Effect of H2S-uptake on the conversion of cyclohexene on Ru- and Pd-promoted molybdena-alumina catalysts

The effect of H₂S on the activity and selectivity of catalysts (Ru/Al₂O₃, Pd/Al₂O₃ and Ru and Pd promoted molydena-alumina) was different (on differnt catalysts and different conversions of cyclohexene). Ru-containing catalysts showed higher sulfur sensitivities than the Pd-containing ones. The sequence of catalysts by their H₂S uptake related to mass of catalyst was PdMo/Al₂O₃RuMo/Al₂O₃Mo/Al₂O₃>Pd/Al₂O₃Ru/Al₂O₃.     

Donorstärken in 1,2-Dichloräthan

Zusammenfassung Kalorimetrische und spektrophotometrische Untersuchungen über die Donorstärke einer Anzahl nicht-wäßriger Lösungsmittel zeigen, daß die relative Reihung der Donorstärken unabhängig von der Natur des Akzeptors ist. Die Donorreihung lautet gegenüber SbCl₅, Jod und Phenol folgendermaßen: Pyridin > Dimethylsulfoxid > Dimethylacetamid Dimethylformamid > > Trimethylphosphat Diphenylphosphoroxychlorid > Diäthyläther > Aceton > Propandiol-1,2-carbonat > Acetonitril > > Selenoxychlorid Phosphoroxychlorid Benzoylchlorid > > Thionylchlorid > Sulfurylchlorid.

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Calorimetric and spectrophotometric work on the donor strength of various non-aqueous solvents have shown that the relative order of donor strength is independent from the nature of the acceptor. The order of donor strength towards SbCl₅, I₂ and phenole is pyridine > dimethylsulfoxide > dimethylacetamide dimethylformamide > trimethylphosphate diphenylphosphonic chloride > diethyl ether > acetone > propane diol-1,2-carbonate > acetonitrile > selenium oxychloride phosphorus oxychloride benzoyl chloride > thionyl chloride > sulfuryl chloride.

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Mit 1 Abbildung     

Preparation and Characterization of Branched β-Cyclodextrins Having Manno-Oligosaccharide Side Chains Derived from Yeast Mannan and Study of Their Functions

Branched -cyclodextrins (-CDs) having manno-oligosaccharide side chains were investigated. Three kinds of monobranched -CDs and five kinds of dibranched -CDs were chemically synthesized using the trichloroacetimidate method. Their structures were analyzed by HPLC, MS, and NMR spectroscopies. The specific interaction between those compounds and mannose-binding lectins (Concanavalin A and Pisum sativum agglutinin) was investigated by inhibition tests of hemagglutinating activity and by using an optical biosensor of the IAsys apparatus with a resonant mirror detector. The results showed that all branched -CDs interactedwith lectins. The binding affinity was 6¹,6⁴-(Man₃)₂- 6¹,6⁴-(Man₂)₂- > 6¹,6⁴-(Man₄)₂--CD when the derivatives were compared on the basis of side chain length and 6¹,6³- 6¹,6⁴- > 6¹,6²-(Man₂)₂--CD when compared on the basis of side chain position.     

Adsorption Kinetic Characteristics of H2S on Activated Carbon

This study compared H₂S adsorption kinetic parameters in both grain adsorption and column adsorption systems. Results indicated that when the nondimensional mass transfer parameter for adsorption column design was included, the axial dispersion (Pe > 1, < 1) and external film resistance (B 1) could be neglected, the fluid viscosity effect was small (Sc = 0.76), and the adsorbate affinity was fine (). Surface and pore diffusion controlled the adsorbent and fluid mass transfer. In addition, spent activated carbon could be treated by a thermal process and then impregnated with NaOH. After the pretreatment, the spent activated carbon could be used for H₂S adsorption. Furthermore, we also propose that the H₂S adsorption reaction on the carbon is due to the formation of sulfur crystals.     

On a large difference in enthalpic virial coefficient among some isomers of alkoxyalcohol

Molar excess enthalpies for aqueous solutions of 3-methoxy-1-butanol (3-MB) and 1-methoxy-2-butanol (M-2B) have been measured at 298.15 K over the whole concentration range with a flow microcalorimeter. From the experimental data, we evaluated the enthalpic interaction parameter h_xx and obtained the following order:h _xx (3 MB) h_xx(M-2B)This large difference in h_xx. provided us some new factors which might have the influence on hydrophobic interaction: fundamental frame, hydroxyl group, and ether oxygen atom.

