Effects of Li $^+$ and Ag $^+$ Ions on the Rotational Barrier in Acetamide and propionamide System

The influences of on the N-C(O) rotational barrier of N,N-dimethylacetamide and N,N-dimethylpropionamide have been investigated. The rotational activation free energy -amide complexes is found to increase with increasing salt concentration. On the other hand, that for -amide complexes increases in the presence of ion up to 0.25 M ion concentration and then decreases as the concentration of ion is further increased. Such an unusual behavior of -amide complexes has been interpreted in terms of ion-pairing and diluent effect on the amides. However, nmr chemical shift data for the amides have shown that both of these ions interact primarily with the carbonyl group in amides.