Effect of radial distribution functions and poisson reparatition of reactants on the analysis of reactions involving long distance energy transfer

Starting from a uniform distribution and knowing the space dependent rate constant, it is possible to express the fluorescence quenching effect. In the case of long distance energy transfer (Forster), we show that the introduction of radial distribution functions and of non-uniform repartition of quenchers has only small effects on the kinetics of such reactions.

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. (Forster) , .

     

Properties and diversity of C18 bonded phases

Summary The effect of the properties of the silica gel matrix, and of the octadecylsilane used, on the chromatographic selectivity of C18 bonded phases is described. Preparation of bonded phases with monochlorodimethyloctadecylsilane is easier because absolute water exclusion is not required in this case. The surface coverage (mol/m²) is smaller than with dichloromethyl- or trichlorooctadecylsilanes, but in these cases a secondary silanization with HMDS is essential to remove newly formed silanol groups. Bonded phases on Si 60 give the largest amount of hydrocarbon per unit column volume, large k values and good selectivity, however, surface coverage and efficiency of these packed columns is less than with Si 100 silica. The chemical properties of the silica surface also influence bonded phase selectivity. Bonded phases should not be compared with only a single eluent, because properties of bonded phases differ with test solutes and test conditions, i.e. eluent composition.Presented at the 14th International Symposium on Chromatography London, September, 1982In Part from Ph. D. Thesis H. Schmidt, Saarbrücken 1978     

X-ray diffraction studies on homologous thallium soaps below the temperature range of the neat phase 1. Calculation and comparison of the structure parameters of unit cells

The results of X-ray diffraction patterns of homologous thallium soaps TlC _n (n-8, 9, 10, 11, 12, 14, 15, 16, 17, 18, 20 and 22) in dependence on the temperature showed that the structures of the phases below the temperature range of the liquid-crystalline neat phase (so called phase C₁, phase C₂, phase I, phase II) are crystalline-like, not liquid-crystalline.As function of the chain length of the fatty acid group, we found the following phase sequences to be a function of temperature: TlC₈: phase Ineat phase: TlC₉–Tl₁₄: phase C₂phase IIphase Ineat phase; TlC₁₅, TlC₁₆: phase C₁phase IIphase Ineat phase; TlC₁₇–TlC₂₂: phase C₁phase IIneat phase.From the X-ray patterns of the thallium soaps were calculated the lattice parameters and the unit cells of these homologues at various temperatures. The comparison between the lattice parameters of the homologues showed, surprisingly, that these parameters were independent of chain length and temperature. This X-ray data are the basis for the following development of structure models of the phase C₁, phase C₂, phase I, and phase II, including the neat phase (see Part 2).     

Binuclear Osmium μ-Oxocarboxylate Complexes [Os2(μ-O)(μ-O2CR)2Cl4L2] (R = CH3, CCl3; L = PPh3, AsPh3) and Their Electrochemical Behavior in Dichloromethane

Cyclic voltammetry and galvanostatic coulometry techniques were used to determine how the redox properties of osmium binuclear -oxocarboxylates [Os₂ ^IV(-O)(-O₂CR)₂Cl₄L₂] (R = CH₃, CCl₃; L = PPh₃ and R = CH₃; L = AsPh₃) are influenced by the nature of the bridging carboxylate ligand RCOO^– and ligand L. It was shown that all compounds in solution of dichloromethane undergo two single-electron reduction processes. The data obtained were compared with the DFT calculations of the electronic structure of the model complexes [Os₂ ^IV(-O)(-O₂CR)₂Cl₄L₂] (R = CH₃, CCl₃; L = PH₃ and R = CH₃; L = AsH₃).     

Universal system for liquid stationary phase classification on the basis of thermodynamical data

Summary Equations modifying Rohrschneider's relationship between I and thermodynamical characteristics values are derived. Polarity in chromatography is discussed as a possibility of stationary phases or absorbents to enter into intermolecular interactions and is determined on the basis of the partial molar free energies of solution (G) of six test substances. A simple method for the calculation of stationary phase polarity in terms of G from retention indices and McReynolds constants is given. Equations are presented for the calculation of stationary phase selectivity utilizing G data tabulated for selected test substances. The thermodynamical basis of selecting a reference phase for a unified system expressing the selectivity of stationary phases which can also be applied for adsorbents is suggested. The energy equivalent to an index unit, G_i.u., is discussed.     

Nature of ethylene complexes on the surface of Ag/SiO2 as evidenced by13C NMR data

The formation of -complexes of C₂H₄ with Ag⁺ on oxidized Ag/SiO₂ catalysts is shown by¹³C NMR. These complexes are similar in nature to those of olefins with silver in solution.

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¹³C , Ag/SiO₂ - C₂H₄ Ag⁺, - .