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Zusammenfassung Mittels eines Fluß-Mikrokalorimeters wurden bei 298.15 K im gesamten Konzentrationsintervall die molaren Überschußenthalpien für wäßrige Lösungen aus 3-Methoxy-1-Butanol (3-MB) und 1-Methoxy-2-Butanol (M-2B) gemessen. Anhand der experimentellen Daten erstellten wir den Enthalpiepaar-Wechselwirkungsparameter h_xx und erhielten folgende Reihenfolge: h_xx(3-MB) h_xx(M-2B)Diese große Abweichung bei h_xx legte uns einige neue Faktoren nahe, die einen Einfluß auf die hydrophobe Wechselwirkung haben können: Grundgerüst, Hydroxylgruppen als auch Sauerstoffatome.

     

EXAFS characterization of Dy and Pd-Dy on alumina catalysts

Two Pd-Dy/-Al₂O₃ catalysts, with 1 wt.% Dy and various Pd loadings (0.1 and 0.5 wt.%) have been investigated by EXAFS at the Dy L_III-edge, and compared with 1 % Dy/-Al₂O₃. The Dy-carrier interaction was found to change with the Pd dispersity.     

Radiochemical determination of intracellular ionic concentrations in alga Hydrodictyon reticulatum

Algal nets of Hydrodictyon reticulatum have been cultivated in the radioactivity labelled medium of different chemical composition. It has been found that the intracellular concentration of sodium, potassium, ammonium, chloride, sulphate and phosphate ions changed in a great extent in the dependence of the experimental conditions. The influx of cations from neutral chloride solutions decreases in the order: ammoniumpotassium, thallium/I/rubidium>cesium>lithiumsodium ions. The intracellular chloride ions can be reversible displaced by bromide or sulphate anions.     

Das Solvosystem Phosphoroxychlorid, 23. Mitt.: Photometrische Titrationen von Chloriden mit Eisen(III)-chlorid

Zusammenfassung Zahlreiche kovalente Chloride bilden mit FeCl₃ in POCl₃ Chloroniumtetrachloroferrate. HgCl₂, BCl₃, TiCl₄, SnCl₄ und PCl₅ geben ein Chloridion, ZnCl₂ und AlCl₃ zwei Chloridionen, letzteres zum Teil auch das dritte Chloridion an FeCl₃ ab. Die Donorstärke nimmt in der Reihe Et₄NClKCl1/2 ZnCl₂ 1/2 AlCl₃>TiCl₄>PCl₅1/3 AlCl₃[SbCl₆]^–HgCl₂ >BCl₃SnCl₄ ab. SbCl₅ ist in POCl₃ ein stärkerer Akzeptor als FeCl₃. Die Unterschiede gegenüber dem Lösungsmittel Phenylphosphoroxychlorid werden diskutiert.Mit 1 Abbildung22. Mitt.:M. Baaz, V. Gutmann undL. Hübner, Mh. Chem.91, 694 (1960).     

The Stability of Monolith CuZSM-5 Catalysts for the Selective Reduction of Nitrogen Oxides with Hydrocarbons: II. Synthesis and Characterization of Bulk Cu(80% ZSM-5 + 20% Al2O3) Catalysts

The effects of ion-exchange conditions and the zeolite Si/Al atomic ratio on the copper contents of Cu(80% ZSM-5 + 20%Al₂O₃) catalysts and on the catalytic activity in the selective reduction of NO with propane were studied. It was found that the synthesis of these catalysts exhibited the same behavior as in the case of bulk CuZSM-5 catalysts containing no Al₂O₃. The copper contents of the catalysts depend on the pH and concentration of copper solutions used for ion exchange, and the maximum activity (NO conversion) is attained even at an exchange level (Cu/Al) close to 100% regardless of pH and the zeolite Si/Al atomic ratio. At 300–400°C, the activity of the test catalysts is 10–20% lower than the activity of CuZSM-5 catalysts containing no Al₂O₃at equal exchange levels. This difference in the activity almost disappeared as the reaction temperature was increased. It was also found that in the Cu(80% ZSM-5 + 20%Al₂O₃) catalysts, an exchange level close to that in CuZSM-5 catalysts is attained by ion exchange from more concentrated solutions. An increase in the exchange level to 100% (by an increase in the pH of a copper solution from 6 to 10, as in the case of CuZSM-5 catalysts), had no effect on the activity.     

