Compared 13C NMR spectra of acetanilide and N-methylacetamide

Acetanilide and N-methylacetamide are both crystals in which the existence of non linear excitations (self-trapped excitons or acoustic polarons) have been postulated as an explanation of the unconventional amide spectroscopy. This theory is debated and a dynamic proton transfer along the hydrogen bond could be an alternative explanation for the unexpected sidebands and temperature dependences. Our compared C-13 NMR study demonstrates a similar behaviour for the EFG at the N-14 atom in these both compounds, indicating a very close electronic density around the nitrogen in both cases, and thus does not confirm the hypothesis of a proton transfer in N-methylacetamide.