Hydrogen peroxide and iodine

Figure 3.14 ipso-substitution reaction of PABA with hydrogen peroxide and iodine. (Reprinted with permission from Langmuir, 17, 7183. Copyright (2001) American Chemical Society.)... 

Wet-Chemical Determinations. Both water-soluble and prepared insoluble samples must be treated to ensure that all the chromium is present as Cr(VI). For water-soluble Cr(III) compounds, the oxidation is easily accompHshed using dilute sodium hydroxide, dilute hydrogen peroxide, and heat. Any excess peroxide can be destroyed by adding a catalyst and boiling the alkaline solution for a short time (101). Appropriate ahquot portions of the samples are acidified and chromium is found by titration either using a standard ferrous solution or a standard thiosulfate solution after addition of potassium iodide to generate an iodine equivalent. The ferrous endpoint is found either potentiometricaHy or by visual indicators, such as ferroin, a complex of iron(II) and o-phenanthroline, and the thiosulfate endpoint is ascertained using starch as an indicator. 

The preparation of Pans-1,2-cyclohexanediol by oxidation of cyclohexene with peroxyformic acid and subsequent hydrolysis of the diol monoformate has been described, and other methods for the preparation of both cis- and trans-l,2-cyclohexanediols were cited. Subsequently the trans diol has been prepared by oxidation of cyclohexene with various peroxy acids, with hydrogen peroxide and selenium dioxide, and with iodine and silver acetate by the Prevost reaction. Alternative methods for preparing the trans isomer are hydroboration of various enol derivatives of cyclohexanone and reduction of Pans-2-cyclohexen-l-ol epoxide with lithium aluminum hydride. cis-1,2-Cyclohexanediol has been prepared by cis hydroxylation of cyclohexene with various reagents or catalysts derived from osmium tetroxide, by solvolysis of Pans-2-halocyclohexanol esters in a manner similar to the Woodward-Prevost reaction, by reduction of cis-2-cyclohexen-l-ol epoxide with lithium aluminum hydride, and by oxymercuration of 2-cyclohexen-l-ol with mercury(II) trifluoro-acetate in the presence of ehloral and subsequent reduction. ... 

A mixture of 1,4-dioxane and water is often used as the solvent for the conversion of aldehydes and ketones by H2Se03 to a-dicarbonyl compounds in one step (Eq. 8.117).331 Dehydrogenation of carbonyl compounds with selenium dioxide generates the a, (i-unsaturated carbonyl compounds in aqueous acetic acid.332 Using water as the reaction medium, ketones can be transformed into a-iodo ketones upon treatment with sodium iodide, hydrogen peroxide, and an acid.333 Interestingly, a-iodo ketones can be also obtained from secondary alcohol through a metal-free tandem oxidation-iodination approach. 

A number of agents have been used to disinfect pressure sores (e.g., povidone-iodine, iodophor, sodium hypochlorite, hydrogen peroxide, and acetic acid) as well as other types of open wounds however, these agents should be avoided as they impair healing. 

Shake 10 parts of powdered iodine with 60 parts of pharmaceutical hydrogen peroxide, and gradually add 30 parts of aq. ammonia. If necessary hydrogen peroxide is added until the further evolution of gas does not occur, and the soln. has acquired a pale yellow colour. The filtered soln. becomes colourless when warmed on a water-bath, and after evaporation, the salt is rubbed with a little aq. ammonia, and dried. 

An attractive modification of this method is to treat the neutralised polythionate solution with neutral hydrogen peroxide and a known excess of standard sodium hydroxide solution on the water-bath and to determine the quantity of acid formed by the amount of standard alkali neutralised during the oxidation.3 All polythionates except the dithionates are completely oxidised to sulphate by heating in a closed tube for one hour with iodine and sodium bicarbonate by titrating the excess of iodine the total polythionate present may be estimated.4... 

Thomas JK (1967) Pulse radiolysis of aqueous solutions of methyl iodide and methyl bromide. The reactions of iodine atoms and methyl radicals in water. J Phys Chem 71 1919-1925 Tsang W, Hampson RF (1986) Chemical kinetic data base for combustion chemistry, part I. Methane and related compounds. J Phys Chem Ref Data 15 1086-1279 UlanskiP, von Sonntag C (1999) The OFI-radical-induced chain reactions of methanol with hydrogen peroxide and with peroxodisulfate. J Chem Soc Perkin Trans 2 165-168 Ulanski P, Bothe E, Hildenbrand K, von Sonntag C, Rosiak JM (1997) The influence of repulsive electrostatic forces on the lifetimes of polyfacrylic acid) radicals in aqueous solution. Nukleonika 42 425-436... 

