Role of Hydroxypropylcellulose in Free Radical Induced Reactions of the Anthraquinone Based Textile Dye, Uniblue A

Radical reactions that involve one-electron reduction and oxidation of the anthraqui none based dye, Uniblue A, are studied by pulse radiolysis in the presence and absence of hydroxypropyl cellulose, a water soluble cellulose model. The dye is readily reduced by e aq - and 2-propanol radicals in aqueous solution. A comparison of the transient spectrum obtained in the reaction of the dye molecules and hydroxyl radicals with those from the reaction with one-electron oxidants, such as SO4 *- and N3*, suggests that hydroxyl radicals react by means of both electron-transfer and adduct formation. In radiolytic experiments where the concentration of hydroxypropyl cellulose greatly exceeds that of Uniblue A, hydroxyl radicals react exclusively with the soluble cellulose to generate cellulose radicals. Subsequent reaction of the cellulose radicals with Uniblue A leads to the formation of the one-electron oxidized form of the dye.