Influence of acidity level in acetonitrile on Hammett!Zuman type correlations on the reduction of α-hydroxyquinones

In this work the voltammetric study in acetonitrile was carried out of a quinones family containing alpha-hydroxy group, anilineperezones (APZs; 2-(1,5-dimethyl-4-hexenyl)-3-hydroxy-5-methyl-6-[4'-(R-2-phenyl)amine]-1,4-benzoquinones) as well as their comparison with their methylated derivatives (APZms; 2-(1,5-dimethyl-4-hexenyl)-3-methoxy-5-methyl-6-[4'-(R-2-phenyl)amine]-1,4-benzoquinones) where R-2 is MeO, Me, H, Br and CN. Through a systemic study that modified the type of electron transfer coupled reactions of the two quinoid systems, linear Hammett-Zuman type variations were found, Delta E-pc = E-pc(R-2 = X) - E-pc(R-2 = H) = rho(pi)sigma(p) + a, with a not equal 0. Therefore, we suggest that the Hammett-Zuman equation simultaneously considers the substituent effect, not only in the electron transfer but also in chemically coupled reactions. Furthermore, we suggest that the magnitude of a of Hammett-Zuman type correlations shows the presence of chemical reactions coupled to the electron transfer, so that a apparently depends on the substituent effect on this type of reactions. (C) 2003 Elsevier Ltd. All rights reserved.