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  • 1
    Electronic Resource
    Electronic Resource
    NMR Observation of the Koch Reaction in Zeolite H-ZSM-5 under Mild Conditions (1995)
    s.l. : American Chemical Society
    Journal of the American Chemical Society 117 (1995), S. 3615-3616 
    Details
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ja00117a032
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  • 2
    Electronic Resource
    Electronic Resource
    Fourier Transform Ion Cyclotron Resonance Studies of Gas-Phase Reactions between Tungsten Ions and Hydrocarbons (1994)
    s.l. : American Chemical Society
    Organometallics 13 (1994), S. 2536-2538 
    Details
    ISSN: 1520-6041
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/om00018a060
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  • 3
    Electronic Resource
    Electronic Resource
    Modelling of the prebiotic synthesis of oligopeptides: silicate catalysts help to overcome the critical stage (1997)
    Springer
    Origins of life and evolution of the biospheres 27 (1997), S. 325-337 
    Details
    ISSN: 1573-0875
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract On the basis of experimental studies of the initial stages of glycine oligomerization in aqueous suspension of zeolite and kaolinite catalysts, a model is suggested for the prebiotic synthesis of oligopeptides from α-amino acids. The formation of linear dipeptides by hydrolysis of one amide bond in the cyclic piperazinedione intermediate (formed from glycine spontaneously) is found to be the critical stage of the reaction. This stage is base catalyzed and its rate increases when pH of the medium goes up. The linear glycyl-glycine yield rises under effect of hydroxyl anions generated from different sources including insoluble silicates and soluble sodium bicarbonate. During prebiotic evolution silicates capable of cation-exchange can serve as local sources of the hydroxyl anions which dramatically accelerate formation of linear dipeptides from cyclic ones. Oligopeptides of higher molecular weight are then easily formed from the linear dipeptides at neutral pH, even in the absence of catalysts or sources of energy (e.g. such as light). The described catalytic synthesis could occur in the proximity of submarine hydrothermal vents.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006571800690
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  • 4
    Electronic Resource
    Electronic Resource
    Carbenium ion properties of octene-1 adsorbed on zeolite H-ZSM-5 (1994)
    Springer
    Catalysis letters 24 (1994), S. 271-284 
    Details
    ISSN: 1572-879X
    Keywords: Octene-1 ; H-ZSM-5 zeolite ; 13C carbon scrambling ; carbenium ion ; 13C CP/MAS NMR ; 2H NMR
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract It is shown that octene-1 adsorbed on zeolite H-ZSM-5 at ambient temperature exhibits carbenium ion properties. Namely: (1) According to2H NMR, the proton of the acidic ≡Al-OH-Si≡ group of the zeolite is transferred into the CH2= group of the octene-1 molecule. (2) According to13C NMR the13C label inserted into the terminal CH2= group of the octene-1 molecule is scrambled over its hydrocarbon skeleton. Thermodynamic and kinetic parameters for carbon scrambling are measured within the temperature range 290–343 K. The zeolite framework is shown to favour the formation of the linear rather than branched carbeniumion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00811800
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  • 5
    Electronic Resource
    Electronic Resource
    13C solid state NMR evidence for the existence of isobutyl carbenium ion in the reaction of isobutyl alcohol dehydration in H-ZSM-5 zeolite (1993)
    Springer
    Catalysis letters 19 (1993), S. 153-158 
    Details
    ISSN: 1572-879X
    Keywords: Isobutyl carbenium ion ; carbon scrambling ; H-ZSM-5 zeolite ; 2DJ-resolved13C solid state NMR ; dehydration of isobutyl alcohol
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Using two-dimensionalJ-resolved and CP/MAS13C NMR, the pathway for the transfer of the13C label from the CH2 group of isobutyl alcohol into the hydrocarbon skeleton of butene oligomers has been elucidated in the course of isobutyl alcohol dehydration inside H-ZSM-5 zeolite. First, the label is transferred selectively into the CH2 group of the isobutyl silyl ether reaction intermediate (IBSE), and then into the CH and CH3 groups of the isobutyl fragment (-CH2CH(CH3)2) of IBSE and/or butene oligomers. Finally, it is scrambled over the carbon skeleton of the oligomers. The obtained data suggest that isobutyl carbenium ion is formed as a reaction intermediate or transition state during the transformation of isobutyl silyl ether into butene oligomers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00771750
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  • 6
    Electronic Resource
    Electronic Resource
    13C CP/MAS NMR study of isobutyl alcohol dehydration on H-ZSM-5 zeolite. Evidence for the formation of stable isobutyl silyl ether intermediate (1992)
    Springer
    Catalysis letters 13 (1992), S. 395-405 
    Details
    ISSN: 1572-879X
    Keywords: Isobutyl alcohol ; dehydration ; H-ZSM-5 zeolite ; isobutyl silyl ether ; di-isobutyl ether ; carbenium ion ; 13C CP/MAS NMR
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Dehydration of isobutyl alcohol selectively labelled with a13C nucleus in the CH2 group (i-BuOH[1−13C]) has been studied on H-ZSM-5 zeolite within the temperature range 296–448 K using13C CP/MAS NMR. The formation of the isobutyl silyl ether intermediate (IBSE) has been detected. It is stable below 398 K. Within the temperature range 398–423 K IBSE decomposes gradually to produce first a butene dimer, probably 2,5-dimethyl-l-hexene and then other butene dimers and oligomers. AtT 〉 423 K scrambling of the selectively labelled carbon of the initial dimeric product over various positions in the carbon skeleton of the final dimers (oligomers) is observed. This is explained in terms of the formation of carbenium ion as the reaction intermediate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00765043