     

Reactions of the Ru3(CO)10(μ-Ph2PCH2PPh2) cluster with enynes RCH=CHC≡CR (R is phenyl or ferrocenyl). Formation of indenone derivatives of triruthenium clusters

The thermal reaction of Ru₃(CO)₁₀(-Ph₂PCH₂PPh₂) (1) with enyne PhCH=CHCCPh afforded the trinuclear ruthenium clusters Ru₃(CO)₆{₃-P(Ph)CH₂PPh₂}{₃-C(Ph)=CHCC(Ph)(1,2-C₆H₄)C(=0)} (2), Ru₃(-H)(CO)₅{₃-P(Ph)CH₂PPh₂}{₃-C(Ph)=CHCC(Ph)(1,2-C₆H₄)C(—0)} (3), and Ru₃(CO)₆(-CO){₃-P(Ph)CH₂PPh₂}{₃-C(C=CPh₂)CH=C(H)Ph} (4) and also two isomers of Ru₃(CO)₅(-CO)(-Ph₂PCH₂PPh₂){₃-C₄Ph₂(CH=CHPh)₂} (5a and 5b). Clusters 2, 3, and 4 were characterized by IR spectroscopy, ¹H and ³¹P NMR spectroscopy, and X-ray diffraction analysis. The reaction of complex 1 with enyne FcCH=CHCCFc gave rise to the Ru₃(CO)₆{₃-P(Ph)CH₂PPh₂}{₃-C(Fc)=CHCC(Fc)(1,2-C₆H₄)C(=0)} (6) and Ru₃(-H)(CO)₅{₃-P(Ph)CH₂PPh₂}{₃-C(Fc)=CHCC(Fc)(1,2-C₆H₄)C(—0)} (7) clusters. According to the spectral data, the latter compounds are isostructural to complexes 2 and 3, respectively.     

Reaktion von Alkyl- und Arylchlorsilanen mit Phosph(III) en-imidamiden

The reaction of RSiCl₃ (R=CH₃, C₂H₅, C₆H₅) and R₂SiCl₂ (R=CH₃) with one mole of the phosphenimidous amides R₂N–P=NR [R=R=Si(CH₃)₃; R=Si(CH₃)₃, R=C(CH₃)₃] yieds a four membered PN₂Si-ring system under elimination of (CH₃)₃SiCl.     

Studies of copper-modified V?Mo oxide catalyst for acrolein oxidation to acrylic acid

Modification of a V–Mo oxide catalyst by copper improves its catalytic properties due to the formation of a variable composition V–Cu–Mo–O phase with varying the ratio Mo/Me (Me=V+Cu).

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T–Cu–Mo–O, Mo/Me, Me=V+Cu.

     

Decomposition of hydrogen molybdenum bronze, H0.30MoO3, upon increasing temperature in various gases

When H_0.30MoO₃ was heated at increasing temperature in H₂, N₂, H₂O, and in vacuum, the total weight loss just corresponded to the weight of 0.15 H₂O in H_0.30MoO₃. On the other hand, when the bronze was heated in CH₃OH vapor, one of the lattice oxygens was removed and the bronze was partly reduced to MoO₂.

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H_0,30MoO₃ H₂, N₂, H₂O , 0,15H₂O H_0,30MoO₃. , CH₃OH, MoO₂.

     

FTIR studies of vitamin E-cholesterol-DPPC membrane interactions in CH 2 region

Binary and ternary mixtures of -tocopherol (T), cholesterol and dipalmitoyl phosphatidylcholine (DPPC) in the form of multilamellar liposomes have been investigated by Fourier Transform Infrared Spectroscopy (FTIR). Investigation of frequencies, bandwidths and band shapes of CH₂ stretching and scissoring bands indicate that the effect of T is dominant in comparison with cholesterol and T decreases the interaction of cholesterol with phospholipid membranes.     

Competitive hydrogenation of binary olefin mixtures in the liquid phase

The effect of a series of alcohol solvents on the selectivity of the competitive catalytic hydrogenation of 1-hexene and 2-methyl-3-butene-2-ol on Pt/SiO₂ catalyst has been investigated. With increasing molecular mass of the alcohol, the rate of hydrogenation of 1-hexene becomes relatively preferred; the same was observed also with branched alcohols compared with those having a straight chain. Systems were found in which the degree of coating of the platinum catalyst with copper affected (or did not affect) the selectivity of the competitive hydrogenation of pairs of olefinic substrates.

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— — 1- 2--3--2- Pt/SiO₂ . 1-, . , ( ) .

     

Comparative study of some commercial chemically bonded phases in classical reversed-phase chromatography and in ion-pair reversed-phase liquid chromatography

Summary The behaviour of various octadecyl commercial bonded phases are compared in classical reversed-phase chromatography and in ion-pair reversed-phase chromatography. Great differences are exhibited by the packings studied according to the polarity of the solutes. Whereas hydrocarbonaceous bonded phases show very similar selectivity versus apolar or weakly polar solutes, great differences are observed when analyzing more polar solutes even when ion-pair reversed-phase chromatography is performed.Presented at the 14th International Symposium on Chromatography London, September, 1982     

Reduction of benzylideneaniline over supported Pd catalysts

In this work we have carried out a study on the liquid phase hydrogenation of benzylideneaniline, using dihydrogen over various supported Pd catalysts. Benzyl-ideneaniline reduction can be classified as insensitive to the catalyst structure. On the other hand, no compensating effect has been observed in performing the reaction over different supported Pd catalysts.

