Medium effect on activation parameters for the kinetics of reaction between β-bromopropionate and thiosulfate ions

Abstract EN

The kinetics of the reaction between β-bromopropionate and thiosulfate ions has been studied at 283 to 333 K in different n-propanol–water mixtures.

The effect of ionic strength and dielectric constant on the rate of reaction was determined.

Variations in the rate as well as activation parameters have been interpreted on the basis of solvation and the dielectric properties of the medium.

Thermodynamic parameters such as free energy of activation (∆E# ), enthalpy of activation (∆H# ), and entropy of activation (∆S# ) have been evaluated as a function of ionic strength and dielectric constant.

The results show that the formation of the activated complex is due to the orientation in the configuration at the activated state rather then the electrostatic interaction among ions.

The isokinetic relation ship has been verified.

An analysis of the activation energy, enthalpy, entropy and polarisation energy reveals that solvation of transition state is larger in higher dielectric constant value which restrict the bond formation process.