KINETICS AND MECHANISM OF INDO-ANILINE DYE FORMATION IN AQUEOUS PEROXIDE SOLUTION

Oxidation of a mixture of para-phenylenediamine (PPD) and phenols gene rates indo-aniline dyes. The process is of special interest with hydro gen peroxide (H2O2), which is used commercially to induce permanent ha ir coloring formation. Although limited reports can be found to discus s the mechanism of indo-aniline formation by other oxidants, e.g., K3F e(CN)6 and O-2, little is known about the mechanism of indo-aniline fo rmation in aqueous peroxide solution. Kinetic studies of indo-aniline formation by H2O2, recently carried out in our laboratories, indicate that indo-aniline is formed through a multiple-step scheme. The rate o f indo-aniline formation was limited by PPD consumption, a kinetically slow step. Both promotion and inhibition of H2O2 on indo-aniline form ation were observed and were accounted for by a mechanism developed ba sed on kinetic modeling.