Iodic Anhydride

When heated it is decomposed into oxygen and iodic anhydride, and ultimately into iodine and o i gen. 

According to H. W. Foote and L. H. Levy, soln. of the alkali chlorates in other molten salts gave f.p. indicating that the mol. wt. under those conditions are normal. A. Rosenheim and 0. Liebknecht48 found the mol. wt. of acid by the f.p. method depend on the concentration, and that the acid in dil. soln. is a monobasic acid, and in cone. soln. the acid is polymerized and exists as a dibasic acid, H2l206. E. Gro-schuff and P. Walden also showed that the electrical conductivity of iodic acid soln. corresponds with a monobasic acid, as is also the case with chloric and bromic acids. The monobasic acid, therefore, can be represented by A. Kekule s type of formula with iodine univalent or C. W. Blomstrand s type of formula, with iodine quinquevalent and iodic anhydride, i.e. iodine pentoxide will be represented ... 

As the equation indicates, it is the anhydride of iodic-acid(V), which is re-formed when water is added to the pentoxide. Mixed with concentrated sulphuric acid and silica, it is a quantitative oxidising agent for carbon monoxide at room temperature ... 

The structure of difructose anhydride II has not yet been determined. McDonald and Jackson76 prepared its hexamethyl ether, which proved to be a crystalline compound melting at 73°. The behavior of the product from the acid hydrolysis of this hexamethyl derivative toward phenylhydrazine suggests that two different trimethyl-D-fructoses are present, the identification of which remains to be accomplished. Lately some evidence concerning the structure of this anhydride has been obtained by the use of per-iodic acid oxidation, as described on page 275. 

Per-iodic acid oxidation78-80 has been used by many investigators in structural studies because this reagent oxidizes selectively the hydroxyls on adjacent carbon atoms. In the course of their studies, McDonald and Jackson81 found that difructose anhydrides I, II and III and diheterolevulosan reduce per-iodic acid to iodic acid in the following respective molecular ratios 2, 1, 1, and 4 moles of acid per mole of anhydride. 

Difructose anhydride I (XI, page 269) contains two pairs of adjacent carbon atoms to which hydroxyl groups are attached (3,4 and 3, 4 ) thus, it would be expected to react with two moles of per-iodic acid. Difructose anhydride III (XII, page 269) contains only one such pair (3,4) in agreement with its consumption of one mole of acid. Diheterolevulosan (X, page 268) requires four moles of acid, one for each of the following pairs of carbon atoms 3,4 4,5 3, 4 4, 5. ... 

Difructose anhydride II reacts with one mole of per-iodic acid. Hydrolysis of its methyl derivative indicates that two different trimethyl-D-fructoses are formed whose combined specific rotations in water amount to between + 20° and + 30°. If we assume that this anhydride, like the other two derived from inulin, is made up of D-fructofuranoses, the facts that have been mentioned allow only three possible structures for this anhydride. 

Several oxidized compounds of iodine have been reported at various times. No doubt many of them are mixtures of iodic or periodic acids or anhydrides with iodine, etc. For example, there is (1) N. A. E. Millon s 8 oxyde soushypoiodique, Ik>019, t.e. I,0,.4Ia0a, formed as a yellow powder by the action of sulphuric acid on iodic acid. Millon regarded this oxide as hypoiodic anhydride, I40 or I09, mixed with a little iodous... 

If the iodine be in large enough excess, the reaction proceeds until the nitric acid is so dil. by the production of water in the reaction, that it has no further action on the iodine even though the acid is cone, enough to keep the iodic acid sparingly soluble and to hold considerable quantities of iodine in soln. The yield of iodic acid by the action of nitric acid on iodine is not very great—about 4 per cent. a much greater yield—about 40 per cent.—is obtained by the action of nitric anhydride... 

This oxide reacts with water, and it is the anhydride of iodic acid,... 

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