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  • Catalysis
  • Reaction mechanisms
  • Wiley-Blackwell  (39)
  • Institute of Physics
  • Molecular Diversity Preservation International (MDPI)
  • 1990-1994  (30)
  • 1960-1964  (9)
Collection
Keywords
Publisher
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Year
  • 1
    Electronic Resource
    Electronic Resource
    Bimolekulare Radikalbildung durch H-Transfer, 2. H-Transferreaktionen mit Phenalen (1993)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 126 (1993), S. 1039-1045 
    Details
    ISSN: 0009-2940
    Keywords: Hydrogen transfer ; Radical formation, molecule induced ; C—H bond dissociation enthalpies, determination of ; Catalysis ; Coal pyrolysis ; Phenalene ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Bimolecular Formation of Radicals by H-Transfer, 2[1]. - H-Transfer Reactions of PhenaleneThe uncatalysed H transfer from phenalane (7) to α1-methyl-styrene (2) and the selfreaction (d) of phenalene (7) are quantitative transformations in the presence of an excess of 9,10-dihydroanthracene (1) (DHA) in diphenyl ether at 200-250°C. In this system phenalene (7) is consumed only in reaction (d) because the phenalenyl radicals (9) are captured by DHA (1) to give phenalene (7) and 9,10-dihydroanthryl radicals (3). The latter disproportionate rapidly. Accordingly, phenalene (7) acts as a catalyst for the hydrogenation of α1-methylstyrene (2) by DHA (1). The activation parameters of the two reactions (e) and (d) were obtained from kinetic experiments between 200-250°C. They allow the determination of the C—H bond enthalpy δHdiss of phenalene (7) (65.3 kcal mol-1) at the methylene position.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19931260426
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  • 2
    Electronic Resource
    Electronic Resource
    Substituierte N,N-Chelat-Liganden - Anwendungen in der Molybdän-katalysierten Olefin-EpoxidationHerrn Prof. Dr. H. Schmidbaur zum 60. Geburtstag gewidmet. (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 2373-2379 
    Details
    ISSN: 0009-2940
    Keywords: Chelating ligands ; Molybdenum complexes ; Peroxo complexes ; Catalysis ; Olefine epoxidation ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Substituted N,N-Chelate Ligands - Applications in Molybdenum-Catalyzed Epoxidation of Olefins*Oxodiperoxomolybdenum complexes 4 of substituted 2-[3(5)-pyrazolyl]pyridines (2a-g) were synthesized in order to control the solubility of these complexes in organic solvents. Alkyl side chains (butyl, octyl, octadecyl) increase the solubility of the complexes and enable spectroscopic investigations in solution. Due to the symmetry of the ligands the peroxo complexes 4 appear in two isomeric forms, with the terminal oxo ligand in the trans position either to pyridine or to pyrazole. The latter isomer of (C5H4NC3H2N2CH2COOEt)MoO(O2)2 (4f) was characterized by an X-ray structure analysis. The alkyl-substituted peroxo complexes are active catalysts for the epoxidation of olefins with tert-butyl hydroperoxide.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19941271206
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  • 3
    Electronic Resource
    Electronic Resource
    Synthesis of Optically Active Bis(2-oxazolines): Crystal Structure of a 1,2-Bis(2-oxazolinyl)benzene ZnCl2 Complex (1991)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 124 (1991), S. 1173-1180 
    Details
    ISSN: 0009-2940
    Keywords: Bis(2-oxazolines) ; Chelating ligands ; Zinc complexes ; Catalysis ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Dinitriles (5-7, 12, 13) react with enantiomerically pure β-amino alcohols (8 - 11,17) under zinc chloride catalysis to give optically active C2-symmetric bis(oxazolines). 1,2-Bis(2-oxazolin-2-yl)benzenes 1a - e are obtained under mild reaction conditions. 1H-NMR spectroscopy indicates the formation of 1:1 complexes 23 of these compounds with ZnCl2. The energy required for a conformational interconversion of zinc dichloride complex 23e was determined by variable-temperature 1H-NMR studies. An X-ray structure analysis was performed with the substituted [1,2-bis(2-oxazolinyl)benzene]zinc dichloride complex 23a.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19911240532
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  • 4
    Electronic Resource
    Electronic Resource
    Zur Synthese und Charakterisierung von Platincyclobutadien-Komplexen durch Reduktion von Hexachloroplatinsäure (1993)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 126 (1993), S. 2393-2396 
    Details
    ISSN: 0009-2940
