The Periodate−Glycol Reaction. 4. Activation Energies, Equilibria, and a Mechanism

Abstract

The reaction of ethanediol with periodate ion has been investigated in detail at six temperatures, seven pH's, and multiple glycol concentrations. From these data, a quantitative determination of rate constants and activation energies as well as equilibrium constants and enthalpies for complex formation has been made as they vary with the applied conditions. The data have been interpreted as either first order with the complex serving as an intermediate or as second order with the complex serving as an inert entity. Additional equilibria that impact the reaction are hydration of IO4- in neutral conditions and the protonation of H5IO6 in acid solutions. In evaluating the data, the following generalization has been applied: Any condition that alters the ground-state energy of a reactant or reactants by an equilibrium process must in turn alter the activation energy by an equal amount. The conclusions that have been made are as follows: (1) IO4- is the primary reactant with ethanediol; H5IO6 is a secondary...