Hydrogenation and hydrogenolysis of methylcyclohexane-1,4-dione on Pt and Pd catalysts

Relative hydrogenation reactivity of the two carbonyl groups of methylcyclohexane-1,4-dione can be estimated beside that of two related compounds, 2- and 3-methyl-cyclohexanones. The reaction is accompanied with hydrogenolysis on Pt and Pd. The less hindered 4-carbonyl group is selectively hydrogenolyzed.

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-1,4- , 2- 3-. Pt Pd. 4- .

     

Inhomogeneity of strong Lewis acid centers on Al2O3 surface

Specificity of the bands at 1630–1620 cm^–1 in IR spectra of coordinatively bonded pyridine has been studied. Three strong Lewis-type acid centers have been revealed on Al₂O₃ surface.

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- 1630–1620 ^–1.

     

Thermal studies on metal complexes of 5-nitroso-pyrimidine derivatives

Four Hg(II) complexes, containing as ligands 6-amino-5-nitrosouracil (AH), 6-amino-3-methyl-5-nitrosouracil (BH) or 6-amino-1-methyl-5-nitrosouracil (CH), have been synthesized and their thermal behaviour studied by TG and DSC techniques: Hg₃Cl₆(AH)₄, HgCl₂(BH)₂· 2 H₂O, HgCl₂(BH)₂ · H₂O and HgC₂· 2 H₂O.The dehydration processes take place in only one step, with enthalpies in the range 40.2–60.0 kJ · mole^–1 H₂O.Pyrolytic processes start between 200 and 250°, in all cases the thermal stability of the corresponding pyrimidine derivative being lower than that of the free ligand. These processes finish between 600 and 750°, with no residue.

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Zusammenfassung Vier 6-Amino-5-nitrosouracil (AH), 6-Amino-3-methyl-nitrosouracil (BH) oder 6-Amino-1-methyl-5-nitrosouracil (CH) als Liganden enthaltende Hg(II)-Komplexe wurden synthetisiert: Hg₃Cl₆(AH)₄, HgCl₂(BH)₂ · 2 H₂O, HgCl₂(BH)₂ · H₂O und HgC₂ · 2 H₂O. Die Dehydratisierungsprozesse verlaufen in nur einem Schritt mit Enthalpien im Bereich von 40.2–60.0 kJ pro mol H₂O. Pyrolitische Prozesse setzen zwischen 200 und 250° ein. In allen Fällen ist die thermische Stabilität der entsprechenden Pyrimidin-Derivate geringer als die der freien Liganden. Diese Prozesse sind zwischen 600 und 750° beendet, wobei kein Rückstand zurückbleibt.

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g₃l₆()₄, gl₂( )₂ · 2 ₂O, gl₂()₂ · ₂O, g₂ · 2 ₂, — 6- -5-, — 6--3- — 6---5- . , 40.2–60.0 · ^–1 ₂. 200 250° 600–750° - . , .

     

Thermal decomposition of palladium-imidazole complexes

Two Pd-imidazole complexes have been synthesized following the reaction of PdCl₂ and imidazole at 12 and 14 metal ligand ratios. Elemental and thermogravimetric analytical data obtained from these compounds illustrate that they have the formulae Pd(IMDAH)₂Cl₂ · 4H₂O and Pd(IMDAH)₃Cl₂ (IMDAH = imidazole), respectively. The mechanism of thermal decomposition for these complexes in air involves initial dissociation of H₂O and IMDAH ligands in the 120–340 °C range, subsequent dissociation of the chloride atoms to form PdO in the 530–570 °C range, and finally formation of Pd metal at 820–840 °C.

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Zusammenfassung In einer Reaktion von PdCl₂ mit Imidazol wurde bei einem metall-Ligandenverhältnis von 12 bzw. 14 zwei Pd-Imidazolkomplexe dargestellt. Auf Grund der Ergebnisse von Elementaranalyse und Thermogravimetrieuntersuchungen besitzen die Verbindungen die Formeln Pd(IMDAH)₂Cl₂·4H₂O bzw. Pd(IMDAH)₃Cl₂ (IMDAH=Imidazol). Der Mechanismus der thermischen Zersetzung dieser Komplexe in Luft umschliesst eine anfängliche Dissoziation (Abgabe von Wasser und IMDAH-Liganden) im Temperaturbereich 120–340 °C, gefolgt von der Bildung von PdO unter Abspaltung der Chloratome bei 530–570 °C sowie die letztendliche Bildung von metallischem Pd bei 820–840 °C.

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, 12 14, . , d()₂l₂· 4₂ d()₃l₂. 120–340°, 530–570°. 820–840°.

     

Thermal conductivity of cemented carbides

The hypothetical salts Li₄SiN₂O and Li₇SiN₃O were sought in the course of studies on the reactions of Li₂SiN₂ and Li₅SiN₃ with lithium oxide, and of LiSiNO with lithium nitride.

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Zusammenfassung In einer Reihe von Studien der Reaktionen von Li₂SiN₂ und Li₅SiN₃ mit Lithiumoxid bzw. LiSiNO mit Lithiumnitrid wurde nach den hypothetischen Salzen Li₄SiN₂O und Li₇SiN₃O gesucht.

