Rate–product correlations for concurrent nucleophilic displacements of halotriazines by hydroxide and alkoxides in water

Abstract

Rates and products of reactions of a fluorotriazine dye 1 with a range of alcohols (including tetrahydropyran-2-methanol, and α- and β-methylglucopyranoside and others given below) have been investigated in dilute aqueous solution at pH 11.2 and 25 °C by ion pair high performance liquid chromatography. The pseudo first-order rate constants when dissected, using product ratios, into contributions from the competing hydrolysis and alcoholysis reactions, show that the rates of hydrolysis are usually unchanged within experimental errors by addition of ca. l% of the alcohols. However, hydrolysis rate constants are enhanced by addition of α- and β-methylglucopyranoside. Second-order constants, calculated from pK_a data (for propan-1-ol, methanol, ethane-1,2-diol, sorbitol, mannitol) for attack by alkoxide, decrease in the order of alcohols listed. Similar data for monosubstitutions of a dichlorotriazine dye 2 show that both rate constants and product ratios are strongly temperature dependent; the medium effect of additives (e.g. urea, salts) was also examined. A non-linear dependence of rate constant with alcohol concentration was observed for reaction of 2 with glucose, and several products were formed. The results illustrate the importance of mass law effects on the rates of these reactions.