Solvolysis rates in aqueous – organic mixed solvents. V. Kinetics of the alkaline decarboxylation of trichloroacetate ion in water – ethanol solutions

Abstract

The kinetics of the alkaline decarboxylation of trichloroacetate ion in ethanol–water solutions have been studied over the temperature range 35.0 to 70.0 °C. The rate of reaction is first order with respect to the trichloroacetate ion and is independent of the concentration of the hydroxide ion. The reactivity is enhanced by increasing the concentration of ethanol in the water–ethanol solutions and the rate of reaction varies with ethanol addition in a nonlinear manner. The rate of reaction increases with the reciprocal of the dielectric constant of the medium and the plot of log k vs. 1/D is approximately linear for solvent mixtures with less than about 0.7 water mole fraction but is strongly curved towards the pure water end. The activation parameters for the reaction show a regular increase in the solvent composition range 0.3 to 1.0 water mole fraction. The results are discussed in terms of the influence of solvent internal pressure and polarity on reactivity and of the increased amount of hydrogen-bonded structure in the water-rich solutions.