Pseudo-first order rate constants (kobs) and product ratios are reported for competing hydrolyses and alcoholyses of the reactive dichlorotriazine dye (2) in water containing small amounts (usually <0.05 M) of added alcohols (methanol, propan-1-ol, and four polyols: α- or β-methylglucopyranoside, mannitol or sorbitol) at pH 11.2. Additional data are reported in the presence of ethane-1,2-diol, prop-2-yn-1-ol and 2,2,2-trifluoroethanol. Dissection of kobs for solvolysis of the dye (DX) into the separate contributions from hydrolysis (kDOH) and alcoholysis (kDOR) shows that kDOH increases in polyol–water mixtures for 2, but not for the monofluorotriazine (1), and kDOH also increases for 2 in aqueous trifluoroethanol. The results are consistent with alkoxide-catalysed hydrolysis for 2, but with an uncatalysed or weakly-catalysed hydrolysis for 1, and provide indirect support for the possibility of a third order process in which hydroxide could act as a base catalyst. Additional kinetic data for 2 in methanol–water mixtures, containing both sodium carbonate and tetraalkylammonium salts, show rate enhancements particularly when the amount of sodium carbonate is low.
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