Polarography of Anthraquinone Derivatives in Dimethylformamide: Effect of Hydrogen Bonding

The polarographic reduction is reported of anthraquinone, some methoxyanthraquinones, hydroxyanthraquinones, and aminoanthraquinones in dimethylformamide. Two reduction steps, each corresponding to the addition of one electron, were obtained for all compounds with the exception of 2-hydroxyanthraquinone, which gave four distinct steps. The introduction of hydroxyl groupings peri to the quinone carbonyl groupings caused the half-wave potentials of both steps to shift to less negative values. The shifts of the first reduction steps have been interpreted in terms of stabilization of the radical-ions by intramolecular hydrogen bonding.