Structures of 3-hydroxy-1-(2-methoxyethyl)-2-methyl-4-pyridinone, its hydrochloride and...

3-Hydroxy-1-(2-methoxyethyl)-2-methyl-4(1H)-pyridinone (1) exists mainly in the quinoid form with a small contribution from the aromatic zwitterion form, while 3-hydroxy-1-(2-methoxyethyl)-2-methyl-4(1H)-pyridinone hydrochloride (2) and 1-ethyl-3-hydroxy-2-methyl-4(1H)-pyridinone hydrochloride hydrate (3) are observed to occur in the aromatic form with a minor contribution from the quinoid resonance form. Different substituents at the ring N position do not have significant geometric effects in either the neutral molecules, as a group, or in the hydrochloride salts.