N-14 NUCLEAR-QUADRUPOLE COUPLING-CONSTANTS OF ACETAMIDE AND ALPHA-FLUOROACETAMIDE

The N-14 nuclear quadrupole hyperfine structures in the rotational spe ctra of acetamide, CH3CONH2, and alpha-fluoroacetamide, FCH2CONH2, hav e been resolved. From the observed patterns, the quadrupole coupling c onstants have been determined with high precision. The results provide evidence of considerable delocalization of the nitrogen lone electron pair. For acetamide, the full coupling tensor has been determined fro m a combined analysis of the ground and first excited state of the met hyl group internal rotation. The spectrum of alpha-fluoroacetamide-[N- 15] has been obtained for the first time, and a refined structure is p roposed.