Iodine as an oxidant

No photoreactions, except incidental photodestruction are known for hexa- and higher helicenes. As already mentioned in 2.1.1. pentahelicene forms benzo[g,h,i]perylene on irradiation in the presence of iodine as an oxidizing agent. Remarkably, the symmetrical benzoderivative (111) does not yield a similar cyclization product. This is ascribed to the antibonding character of the ji-orbitals at C-(l) and C-(14) involved in the expected photoreaction as appeared from EHMO calculation 17b). 

Iodine as an Oxidant. Brunner and Chuard concluded that iodine had no action on D-glucose. The sugar was treated with iodine and dilute ethanol in the presence of succinic acid at 110° for several hours from the brown reaction mixture a monoiodosuccinic acid was obtained, but the D-glucose was apparently unaltered. 

Oxidation. The use of iodine as an oxidant is exemplified by a procedure for the preparation of dibenzoyl disulfide. A solution of potassium hydroxide in absolute ethanol is saturated with hydrogen sulfide and treated with benzoyl chloride at 15°. The potassium chloride formed is removed by filtration, and iodine is added to the filtrate in the amount required to complete the oxidation. 

Staich, which forms a blue complex with triiodide ion, is a widely used specific indicator in oxidation/reduction reactions involving iodine as an oxidant or iodide ion as a reductant. A starch solution containing a little triiodide or iodide ion can... 

Iodine solutions can be standardized against anhydrous sodium thiosulfate or barium thiosulfate monohydrate, both of which are available commercially. The reaction between iodine and sodium thiosulfate is discussed in detail in Section 20B-2. Often, solutions of iodine are standardized against solutions of sodium thiosulfate that have in turn been standardized against potassium iodate or potassium dichromate (.see Section 20B-2). Table 20-6 summarizes methods that use iodine as an oxidizing agent. 

It is evident that the condensation of aniline with a substituted acrolein to yield quinoline involves the loss not only of water but of two hydrogen atoms as well. Therefore, the illustrative mechanism is proposed here for the reaction between a simple aniline and acrolein using iodine as an oxidizing reagent. 

Scheme 50 Cu-catalyzed cross-dehydrogenative coupling of (hetero)arenes using iodine as an oxidant.

Electrocyclization - helicenes. Brief cover reviews of the synthesis of helicenes were published.In the formation of helicenes and substituted phenanthrenes via the photochemical electrocyclization of diaryl-ethenes in the presence of iodine as an oxidant, the addition of THF... 

An attempted synthesis of a higher oxidation state complex using iodine as an oxidant for 35 in tetrahydrofuran led to the formation of the iodoplatinum(II)... 

Noroozifar, M. and M. Khorasani-Motlagh. 2003. Solid-phase iodine as an oxidant in flow injection analysis Determination of ascorbic acid in pharmaceuticals and foods by background correction. Talanta 61 173-179. 

Iodine has been used as an oxidizing titrant for a number of compounds of pharmaceutical interest. Earlier we noted that the reaction of with 13 pro-... 

Iodine pentafluoride is commercially available at a minimum purity of 98% (108). Iodine heptafluoride is the principal impurity and maintained at less than 2%. Free I2 and HF are minor impurities. Iodine pentafluoride is shipped as a Hquid in steel cylinders in various quantities up to 1350 kg cylinders. It is classified as an oxidizer and poison by DOT. 

The iodides of the alkaU metals and those of the heavier alkaline earths are resistant to oxygen on heating, but most others can be roasted to oxide in air and oxygen. The vapors of the most volatile iodides, such as those of aluminum and titanium(II) actually bum in air. The iodides resemble the sulfides in this respect, with the important difference that the iodine is volatilized, not as an oxide, but as the free element, which can be recovered as such. Chlorine and bromine readily displace iodine from the iodides, converting them to the corresponding chlorides and bromides. 

Several organohypervalent iodine reagents have been used for the oxidation of alcohols and phenols such as iodoxybenzene, o-iodoxybenzoic acid (IBX), bis(trifluoroa-cetoxy)iodobenzene (BTI), and Dess-Martin periodinane etc. But the use of inexpensive iodobenzene diacetate (IBD) as an oxidant, however, has not been fully exploited. Most of these reactions are conducted in high boiling DMSO or toxic acetonitrile media that results in increased burden on the environment. 

