Electrochemistry in media of intermediate acidity. VII. Redox equilibria of anthracene cation radicals, dications, and cationic addition products

Abstract

The redox behavior of anthracene, 9-phenylanthracene, and several 9,10-disubstituted anthracenes was examined in both acidic and aprotic media. Reversible or quasireversible cation radical-dication redox couples were observed for the 9,10-diarylanthracenes. In the presence of trifluoroacetic acid the dications of 9,10-disubstituted anthracenes react to give 9-trifluoroacetoxy substituted cations. Similar cations substituted at the 9 position with hydroxy and methoxy were observed and their spectral data recorded. Arenium ions (protonated anthracenes) were found to undergo anodic oxidation about 1.5 V more anodic than the parent bases.

Bidentate and Tetradentate β‐Aminovinyl Trifluoromethylated Ketones and Their Copper(II) Complexes: Synthesis, Characterization and Redox Chemistry

“…The irreversible nature of these steps corresponds to the formation of an unstable radical cation of the enaminone moiety [47] and the anthracenyl moiety for L6H and L12H 2 . [48] All the ligands exhibited a first one-electron irreversible reduction step at -2.02, -1.56, -1.46 and -1.58 V (peak potentials at 0.2 V s -1 ) for L1H, L3H, L6H and L12H 2 , respectively, which correspond to the formation of unstable radical anions, with L6H the easiest to be reduced; the irreversible nature of these steps indicates that a chemical reaction follows the initial electron transfer and gives rise to the formation of a new product and not the dianion. [49] For L1H, a second reversible reduction step was observed at -2.44 V (peak potential at 0.2 V s -1 ; potential standard E 0 = -2.38 V, peak separation close to 0.12 V), which may be attributed to the reduction of the product that was formed after the initial electron transfer.…”

Properties of aromatic ions generated at electrodes

“…The voltammegram takes the form of The reaction of the electrode-generated intermediate with impurities in the reaction medium has been found to be a major cause for the failure to observe reversible cyclic voltammograms for many electrode processes involving aromatic compounds (Refs. 20,21,[23][24][25] Another way of suppressing a reaction following charge transfer is to add a reagent to reverse the reaction. It was demonstrated that the reversible potentials for the oxidation of a nurober of phenols, the cation radicals of which undergo very rapid deprotonation, could be obtained in dichloromethane saturated with fluorosulfonic acid.…”

“…An alternative mechanism for the reaction is given by eqns. (24)(25) in which the rate determining step is the atom transfer reaction. There is no firm evidence which rules this mechanism out and it appears more likely since even alkyl fluorides, which should be very hard to reduce undergo the reaction.…”

Prediction of the electrochemical oligomerization of p-tert-butyl anisole by analyses of the electrolysed solution

“…Only pyrrole can be polymerized in water [6][7][8]. To favour the coupling reaction of alkyl benzene, which is extremely important regarding the oxidative dimerization and polymerization, the competing side reaction of the radical cation with water must be suppressed by the use of dry medium [9].…”