Comparative studies in the 19F and 1H NMR chemical shifts in 2,2-difluorohalogenated propanes

Article abstract of DOI:10.1016/0022-1139(95)03347-5

Fluorine-19 chemical shifts were compared with ¹H chemical shifts in CF₃-CF₂-R versus CH₃-CF₂-R, CF₂Cl-CF₂-R versus CH₂Cl-CF₂-R and CFCl₂-CF₂-R versus CHCl₂-CF₂-R, where R is a substituted methyl group containing all combinations of H, Cl and F. A good linear relationship was found between the ¹⁹F and ¹H NMR chemical shifts. Conformational analysis using MNDO calculations was applied to the CF₃-CF₂-R and CH₃-CF₂-R series to clarify the interaction between the terminal substituents. In halogenated propanes, ¹⁹F and ¹H chemical shifts are mainly affected by the through-space interaction between the terminal substituents rather than the electro-negativity.