The Oxidation of Iodide to Iodite and the Reduction of Iodate to Iodite in Iodine Solutions of Permanganate and Some of the Carboxylic Acids

Abstract

Permanganate oxidises small amounts of iodide to iodite in the presence of malonic, citric or malic acid. The colourless reaction mixtures always have an oxidising capacity equivalent to four times the concentration of the iodide originally taken. In mixtures of permanganate and one of these acids, iodate is reduced to its 2/3 oxidising capacity, showing the formation of iodite. A mechanism for this has been suggested. Iodine is the product in the first stage of the oxidation of iodide, which is further oxidised to iodite or iodate or which may react with the oxidation products of the organic acids. Citric acid probably gives a number of such iodinated products, one of which is solid.

Citric Acid

“…At 100 °C, it was observed that acetone dicarboxylic acid is decarboxylated to acetone [267] The same products are formed when citric acid is oxidized by acidic solutions containing mixtures of potassium permanganate with KIO 3 , KI or I 2 , but also yellow solid is precipitated, probably tetraiodoacetone (CHI 2 ) 2 CO [269]. The oxidation reactions of citric acid by periodic acid were also discussed by Melangeau and Rubman [270].…”