Abstract
Solvent plays a significant role in the kinetics of any reaction in solution. The reactions that occur between ions of similar charges, ions with dissimilar charges, ion and neutral molecules, and-or, between neutral molecules/compounds, solvent or solvent-solvent mixture, and-or, reaction media show a distinct effect in each case. The solvent or solvent-solvent mixture, and-or, reaction media may either increase the rate of reaction or decrease it or may not even affect it when the rate constant is measured as a function of the dielectric constant of the reaction media. The transition state theory of reactions in solution correlates the rate constant with the dielectric constant, and provides a straight-line formulation. The charges on the reactants help to predict whether the rate of the reaction will be increased or decreased or will stay constant as the dielectric constant of the reaction media is varied. However, this is not always the case. There is no simple correlation of the rate constant and the dielectric constant of reaction media as described by the transition state theory. This chapter reveals the facts beyond this correlation. The kinetics of the redox reaction between Fe(III) based metal complex and iodide was studied in four different reaction media. The effect of the ionic strength was also revealed to identify the reactive species that are involved in the rate-determining step of the reaction to surface the role of the solvent or the mixture of solvents in the redox kinetics and mechanism. This study showed a prominent effect of the solvents on the kinetics and mechanism of the reaction.