    Keywords: Platinum complexes ; Cyclobutadiene complexes ; Alkyne dimerization ; Catalysis ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthesis and Characterization of Platinumcyclobutadiene Complexes by the Reduction of Hexachloroplatinic AcidHexachloroplatinic acid is reduced in 1-butanol in the presence of an alkyne R-C≡C-R′ (R, R′ = Me, Et, nPr) to give platinumcyclobutadiene complexes [PtCl2(C4R2R2′)] (1). H[PtCl3(CH3CH2CH=CH2)] (2) is an intermediate which is isolated as bis(triphenylphosphoranylidene)ammonium salt (PPN-salt) [PPN][PtCl3(CH3CH2CH=CH2)] (3). The molecular structure of [PtCl2(C4Et4)] (1b) shows in the solid state a planar cyclobutadiene ring with internal bond angles of 93(3) and 87(2)°. The Pt-C bond lengths are 208(2) and 210(2) pm. The ethyl groups are pushed out of the ring plane, away from the Pt atom, with an angle of 7(2)°.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19931261108
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  • 5
    Electronic Resource
    Electronic Resource
    Fe(I)-Mediated Regio- and Stereoselective C—C/C—H Bond Activation of Internal Methylene Groups of α,ω-Diphenylalkanes (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 261-265 
    Details
    ISSN: 0009-2940
    Keywords: Bond activation ; C—H ; C—C ; Iron chemistry ; Reaction mechanisms ; Chelate effects ; Tandem mass spectrometry ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: For three α,ω-diphenylalkanes the mechanistic details of the Fe+-mediated activation of C—H and C—C bonds in the gas phase have been elucidated by isotopic labelling experiments. The unimolecular reactions, i.e. dehydrogenation of the alkane chain, formation of ethylene from internal methylene groups, and generation of toluene, proceed largely with high selectivity. Particularly interesting are the results for the dehydrogenation of the Fe+ complex 3-Fe+ of 1,8-diphenyloctane which involves to 93% the internal methylene groups C-4/C-5. In addition, the study of the stereoisotopomers 3c-d provides evidence for the operation of isotopically sensitive branching (“metabolic switching”) in the reaction, and the analysis of the data suggests that the selectivity of the reaction is, most likely, due to a sandwich-type structure.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19941270136
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  • 6
    Electronic Resource
    Electronic Resource
    Bimolekulare Radikalbildung durch H-Transfer, 7. Katalyse der Transferhydrierung von α-Methylstyrol durch 9,10-Dihydroanthracen mit 7H-Benz[de]anthracen (1994)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 127 (1994), S. 691-696 
    Details
    ISSN: 0009-2940
    Keywords: Molecule-induced radical formation, kinetics of ; Catalysis ; ESR spectroscopy ; Radical clock ; Isokinetic relationship ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Bimolecular Formation of Radicals by H-Transfer, 7[1].  -  Bimolecular Formation of Radicals via H-Transfer with Catalysis by 7H-Benz[de]anthraceneThe transfer hydrogenation of α-methylstyrene (2) by 9,10-dihydroanthracene (1) (DHA) with 7H-benz[de]anthracene (8) as a catalyst proceeds already at 210-260°C. Isotopic labeling, ESR spectroscopy, radical clock experiments, solvents effects, and thermochemical calculations support the postulated stepwise radical mechanism induced by bimolecular formation of radicals.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19941270419
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  • 7
    Electronic Resource
    Electronic Resource
    Optimization in organic synthesis. An approach to obtaining kinetic information by sequential response surface modelling. Outline of the principles (1993)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 7 (1993), S. 341-367 
    Details
    ISSN: 0886-9383
    Keywords: Reaction kinetics ; Initial rate ; Kinetic order ; Response surface modelling ; Canonical analysis ; Organic synthesis ; Optimization ; Reaction mechanisms ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A method is presented by which it is possible to estimate the initial rate of chemical reactions when the experimental conditions are varied according to a response surface design. The method is intended as a complementary method for analysing data obtained from experiments in synthetic chemistry when the objective is to optimize the yield of the reaction.Data obtained by simulations have been used to develop the method. From the simulated reactions it is shown that sequential analysis of the chemical yield of the reaction makes it possible to estimate models which describe how the parameters of the response surface of the yield vary over time. The derivatives of these time functions of the response surface parameters can be used to define a rate function which describes how the variations in the experimental conditions influence the rate of the reaction.It is shown how such rate functions can be used to afford reasonable estimates of the initial rates of the reaction. The initial reaction rates thus estimated can be used to determine the kinetic order of the reactants and also to provide estimates of the activation energy of the reaction.A thorough discussion of how canonical analysis of the rate function may assist in the elucidation of reaction mechanisms is given.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cem.1180070503
