Kinetic and spectroscopic study of heterogeneous oxidation of azo dyes using hypochlorite

Abstract

A combined kinetic and spectroscopic investigation is described of the heterogeneous oxidation (by hypochlorite) of an azo dye (Remazol Red RB) reactively bound to cotton. It is shown that the physical state of bound dye (e.g. its pKA and tautomeric form) and its oxidation profile with pH are similar to those of dye in homogeneous solution. Analyses are presented which suggest that the mechanism of oxidation in the two environments is similar. The oxidation of azo dyes of pyrazolone and pyridone types occurs at similar rates to arylazonaphthol dyes. This suggests that oxidation kinetics are independent of groups attached either side of the azo linkage, confirming that the site of attack is the more nucleophilic nitrogen atom of the azo group of the common anion.