Abstract: The kinetics of oxidation of glycol by dihydroxydiperiodato nickelate (Ⅳ) complex (DDN) was studied by spectrophotometry in aqueous alkaline medium in a temperature range of 25-40℃. The reaction was found to be first order with respect to Ni(Ⅳ) and also to be first order with respect to glycol. The rate increases with the increase in [OH ] and decreases with the increase in [IO₄^-], showing that dihydroxymonoperiodatonickelate (Ⅳ)(DMN) is the reactive species of oxidant. Salt effect indicated that the reaction is of ion-dipole type. No free radical was detected. Amechanism of an inner-sphere two-electron transfer reaction involving a preequilibrium between DDN and DMN is proposed, and the rate equation derived from the mechanism can explain all experimental observations. Activation parameters of the rate-determing step and the equilibrium constants were calculated.

Key words: Dihydroxydiperiodatonickelate (Ⅳ), Glycol, Redox reaction, Kinetics and mechanism