H–F Coupling constants and hindered internal rotation in NN-dimethyltrifluoroacetamide

The 1H n.m.r. spectra of NN-dimethyltrifluoroacetamide which have been recorded in various solvents, exhibit two H–F coupling constants which are believed to arise from different coupling mechanisms. The high-temperature rotationally averaged spectrum shows that the two H–F coupling constants have the same sign. The activation parameters for the hindered internal rotation about the central C–N bond have been redetermined by line-shape analysis of the temperature-dependent high-resolution 1H n.m.r. spectra.