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  • 1
    Electronic Resource
    Electronic Resource
    Quantitative 2D EXSY and Dynamic 19F-NMR Studies of the Dynamic Behaviour of the Bidentate Chelate Complex Ga(fox)3 (fox = 5-fluoro-8-hydroxyquinoline) (2000)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 2000 (2000), S. 545-550 
    Details
    ISSN: 1434-1948
    Keywords: Coordination chemistry ; Gallium(III) ; Dynamik 19F NMR ; EXSY ; Kinetics of ligand exchange ; Bailar and Rây-Dutt mechanisms ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The rates of intramolecular rearrangement of the meridional isomer of the metal tris-chelate complex [Ga(fox)3, fox = 5-fluoro-8-hydroxyquinoline] in DMF solution were measured using 1D NMR line shape analysis and 2D EXSY spectra. The rates of exchange kab, kbc and kac between the three non-equivalent ligands a, b and c were determined. The values of the activation parameters were obtained. ΔH
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 2
    Electronic Resource
    Electronic Resource
    Conformational studies on 2-fluoro-1,2-disubstituted ethanes by NMR spectroscopy. Influence of electronegativity on vicinal proton-proton and fluorine-proton coupling constants (1983)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 21 (1983), S. 361-366 
    Details
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The analysis of the ABKX spectra of thirteen compounds of the series RC(H-K)(F-X)C(H-A)(H-B)X gave the four vicinal proton-proton and fluorine-proton coupling constants. These coupling constants of conformationally mobile structures were used (i) to calculate the populations of the rotational states of the —CHF—CH2— bond, (ii) to calculate the vicinal trans proton-proton J(HH)t and gauche and trans fluorine-proton coupling constants J(FH)g and J(FH)t and (iii) to give the unambiguous assignment of protons H-A and H-B. The dependence of the gauche and trans coupling constants with substituent electronegativity is explored. The results extend known correlations towards smaller electronegativity values. More quantitatively, the results and those in the literature, excluding those where deformations of torsional or bond angles occur, give a good fit of the data: a linear fit for J(HH)t = 15.0-0.77 Σ(ΔE), an exponential fit for J(FH)g = 15.35 exp [-0.266 Σ (ΔE)] and a linear fit for J(FH)t = 65.75 - 7.52 Σ (ΔE), where Σ (ΔE) is the sum of the electronegativity difference between hydrogen and the six atoms or groups on the CH—CF fragment.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/omr.1270210605
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  • 3
    Electronic Resource
    Electronic Resource
    19F and 1H NMR of aldimines of fluoroamino acids with pyridoxal-5′-phosphate (1981)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 16 (1981), S. 129-132 
    Details
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 1H and 19F NMR spectra were obtained for six Schiff bases (aldimines) formed by pyridoxal-5′-phosphate (PLP) with four fluorinated or their two parent non-fluorinated α-amino acids (phenylalanine and α-aminobutyric acid). pKA Values were derived from 1H and 19F titration curves. The imine nitrogen of the aldimines is very basic (∼13) and sensitive to the electron withdrawing effect of fluorine. The pyridine nitrogen is less basic in the aldimines (∼7) than in PLP (8.12) and is less sensitive to the electron withdrawing effect of the fluorine than is the imine nitrogen. The phosphate group has a pK in the same range (∼6) and the chemical shifts of some nuclei are sensitive to both pK values. Protonation of the aldimine causes the 1H signal to shift downfield at the methyl protons of the pyridine ring and at the aldehydic proton of the aldimine for the high pK value (except for the aldimines prepared from the β-fluorophenylalanine), but upfield at the aromatic proton and at the aldehydic proton of the aldimine for the low pK. Protonation of the aldimine causes the 19F signal of an aryl fluorine to shift downfield but gives an upfield shift at a β-fluorine. These data are related to the highly conjugated electronic structure of the Schiff bases.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1270160214
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  • 4
    Electronic Resource
    Electronic Resource
    Three-bond carbon-fluorine coupling constants in substituted 3-fluoropropanes and 3-fluoropropanoates (1986)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 24 (1986), S. 337-342 
    Details
    ISSN: 0749-1581
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Three-bond carbon-fluorine coupling constants of 32 substituted 3-fluoropropanes and 3-fluoropropanoates were measured. From these values and from those of other alicyclic compounds already known in the literature, it can be established that the influence of molecular parameters on 3J(FC) depends on the nature of the coupled carbon. When this carbon belongs to an alkyl group, the main molecular parameter is the dihedral angle [J(FC)g = 1.2 Hz and J(FC)t = 11.2 Hz]. When the carbon belongs to a carbethoxy group, more complex effects are observed: for one series the main parameter is the dihedral angle [J(FC)g = 0 Hz and J(FC)t = 20 Hz], and for other series the electronegativity and orientation of substituents particularly influence J(FC)g. Conversely, the diastereoisomers can be unambiguously identified from the 3J(HH), 3J(FH) and 3J(FC) values of both diastereoisomers.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1260240413
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  • 5
    Electronic Resource
    Electronic Resource
    Configurational assignment of β-fluoro-β-phenylamines using 1H and 19F NMR (1988)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 26 (1988), S. 621-624 
    Details
    ISSN: 0749-1581
    Keywords: 1H NMR ; 19F NMR ; Configurational assignment ; β-Fluoro-β-phenylamines ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The 1H and 19F NMR parameters [δH-α, δH-β, δF, 3J(HH) and 3J(FH)] of β-fluoro-β-phenylamines of the two series PhCHFCH2NR1R2 and PhCHFCH(R)-NR1R2 in CDCl3 (amine form) and in CD3OD (protonated amine form) and those of the corresponding β-hydroxy-β-phenylamines were measured. It is shown that for the protonated amines the predominant conformation is that in which the ammonium group is antiperiplanar to the phenyl group, especially for tertiary amines. Assignment of the diastereoisomers of the PhCHFCHRNR1R2 series can be made with the NMR parameters of the protonated amines: high (low) 3J(HH) values, low (high) 3J(FH) values, 19F chemical shifts to high (low) frequency are those for the threo (erythro) isomers.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1260260718
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  • 6
    Electronic Resource
    Electronic Resource
    2-fluoro-2-phenylacetic acid. 4For Part 3, see Ref. 1. - Configuration of its esters with substituted-phenyl alcohols by 19F NMR (1991)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 29 (1991), S. 759-761 
    Details
    ISSN: 0749-1581
    Keywords: 2-Fluoro-2-phenylacetic acid ; Chiral derivatizing agent ; Configuration of secondary alcohols containing substituted-phenyl groups ; Fluorine NMR ; Effect on δF across the space ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The use of 2-fluoro-2-phenylacetic acid as a chiral derivatizing agent allowed the distinction, by means of fluorine NMR spectroscopy, of enantiomers of alcohols L1CH(OH)L2 converted into the diastereoisomeric esters PhCHFCO2CHL1L2. The δF(RR) and δF(RS) fluorine chemical shifts of diastereoisomeric esters obtained from series of alcohols containing a substituted-phenyl group (L1 or L2 = ZPh), and the ΔδF chemical shift differences, were linearly related to the Hammet σ parameter of Z. The ΔδF originates from the different electronic effects of L1 and L2 groups on the fluorine atom, through space, in a minor conformation. A classification of the ZPh effects on δF with respect to Ph is obtained. The configuration of substituted-phenyl secondary alcohols, ZPhCH(OH)L, can be determined with the aid of the δF values of esters formed with PhCHFCO2H if the configuration of the unsubstituted alcohol PhCH(OH)L is known.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1260290803
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