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  • 1
    Electronic Resource
    Electronic Resource
    Neue Wege zu Bis[(cyclopentadienyl)cobalt]-μ-(η5-2,3-dihydro-1,3-diborolyl)-Tripeldeckerkomplexen über Wasserstoff-Verschiebungsreaktionen in Derivaten des 4,5-Diisopropyliden-1,3-diborolans, des 2,4,5-Triisopropyliden-1,3-diborolans und des Benzo-1,3-diborafulvensHerrn Professor Dr. Wolfgang Sundermeyer zum 65. Geburtstag gewidmet. (1993)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 126 (1993), S. 2197-2203 
    Details
    ISSN: 0009-2940
    Keywords: 1,3-Diborolyl complexes, bis[η5-cyclopentadienyl)cobalt] ; 1,3-Diborolane, 4,5-diisopropylidene- and 2,4,5-triisopropylidene- ; Benzo-1,3-diborafulvene ; Electrochemistry ; ESR ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: New Routes to Bis[(cyclopentadienyl)cobalt]-μ-(η5-2,3-dihydro-1,3-diborolyl) Triple-Decker Complexes by Hydrogen Shift Reactions in Derivatives of 4,5-Diisopropylidene-1,3-diborolane, 2,4,5-Triisopropylidene-1,3-diborolane, and Benzo-1,3-diborafulveneThe 31 VE dicobalt triple-decker complexes 6, 7a, 7b, c, 8a, b, and 9a, b with bridging 2,3-dihydro-1,3-diborolyl ligands are prepared. The reaction of the 1,3-diborole 1 with [(C5Me5)-Co(C2H4)2] leads to the sandwich complex 5, which is treated with [(C5H5)Co(C2H4)2] to yield unsymmetrical 6. The 4,5-diisopropylidenetrimethyl-1,3-diborolane 3 undergoes a metal-induced 1,5-hydrogen shift and reacts with [(C5H5)Co(C2H4)2] to form the triple-decker 7a. The reaction of the 2,4,5-triisopropylidene-1,3-diborolane 4 with [(C5H5)Co(C2H4)2] leads to a mixture of the triple-deckers 7b/c, formed by intermolecular hydrogen shift. The benzo-1,3-diborafulvene derivatives 2b and 2c also react with [(C5H5)Co(C2H4)2] to give the triple-decker 8b and a mixture of 9a, b. In addition, the trinuclear complex 8c is obtained in low yield. The new paramagnetic triple-decker complexes have been analyzed by NMR and ESR spectroscopic measurements as well as by electochemistry. The constitutions of 7b/c, 8b, 8c, and 9a/b have been confirmed by X-ray structure analyses. The complexes are iso-structural, the Co - Co distances range from 3.277(1) (7b/c) to 3.316(1) Å for 8c.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19931261006
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  • 2
    Electronic Resource
    Electronic Resource
    Finding suspected causes of measurement error in multivariate environmental data (1993)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 7 (1993), S. 165-176 
    Details
    ISSN: 0886-9383
    Keywords: Measurement error ; Outliers ; Environmental ; Quality control ; Multivariate kurtosis ; Generalized distance ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Environmental data are usually multivariate, with the variables conforming to some correlation structure. Occasionally, measurements which do not conform in structure or magnitude may occur in one or more variables. It is important (1) to characterize these discordancies in terms of the disturbed variables and the direction and magnitude of the anomalous error and (2) to associate each discordant observation with a specific cause of measurement error in order to prevent further mismeasurement. We describe a procedure for identifying suspected causes of discordant observations in otherwise multinormal data sets. Variables are assigned to groups, each of which is associated with a specific cause of measurement error. Discordant observations are identified with the generalized distance test or the multivariate kurtosis test. Suspected causes of measurement error are identified by repeating the tests with one of the groups of variables omitted in each analysis. The procedures are evaluated with simulated data sets having a correlation structure similar to that of a large environmental data set.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cem.1180070304
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  • 3
    Electronic Resource
    Electronic Resource
    Enzymatic and chromatographic chiral discrimination of racemic (thio)glycidyl esters: Part II. Optical resolution of racemic (thio)glycidyl esters on modified cellulose chiral stationary phases (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 5 (1993), S. 255-257 
    Details
    ISSN: 0899-0042
    Keywords: cellulose tris(3,5-dimethylphenyl carbamate) ; cellulose tribenzoate ; chiral HPLC ; enantiomers ; temperature dependence ; chiral recognition ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Chiral chromatography on cellulose tris(3,5-dimethylphenyl carbamate) (Chiralcel OD) and cellulose tribenzoate (Chiralcel OB) coated stationary phases has been successfully used for the optical resolution of rac-(thio)glycidyl esters (acetate, propionate, butyrate). Glycidyl esters could sufficiently be resolved on the OD column whereas for the thio analogues baseline resolution is obtained on CSP OB using hexane/2-propanol mobile phases. The separation factor (α) and resolution (RS) depend on column temperature, eluent composition, and flow rate, respectively. Best results were obtained for the butyrates and at low temperatures in general. © 1993 Wiley-Liss, Inc.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530050413
