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  • Analytical Chemistry and Spectroscopy  (4)
  • 19F NMR  (1)
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  • 1
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 3 (1976), S. 88-90 
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Isomeric chlorinated biphenyls are observed to yield very similar mass spectra, rarely exhibiting a [M — Cl]+ fragment of any siVgnificant magnitude. However, those isomers containing three ortho chloro substituents display a relatively intense [M — Cl]+ fragment. A rationalization for this observation is put forth on the basis of the relative stabilities of both product and reactant.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Unimolecular and collision induced decompositions of the major ions of selected polychlorinated biphenyls in the field free region between the magnetic and electric sectors of a reversed Nier-Johnson instrument were studied. Loss of a single chlorine atom is associated with a wide range of kinetic energy releases but still can be correlated by a single reaction mechanism. Loss of two chlorines is interpreted as a rapid sequential loss from isomerized molecular ions for all but one compound. The decompositions which metastable ions undergo are not always the same as those of high energy ions in the source. Correlations between substituent positions and kinetic energy release can be made for the [M]+·→[M—Cl]+ and [M—Cl2]+· processes.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 21 (1983), S. 173-176 
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The 13C—13C spin coupling constants have been determined in substituted [1-13C]tetrahydronaphthylenes, [5-13C]hexahydrobenzanthracenes and [5-13C]benzanthracene. In addition, the 13C—13C spin coupling constants for 7-hydroxy[7-13C]benzopyrene, trans-7,8-dihydro[7-13C]benzopyrene-7,8-diol and trans-7,8-dihydro[10-13C]benzopyrene-7,8-diol are reported, together with the one-bond carbon-carbon coupling constants between C-4 and C-5 in selected 4,5-disubstituted benzopyrenes. Values for the directly bonded coupling constants and long-range coupling constants are similar to those reported previously for other aromatic and aliphatic systems. Substituent effects on carbon-carbon coupling are compared for similarly substituted cyclic and acyclic systems.
    Additional Material: 3 Tab.
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  • 4
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 30 (1992), S. 723-732 
    ISSN: 0749-1581
    Keywords: 19F NMR ; Fluorinated calcium chelators ; Enhanced relaxation characteristics ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The fluorinated calcium ion chelator 5F BAPTA [1,2-bis(2-amino-5-fluorophenoxy)ethane-N, N, N′, N′-tetra-acctic acid] was used for the determination of cytosolic Ca2+ ion levels in cells and tissues by 19F NMR. The possibility of enhancing the sensitivity of these measurements by modifying the relaxation behavior of the chelator was evaluated. These strategies involved the design of a chelator with reduced T1 value viz. 5F RBAPTA {1,2-bis [2-amino-4-(1-carboxy-2-methyl-2-propyl)-5-fluorophenoxy]ethane-N, T, N′, N-tetraacetic acid}, and the evaluation of chelator with slower exchange characteristics, viz 5F BenzEGTA [1-(2-amino-5-fluorophenoxy)-2-(2-aminoethoxy)ethane-N, N, N′, N′-tetraacetic acid]. Both analogs exhibit chemical shift differences on calcium complexation which are similar to those of the parent compound, 5F BAPTA. In the case of BenzEGTA, a considerably greater pH dependence of the apparent calcium, dissociation constant, KD, also results from the presence of a tertiary amine with a pK value above the physioligical range. Additionally, the synthetic approach used for RBAPTA can lead to wide variety of derivatives with variable chemical, biochemical and NMR properties.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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