15N and 13C NMR study of protonated monoaminopyridines in CDCl3-DMSO

The 2-, 3- and 4-amino-pyridine and their protonated forms, obtained by reaction with pyridinium chloride, were investigated by 15N NMR spectroscopy. Exhaustive evidence has been found that the protonation occurs mainly on the annular nitrogen. Protonation of 4-aminopyridine by dehydrohalogenation of 1,1,2,2-tetrachloroethane (TCE) was also studied by 13C NMR spectroscopy, which indicated that the protonation occurs via the formation of adducts.