NMR and Double Resonance Spectra of the Deuterodifluoroethylenes
The ambiguity in the relative signs of JHH′ and JHF in the three difluoroethylene isomers has been removed by analysis of the NMR spectra of the monodeuterodifluoroethylenes. The relative signs obtained in this way are the same as those suggested by comparison of the coupling constants of various fluoro-olefins, with the exception that JHH(cis) is of the same sign as JHF(gem) while JFF(cis) is opposite in sign to JHF(gem) in cis-1,2-difluoroethylene. These assignments are confirmed using the nuclear Overhauser effect. Detailed analysis of the Overhauser effect further indicates the relative importance of various proton, deuteron, and fluorine relaxation mechanisms in these molecules. The deuterium isotope effects on the fluorine chemical shift for deuterium substitution gem, trans, and cis, respectively, to a fluorine atom in these molecules fall in the following ranges: (19.6–20.2 cps) gem, (10.3–16.8 cps) trans, (8.2–11.7 cps) cis. The effects of substitution of two deuterium atoms on the F19 chemical shifts are simply additive.
Kanazawa, Yoko, John D. Baldeschwieler, and Norman C. Craig. 1965. "NMR and Double Resonance Spectra of the Deuterodifluoroethylenes." Journal of Molecular Spectroscopy 16(2): 325-348.
Journal of Molecular Spectroscopy
Chemistry and Biochemistry