Hydrogen peroxide and organic hydroperoxides can be reduced by molybdate-activated iodide [Allen et al. 1952 reactions (13) and (14)]. The iodine atoms formed in these reactions combine to iodine which complexes with iodide [reactions (15) and (16)], and it is this I3- complex which is measured (s(3540 nm) = 25,000 dm3 mol-1 cm-1)... 

Ketones, I COR2, have been converted to their -dihydroperoxides (112) using a green oxidant, aqueous 30% hydrogen peroxide, with iodine as catalyst.337 The iodine may enhance the electrophilic character of the carbonyl carbon and/or the nucleophilicity of the hydrogen peroxide. The reaction has also been extended to... 

As a unique reaction with the Fenton system, the alkylation of heteroaromatics with alkyl iodide, hydrogen peroxide, and dimethyl sulfoxide in the presence of FeS04 can be carried out. This reaction comprises of the initial formation of reactive HO by the reaction of FeS04 and hydrogen peroxide, reaction of HO on the sulfur atom of dimethyl sulfoxide to form CH 3 and methanesulfinic acid (SH2 reaction), reaction of CH3 on the iodine atom of alkyl iodide via SH2 pathway to form more stable R and methyl iodide, and then addition of R to the a-position of y-picoline (1) to form an addition-intermediate radical which is rearomatized under oxidative conditions to 2-alkyl-4-methylpyridine (2) [15, 16]. 

In the presence of hydrochloric acid or hydrobromic acid the oxidation of hydriodic acid may proceed further, the iodine being converted into iodic acid possibly by way of iodine trichloride or bromide. However, periodic acid is reduced to iodic acid by hydrogen peroxide and in dilute solution partial reduction even to iodine may occur.10... 

Ley and Barton s observation that di-4-methoxyphenyltelluride could be used catalytically was the first entry into the use of in situ generated selenoxides or telluroxides as catalysts. As shown in Fig. 8, a variety of different nucleophiles can be introduced via the selenoxide or telluroxide followed by reductive elimination to generate oxidized product and reduced selenide or telluride. If the nucleophile is relatively inert to oxidation by hydrogen peroxide, then the reduced selenide or telluride can be reoxidized by hydrogen peroxide and the overall oxidation of the nucleophile becomes catalytic in the selenide or telluride. In the case of thiols, disulfides are the final product and the selenides or tellurides exhibit thiolperox-idase-like activity 60-62 64 82 83 If halide salts (chloride, bromide, iodide) are the nucleophiles, then positive halogen sources are the oxidized products and the selenides and tellurides exhibit haloperoxidase-like activity.84-88 The phenoxypro-pyltelluride 59 has been used as a catalyst for the iodination and bromination of a variety of organic substrates as shown in Fig. 24.87... 

Fig. 24 Iodination and bromination of organic substrates with hydrogen peroxide and sodium iodide or bromide in the presence of phenoxypropyltelluride 59.

These reactions proceed so regularly that they may be followed up quantitatively. Ferric salts have no catalytic influence upon these reactions.1 Iron salts, however, can act as oxygen-carriers in the absence of such powerful oxidisers as hydrogen peroxide and potassium permanganate. Thus, for example, it is well known that, upon exposure to sunlight, iodine is ordinarily liberated from a solution of mercuric iodide in potassium iodide. Curiously enough, if traces of iron salts are rigidly excluded, the liberation of iodine does not take place.2... 

Oxidations of thiocyanate ion by nitrous and nitric acids and by peroxomono-sulphate and peroxodisulphate are considered under the oxidants (p. 293 and 350). Oxidation by hydrogen peroxide and by iodine will be considered here. 

In the presence of a small amount of ascorbic acid, the I2 formed is reduced back to iodide. When all the ascorbic acid is consumed, iodine is liberated, and the sudden appearance of iodine can be made visible with variamine blue (Landolt effect). The time to the appearance of iodine is measured. The reaction of hydrogen peroxide and iodide is much faster in the presence of molybdate, probably because of the reactions... 

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