NMR studies and rotational isomerism in fluoroacetones. II. Fluoroacetone and 1,1-difluoroacetone

Abstract

The solvent dependences for fluoroacetone and 1,1-difluoroacetone are reported for the following NMR parameters: proton and fluorine chemical shifts, four-bond HH coupling constants, one-bond C-H coupling constants, and geminal and four-bond HF coupling constants; the temperature dependences of the HF couplings are also reported. It was found that these parameters (except for the fluorine shifts, 4J HH and 1J CH) could be used, at least qualitatively, to follow changes in the relative populations of rotational conformers. Finally, the variation of 2J HF with solvent dielectric constant (ε) was found to be smooth enough to make possible an estimation of ε for nonhydrogen-bonding solvents.