CORRELATION TIMES AND QUADRUPOLE COUPLING-CONSTANTS IN LIQUID N-METHYLFORMAMIDE AND N-METHYLACETAMIDE

Longitudinal H-1, C-13 and N-15 nmr relaxation rates were measured in the liquid phase for N-methylformamide (NMF) over the temperature rang e 228-328 K and for N-methylacetamide (NMA) over the range 300-378 K. Rotational correlation times were determined for the formyl C-H and th e N-H bonds. The motion of both molecules is anisotopic, particularly that of N-methylacetamide. The activation energies are 5.6 kJ/mol for C-H and 19.7 kJ/mol for N-H in NMF and 20.4-22.5 kJ/mol for N-H in NMA . Quadrupole coupling constants were determined by relaxation measurem ents for the nuclei N-14 and H-2. The quadrupole coupling constant for the amide deuteron in NMF is temperature dependent and varies from 19 3 to 206 kHz. For NMA this quadrupole coupling constant falls into the range 178 to 238 kHz. The quadrupole coupling constant for the formyl H-2 in NMF (151-169 kHz) is temperature independet while for the N-14 (NMF: 1.85-2.40 MHz; NMA: 1.65-2.45 MHz) it is temperature dependent.