The Kinetics of the Chromic Acid Oxidation of Isopropyl Alcohol: The Induced Oxidation of Manganous Ion

1. Isopropyl alcohol ``induces'' the chromic acid oxidation of manganous salts to MnO₂. The limiting induction factor (ratio of moles of MnO₂ to moles of acetone formed) is one‐half. 2. In the presence of manganous ion the rate at which chromic acid is reduced by isopropyl alcohol is decreased; the maximum decrease in rate observed under a wide variety of experimental conditions is 50 percent. 3. These facts, together with the previously determined reaction kinetics, demand the formation of an intermediate chromium compound in which chromium has the valence four or five. 4. Within chemically reasonable limits, all the reaction mechanisms involving such transitory intermediates have been examined. In the presence of manganous salts the only possible mechanism is $$\begin{array}{c}{\mathrm{HCrO}}_4^{-}+{\mathrm{CH}}_3{\mathrm{CHOHCH}}_3\to {\mathrm{Cr}}^4+{\mathrm{CH}}_3{\mathrm{COCH}}_3,\\ {\mathrm{Cr}}^4+{\mathrm{Mn}}^{\mathrm{++}}\to {\mathrm{Cr}}^{\mathrm{+++}}+{\mathrm{Mn}}^{\mathrm{+++}},\\ 2{\mathrm{Mn}}^{\mathrm{+++}}\text{+2}{\mathrm{H}}_2\mathrm{O}\to {\mathrm{Mn}}^{\mathrm{++}}+{\mathrm{MnO}}_2\text{+4}{\mathrm{H}}^{+}.\end{array}$$ In the absence of manganous salts several mechanisms (all of which are listed) are possible.