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  • 1
    Electronic Resource
    Electronic Resource
    Enantioselective synthesis of highly functionalized 4-piperidones by the asymmetric imino-diels-alder reaction of chiral 2-amino-1,3-butadienesAbbreviations used in this article: NaHMDS: sodium bis(trimethylsilyl)-amide; TMS: trimethylsilyl; MOM: methoxymethyl; TBDMS: tert-butyldimethylsilyl; 3-Fu: 3-furyl; p-MeOPh: 4-methoxyphenyl; o-BrPh: 2-bromophenyl; p-BrC6H4CO: 4-bromobenzoyl; (R)-MPTA: (R)-α-methoxy-α-Phenyl-α-trifluoromethylacetyl. (1996)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 2 (1996), S. 805-811 
    Details
    ISSN: 0947-6539
    Keywords: asymmetric Diels-Alder reactions ; butadienes ; Diels-Alder reactions ; piperidones ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Chiral 2-amino-1,3-butadienes 1 derived from commercially available (S)-2-methoxymethylpyrrolidine react with aromatic N-trimethylsilylaldimines and N-phenylaldimines in the presence of ZnCl2 to give, after the reaction workup, 4-piperidones 4 and 6, respectively, with moderate to very high enantiomeric excesses. In addition, the absolute configurations of derivatives of 4 a and 4 g were determined by circular dichroism and NMR spectroscopy on the Mosher ester, respectively.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chem.1460020710
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  • 2
    Electronic Resource
    Electronic Resource
    On the Stability of the Schiff Bases of Pyridoxal 5′-Phosphate with Polypeptides Containing L-Lysine (1991)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 74 (1991), S. 1749-1756 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We determined the apparent equilibrium constant of formation, KpH, of the Schiff bases of pyridoxal 5′-phosphate (PLP) and poly- and copolymers containing L-lysine, as a function of pH at 25° and a constant ionic strength of 0.1 M. The KpH values obtained at acidic and neutral pH were larger that those reported for Schiff bases of PLP and hexylamine. We determined calorimetrically ΔH of formation of Schiff bases of PLP and poly(L-lysine) (-4.5′kcal/mol), and PLP and hexylamine (-3.4 kcal/mol) at pH 7.00. Semi-empirical theoretical calculations (INDO and AMI methods) of a model compound of Schiff base of PLP and polypeptide containing L-lysine show the capability of specific interactions between groups of PLP and the peptide skeleton.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19910740817
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  • 3
    Electronic Resource
    Electronic Resource
    Simultaneous determination of rare earths by x-ray fluorescence spectrometry using a fundamental parameters method (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    X-Ray Spectrometry 22 (1993), S. 362-367 
    Details
    ISSN: 0049-8246
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Concentrates extracted from a lateritic mineral deposit were analysed for their rare earth (RE) content by energy-dispersive x-ray fluorescence (XRF) spectrometry. The L emission lines of the lanthanides were excited with the 22.1 keV Ag K radiation from an annular Cd-109 radioisotope source. The problem of the extensive overlap of the L lines were solved by the AXIL program for deconvolution of XRF spectra. Individual REs were quantified by preparing semi-transparent pellets of the concentrate with starch which served as dilutant and binder. This allowed correction for sample absorption with the light matrix program of the QXAS analysis package based on the fundamental parameter method. The method allowed the simultaneous determination of 12 rare earths contained in the sample, with a reproducibility of 2.0-29% and accuracy in the range 1.5-24% relative error without the use of standard materials. Detection limits achieved were in the range of 340 ppm for the heavy REs and 4000 ppm for the light REs.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/xrs.1300220508
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  • 4
    Electronic Resource
    Electronic Resource
    Pyruvate kinase activity and response to allosteric effectors in rat erythrocytes and reticulocytes fractionated by multiple partitioning in aqueous two-phase systems (1987)
    New York, NY [u.a.] : Wiley-Blackwell
    Cell Biochemistry and Function 5 (1987), S. 301-307 
    Details
    ISSN: 0263-6484
    Keywords: Pyruvate kinase ; allosteric effectors ; erythrocytes ; reticulocytes ; counter-current distribution ; two-phase systems ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Specific activity of pyruvate kinase decreases as the age of rat erythrocytes increases in fractions obtained by counter-current distribution in dextran-polyethylene glycol biphasic systems; the enzyme is inhibited by ATP and activated by fructose-1,6-bisphosphate at low phosphoenol pyruvate concentrations. Specific activity does not change in fractions from 〉 95 per cent-rich reticulocytes (anaemic rats); the enzyme is inhibited by ATP but not activated by fructose-1,6-bisphosphate. These results can be explained on the basis of different pyruvate kinase isozymes and suggest that decrease in activity is not affecting regulatory properties during erythrocytes aging.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cbf.290050409
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  • 5
    Electronic Resource
    Electronic Resource
    Estimation of primary radical and macro-radical transfer, re-initiation and cross termination constants of retareded free radical polymerization by computational by computational technique (1987)
    Weinheim : Wiley-Blackwell
    Acta Polymerica 38 (1987), S. 21-23 
    Details
    ISSN: 0323-7648
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die kinetischen Konstanten der retardierten, freiradikalischen Polymerisation wurden nach der Methode der kleinsten Quadrate mit Hilfe eine nichtlinearen Logarithmus bestimmt. Ein allgemeines Schema der degradativen Übertragung von primaären Radikalen und Makroradikalen wird vorgestellt.