Crystal structure and electronic properties of bis(mepirizole) copper(II) perchlorate. Correlation between the electronic spectrum and CuN4 chromophore distortion from tetrahedral symmetry

Summary The crystal structure of the title compound has been determined from single-crystal x-ray diffraction data. The crystals are tetragonal, space group P4₂2₁2, withz=2 in a unit cell of dimensionsa=b=9.575(2),c=16.135(5) Å. The structure was solved by the usual Patterson and Fourier techniques, and was refined by least-squares analysis to an R value of 0.057 for 545 observed reflexions. Two mepirizole molecules are arranged in a flattened tetrahedral manner (average Cu-N, 1.974 Å) around Cu, and coordinated through N atoms. The dihedral angle between N-Cu-N planes of the two ligands is 53.6+°. This geometry seems to result from steric interaction between the ligands.The e.s.r. spectrum is axial (g g > 2.0). A study of the maximum d-d transition as a function of CuN₄ chromophore distortion from T_d symmetry is reported.4-Methoxy-2-(5-methoxy-3-methyl-pyrazol-1-yl) -6-methylpyrimidine.     

A Highly Efficient Chelating Polymer for the Adsorption of Uranyl and Vanadyl Ions at Low Concentrations

A new polymer containing double amidoxime groups per repeating unit was synthesized to enhance the metal ion uptake capacity. The adsorption properties of this new polymeric adsorbent, amidoximated poly(N,N-dipropionitrile acrylamide), for U(VI), V(V), Cu(II), Co(II) and Ni(II) ions were investigated by batch and flow-through processes at very low concentration levels (ppb). The chelating polymer showed high adsorption capacity for uranyl as well as vanadyl ions. In selectivity studies from a mixture of metal ions in aqueous solutions, the adsorbent showed high selectivity for uranyl and vanadyl ions in the following order: U(VI) > V(V) Co(II) = Cu(II) Ni(II) as determined by calculating the distribution coefficients D, of corresponding ions. The adsorption of uranyl and vanadyl ions from natural seawater by the new adsorbent was also examined in flow through mode.     

<Emphasis Type="Italic">In vitro</Emphasis> inhibitory effect of polyoxometalates on human tumor cells

H₇[NiV₁₃O₃₈] was synthesized from K₇[NiV₁₃O₃₈] using an ion exchange method. Then Pr₂H[NiV₁₃O₃₈] was obtained by double decomposition of H₇[NiV₁₃O₃₈] with Pr₂(CO₃)₃. The actual amount of praseodymium measured by elemental analysis coincides with the designed amount of praseodymium in Pr₂H[NiV₁₃O₃₈]. The i.r. spectra suggested that the [NiV₁₃O₃₈]^7– anion did not collapse after the ion exchange and double decomposition. The ⁵¹V n.m.r. spectrum of Pr₂H[NiV₁₃O₃₈] showed four peaks and their ratio of the relative intensity was 4:4:4:1. This result agrees with the chemical environment of V atoms in the [NiV₁₃O₃₈]^7– anion. In vitro antitumor activities of polyoxometalates on several human tumor cells have been investigated using the MTT method. Pr₂H[NiV₁₃O₃₈] is the most effective polyoxometalate tested in this study for inhibiting KB cell. Pr₂H[NiV₁₃O₃₈] also showed remarkable inhibitory effect on some other tumor cells: HCT, Bel, B₁₆, BCAP and ESCL cells. These results indicate that Pr₂H[NiV₁₃O₃₈] is a potent broad spectrum antitumor agent. The structure type of polyoxometalates greatly influences their antitumor activity: the order of structure type for inhibiting KB cell is: [NiV₁₃O₃₈]^7–>[Mo₇O₂₄]^6–>Anderson structure Keggin structure Dawson structure. Moreover, the nature of the polyatom in the polyoxometalates also greatly influences their antitumor activity: the polyatom order for inhibiting KB cell is: V>Mo W. On the other hand, the nature of the counter cation and the heteroatom in the polyoxometalates exerted a relatively small influence on the inhibitory effect against the KB cell, although the praseodymium salt of [NiV₁₃O₃₈]^7– showed a higher antitumor activity than its potassium salt.     

