Kinetic Studies of Catalyzed Chromic Acid Oxidation of Propionaldehyde by Picolinic Acid

The chromic acid oxidation of propionaldehyde in the presence of picoIinic acid proceeds much faster than that of propionaldehyde alone. It is shown that picolinic acid is an effective catalyst. The rate law governing this catalysis is rate=k[HCrO₄^?][PA]-[CH³CH²CHO][H⁺]²/(a+b[H⁺]+c[H⁺]²). A mechanism consistent with the rate law was proposed: picolinic acid reacts with chromic acid to form a cyclic intermediate complex C¹, C¹ further reacts with a molecule of hydrated aldehyde to give a termolecular complex C² and a hydrogen ion, C² then undergoes oxidative decomposition in the next step to give products.