NMR-STUDIES IN THE HETEROCYCLIC SERIES .32. EXPERIMENTAL (C-13 AND N-15 NMR-SPECTROSCOPY) AND THEORETICAL (6-31G) STUDY OF THE PROTONATION OF N-METHYLAZOLES AND N-METHYLBENZAZOLES

The C-13 and N-15 NMR spectra of 11 N-methyl derivatives of azoles and benzazoles (imidazole, pyrazole, 1,2,4-triazole, indole, benzimidazole, 2H-indazole, 1H-indazole, 2H-benzotriazole, 1H-benzotriazole and carbazole) in trifluoroacetic and sulphuric acid are reported. Quaternary salts were used as model compounds. In the case of azoles (from pyrrole to pentazole) ab initio calculations at the 6-31G level were carried out to determine the protonation site.