Formation of a Dimer with a Double Hydroxo Bridge in Nitric Acid Solutions of the Nitrosotetranitrohydroxo Complex of Ruthenium(II). Crystal Structure of K2[RuNO(NO2)3(μ-OH)]2

Fine yellowish orange crystals of the binuclear complex K₂[RuNO(NO₂)₃(-OH)]₂ were obtained by the reaction of K₂[RuNO(NO₂)₄OH] with a stoichiometric amount of 0.8 M nitric acid at room temperature. The compound was investigated by IR spectroscopy, X-ray phase analysis (DRON-3M, CuK radiation), and X-ray diffraction analysis (Nonius CAD-4, MoK radiation, graphite monochromator, scan mode, 1406 reflections). The crystals are poorly soluble in water and practically insoluble in ethanol and acetone; the compound is stable when stored in air. Crystal data for H₂K₂N₈O₁₆Ru₂ are: a = 8.596(2), b = 10.111(1), c = 9.537(1) , = 104.42(1)°, V = 802.8(2) ³, space group , Z = 2, _calc = 2.691 g/cm³. The structure is built of [RuNO(NO₂)₃(- complex anions and K⁺ cations.     

Free Phosphoric Acid of Diatomite-Phosphate Solid Acid and its Catalytic Performance for Propylene Oligomerization

Free phosphoric acid in the diatomite-phosphate solid acid catalysts was characterized by means of ion chromatography (IC), Hammett pH indicators and chemical titration. The results show that the free phosphoric acid is composed of 535 wt.% H₃PO₄, 17 wt.% H₄P₂O₇ and < 1 wt.% polyphosphoric acid, and its composition determines the acid strength distribution of the catalyst. When the total amount of free phosphoric acid containing >3 wt.% H₄P₂O₇ is within 9 26 wt.% (in P₂O₅), the catalyst shows higher catalytic activity for propylene oligomerization with propylene conversion >75wt.%. Besides, free phosphoric acid has an important effect on the catalytic selectivity. The relationship between them is discussed.     

On concentration self-quenching of chromium phosphorescence in K3[Cr x Co1−x (CN)6] mixed crystals

The self-quenching of chromium phosphorescence in K₃[Cr_xCo₁-x(CN)₆] mixed crystals has been studied in the range of very high chromium concentration and a minimum in emission quantum yield has been found at about 80% Cr. Comparison of the Cr emission intensities from K₃[Cr(CN)₆] doped with 1% of various impurities suggests that the impurity quenching observed in the range 90 to 100% Cr may be a result of the site asymmetry introduced by the impurity. It is suggested that at least two mechanisms of self-quenching are operative in this concentration range and the nature of these is discussed in relationship to present theories of radiationless transitions.

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Zusammenfassung Die Eigenlöschung der Cr(III)-Phosphoreszenz wurde in K₃[Cr_xCo₁-x(CN)₆]-Mischkristallen im Bereich hoher Cr-Konzentrationen untersucht. Die Quantenausbeuten der Emission zeigten ein Minimum bei etwa 80% Cr. Ein Vergleich der Lumineszenzintensitäten von K₃[Cr(CN)₆] mit 1% verschiedener Zusätze läßt vermuten, daß die im Bereich von 90–100 % Cr beobachtete Löschung von einer durch die Verunreinigung verursachten Gitterstörung herrührt. — Es wird angenommen, daß in dem untersuchten Konzentrationsbereich mindestens zwei Mechanismen der Eigenlöschung wirksam sind, die anhand der gegenwärtigen Theorien der strahlungslosen Übergänge diskutiert werden.

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Résumé L'auto étouffement du chrome phosphorescent à partir de K₃[Cr_xCo₁-x(CN)₆], cristaux mélanges avait été étudié dans la région de très haute concentration de chrome et un minimum d'émission quantique, il en résultait environ 80% Cr. Comparé à l'intensité d'émission de chrome à partir de K₃[Cr(CN)₆] contaminé par 1% de diverses impuretés indique que l'étouffement d'impureté qui était observé dans la région de 90 à 100% Cr, peut être le résultat de l'emplacement assimétrique introduit par l'impureté. — II a été suggéré qu'au moins deux mécanismes d'auto étouffement sont à l'oeuvre dans cette région de concentration et leur nature décrite en relation avec les présentes théories de transitions sans radiation.

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Dedicated to the memory of Professor Hans-Ludwig Schläfer.     

