The Electronic Spectrum of p-Benzosemiquinone Anion in Aqueous Solution

The electronic spectrum of p-benzosemiquinone anion in aqueous solution formed through the oxidation of hydroquinone with manganese dioxide was measured at room temperature. The absorption maxima were found at 430, 404, and 316 mμ with shoulders at 371 and 310 mμ. It was confirmed that these absorption maxima are due to the same species p-benzosemiquinone anion, on the ground that their kinetic behaviors are the same. The molar extinction coefficients of the absorption maxima and the oscillator strengths of the absorption bands were estimated.