Studies on Ultraviolet Spectra of Hydroxyanthraquinones

Abstract

In the ultraviolet spectra of hydroxyanthraquinone derivatives, the absorption appearing in shorter wave lengths region than 250mμ is very important, though it has been neglected to date. When anthraquinones have one, two, three, and four hydroxyl groups, λmax appears at 222.5, 225, 230±2.5, and 236mμ, respectively. These maxima are independent of the nature of the hydroxyl groups, as at α or β, but the intensity value depends chiefly on the number or α-hydroxyls. The intensity of maximum absorption at 270mμ (ca.) depends on the β-hydroxyl group and the log ε value above 4.1 shows the presence of a β-hydroxyl group and the value below 4.1 denies it. Therefore, it would be possible to predict the number of hydroxyls and α:β ratio from the ultraviolet absorption curve. Further, hydroxyanthraquinone derivatives with 1, 4-dihydroxyl in the molecule exhibit a shift in the visible region and the absorption maximum appears at above 480mμ.