PMR spectra of protonated pyrazine and quinoxaline N-oxides

The dependence of the chemical shifts of the protons of quinoxaline and quinoxaline and pyrazine N-oxides and N,N-dioxides on the acid concentration was studied. The changes in the PMR spectra on passing from the neutral bases to the monocations were examined. The first protonation of pyrazine and quinoxaline N-oxides occurs at the N₄ nitrogen atom.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 846–852, June, 1971.