13C NMR spectra of 7-substituted 8-mercaptoquinolines

The¹³C NMR spectra of 7-substituted [7-CH₃, 2,7-(CH₃)₂, 7-Cl, 7-Br, and 7-SCH₃] 8-mercaptoquinolines and 8-methylmercaptoquinolines were examined. It is shown that the changes in the¹³C chemical shifts of the quinoline ring in the spectra of 7-substituted 8-mercaptoquinolines are in good agreement with the additive contribution of the increments of the substituents, i.e., their conjugation with the ring is not disrupted. The conjugation of the SCH₃ group with the quinoline ring in 7-substituted 8-methylmercaptoquinolines is disrupted as a consequence of steric hindrance, and this leads to a decrease in the increments of this group. The data obtained are compared with the results of a calculation within the CNDO/2 approximation. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 801–805, June, 1980.