The reaction of triphenodioxazine dyes with bleaching agents, hypochloriteand hydrogen peroxide, in aqueous solution

The reaction of four triphenodioxazine (TPDO) reactive dyes on cellulosic f ilms with bleaching agents, hypochlorite and hydrogen peroxide (HP), was ex amined in the aqueous solutions and redox potentials for two dyes were meas ured by cyclic voltammetry. The reaction of TPDO dyes on cellulosic films w ith HP at different pHs implied a nucleophilic reaction with HP anions, whi le the reaction with hypochlorite implied an electrophilic one with undisso ciated species of hypochlorite and a nucleophilic one with hypochlorite ani on, although the relative reactivity among TPDO dyes was attributed mainly to the electrophilic one. The rates of hypochlorite bleaching for 4,1 1-bis (vinylsulfonyl)TPDO dyes on cellulosic film were smaller than those for 3,1 0-bis(disubstituted triazinyliminoethylimino)TPDO dyes, while the rates of HP bleaching showed the reverse relation. Oxidative bleaching of TPDO dyes on cellulosic films by hypochlorite and HP decomposed TPDO chromophore to l eave only reactive groups bound with cellulose, although each reaction mech anism is different. (C) 2000 Elsevier Science Ltd. All rights reserved.