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  • 4
    Electronic Resource
    Electronic Resource
    Enzymatic and chromatographic chiral discrimination of racemic (thio)glycidyl esters: Part I. A chemoenzymatic approach to both enantiomers of thioglycidyl esters (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 5 (1993), S. 250-254 
    Details
    ISSN: 0899-0042
    Keywords: enzymic kinetic resolution ; porcine pancreatic lipase (PPL) ; hydrolysis ; transesterification ; acylation ; enol esters ; chiral HPLC ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Both hitherto unknown (+)-(R)- and (-)-(S)-thioglycidyl esters, (R)-(2) and (S)-(2), have been synthesized with different high enantiomeric excesses (ee) by two routes from the corresponding rac-glycidyl esters rac-(1). The first includes a porcine pancreatic lipase (PPL)-mediated kinetic resolution of these esters followed by sulfuration with practically complete inversion to the (+)-(R)-enantiomer (+)-(R)-(2) (36-86% ee). (-)-(S)-Thioglycidyl esters (-)-(S)-(2) are obtained by the reverse reaction sequence (43-80% ee). In the latter case the hydrolysis rate is lower than that of analogous glycidyl esters. Moreover, the dependence of enantiomeric excess on the size of the acyl-group is of the opposite tendency. Therefore, in both cases suitable selection of the acid residue gives rise to maximum enantioselectivity. The irreversible lipase-catalyzed acylation of rac-glycidol and rac-thioglycidol, however, was found to be a less suitable alternative. The enantiomeric excess of recovered homochiral esters was determined by chiral chromatography using modified cellulose stationary phases (OB, OD). © 1993 Wiley-Liss, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530050412
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  • 5
    Electronic Resource
    Electronic Resource
    Model-Based On-Line Analysis of Disperse Systems on the example of digital fourier spectroscopyDedicated to Professor Friedrich Löffler on the occasion of his 60th birthday (1993)
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 10 (1993), S. 339-346 
    Details
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: With progress in the advancement of measuring techniques and information processing, it is increasingly possible to analyse even complex signals with on-line methods. After fundamental considerations concerning the evaluation of such signals, digital Fourier spectroscopy is explained as an example of a new development. With this method the image of a particle collection will be transformed by the Fourier transformation. Methods such as used with laser diffraction spectrometry are applied to calculate back to the particle size distribution. After a description of the principles of the procedure, its application is demonstrated by different examples. It can be shown that digital Fourier spectroscopy is superior to conventional image analysis methods especially if the particle density in the image is high and the particles overlap. In a further development step it should be possible to determine the particle size distribution of the bulk from an image of its surface.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ppsc.19930100608
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  • 6
    Electronic Resource
    Electronic Resource
    On-line high performance liquid chromatography  -  multidimensional gas chromatography and its application to the determination of stilbene hormones in corned beef (1993)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 16 (1993), S. 479-482 
    Details
    ISSN: 0935-6304
    Keywords: On-line HPLC-GC-GC ; Multidimensional Chromatography ; Stilbene hormones ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The combination of high performance liquid chromatography interfaced on-line with multidimensional gas chromatography (HPLC-GC-GC) is described. The HPLC column was interfaced to the GC via an on column interface, with automated pneumatic control of solvent evaporation and GC column switching. Cryogenic cold trapping was used for analyte focusing at the head of the first, non-polar GC capillary column and optionally at the head of the second, polar column. The determination of stilbene hormones in corned beef as their methylated derivatives by flame ionization detection is described.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240160807
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  • 7
    Electronic Resource
    Electronic Resource
    Extending the scope of enantiomer separation by capillary supercritical fluid chromatography on immobilized polysiloxane-anchored permethyl-β-cyclodextrin (Chirasil-Dex) (1993)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 16 (1993), S. 215-223 
    Details
    ISSN: 0935-6304
