有機化合物の分光化学的研究 (第7報)

ピリジンN-オキシド及びキノリンN-オキシドの塩基度ついて

抄録

Dissociation constant, pKa, of pyridine and quinoline 1-oxides was determined spectrochemically and the respective values of 0.56±0.01 and 0.70±0.07 were obtained. These values are far smaller than those (4.04-4.96) of aliphatic, tertiary amine N-oxides. This was assumed to be chiefly due to the resonance of heterocyclic N-oxides as shown in (II) and its contribution was calculated to be 5.2-5.6kcal./mole from equation (4). These values agree well with the tendency of the shift of absorption spectra. Dissociation constant becomes larger when an amino group is introduced into the 4-position and this was assumed to be due to the contribution of an ionic resonance structure such as shown in (V). The fact was comparatively examind with pyridine derivatives.