Periodic acid dihydrate, oxidant

A solution of 1 g. of cholesterol a-oxide in 30 ml. of hot acetone is treated with a solution of 0.625 g. of periodic acid dihydrate in 10 ml. of water." Before all the precipitated oxide has redissolved, thin plates of cholestane-3/3, 5a,6(8-triol begin to separate. The mixture is refluxed for one half hour, cooled, and the product collected yield 0.83 g. (81%), m.p. 231-232°. A second crop of material (0.14 g.) melted at 225-226°. 

Aromatic iodination [1, 497, after citation of ref. 12]. Polyalkylbenzenes having bulky groups are not reactive toward iodine alone but may react in the presence of an oxidizing agent. In a detailed study of agents used in this connection (silver perchlorate, mercuric oxide, iodic acid, potassium persulfate, etc.) Japanese investigators123 found the combination of iodine with periodic acid dihydrate to be the most satisfactory. 

Periodates are the metal salts of periodic acid [10450-60-9], The general formula of these compounds is M(I04)j, , where M is a metal ion having the valency x. Periodic acids occur in two forms the meta acid, HIO4, and the ortho acid, H5IO6, which is the dihydrate of meta acid. Periodic acid is a much weaker acid than perchloric acid and is reduced to iodic acid by nitrous and sulfurous acids. Potassium periodate [7790-21-8] is the only metal periodate of commercial use. It is used as an oxidizing agent and for colorimetric analysis of manganese. 

In a 2-L, three-necked flask fitted with a mechanical stirrer, a dropping funnel, and a reflux condenser, a solution of 120 g (0.400 mol, 20% excess) of sodium dichromate dihydrate and 135 g (1.33 mol) of 96% sulfuric acid in 500 mL of water is added over a 40-min period to a well-stirred mixture of 128.0 g (1.00 mol) of 4-ethylcyclohexanol in 200 mL of water. Within 2 min, the mixture becomes greenish-black, and the temperature rises from 30 to 68 °C during the addition of the first half of the oxidizing solution. Immediately after the addition has been completed, the temperature starts dropping and, within 5 min, decreases to 55 °C. The mixture is cooled and extracted twice with 400 mL of ether-pentane (3 1). The extracts are washed several times with water, dried, and evaporated to yield 113.6 g (90%) of 4-ethylcyclohexanone bp 109-112 °C at 50 mm of Hg. 

Elmore, D. T. (1993) in Second Supplements to the 2nd Edition of Rodd s Chemistry of Carbon Compounds, Volume 1, Part D Dihydric alcohols, their oxidation products and derivatives, Ed. Sainsbury, M., Elsevier, Amsterdam, pp. 167-211 Elmore, D. T. (1995) in Amino Acids, Peptides, and Proteins, A Specialist Periodical Report of The Royal Society of Chemistry, Vol. 26, Ed. Davies, J. S., Royal Society of Chemistry, London (preceding volumes cover the literature of peptide chemistry back to 1969 (Volume 1))... 

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