Oxidation of iodine

There appears to be only one true oxide of iodine, diiodine pentoxide, IjOs- It is a white solid prepared by heating iodic acid(V) to 450 K ... 

C. HIO is prepared by oxidation of iodine with perchloric acid, nitric acid, or hydrogen peroxide or oxidation of iodine in aqueous suspension to iodic acid by silver nitrate. Iodic acid is also formed by anodic oxidation at a platinum electrode of iodine dissolved in hydrochloric acid (113,114). 

The endothermic radical lO has also been studied in the gas phase the interatomic distance is 186.7 pm and the bond dissociation energy 175 20kJmol . It thus appears that, although the higher oxides of iodine are much more stable than any oxide of Cl or Br, nevertheless, lO is much less stable than CIO (p. 849) or BrO (p. 851). Its enthalpy of formation and other thermodynamic properties are A//f(298K) 175.1 kJmol", AGf(298 K) 149.8 kJmol-, 5°(298 K) 245.5 J K- mor . 

Of the oxides of iodine that have been reported, the most common is I205, which is prepared by the dehydration of HI03. 

In actual practice, either carbon tetrachloride or chloroform is usually added so as to make the endpoint distinctly visible. Iodine is liberated at the initial stages of the titration which renders the chloroform layer coloured. At that material point when all the reducing agent under estimation has been duly oxidized, the iodate completes the oxidation of iodine and iodide to I+, and hence the colour from the chloroform layer disappears. 

The anodic chlorination in some cases allows one to achieve better regioselec-tivities than chemical alternatives (p/o ratio of chlorotoluene in chlorination of toluene anodic 2.2, chemical alternative 0.5-1.0) [215]. Anodic oxidation of iodine in trimethyl orthoformate afforded a positive iodine species, which led to a more selective aromatic iodination than known methods ]216]. Aryliodination is achieved in good yield, when an aryhodide is oxidized in HOAc, 25% AC2O, 5% H2SO4 in the presence of an arene ]217, 218]. Alkyl nitroaromatic compounds, nitroaromatic ketones, and nitroanihnes are prepared in good yields and regioselectivity by addition of the corresponding nucleophile to a nitroarene and subsequent anodic oxidation of the a-complex (Table 13, number 11) ]219, 220]. 

It also may be produced by oxidation of iodine with concentrated nitric acid ... 

Another method of preparation involves oxidation of iodine with hydrogen peroxide ... 

Mecfianism of Action A thiourea derivative that blocks oxidation of iodine in the thyroid gland and blocks synthesis of thyroxine and triiodothyronine. Therapeutic Effect Inhibits synthesis of thyroid hormone. 

Astatine has properties very similar to those of iodine, but has a more metallic character. The oxidation of astatide to astatine occurs at a potential ca. 0.4 V less positive compared to that for the oxidation of iodine. Fundamental information about the redox chemistry of astatine is available in an earlier review [158] and standard data collections [14]. A summary of the approximate standard potentials and known redox states is given in Scheme 8. 

Bromic acid was discovered by A. J. Balard 2 in 1826 and described in his classical memoir, Sur une substance particuliire contenue dans Veau de la met A. J. Balard was of course guided in this work by the analogy which he found between bromine and iodine. Iodic acid was discovered by J. L. Gay Lussac and H. Davy 3 in 1813 and, in 1831, A. Connell obtained it by the direct oxidation of iodine by nitric acid. 

Iodates. Iodates are stable at room temperatures but lose oxygen on heating. Metallic iodates, although stable and safe to handle, should be kept out of contact with organic substances and other combustible materials, because such mixtures are explosive. Iodates can be prepared by oxidation of iodine to iodic acid, followed by neutralization with an oxide or hydroxide or by electrolytic oxidation of an iodide solution (105,106). 

Of the older methods for the preparation of periodic acid, the most satisfactory for obtaining large quantities is the electrolytic oxidation of iodic acid at an anode of platinum plated with lead dioxide, the cathode solution being dilute nitric acid.1 The iodic acid for this preparation is conveniently prepared by the electrolytic oxidation of iodine.1 However, periodic acid prepared in this way often contains... 

Kruus P, Entezari MH. Effect of frequency on sonochemical reactions I. Oxidation of iodine. Ultrason Sonochem 1996 3 19-24. 

Iodine pentoxide is a white solid substance that, at ordinary temperatures, is entirely stable. It cannot be prepared by direct synthesis from iodine and oxygen, because when cold the elements combine too slowly, and when heated the compound is unstable. It may be readily prepared by the direct oxidation of iodine by means of strong oxidizing agents, such as concentrated nitric acid or chlorine. One method for the oxidation of iodine has already been illustrated under the preparation of potassium iodate, but... 

Iodination probably involves an electrophilic aromatic substitution with the iodine cation (I+) acting as the electrophile. The iodine cation results from oxidation of iodine by nitric acid. 

The only example of this type of compound is IF7. This is the result of several factors, among them the large size of the iodine atom and the easier oxidation of iodine to a +7 oxidation state. Also, the combination of iodine with fluorine represents the largest electronegativity difference possible for interhalogens. The compound is prepared by the reaction of fluorine with IF5 at elevated temperatures ... 

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