Nonaqueous Polarography of Quinones. VI. Polarography of Linear Aromatic p-Quinones

The half-wave potential (E1/2) and diffusion current constant (ID) of three linear aromatic p-quinones, 1, 4-anthraquinone (I), 5, 12-naphthacenequinone (II), and 6, 13-pentacenequinone (III), were measured under identical conditions by the nonaqueous polarography in glacial acetic acid containing 0.25N ammonium acetate. The half-wave potential of (I), (II), and (III) was +0.027 v., -0.345 v., and -0.447 v. vs. SCE, respectively. The ease with which they are reduced at the dropping mercury electrode is in the descending order of 1, 4-anthraquinone, 5, 12-naphthoanthraquinone, and 6, 13-pentacenequinone. This order agrees with the resonance theory as in the case of quinones described in previous papers.