Correlation of electronic transitions and redox potentials measured for pyrocatechol, resorcinol, hydroquinone, pyrogallol, and gallic acid with results of semi-empirical molecular orbital computations – A useful interpretation tool

Cyclic voltammogram (CV) electrochemical measurements for pyrocatechol, resorcinol, hydroquinone, pyrogallol, and gallic acid in strong alkaline solution produced observable oxidation–reduction potentials for each hydroxy group present except for resorcinol. UV absorption spectra were also observed for the diluted solutions. Semi-empirical molecular orbital computations were conducted for these molecules of C2v point group symmetry to determine the character and energies to aid interpretation of the experimental results. CV oxidation removed a π-electron by a radiationless π–π* transition followed by an electron shift from a negative oxygen to the positive aromatic π-system indicated by an observable σ–π* transition. Simple semi-empirical computations correlated with measured excited electronic states during electron transfer.