Geometry and intermolecular structure ofN-methylformamide in the liquid phase as measured by neutron scattering

Abstract
Neutron diffraction measurements have been carried out on two samples of liquid N-methylformamide with different isotopic composition (DCONDCD3 and DCONHCD3). The experiments were performed under normal conditions up to a momentum transfer of 22·9 Å-1. Refined intramolecular structure parameters describing equally well both experiments have been obtained. The N-H distance in particular could be evaluated accurately using a modified contrast method. There is some evidence that the H … O intermolecular distance is detectable in spite of overlapping intramolecular distances and of an increased delocalization of the π electron system in the liquid phase with respect to the gas.