13C and 1H NMR spectroscopic studies on the structure of N-methyl-3-pyridone and 3-hydroxypyridine

Carbon and proton NMR spectra of 3-hydroxypyridine and its O-methyl and N-methyl derivatives have been analysed, and are compared with the spectra of the corresponding 2- and 4-substituted pyridines. It is shown, that contrary to quantum chemical predictions and in agreement with chemical experience, 3-hydroxy-pyridine has a phenolic structure in solution. For the N-methyl derivative, however, carbon and proton NMR data clearly demonstrate that this compound should be formulated as N-methyl-3-pyridone. The general problem of the 3-pyridones is discussed on the basis of calculated π-electron densities, IR and NMR data.