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

摘要

The influences of LiNO3 and AgNO3 on the N-C(O) rotational barrier of N,N-dimethylacetamide and N,N-dimethylpropionamide have been investigated. The rotational activation free energy (ツG×) for Li+-amide complexes is found to increase with increasing salt concentration. On the other hand, that for Ag+-amide complexes increases in the presence of Ag+ ion up to 0.25 M ion concentration and then decreases as the concentration of Ag+ ion is further increased. Such an unusual behavior of Ag+-amide complexes has been interpreted in terms of ion-pairing and diluent effect on the amides. However, 13C nmr chemical shift data for the amides have shown that both of these ions interact primarily with the carbonyl group in amides.