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  • 7
    Electronic Resource
    Electronic Resource
    13C CP/MAS and2H NMR study of tert-butyl alcohol dehydration on H-ZSM-5 zeolite. Evidence for the formation of tert-butyl cation and tert-butyl silyl ether intermediates (1992)
    Springer
    Catalysis letters 13 (1992), S. 407-422 
    Details
    ISSN: 1572-879X
    Keywords: tert-butyl alcohol ; dehydration ; H-ZSM-5 zeolite ; tert-butyl cation ; tert-butyl silyl ether ; mechanism of reaction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The dehydration reaction of tert-butyl alcohol, selectively labelled with13C in CH3 or C-O groups (t-BuOH[2−13C2] andt−BuOH[1-13C]), as well as selectively deuterated in methyl groups (t-BuOH[2-2H9]), was studied on H-ZSM-5 zeolite simultaneously with13 C CP/MAS and2H solid state NMR. When adsorbed and dehydrated on zeolite at 296 K,t-BuOH[2−13C1] andt-BuOH[1−13C] give rise to identical13C CP/MAS NMR spectra of oligomeric aliphatic products. This is explained in terms of the fast isomerization of the tert-butyl hydrocarbon skeleton via the formation of tert-butyl cation as the key reaction intermediate. An alkoxide species, most probably tert-butyl silyl ether (t-BuSE), was also detected as the “side” reaction intermediate. This intermediate was stable within the temperature range 296–373 K and decomposed at 448 K to produce additional amounts of final reaction products, i.e. butene oligomers. NMR data point to the existence of equilibria between the initial tert-butyl alcohol, tert-butyl cation and butene that is formed from the intermediate carbocation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00765044
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  • 8
    Electronic Resource
    Electronic Resource
    Ion-cyclotron resonance study of elementary stages of the catalytic oxidation of CO by N2O in the presence of VIA-group metal ions (1993)
    Springer
    Catalysis letters 21 (1993), S. 353-360 
    Details
    ISSN: 1572-879X
    Keywords: Ion-cyclotron resonance ; gas phase catalytic oxidation ; nitrogen monoxide ; carbon monoxide ; MOx + ; rate constants ; bond energies
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Gas phase reactions of Mo+ and W+ ions with the molecules of various oxidants (NO, O2, N2O, CH2O, C2H4O) were studied using ion cyclotron resonance. In oxidation with N2O the mono-, di- and trioxide metal cations are formed consecutively. The trioxide MO3 + ions of both metals react with CO to form CO2 and MO2 + ions. In this way, catalytic reaction N2O + CO → N2 + CO2 occurs in the gas phase with MoO3 + /MoO2 + and WO3 +/WO2 + couples as catalysts. The rate constants have been measured for both stages of the catalytic cycle as well as for the stages of the catalyst preparation. Metal-oxygen bond energies were estimated for MoOx + and WOx + species with various x. The mechanism of CO oxidation with MoOx + and WOx + cations as catalysts in the gas phase is discussed in comparison with that for the oxidation over classical solid oxide catalysts.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00769487
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  • 9
    Electronic Resource
    Electronic Resource
    Catalysis by molecular design (1996)
    Springer
    Topics in catalysis 3 (1996), S. 1-76 
    Details
    ISSN: 1572-9028
    Keywords: catalysis by molecular design ; metal complexes ; outer-sphere coordination ; anchored metal complexes ; anchored organometallics ; metal single crystals ; small supported metal particles ; oxides ; zeolites ; heteropolyacids ; nontraditional oxidants ; biomimetic catalysis ; new carbon materials ; new catalytic technologies
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The possibilities of molecular design in the development of new catalysts and catalytic technologies are discussed with the data obtained recently at the Boreskov Institute of Catalysis as particular examples. Examples from the following areas are presented: homogeneous catalysis with metal complexes, heterogeneous catalysis with anchored metal complexes, heterogeneous catalysis with catalysts prepared via anchored metal complexes and organometallics, catalysis of olefin polymerization, catalysis by metals, catalysis by oxides, catalysis by zeolites, catalysis by heteropolyacids, catalysis with nontraditional oxidants and biomimetic catalysis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02431177
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  • 10
    Electronic Resource
    Electronic Resource
    Alkene oxidation catalyzed by transition metal substituted Keggin-type heteropolyanions (1996)
    Springer
    Topics in catalysis 3 (1996), S. 313-325 
    Details
    ISSN: 1572-9028
    Keywords: transition metal substituted heteropolytungstates ; alkene oxidation ; epoxidation mechanisms ; oxidant activation ; tert-butyl hydroperoxide ; iodosylbenzene ; dioxygen ; isobutyraldehyde
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Alkene oxidations with various oxidants (tert-butyl hydroperoxide, iodosylbenzene and molecular oxygen in the presence of isobutyraldehyde (IBA)) catalyzed by transition metal monosubstituted heteropolyanions, PW11MO 39 n− (PW11M; M=CoII, MnII, CuII, TiIV, RuIV, VV and NbV), have been studied. Orders of catalytic activity of PW11M are different for the oxidants studied. Radical chain mechanisms are proposed fort-BuOOH and O2/IBA. Preliminary coordination of the oxidant to PW11M is not a necessary step of its homolytic activation. Epoxidation with PhIO requires its coordination to the catalyst and most likely includes the formation of active metal-oxo species.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02113857
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