37Cl/35Cl and13C/12C isotope effects on the fluorine shielding in several two-carbon chlorofluorocarbons
| Autor: | Olivier Jarjayes, Claude Wakselman, Marc Tordeux, Claude Béguin |
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| Rok vydání: | 2001 |
| Předmět: |
Isotope
010405 organic chemistry Inorganic chemistry Relaxation (NMR) chemistry.chemical_element General Chemistry Fluorine-19 NMR 010402 general chemistry 01 natural sciences Spectral line 3. Good health 0104 chemical sciences chemistry 13. Climate action Kinetic isotope effect Fluorine Chlorine Physical chemistry General Materials Science Carbon |
| Zdroj: | Magnetic Resonance in Chemistry. 39:301-310 |
| ISSN: | 0749-1581 |
| Popis: | Isotope effects on the chemical shift (IECS) of 19F bonded through two or three bonds to the isotopes 35Cl and 37Cl are reported for a wide range of two-carbon chlorofluorocarbons (and, for a few cases, with the isotopes 79Br and 81Br, for two-carbon bromofluorocarbons). These IECS through two bonds were found to range, for one chlorine atom, from −5.0 to −7.6 ppb for aliphatic compounds and from −4.5 to −6.4 ppb for olefinic compounds. The IECS through three bonds were found to be less than −1.15 ppb. No deviation from additivity was detected for the IECS when several equivalent chlorine atoms are present. The broadening of the 19F lines, due to scalar relaxation arising from 19F–37s35Cl spin–spin interactions, ranges from 0.32 to 2.50 Hz in our series and are related to the 2J(Cl, 19F)T1(Cl) term. IECS of 19F bonded through one or two bonds to the isotopes 13C and 12C are also reported for the same series. Several correlations, related to structural information, can be made and discussed between these IECS [13s12C IECS through two bonds as a function of 1J(13C, 19F) spin–spin coupling constants and 13s12C IECS as a function of 37s35Cl IECS]. 37s35Cl IECS can also be observed on 13C satellites of 19F spectra. For non-symmetrical compounds, the dependence of these signals on the 37s35Cl IECS is the same as that for the main 19F signal; however, for the centrosymmetrical compounds, the main 19F signal appears to be sensitive to all the chlorine atoms, whereas the 13C satellites seem to be sensitive only to the directly bonded chlorine. Copyright © 2001 John Wiley & Sons, Ltd. |
| Databáze: | OpenAIRE |
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