Electrochemical Reduction of Aza-heteroaromatic Compounds Part I. Polarographic Reduction of Aza-heteroaromatic Compounds and Its Theoretical Consideration

Abstract

Polarograms of methiodides of quinoline, isoquinoline, 3, 4- 5, 6- 7, 8-benzoquinoline, o-, m-, and p-phenanthroline were measured in aqueous solvents. Those obtained in aqueous solvents were complicated owing to adsorption of the reduced products on mercury surface, but those obtained in aprotic solvents were well-defined. All these compounds were reduced stepwise (le, le+H+) even in aqueous buffered solutions as well as in aprotic solvents. The energy difference between the two reduction steps was extraordinarily large in comparison with that of the corresponding free bases. The first half-wave potentials of these compounds were well correlated with the energies of lowest vacant molecular orbitals calculated by simple Huckel methods.