UV, H-1 AND C-13 NMR, IR, AM1 AND PM3 STUDIES ON THE PROTONATION OF AMINOPYRIDINE N-OXIDES

An investigation of single and double protonation on the UV, H-1 and C -13 NMR spectra of 2-, 3- and 4-aminopyridine N-oxides and their N-met hyl and N,N-dimethyl derivatives confirms that aminopyridine N-oxides in dilute acids are preferentially protonated on the oxygen atom and d iprotonated in concentrated acids; computed values of the proton affin ities are in agreement with the above interpretations.