Conformational and substituent effects in the ¹⁹F spectra of C₇–C₁₀ straight‐chain chlorofluoroalkanes

Abstract

One- and two-dimensional fluorine NMR spectra of straight-chain chlorofluoroalkanes having 7-10 carbons were obtained and interpreted. Spectral assignments were based primarily on indirect spin-spin correlations. A scale of chlorine substituent effects was developed. The effects of asymmetric CFCl centers on chemical-shift differences in nearby CF2 groups were analyzed in terms of molecular conformational effects. Spin-spin coupling patterns of CF3 groups were elucidated.

Concerning the origin of 19F19F NMR COSY and NOESY connections in the spectra of perfluorooctanoic acid, RF‐palmitic acid‐F13 and diethyl perfluorosuberate

“…A recent study of chlorofluoroalkanes included three molecules which are symmetric about a center. 27 The 19 F-19 F COSY connections were interpreted in a similar fashion to those presented here for 3.…”

19F and 13C spectra of fluorinated and partially fluorinated vinyl alkyl ethers

“…CF 2 groups next to oxygen have shifts of À88 AE 1 ppm, except in 2, where the position next to terminal CF 3 leads to added shielding of about 5 ppm. A CF 2 group in a long perfluoroalkyl chain typically has a shift of about À123 ppm [9]. In 4, the b CF 2 group is shielded by the effect of the oxygen and the g group is shielded because it is next to the terminal CF 3 , with the result that their resonances overlap to such an extent that, at the magnetic field available, they could not be disentangled.…”