NMR studies of rotamers with multi-substituted amides

Rotamers existed in the multi-substituted amide play an important role in the chemical reactivity function. Diverse chemical reactivity of substrates which contain an amide group is significantly affected by their rotamers. In this paper, rotamers of amides were studied and confirmed by means of NMR spectra. It was found that the ratio of related rotamers of amides depend on the amides bulk. When the nitrogen atom is located in the ring rigid structure, the rotation of C-N bond is limited and it is difficult to produce rotational isomers. In addition, we also found that substituted groups in phenyl ring cannot affect the ratio of related rotamers.