The dimerization of radical anions of aromatic carboxylic acids competing with the self-protonation reaction

Article abstract of DOI:10.1007/BF00697034

Quantum-chemical calculations (CNDO/2) of the theoretical relationship between the rate constants for the dimerization and self-protonation of radical anions show that dimer formation in the one-electron electroreduction of aromatic carboxylic acids (benzoic (1), 1-naphthoic (2), and 9-anthroic (3)) is most probable for 1.It is established that during the constant potential electrolysis (CPE) of 1 a mixture of "head-to-tail" dimers is formed in the presence of 0.1 M Bu4NClO4 (DMF).Their ratio depends on the amount of electricity passed through the solution.The CPE of 2 in the presence of 20 percent H2O affords 1,4-dihydro-1-naphthoic acid in up to 70 percent yield.The high yield ( ca. 70 percent) of 9,10-dihydro-9-anthroic acid during the CPE of 3 can be accounted for the decomposition of the dimeric product followed by protonation of the anionic species. - Key words: dimerization, self-protonation, aromatic carboxylic acids, electroreduction, radical anions.