The kinetics of alkaline hydrolysis of 2-chloro-3,5-dinitrobenzotrifluoride 1 and 1-chloro-2,4-dinitrobenzene 2 were studied in various acetonitrile-water (AN-H 2 O) mixtures (10-90% w/w) at different temperatures. Thermodynamic parameters H # and S # show great variation, whereas G # appears to vary little with the solvent composition presumably due to compensating variations. The results are discussed in terms of the solvent parameters such as preferential solvation, dielectric constant, polarity/polarizability, and hydrogen bond donor and acceptor parameters. It has been found that the factors controlling the reaction rates are the desolvation of OH − , the solvophobicity of the medium, and free water molecules in rich AN mixed solvent. The data showed that the solvatochromic parameters of (AN-H 2 O) mixed solvent are destroyed in the presence of excess OH − . C