    Keywords: Enantioselective capillary (open-tubular) SFC ; Polysiloxane-anchored cyclodextrin stationary phase ; Immobilized Chirasil-Dex ; Separation of cyclodextrin derivatives by SFC ; Non-steroidal anti-inflammatory drugs (NSAIDs) ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Immobilized polysiloxane-anchored permethyl-β-cyclodextrin (Chirasil-Dex) with a cyclodextrin content of approximately 30 % by weight, previously employed as a versatile chiral stationary phase for the separation of enantiomers by GC, has been used for the separation of enantiomers by capillary supercritical fluid chromatography (SFC). A considerable number of racemates could be resolved, e.g. aromatic alcohols, amino alcohols (TFA derivatives), and underivatized acids. Many pharmaceutical compounds were among those analyzed, including several NSAIDs (e.g. ibuprofen and ketoprofen), a steroidal drug (nor-gestrel), a barbiturate (hexobarbital), and others.Among the racemates resolved were many which cannot be analyzed by GC owing to low volatility or decomposition at elevated temperatures. For two racemates, analysis temperature and mobile phase density were systematically varied to give constant analysis times or capacity factors k. Low temperatures (ca 60 °C) yielded the best separation in term of separation factor, α, or resolution, Rs, even though higher densities had to be used. In comparison with GC, capillary SFC was able to furnish higher separation factors and similar resolution. The applicability of capillary SFC for the analysis of mixtures of cyclodextrin derivatives, e.g. those used in the synthesis of Chirasil-Dex, was, furthermore, demonstrated.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240160403
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  • 8
    Electronic Resource
    Electronic Resource
    Chirasil-Dex-TFA: A new polysiloxane-bonded and immobilizable cyclodextrin stationary phase for enantiomer separation by GC (1993)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 16 (1993), S. 289-298 
    Details
    ISSN: 0935-6304
    Keywords: Enantioselective GC ; Polysiloxane-anchored cyclodextrin stationary phase ; Chirasil-Dex-TFA ; Immobilized 2,6-di-O-alkyl-3-O-acyl-cyclodextrin ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Heptakis(2,6-di-O-methyl-3-O-trifluoroacetyl)-†-cyclodextrin has been chemically bonded to a polydimethylsiloxane via an octamethylene spacer and subsequently immobilized on to the surface of fused silica capillaries, the first time a cyclodextrin derivative with mixed substituents has been immobilized in this way. The enantioselectivity of the new chiral stationary phase has been investigated as a function of the cyclodextrin content. It was found to be higher than that reported for heptakis (2,6-di-O-methyl-3-O-trifluoroacetyl)-†-cyclodextrin or hepta-kis(2,6-di-O-methyl-3-O-acetyl)-†-cyclodextrin dissolved in polysiloxane (e.g. OV-1701). The degree of immobilization was over 90 %. The temperature stability is, however, inferior to that of Chirasil-Dex (a permethylated cyclodextrin): the maximum operating temperature is approximately 200 °C.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240160506
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  • 9
    Electronic Resource
    Electronic Resource
    Elucidation of the structure of drug degradation products by on-line coupled reversed phase HPLC-GC-MS and on-line derivatization (1993)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 16 (1993), S. 708-712 
    Details
    ISSN: 0935-6304
    Keywords: Reversed phase HPLC-GC-MS ; On-line derivatization ; Diazomethane ; MSTFA ; Bromination ; Loop-type interface ; Structure elucidation ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Degradation products obtained under severe alkaline stress of the drug substance ENA 713, a compound developed for the treatment of DAT (dementia of the Alzheimer type), have been identified by on-line coupled reversed phase HPLC-GC-MS as 3-hydroxyaceto-phenone and 3-hydroxystyrene. Their structures were proven by mass spectroscopic investigation of the products obtained by on-column derivatization during LC-GC transfer. On-column trimethyl-silylation and bromination of the degradation products during the transfer were achieved by the introduction of the reagent via the loop-type interface. The usefulness of the technique was further demonstrated by the on-column methylation of carboxylic acids with diazomethane solution (using naproxen as model compound). First results are also given of the use of the liquid-liquid extraction unit of the LC-GC interface for extractive derivatization during reversed phase HPLC-GC-MS transfer.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240161207
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  • 10
    Electronic Resource
    Electronic Resource
    Analysing the complexation of amino acids and peptides with β-cyciodextrin using electrospray ionization mass spectrometry (1993)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 7 (1993), S. 949-952 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The formation of non-covalently bound inclusion complexes between ß-cyclodextrin and peptides containing aromatic acid residues has been confirmed by elcctrospray ionization mass spectrometry. This preliminary study has indicated that phenylalanine and tryptophan residues can form 1:1 complexes with ß-cyclodextrin whereas no evidence for such a complex could be found for tyrosine residues. Bradykinin, which contains two phenylalanine residues, formed both 1:1 and 1:2 complexes.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290071017
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