Carbonyl Carbon and Nitrogen Chemical Shift Tensors of the Amide Fragment of Acetanilide and N-Methylacetanilide

Abstract

Both carbon-13 and nitrogen-15 solid-state NMR spectroscopy have been employed to characterize the carbonyl carbon and nitrogen chemical shift (CS) tensors of the amide fragment of (Z)-acetanilide (I) and (E)-N-methylacetanilide (II). These two related compounds exhibit very different structural features in the solid state, as shown by previous X-ray diffraction studies. The orientation of the principal axis system (PAS) of both the carbon and nitrogen CS tensors has been determined using dipolar-chemical shift NMR spectroscopy in conjunction with IGLO chemical shielding calculations. For I and II, the carbon CS tensors are found to be very similar