Analogs of pyrimidine nucleosides

N₁-(-Tetrahydrofuranyl)- and N₁-(-tetrahydropyranyl)uracils and the corresponding 6-azauracils have been obtained by the condensation of bistrimethylsilyl derivatives of uracils and 6-azauracils with-chlorotetrahydrofuran and-chlorotetrahydropyran. The superiority of the silyl method over the mercury method used previously has been demonstrated.For part III, see [9].     

Further studies on dppm-stabilized mixed-metal clusters: X-ray structure of PdPtCoCl(CO)3(μ-dppm)2 1

The metalloligated mixed-metal cluster [PdPtCo₂(CO)₇(-dppm)₂] (2) (dppm = -Ph₂PCH₂PPh₂) possesses numerous potential reaction centers (e.g., metal(s), metal-metal bonds, CO, and dppm ligands) and this has previously led to an investigation of the site selectivity of reactions with nucleophiles. The exocyclic CO(CO)₄ fragment was substituted with a chloride ligand and the resulting chiral, triangular cluster PdPtCoCl(CO)₃(-dppm)₂ (4) has been structurally characterized. The Pd-Co and Pt-Co edges of this almost equilateral triangle are bridged by a dppm ligand, and two of the three carbonyls borne by the Co atom are semi-triply bridging above and below the plane of the metals. The Co(CO)₃P fragment behaves as an anionic 4-electron donor organometallic bridging group toward thed ⁹-d ⁹ Pd(I)-Pt(I) unit. Crystal data for4, monoclinic space groupP2₁/n with Z=4 in a unit cell of dimensionsa=12.291(3),b=19.321(4),c=23.680(5) Å,=100.05(2)°. The structure has been solved from diffractometer data by Patterson, Fourier methods and refined by full-matrix least squares on the basis of 3512 observed reflections (l>3) toR(F) andR _w(F) values of 0.059 and 0.061.Dedicated to Professor L. F. Dahl on the occasion of his 65th birthday, with our sincere congratulations and best wishes.     

Stereospecific coordination ofl-hydroxyproline esters with triosmium clusters

The reactions of cluster (-H)Os₃(CO)₁₀(-OH) with ethyl and isopropyl esters ofl-oxyproline were studied. In the presence of Me₃NO intermediate complex (-H)Os₃(CO)₉(-OH)L (L — isopropyl ester ofl-oxyproline) is formed, which slowly converts to the more stable cluster (-H)Os₃(CO)₉ . Cluster complexes containing chelate-bridging heterocycles were also obtained by heating (-H)Os₃(CO)₁₀(-OH) with esters ofl-oxyproline. In both cases, only one of the possible diastereomeric complexes (-H)Os₃(CO)₉ (R = Et, Prⁱ) is formed, which indicates that the reactions are stereospecific. Based on analysis of Dreiding's models, an attempt to determine the absolute configuration of the obtained clusters was made.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2021–2025, October, 1995.     

Photolysis of 2-dialkylamino-3-amino(or alkylamino)-1,4-naphthoquinones

Using¹H and¹³C NMR spectroscopy, naphthodihydroimidazolediols were identified as the primary products of photolysis of 2-dialkylamino-3-amino(alkylamino)-1,4-naphthoquinones. Their further non-photochemical (thermal) transformations depend on their structure and on the photolysis conditions.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 358–362, February, 1993.     

NMR Spectral Assignment of Per-substituted Key-Intermediates of β-Cyclodextrin and Implications in the Structures of the Derivatives

The compounds, 6-per-O-(t-butyldimethylsilyl)--cyclodextrin(1), 2,3-per-O-benzyl-6-per-O-(t-butyldimethylsilyl)--cyclodextrin(2), 2,3-per-O-benzyl--cyclodextrin (3),2,3,6-per-O-benzyl--cyclodextrin (4),2,3,6-per-O-benzoyl--cyclodextrin (5), are used as keyintermediates in the synthesis of selectively substituted -CD derivatives. Simple and assignable ¹H and ¹³C NMR spectra (chemical shifts and coupling constants) were obtained for compounds1–4 indicating C₇ symmetry, ⁴C₁ glucose conformation and major arrangement of H6, H6' atoms at the primary side. The derivative 5, however, gave very broad peaksat room temperature. The peaks could partially be assigned at 270 K, but the broadening was still present at 220 K. This implies that there exist several conformers of similar energyand C₁ symmetry that continuously interchange, since there is not a single type of stabilizing interaction thatpredominates. We attributed this phenomenon to the presence of the carbonyl group, which probablydisfavors - stacking and induces random arrangements of the aromatic rings.