HOMOGENEOUS MODELS FOR THE CHEMICAL SELECTIVITY OF REACTIVE DYES ON COTTON - DEVELOPMENT OF PROCEDURES AND CHOICE OF MODEL

Rates and products of reactions of a dichlorotriazine dye (CI Reactive Orange 4) with a range of alcohols (methanol, propan-1-ol, propan-2-o l, tetrahydropyran-2-methanol, ethane-1,2-diol, alpha- and beta-methyl glucopyranosides, mannitol and sorbitol) have been investigated in dil ute aqueous solution at pH 11.0 and 25.0 degrees C by ion-pair HPLC. T he pseudo-first-order rate constants have been separated into contribu tions from the competing hydrolysis and alcoholysis reactions. Additio n of alcohol increases the rates of both hydrolysis and alcoholysis re actions. Product selectivity increases from 74 for 0.132 mol/l propan- 1-ol to 2400 for 0.132 mol/l mannitol and differs even for stereoisome rs. It is concluded that, despite its simplicity, methanol is a suitab le model alcohol for probing the major factors influencing the chemica l selectivity of reactive dyes in homogeneous solutions.