Title: Periodic Acid
CAS Registry Number: 10450-60-9
Molecular Formula: H5IO6
Molecular Weight: 227.94
Percent Composition: H 2.21%, I 55.67%, O 42.11%
Literature References: Prepd by electrolytic oxidation of iodic acid or from barium periodate and nitric acid: Willard, Inorg. Synth. 1, 172 (1939). Chemistry of periodic acid and periodates: H. Siebert, Fortschr. Chem. Forsch. 8, 470 (1967). Periodic acid and periodates in organic and bioorganic chemistry: A. J. Fatiadi, Synthesis 1974, 229. Book: G. Dryhurst, Periodate Oxidation of Diol and Other Functional Groups (Pergamon Press, New York, 1970).
Properties: Monoclinic, hygroscopic crystals. mp 122°; dec 130-140° forming I2O5, H2O, and O2. Freely sol in water. A 38% w/w soln had d417 1.3875. Sol in alcohol, slightly in ether. Soly in nitric acid (d 1.42) at 26° = 7.82 g/100 ml. When aq solns are evapd at room temp the "ortho" acid H5IO6 crystallizes out. If this is heated in a vacuum at 100° and 12 mm it loses water and is converted to the "meta" acid HIO4, an intermediate H4I2O9 being formed at 80°. Periodic acid is a dibasic acid, much weaker than perchloric acid. K1 at 25° = 2.3 ´ 10-2; K2 = 2 ´ 10-6. Very easily reduced to iodic acid by nitrous or sulfurous acids and even by hydrochloric and sulfuric acids. Oxidizes organic material.
Melting point: mp 122°
Density: d417 1.3875; d 1.42
Use: In organic synthesis. |