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  • Analytical Chemistry and Spectroscopy  (3)
  • 199Hg chemical shifts  (1)
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  • 1
    Digitale Medien
    Digitale Medien
    N.m.r. studies of the keto-enol tautomerism of acylthioacetamidesChelates of β-dicarbonyl compounds and their derivatives, Part 51. (1977)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 10 (1977), S. 151-156 
    Details
    ISSN: 0030-4921
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Acetylthioacetamides exist as different keto and enol isomers in chloroform solutions. The keto form with intramolecular hydrogen bonding between the NH and the carbonyl group is the dominant keto isomer. On the other hand the enol forms with intramolecular hydrogen bonding between the OH and the thioketo group are the dominant enol isomers in the temperature range 60°C to -60°C. The thermodynamic data of the keto-enol equilibria were obtained by measuring the intensities of appropriate high resolution proton signals as a function of temperature. At low temperatures all lines characteristic of the enol forms are doubled in the N-phenyl-substituted derivatives because the rotation of the NH—C6H5 group around the C—N bond becomes slow and the chemical shifts characteristic of the E and Z isomers are different. We estimated approximate thermodynamic data of the E/Z equilibrium in some of the compounds. The changes of the line shape as well as the chemical shifts as a function of temperature indicate the presence of various additional exchange processes. In order to obtain further information we performed curve fittings of the chemical shifts of one acetylthioacetanilide and of a series of monothio-β-diketones (studied in another paper) assuming a fast two site exchange process. On the basis of the results obtained a reaction scheme for N-substituted acylthioacetanilides in solution is proposed.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/mrc.1270100135
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  • 2
    Digitale Medien
    Digitale Medien
    Hydrolysis of γ-[1-methyl-5-bis(β-chloroethyl) amino-2-benzimidazolyl]butyric acid. Studied by 1H NMR (1982)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 19 (1982), S. 15-20 
    Details
    ISSN: 0030-4921
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: High resolution 1H NMR is applied to the study of hydrolysis and equilibria in the complex system of γ-[1-methyl-5-bis(β-chloroethyl)amino-2-benzimidazolyl]butyric acid and D2O. Kinetic data for the individual hydrolytic steps are obtained for the first time. The hydrolytic reactions are pseudo first order. The differences in the activation energies of the two hydrolysis steps are accounted for by different intermediates. Furthermore, equilibrium constants for the deuteration of the N mustard group in the individual products are quantitatively estimated. They show an increase of the basicity of N mustard with hydrolysis. The applicability of the 1H NMR method is restricted to a pD range of 0.5-4.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/mrc.1270190105
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  • 3
    Digitale Medien
    Digitale Medien
    199Hg NMR of aqueous solutions of inorganic mercury salts. Chemical shifts of HgCl2 - n with n = 0-4 (1993)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 31 (1993), S. 548-551 
    Details
    ISSN: 0749-1581
    Schlagwort(e): Mercury chlorides ; 199Hg chemical shifts ; Chemical exchange ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: 119Hg NMR chemical shifts of the stable mercury species HgCln2 - n with n = 0-4 were determined by a least-squares algorithm from 199Hg chemical shifts measured in 50 mM aqueous mercury solution as a function of the chlorine concentration at 25°C. The concentrations of the corresponding mercury species in the solutions necessary in this special procedures were calculated by using published equilibrium constants. The results relative to dimethyl-mercury are -2256 ppm (Hg2+), -1897 ppm (HgCl+), -1560 ppm (HgCl2), -1436 ppm (HgCl3-) and -1152 ppm (HgCl42-) with maximum errors of ±5 ppm.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/mrc.1260310606
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