Conformations and Vibrational Dynamics of Six Monoalkyltrifluoroacetamides. Low-Resolution Microwave and Gas-Phase NMR Spectroscopic Studies

Article abstract of DOI:10.1021/j150659a016

Low resolution microwave spectra of six N-alkyltrifluoroacetamides (F3C(O)NHR; r = CH3, C2H5, i-C3H7, n-C3H7, i-C4H9, t-C4H9) display band series consistent with a single species having the R group oriented syn to the carbonyl moiety. ⁵J_H-F coupling constats observed in gas- and liquid-phase NMR spectra of N-methyltrifluoroacetamide confirm this assignment.For each molecule the observed rotational constats, anomalously broad microwave bandwidths, and absence of resolvable fine structure are consistent with predicted effects of rapid intramolecular vibrational redistribution (IVR).Sufficient state density for IVR in these molecules occurs at low internal energies.