The Solvent and Temperature Dependence of H-H, H-F and F-F Coupling Constants in Difluorethylenes.
KENTUCKY UNIV LEXINGTON DEPT OF CHEMISTRY
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Solvent and temperature induced variations of H-H, H-F and F-F coupling constants in cis and trans 1,2-difluoroethylene and 1,1-difluoroethylene are reported. These data, in conjunction with previous results, confirm that orientation of the solute dipole affects the magnitude of the solvent effect on geminal H-H and H-F coupling constants. Dipole orientation is not a factor in determining solvent effects on vicinal H-F and F-F coupling constants. The dipole induced solvent electric field is the primary causative factor producing the observed changes, but dispersion forces and specific interactions are also important. The best fit for a regression analysis of coupling constants against solvent parameters is of the form JobsJo ARBD. Where R and D represent reaction field and dispersion field terms. A and B are opposite in sign. Rough values of H and S are reported for weak solute-solvent complexes characterizing specific interaction effects. An apparent dicotomy is reported where one coupling constant in a molecule is solvent dependent, but another is not even though the same nuclei are involved in both couplings. Author
- Organic Chemistry
- Physical Chemistry