofenatmosphäre (N₂ oder O₂) und ist stark exotherm (s. DSC-Kurven in Abb. 1). Die TG-Kurven lassen erkennen, dass zweikernige Komplexe im allgemeinen etwas weniger stabil als die entsprechenden einkernigen Komplexe sind, im Falle von [Cu(NiL₂)Cl₂(H₂O)₂], aber die Anlagerung von Liganden an das Kupfer zu einer drastischen Verminderung der Stabilität führt.

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- -2- . - , . ( ) , -, . , , , , [Cu(NiL₂)Cl₂(H₂O)₂], .

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This work was carried out with financial support by MPI National Project.     

On the compensation effect

Arrhenius equation is popularly used to relate the change in the rate constant with temperature. The linearized form of Arrhenius equation has often been used to establish a relation between InA andE for a series of related reactions. Occurrence of such a compensating behavior between InA andE has been widely reported in the literature. The validity of the compensation effect has been heatedly debated. Compensation effect can arise from computational artifact or can arise from various chemical factors. This depends entirely on the data set used to establish the compensation behavior. This article stresses the importance of statistical analysis and the use of simple Arrhenius plots to draw conclusions regarding the occurrence of compensation effect. With the help of a few examples, some checkpoints to draw conclusions regarding the occurrence of true or false compensation effect are suggested.

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Zusammenfassung Die Arrhenius-Gleichung wird gewöhnlich zur Beschreibung des Zusammenhanges zwischen Geschwindigkeitskonstante und Temperatur benutzt. Die linearisierte Form der Arrhenius-Gleichung wurde dazu benutzt, eine Beziehung zwischen InA undE für eine Reihe von Reaktionen des gleichen Typs aufzustellen. Ein solches Kompensationsverhalten von InA undE wurde in der Literatur beschrieben, die Realität des Kompensationseffektes war jedoch Gegenstand heftiger Debatten. Ein Kompensationseffekt kann durch ein Rechenartefakt vorgetäuscht oder aber durch verschiedene chemische Faktoren bedingt sein. Dies hängt ausschließlich von der für den Nachweis des Kompensationsverhaltens aufgestellten Datenfolge ab. Dieser Artikel unterstreicht die Wichtigkeit der statistischen Analyse und die Verwendung einfacher Arrheniusgeraden für sich auf das Vorliegen eines Kompensationseffektes beziehende Schlußfolgerungen. An Hand einiger Beispiele werden einige Kontrollmöglichkeiten zur Unterscheidung tatsächlicher und vorgetäuschter Kompensationseffekte aufgezeigt.

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. In . In . . , . , . , , . .

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