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  • 8
    Electronic Resource
    Electronic Resource
    Ultratrace determination of molybdenum in the presence of 2-(2′-thiazolylazo)-p-cresol by catalytic-adsorptive stripping voltammetry (1994)
    Weinheim : Wiley-Blackwell
    Electroanalysis 6 (1994), S. 333-339 
    Details
    ISSN: 1040-0397
    Keywords: Molybdenim ; Adsorptive stripping voltammetry ; Catalysis ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The adsorptive collection of the molybdenum (VI) complex of 2-(2′-thiazolylazo)-p-cresok (TAC), coupled with the catalytic current of the adsorbed complex, yield an ultrasensitive voltammetric procedure for the determination of molybdenum. Optimal experimental conditions were found with the use of a stirred acetate buffer (pH 2.9) supporting electrolyte, a TAC concetration of 1.0 × 10-5 M, and a concentration of 0.1 M potassium nitrate. In addition, a preconcentration potential of -0.13 V (vs. Ag/AgCl), equilibrium time of 30 seconds, and an anodic scan rate of 200 mV/s from -0. 93 to -0. 20 was used. A catalytic effect was observed when nitrate was present. The response was found to be linear over a concentration range of 0.0 to12.0 μg L-1 Mo (VI). For a preconcentration time of 3 minutes, the detection limit was found to be 11 pM. Possible interferences by anions and other trace metals were investigated. The interference by copper may be masked by CDTA, and sequential determination with molybdenum is possible. The merits of the procedure are demonstrated in the analysis of sea and mineral water.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/elan.1140060411
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  • 9
    Electronic Resource
    Electronic Resource
    Ligand-catalyzed metal ion reduction: Kinetics and analytical applications of nickel reduction catalyzed by nicotinamidePaper presented at the 4th International Symposium “Kinetics in Analytical Chemistry”, Erlangen, September 1992. (1994)
    Weinheim : Wiley-Blackwell
    Electroanalysis 6 (1994), S. 1051-1056 
    Details
    ISSN: 1040-0397
    Keywords: Nickel ; Nicotinamide ; Catalysis ; Polarography ; catalytic wave ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The catalytic reduction of Ni (II) in the presence of nicotihamide (NA) at pH 〈 7 was studied by direct-current and differential-pulse polarography (DPP). The prewave (with E1/2 around -0.78 V (versus saturated calomel electrode (SCE)) shows the typical behavior of an electrode process with regeneration of the reactant by a second-order, rate-determining chemical reaction. This reaction consists in the formation of the reducible nickel complex. The kinetics of the electrode process was studied by means of an adapted form of the equation derived by Koutecký for electrochemical reactions with a parallel chemical step. The rate constant for the formation of nickel-nicotinamide complex is slightly dependent en pH and buffer composition and ranges between 4.5 and 6.7 × 103 mole-1 L s-1. This electrode process enables the selective determination of Ni (II) in presence of a large excess of cobalt. For example, nickel impurity in cobalt salts can be determined by DPP, in acetate buffer (pH 4.6) containing 0.01 M nicotinamide and about 0.1 M cobalt salt sample.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/elan.1140061123
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  • 10
    Electronic Resource
    Electronic Resource
    Amperometric response of mediating layers on electrode surfaces to Gaussian concentration profiles in flowing streams (1992)
    Weinheim : Wiley-Blackwell
    Electroanalysis 4 (1992), S. 751-756 
    Details
    ISSN: 1040-0397
    Keywords: Catalysis ; flow analysis ; modified electrodes ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A model for a layer, containing catalytic centers, coated on an electrode and used for the mediation of analyte in a flowing stream is proposed and solved. The model applies to a situation of a Gaussian concentration profile of analyte impinging on the outer edge of the mediating layer. It was found that the important parameters that limit the current magnitude are the diffusion coefficient of the analyte through the layer, the effective electron diffusion coefficient through the layer and the rate of reaction between the mediator and the analyte. On evaluation of literature data, it was found that layers, high catalyst loading and with high rates of electron exchange, lead to linear peak current height versus concentration plots.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/elan.1140040803
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