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Li₂SiN₂ Li₅SiN₃ LiSiNO Li₄SiN₂O Li₇SiN₃O.

     

Hydrodemetallation and the promoter effect of vanadium compounds on a Co?Mo/Al2O3 hydrodesulfurization catalyst

The effect of the vanadium compounds [VO(phthalocyanine)], [VO(salen)] [salen=N,N-ethylenebis(salicylideneiminate)], petroporphyrins, and metal-free phthalocyanine on the hydrodesulfurization of thiophene over a Co/Mo/Al₂O₃ catalyst (350°C, 1 atm) is described. The compound [VO(salen)], which decomposes, acts as a promoter at low V (0.1–0.2 wt. %); the other compounds deactivate the catalyst, an effect which is due to the whole molecule binding to the catalyst in the same way as a nitrogen base.

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[VO()], [VO()] [=N,N-- ()], , , Co–Mo/Al₂O₃ (350°C, 1). [VO()], , V (0,1–0,2 . %-); , , .

     

Spectral dependence of photocatalytic CO oxidation on rutile

In the region of intrinsic rutile adsorption, CO oxidation follows a redox mechanism via the interaction of CO with O^– ion-radicals, and the photocatalytic activity is determined by the density of 2p states close to the top of the valence band.

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CO CO - O^–, 2- .

     

Image processing using the Briggs-Raucher oscillating chemical reaction

Some images obtained by illuminating the Briggs-Raucher oscillating chemical reaction are illustrated. This reaction gives more distinct and contrasty images than the Belousov-Zhabotinskii reaction.

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-. , , -.

     

Heterogeneous reactions of solid nickel(II) complexes XXIII

The thermal decompositions of the following compounds were studied: Ni(NCO)₂(3-Etpy)₄. (I), Ni(NCO)₂(3-Clpy)₄ (II), Ni(NCO)₂(3-Brpy)₄ (III), Ni(NCO)₂(3-NH₂py)₄ (IV), Ni(NCO)₂(3-Clpy)₂·2H₂O (V) and Ni(NCO)₂(3-Brpy)₂·2H₂O (VI). The release of volatile ligands (3-Rpy and H₂O) is a two-step process, Ni(NCO)₂(3-Etpy)₂ (VII), Ni(NCO)₂(3-Clpy)₂ (VIII), Ni(NCO)₂(3-Brpy)₂ (IX) and Ni(NCO)₂(3-NH₂py)₂ (X) being formed as intermediate complexes. The loss of the last molecules of volatile 3-Rpy ligands is accompanied by NCO ligand decomposition. The spectral and magnetic data indicated pseudooctahedral configuration for all complexes I-X.

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Zusammenfassung Die thermische Zersetzung der folgenden Verbindungen wurde untersucht: Ni(NCO)₂(3-Etpy)₄ (I), Ni(NCO)₂(3-Clpy)₄ (II), Ni(NCO)₂(3-Brpy)₄ (III), Ni(NCO)₂(3-NH₂py)₄ (IV), Ni(NCO)₂(3-Clpy)₂·2H₂O (V) und Ni(NCO)₂(3-Brpy)₂·2H₂O (VI). Die flüchtigen Liganden (3-Rpy und H₂O) werden in zwei Schritten abgegeben, wobei Ni(NCO)₂(3-Etpy)₂ (VII), Ni(NCO)₂(3-Clpy)₂ (VIII), Ni(NCO)₂(3-Brpy)₂ (IX) und Ni(NCO)₂(3-NH₂py)₂ (X) als intermediäre Komplexe gebildet werden. Die Abgabe der letzten Moleküle der flüchtigen 3-Rpy-Liganden geht mit der Zersetzung des NCO-Liganden einher. Die spektrometrischen und magnetischen Daten weisen auf eine pseudooktaedrische Konfiguration aller Komplexe (I-X) hin.

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: Ni(NCO)₂(3-Etpy)₄ (I), Ni(NCO)₂(3-Clpy)₄ (II), Ni(NCO)₂(3-Brpy)₄ (III), Ni(NCO)₂(3-NH₂py)₄ (IV), Ni(NCO)₂(3Clpy)₂·2H₂O(V) Ni(NCO)₂(3-Brpy)₂·2H₂O (VI). (3-Rpy H₂O) , Ni(NCO)₂(3-Etpy)₂ (VII), Ni(NCO)₂(3-Clpy)₂ (VIII), Ni(NCO)₂(3-Brpy)₂ (IX) Ni(NCO)₂(3NH₂py)₂ (X). . .

     

Coumarin composition of Seseli grandivittatum

Summary From the roots ofSeseli grandivittatum, together with -sitosterol and (–)-3R-decursinol, found in nature for the first time, and its angelate, we have isolated two new compounds which we have called grandivittin and grandivittinol.On the basis of IR, PMR, and mass spectra and chemical transformations, the structure of 3-senecioyloxy-3,4-dihydro-3R-xanthyletin is proposed for grandivittin, and 7-hydroxy-6-(3-hydroxy-2-senecioyloxyisopentyl) coumarin for grandivittinol.Leningrad Sanitary-Hygienic Medical Institute. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 640–646, September–October, 1977.     

