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

The reaction of four triphenodioxazine (TPDO) reactive dyes on cellulosic films with bleaching agents, hypochlorite and hydrogen peroxide (HP), was examined in the aqueous solutions and redox potentials for two dyes were measured by cyclic voltammetry. The reaction of TPDO dyes on cellulosic films with HP at different pHs implied a nucleophilic reaction with HP anions, while the reaction with hypochlorite implied an electrophilic one with undissociated species of hypochlorite and a nucleophilic one with hypochlorite anion, although the relative reactivity among TPDO dyes was attributed mainly to the electrophilic one. The rates of hypochlorite bleaching for 4,11-bis(vinylsulfonyl)TPDO dyes on cellulosic film were smaller than those for 3,10-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 leave only reactive groups bound with cellulose, although each reaction mechanism is different.