Oxidation studies. II. Oxidation of water and tertiary alcohols by cobaltic ions

Abstract

Studies on oxidation of water by cobaltic ions in perchloric, nitric and sulfuric acid media in the temperature range 20-30°C. at constant ionic strength of 2.2 M were carried out. An overall order of 3/2 for cobaltic ion concentration was observed in perchloric, nitric acid media and at low [Co³⁺]<4×10⁻³ M in sulfuric acid medium. At high [Co³⁺] in sulfuric acid medium an order 2 was observed. In all the three acid media an inverse dependence of the rates on [H⁺] was noticed. From the experimental results, an acid-independent reaction path was inferred in perchloric and nitric acid media. The effect of ionic strength, HSO₄⁻ and initially added cobaltous ions as well as temperature was studied. Suitable reaction schemes were suggested to explain the experimental results and activation energy values for some of the rate parameters were evaluated. Kinetic studies on oxidation of tertiary amyl and tertiary butyl alcohols in sulfuric acid medium and that of the former in perchloric acid medium were carried out. The reaction rates were found to vary linearly with [Co³⁺] and [Alcohol]. From the effect of acidity and of [HSO₄⁻] in H₂SO₄ medium on the reaction rates it was concluded that in HClO₄ medium CoOH²⁺ species were the active entities while in H₂SO₄ medium Co³⁺ as well as CoOH²⁺ species were the active entities. The influence of ionic strength, temperature, etc., on the raction rates were studied and activation energy values for some rate constants were evaluated.