Triterpene glycosides of Gypsophila trichotoma III. Structure of trichoside B

Summary The structure of trichoside B — a gypsogenin tetraoside fromGypsophila trichotoma Wend. — has been established. The glycosidic carbohydrate chain is O--D-glucopyranosyl-(1 3)-O--D-glucuronopyranosyl and the acyloside chain is O--D-glucopyranosyl-(1 4)-O--D-galactopyranosyl.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 431–434, July–August, 1971.     

SCF Xα DW nuclear magnetic screening tensor calculations

Conclusions Calculations have been performed on the nuclear magnetic screening tensors for molecules via perturbation theory and the X DW method, and a comparison is made with results from other methods. Although the absolute errors in the for the molecules are appreciable, the relative errors in determining the NR chemical shifts are much less (see for example, the shift for CO relative to CH₄), which is a hopeful factor leading one to expect that X DW can be widely used in analyzing NMR spectra. At the same time, X DW can closely reproduces the anisotropy, which is particularly important for compounds such as V₂O₅ or its derivatives, which show very large anisotropy in the magnetic screening tensors.Catalysis Institute, Siberian Branch, Academy of Sciences of the USSR. Translated from Zhurnal Strukturnoi Khimii, Vol. 29, No. 5, pp. 32–36, September–October, 1988.     

Synthesis of a Calix[4]arene Containing 'Hard' and 'Soft' Metal Ion Binding Sites

Co-receptor 1,3-calix[4]-di(aza-benzo)crown-crown-6 (1-H) designed with one calix[4]arene in a 1,3-alternate conformation and hard and soft metal ion binding sites has been prepared according to three pathways (A-C). Pathway B, consisting of two different 1 + 1 condensations with ditosylate derivatives, was shown to be the most efficient.     

Fluorination of polyfluoroalkoxy derivatives of sulfur tetrafluoride by elemental fluoride

Conclusions The feasibility was demonstrated for the preparation of mono- and bis(,,-trihydro-perfluoroalkoxy) derivatives of sulfur hexafluoride by the fluorination of the corresponding sulfur tetrafluoride derivatives with elemental fluorine.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 8, pp. 1906–1908, August, 1988.     

New specific methods for the detection of chromium(VI) and vanadium(V) using primaquin

Summary New specific methods have been developed for the detection of chromium(VI) and of vanadium(V), based on the formation of a purple color with primaquin in concentrated sulfuric acid solution. The identification limits and dilution limits have been determined to be 0.05g, 11 000 000 for chromium(VI) and 0.1g, 1500 000 for vanadium(V) respectively.

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Neue spezifische Methoden zum Nachweis von Cr(VI) und V(V) mit Primachin

Zusammenfassung Die neu ausgearbeiteten Methoden sind spezifisch und beruhen auf der Bildung einer Purpur-Färbung mit Primachin in konz. Schwefelsäure. Die Nachweisgrenzen und Verdünnungsgrenzen betragen 0,05g bzw. 11 000 000 für Cr(VI) und 0,1g bzw. 1500 000 für V(V).

     

Couplage vibronique et anisotropie paramagnétique dans un complexe cubique 2 T 2 soumis à un champ trigonal

The influence of vibronic coupling on the average paramagnetism and the paramagnetic anisotropy of a cubic complex, the electronic ground state ²T₂ of which is perturbed by a trigonal field, is investigated. It is necessary to introduce the following parameters: the spin-orbit coupling coefficient , the vibronic coupling coefficient x, the frequency _g3 of the E modes of vibration, the splitting of the ² T ₂ level in the trigonal field and the covalence parameter k.For given x and , the influence of the vibronic coupling is more important if in the trigonal field the electronic ground state of the complex is ²E than if it is ²A. For given x and v (=/), the smaller ¦¦, the greater the influence of vibronic coupling. The respective effects of vibronic coupling and covalence are compared. Finally, the case of the first row transition-metal complexes is briefly discussed.     

Meldrum's acid — A reagent for the synthesis of unsaturated γ-lactones and Β-acylacrylic acids

The thermal cyclization of 2,2-dimethyl-5-(2-aryl-2-oxoethyl)-1,3-dioxan-4,6-diones forms 5-aryl-, butenolides. Regioselective chlorination of 2, 2-dimethyl-5-[2-aryl(alkyl)-2-oxoethyl]-1,3-dioxane-4,6-diones by SO₂Cl₂ gives the 5-chloro derivatives; these are cleaved by aqueous AcOH to the E--acylacrylic acids, which are synthones for unsaturated -lactones.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 5, pp.1212–1214, May, 1991.     

Synthesis of 3′,5-di(piperidin-2-yl)-2, 4′-bipyridyl from anabasine

The possibility of the formation of 3,5-di(piperidin-2-yl)-2,4-bipyridyl by the dehydrogenative condensation of anabasine in the presence of metallic sodium at 50–60C has been shown.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1076–1077, August, 1973.