    Notes: The kinetic constants of retarded free radical polymerization mechanism were estimated by a nonlinear least-squares algorithm. A general picture of primary radical and macro-radical degradative transfer is presented.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/actp.1987.010380105
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  • 6
    Electronic Resource
    Electronic Resource
    Determination of Pollutant Phenols by Capillary High-Performance Liquid Chromatography with UV Detection (2000)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 23 (2000), S. 367-372 
    Details
    ISSN: 0935-6304
    Keywords: Capillary HPLC ; gradient elution ; temperature programming ; phenolic compounds ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---This paper describes a liquid chromatographic method using a reversed phase capillary column coupled to an UV detector for the quantitation of thirteen pollutant phenols. Chromatographic separation was carried out with gradient elution at 25.0 ± 0.1°C. The two major anisocratic elution modes (gradient elution and temperature programming) were evaluated. The detection limit range was 10-81 pg (100 nL injected). The chromatographic method combined with liquid-liquid extraction was applied to analysis of these compounds in river water. Recoveries of 75-103% were achieved for most of them.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    The site of radical attack at the furan ring from MNDO calculations (1992)
    Basel : Wiley-Blackwell
    Die Makromolekulare Chemie, Theory and Simulations 1 (1992), S. 99-103 
    Details
    ISSN: 1018-5054
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The semi-empirical SCF MNDO method has been used to calculate the radical reactivities for each reaction site in some neutral furan molecules as the average of the HOMO and LUMO probabilities both in 2pz atomic orbitals1SCF: Self-consistent field; MNDO: modified neglect of differential overlap; HOMO: highest occupied molecular orbital; LUMO: lowest unoccupied molecular orbital.. The carbon atoms C5 and C2 of of the furan ring are the most favoured sites except for the furan derivatives holding a double bond in the substituent group. Also the SOMO2SOMO: Single occupied molecular orbital. probabilities of the radicals formed by addition of a hydrogen atom or a vinyl acetate model radical were calculated. Thus, once a radical is added to the C5 position the resulting radical can be partially localized on the carbon C2. Furthermore, the enthalpy of reaction for several radicals was estimated by using the calculated heats of formation of the neutral furan molecules and their radicals. The radical addition to the carbon C 5 resulted in the most exothermic reaction in comparison with other reaction sites of the molecule. However, no correlation was found between the calculated enthalpies and the degradative-transfer kinetic constants experimentally determined for the radical polymerization of vinyl acetate in the presence of the furan compounds under study.
    Additional Material: 5 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mats.1992.040010205
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  • 8
    Electronic Resource
    Electronic Resource
    Kinetic parameters in non-stoichiometric epoxy-resin/m-xylylenediamine reactions (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 47 (1993), S. 533-541 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The curing reaction of bisphenol A epoxy resin has been widely studied. We have found that when initial reactants are highly pure the reaction epoxy resin/m-xylylenediamine follows a predominantly autocatalytic path independent of the temperature. The purpose of this study was to discern if the kinetic model is appliable at high values of amine/epoxy equivalent ratio. Because of the nature and reactivity of m-xylylenediamine (m-XDA), the studies were carried out at low temperatures. Also, in order to obtain information about the formation mechanism of the system, different parameters such as reaction orders, activation energies, and reaction rate variation with concentration have been studied at different (1.5 : 1, 2 : 1, and 3 : 1) amine/epoxy equivalent ratios. © 1993 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1993.070470313
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  • 9
    Electronic Resource
    Electronic Resource
    Kinetic effects on the impurities in epoxy-resin/m-xylylenediamine reaction (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 41 (1990), S. 2155-2167 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Different isolated or competitive mechanisms have been experimentally observed in order to predict the kinetics of an epoxy - amine reaction in terms of various mathematical models based on different possibilities of reaction. Impurities such as water, glycols, and in general all donors of active hydrogen even at low concentrations significantly change the course of the reaction. We therefore decided to study the curing reaction of the epoxy resin, first as a commercial product and later purified, with m-xylylenediamine of known purity. The extent of cure has been followed and determined by differential scanning calorimetry (DSC) and infrared spectroscopy (FT-IR). Purity, epoxy content and OH content were measured by liquid chromatography HPLC and wet analysis.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1990.070410920
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  • 10
    Electronic Resource
    Electronic Resource
    Synthesis of stereoregular polygluconamides from D-glucose and D-glucosamine (1995)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 33 (1995), S. 299-305 
    Details
    ISSN: 0887-624X
    Keywords: polygluconamides ; stereoregular polyamides ; stereoregular nylons ; chiral polyamides ; chiral nylons ; aminoaldonic acids ; sugar polyamides ; carbohydrate monomers ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Two stereoregular polygluconamides, one (3) of polypeptide-type and the other (16) being a polycaproamide containing four stereocenters in the main chain of the repeating unit, have been prepared from D-glucosamine and D-glucose, respectively. The new polyamides were characterized by elemental analysis, and IR, 1H- and 13C-NMR spectroscopies. The molecular weights for 3 and 16 were estimated as 25,000 and 67,000, respectively, on the basis of viscosimetric measurements. Both polyamides display high optical activity; they are highly hydrophilic and readily soluble in water as well as in a variety of organic solvents including chloroform. Polyamide 16 is highly crystalline and yields resistant films with spherulitic texture. © 1995 John Wiley & Sons, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1995.080330211
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