Anthracene anion, nucleophilic

An orbital symmetry analysis showed that a transition state for nucleophilic addition formed from a (4n + 1) cation-radical, e.g., 18, and a halide ion would involve orbital interactions energetically unfavorable in symmetry terms and thus prejudice such a transition state in favor of electron transfer to which similar restrictions do not apply. On the other hand, 19 is isoelec-tronic with the anthracene anion-radical and is thus a (4n + 3) species. The transition state for addition of halide becomes energetically favorable in symmetry terms in this instance. 

In the pioneering papers of Wawzonek et al. [15,186] it was demonstrated that CO2 can be added to cathodically reduced hydrocarbons to yield dihydrodicarbonylates. Examples of this kind of reaction include naphthalene [186,187], anthracene [15], 9,10-diphenylanthra-cene [15], phenanthrene [186], butadiene [187], stilbene [15], and diphenyl acetylene [187]. The mechanism is assumed to be analogous to that for protonation, with the essential steps being nucleophilic addition by an anion radical and subsequently by an anion [188]. 1,4-Addition to naphthalene suggests that carboxylation is kinetically controlled formation of dihydromonocarboxylates indicates competition with protonation. Mechanisms involving CO2 have to be considered for those hydrocarbons that are reduced at more negative potentials than [189], and for the electroinactive norbornadiene, which... 

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