Abstract: | Substituent effects of methyl and amino groups on the chemical shifts of pyrimidine have been investigated by 1H and 13C n.m.r. and compared with similar data obtained for benzene and pyridine. Taking into account pairwise interactions, the chemical shifts calculated by using an additivity relationship are in very good agreement with the experimental results, except for some hindered pyrimidines. This study enabled us to assign the 13C n.m.r. spectra of some trisubstituted pyrimidines. |