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  • ethyl pyruvate  (3)
  • 2000-2004  (1)
  • 1995-1999  (2)
  • 1
    Electronic Resource
    Electronic Resource
    Enantioselective hydrogenation of ethyl pyruvate in supercritical fluids (1995)
    Springer
    Catalysis letters 34 (1995), S. 1-9 
    Details
    ISSN: 1572-879X
    Keywords: enantioselective hydrogenation ; supercritical fluids ; ethyl pyruvate ; cinchonidine ; Pt/alumina ; CO-poisoning
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The enantioselective hydrogenation of ethyl pyruvate to (R)-ethyl lactate has been studied using gases under supercritical conditions as solvents. The catalyst was a 5 wt% Pt/alumina modified with cinchonidine. In supercritical ethane the reaction time could be reduced by a factor of 3.5 compared to toluene under similar conditions, without any loss in enantioselectivity. A further advantage of ethane is that the enantioselectivity remains high even at high catalyst/reactant ratio, which is interesting in view of a possible application of a continuous fixed-bed reactor for this reaction. A strong catalyst deactivation was observed in supercritical CO2, which is due to the reduction of CO2 on Pt as indicated by FTIR.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00808315
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  • 2
    Electronic Resource
    Electronic Resource
    Adsorption mode of ethyl pyruvate on platinum: an in situ XANES study (2000)
    Springer
    Catalysis letters 66 (2000), S. 109-112 
    Details
    ISSN: 1572-879X
    Keywords: ethyl pyruvate ; in situ XANES ; enantioselective hydrogenation ; platinum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The adsorption of ethyl pyruvate on Pt(111) has been studied by in situ XANES measurements in the presence and absence of hydrogen. Depending on the hydrogen and ethyl pyruvate pressure, the C and O K‐edge spectra exhibit distinctly different angular dependence. Without hydrogen ethyl pyruvate is oriented preferentially perpendicular to the surface, indicating bonding via the O lone pairs. In the presence of hydrogen the mean orientation is more tilted towards the surface. Likely, ethyl pyruvate also interacts with Pt via its π system under these conditions. The observed angle‐dependent shift of the energy of the π* and σ* resonances indicates the coexistence of differently adsorbed ethyl pyruvate species. The experimental findings demonstrate the importance of the in situ approach for unraveling the adsorption mode of ethyl pyruvate in the enantioselective hydrogenation over cinchona‐alkaloid‐modified Pt.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1019047622959
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  • 3
    Electronic Resource
    Electronic Resource
    Chiral nitrogen compounds as new modifiers for the enantioselective hydrogenation of ethyl pyruvate (1995)
    Springer
    Catalysis letters 31 (1995), S. 143-151 
    Details
    ISSN: 1572-879X
    Keywords: enantioselective hydrogenation ; chiral modifier ; ethyl pyruvate ; Pt/alumina
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The enantioselective hydrogenation of ethyl pyruvate to (R)- or (S)-ethyl lactate has been studied over alumina- and carbon-supported Pt-metal catalysts modified by various heterocyclic N-compounds and substituted amides. The reactions were carried out under mild conditions in acetic acid; other solvents had a detrimental effect on enantioselectivity. An enantiomeric excess (ee) of 67% and a rate acceleration by a factor of 6, compared to the unmodified catalyst, was observed with alumina-supported Pt modified by (R)-1-(1-naphthyl)ethylamine. In contrast, carbon-supported Pd, Ru and Rh were non-selective and only little active. The studies indicated that besides naphthyl or quinolyl groups, two separate phenyl groups or one phenyl group together with two amino groups can provide a suitable anchoring of the chiral modifier on the Pt surface. The nature of interaction between the modifiers and ethyl pyruvate is briefly discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00808828
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