Neutron and X-ray scattering experiments on fully deuterated liquid N-methylacetamide CD3CONDCD3 at various temperatures and under pressure

A structural investigation of liquid N-methylacetamide (NMA) was performed in the 308–383 K temperature range by both neutron and X-ray diffraction and using only neutron diffraction at 308 K and pressures of up to 4 kbar. The analysis of experimental data yields the total structure factor, the molecular form factor, and the distinct pair correlation function. The spectra obtained are consistent with the presence of hydrogen-bonded open chain in the liquid state. Surprisingly, our measurements clearly show, in contrast to similar liquids, that the N⋯O and D⋯O lengths increase in liquid NMA with increasing temperature, while no significant variation is observed with increasing pressure.