Vibrational spectroscopy of N-methylacetamide revisited

Although a lot of work has been performed on the vibrational analysis of N- methylacetamide (NMA), some uncertainties and even contradictions remain, m ainly due to the fact that the structure of NMA at room temperature is not stable due to traces of water or due to the fact that the authors only stud ied the infrared or the Raman spectra. On the basis of the infrared and Ram an spectra in the -196 degreesC to +100 degreesC temperature range, we have shown that the effects of temperature on the structure and the changes in the strength of the hydrogen bonding within a structure elucidate a lot of the complexity of the solid state vibrational spectra of NMA. Force field c alculations on the monomer and multimers (n = 6) and solution spectra of NM A and the N-deuterated compound are used to provide a better understanding of the influence of hydrogen bonding on the typical amide fundamentals. Nin e typical so-called "amide bands" have been further characterized.