Abstract
Examinations were made on the complex formation and solubilizing action of N-substituted and ring substituted acid amides from quantum chemical approach by using the Huckel method. 1) On the basis of molecular orbital considerations, N-substituted pyridinecarboxylic acid amides, except N, N-dimethylnicotinamide, were expected to have electron accepting tendency. In ring substituted benzamides, nitro-substituted acid amides would have electron accepting tendency, but those substituted with amino, chloro, or hydroxyl would have electron-accepting and donating tendencies. 2) N-Substituted pyridinecarboxylic acid amides and ring substituted benzamides formed stable complexes with solubilizates which have electron-donating tendency in aqueous solution, but those which have electron accepting tendency or little donating tendency formed little or no complexes with solubilizates. 3) Degree of complexation of N-substituted pyridinecarboxylic acid amides and ring substituted benzamides which have a high π-electron density on the oxygen atom in acidamide group was found to be much higher than that of substituted acid amides which have a low electron density. Within a homologous series, formation constant of complexes had a linear relationship with π-electron density on the oxygen atom in acid-amide group. 4) Molecular weight of the solubilizates was correlated with the formation constant of complexes.