Theory Iodine in aqueous solution acts as an oxidizing agent which forms the basis of assay methods involving direct titration with iodine. Thus, we have ... 

In oxidation-reduction methods bromine is employed as an oxidizing agent in place of iodine, because it is reduced quantitatively be the readily oxidized pharmaceutical organic substances in a reaction which results in either water-insoluble bromine substitution products, for instance ... 

As it has been discussed earlier, iodine cannot be used directly as an oxidizing agent in such type of assays, whereas the liberated iodine quantitatively produced by the oxidation of iodide with bromine (excess) may be assayed by titrating against sodium thiosulphate solution. 

Potassium bromate can also be employed as an oxidizing agent in the assay of a number of pharmaceutical substances, namely mephenesin, phenol, and sodium salicylate. This particular method solely depends upon the formation of iodine monobromide (IBr) in relatively higher concentration of hydrochloric acid solution. 

Iodine pentoxide is used for analysis of carbon monoxide and for CO removal from air. It also is used as an oxidizing agent in other oxidation reactions. 

To prevent dimerization the concentration is kept low (10 3mol/l) but lower concentrations are allowed, when required by the bad solubility of the precursor. As an oxidizing agent 5.0 mol-% iodine in an atmosphere of air is frequently used. To prevent oxidation of the endproduct sometimes deaeration of the solvent and use of 100 mol- % iodine may be a better choice. Other useful agents are k-acceptors like tetracyanoethylene (TCNE) in dichloromethane as solvent. In most cases the helicenes are well separated from the irradiation mixture by evaporating the solvent and chromatography of the residue. In cases where the separation of the helicene and cis-olefin is difficult it is of advantage to irradiate until the olefin has completely reacted. 

The periodinane (10) may also be prepared from o-iodobenzoic acid by oxidation with potassium bromate and then treatment with acetic anhydride18 (see Expt 6.36 for detailed formulation). It should be noted that the organic derivatives of pentacoordinate iodine(v) are termed periodinanes.18b This compound (the systematic name is l,l,l-triacetoxy-2,l-benzoxiodol-3(3//)-one) has found use as an oxidant of primary alcohols to aldehydes and alicyclic ketones to secondary alcohols it is claimed to have advantages over the chromium-based oxidation reagents. 

A volatile iodine species, neither elemental nor organic, which has been found in steam/air atmospheres, has been identified as hypoiodous acid (HOI) (Cartan et al., 1968). In water-cooled power reactors, any fission products released from fuel will pass into hot alkaline water and thence to a steam-air mixture. These conditions are thought to favour the formation of HOI (Keller et al., 1970), but the evidence is indirect. For example, tests for elemental iodine or iodine with an oxidation state higher than that of HOI gave negative results. 

Recently, Moussa (122) has described a modified procedure to improve the stability of the color, the speed, and the sensitivity of assay. In this procedure, the reaction is carried out in 2-propanol medium (instead of water), triethanolamine is used as a buffer, and iodine is used as an oxidant. The detection limit of this method is 10 yg of vitamin B. ... 

If 25.0 mL of an iodine solution is equivalent as an oxidizing agent to 0.125 g of K2Cr207, to what volume should 1000 mL be diluted to make a solution 0.0500 M The half-reaction for the iodine is... 

Canthaxanthine (53) is to be regarded as an oxidative metabolite of P-carotene (1). In its industrial production, 4,4 -diacetoxy-p-carotene (52) is used as a starting compound, being hydrolyzed and oxidized 51). This compound, in turn, is obtained by the dimerization of 4-acetoxy-retinal or its phosphorus ylide (51), according to one of the methods described above48. The reaction of 4-oxo-Cls-phosphonium salt (54) with C10 dialdehyde (22) likewise leads to canthaxanthine (53)48b). In a further production process, P-carotene (1) is directly oxidized with chlorate, under catalysis with iodine 49). 

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