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Pd , . . Pd , .

     

Thermodynamics of solution of alcohols in <Emphasis Type="Italic">p-n</Emphasis>-alkoxycynnamoyloxy-<Emphasis Type="Italic">p′</Emphasis>-cyanoazobenzene mesomorphic phases by gas chromatography

Thermodynamic characteristics of solution of n-alcohols in p-n-alkoxycynnamoyloxy-p-cyanoazobenzene liquid crystalline phases at infinite dilution are obtained. For each of the mesogens studied, the solubility of sorbates in the nematic phase is higher than in smectic. Increasing alkyl chain length in sorbates decreases their solubility in mesomorphic phases, whereas increasing alkyl chain length in liquid crystals exerts the opposite effect. The greater endothermic effect of solution of alcohols corresponds to higher entropy and positive deviations from ideality.Translated from Zhurnal Obshchei Khimii, Vol. 74, No. 8, 2004, pp. 1300–1305.Original Russian Text Copyright © 2004 by Blokhina, Sharapova, Olkhovich.This revised version was published online in April 2005 with a corrected cover date.     

Polymeric membrane sodium-selective electrodes based on calix[4]arene ionophores

Six kinds of tetra alkylester type calix[4]arene derivatives, (R₁=R₂=CH₃1, C₂H₅2, C₃H₇3,n-C₄H₉4,t-C₄H₉5,n-C₁₀H₂₁6), a diethyl-didecyl mixed ester type (R₁=C₂H₅, R₂ =C₁₀H₂₁7), and three kinds of lower rim bridged types (R₁=C₂H₅, R₂–R₂=(CH₂)₁₀8, (CH₂)₁₂9, (CH₂)₂(OCH₂CH₂)₃10) were characterized by electrochemical measurement to elucidate the effect of the length of the alkyl group of alkoxycarbonyl substituents on Na⁺ selectivity. To obtain excellent Na⁺ selective ionophores, introduction of short chain alkyl groups rather than long chain ones, such as a decyl group, and maintenance of sufficient solubility of the calix[4]arene derivatives in the membrane solvent are required concurrently. Among the calix[4]arenes tested, 25,26,27,28-tetrakis[(ethoxycarbonyl)methoxy]-p-tert-butylcalix[4]arene2, and the diethyl-didecyl mixed ester type derivative7 are the best ionophores for a Na⁺ selective electrode. On the other hand, sodium selectivity of the bridged type derivative9 is comparable or even superior to that of the known bis(12-crown-4).This paper is dedicated to the commemorative issue on the 50th anniversary of calixarenes.     

Identifiability of first order reaction systems

The question of the possibility to determine all the unknown parameters of kinetic models is considered. A simple algebraic condition for structural identifiability in first order reaction systems is given.

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. .

     

Phase identification in Ti/TiN diffusion couples with the Kossel technique

A Ti/TiN diffusion couple, which had been prepared by isothermal annealing of a Ti sheet in nitrogen atmosphere at 1091 °C and quenched in water, was investigated by Kossel microdiffraction. Kossel patterns were obtained from all phases present in the diffusion couple (-Ti(N), -Ti₃N_2–x, -Ti₄N_3–x and -TiN_1-x)It could be shown that the Kossel technique has a superior lateral resolution (10 m) compared to commercially used X-ray microdiffraction methods, especially in the case of weak X-ray radiation.     

Redistribution kinetics of isotope molecules due to reversible bimolecular reactions with several atomic channels

Isotope kinetic equations for reversible bimolecular reactions describe the rearrangement of atoms in activated complexes. It has been established from the model reaction CH₄+HCH₃+H₂ that the isotopic homoexchange of methane via two atomic channels is given by one set of equations with different sets of parameters.

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- . CH₄+HCH₃+H₂ , .

     

Diffuse reflectance spectroscopic studies of supported molybdenum oxide catalysts for propene metathesis

Diffuse reflectance spectra of 10 wt.% MoO₃ supported on -Al₂O₃ and SiO₂ have been measured after various steps of treatment. -Al₂O₃ was pretreated by 0.05 and 1.0 wt.% KOH. The comparison of spectral data and catalytic properties allows to predict the optimal oxidation state of molybdenum ions in surface clusters (approximately Mo⁵⁺), necessary to obtain supported MoO₃ catalysts for propene metathesis with high activity and selectivity.

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, -Al₂O₃ SiO₂ 10% . . -Al₂O₃ 0,05% 1,0% KOH. ( Mo⁵⁺), .