A kinetic and thermodynamic study of fast reactions in mixed aqueous solvents by the pressure jump technique



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The change in the rate constants and stability constants of the one-to-one nickel(II) malonate complex was studied as a function of changing structure and macroscopic properties of the solvent at different temperatures. The favorable equilibrium constant, forward rate constant and entropy change of the nickel(II) malonate system allowed the use of the pressure jump technique to study the solvent effect on the thermodynamic and kinetic properties of the system. Small amounts of dioxane were used to vary the solvent properties because of its complete misicibility with water, low dielectric constant, and neutral nature. The variations in the kinetic and thermodynamic parameters of the nickel(II) malonate system in the various water-dioxane solvent systems are explained on the basis of the solvent structure promotion and breaking ability of dioxane. The equilibrium constants of nickel(II) malonate at different temperatures and in the various water-dioxane systems were determined from spectrophotometric data.