Iodates reaction scheme

This apparently simple reaction comprises a complex homogeneous catalytic oscillatory process involving numerous iodine intermediates [4,5,7-9,25,27,29,30,32-92]. The global reaction (D) is the result of the reduction (R) of iodate to iodine and the oxidation (O) of iodine to iodate by the following complex reaction scheme ... 

Iodine in water can be present in a number of chemical forms including the familiar iodide ion, r, the volatile form, l2(aq), and the highly oxidised iodate ion, lOs, as well as a munber of transient forms with oxidation states intermediate between those of the more familiar forms. Even under normal conditions, there is some tendency for interconversions among these forms, but the conversion processes can be glacially slow under normal conditions. A radiation field can greatly accelerate the formation of various chemical forms of iodine in water. Products of water radiolysis can oxidise the iodide ion to form molecular iodine following a reaction scheme that is summarily described by ... 

Because ODA has been identified as a potential human carcinogen [61], alternative postcolumn derivatizations were evaluated. The method introduced by Weinberg and Yamada [62] is based on the postcolumn derivatization of bromate with bromide under acidic conditions to yield tribromide, Brg, which can be detected by UV at 267 nm. The reaction scheme was already described by Eqs. (8.41) and (8.42) in Section 8.2.I.2. In addition to bromate, this method can also be used for determining other oxyhalides such as iodate and chlorite. 

Following the proposed method of Weinberg and Yamada, SahU and von Gunten [63] developed a derivatization technique for the determination of bromate, iodate, chlorite, and nitrite that generates hydroiodic acid (HI) in situ from potassium iodide. The reaction scheme for bromate is as follows ... 

The various reactions of bromates and iodates are summarized in the. schemes on p. 866. The oxidation of halates to perhalates is considered further in the next section. 

As depicted in the following scheme, in the presence of sodium iodate and pyridine, several 5,6-dihydroxylated benzofuran derivatives were synthesized via an oxidation-Michael addition of P-dicarbonyl compounds to catechols in a one-pot procedure <06TL2615 06JHC1673>. A novel additive Pummerer reaction of 2-benzo[fc]furan sulfilimines with carbon nucleophiles derived from P-dicarbonyl compounds was also employed to the synthesis of 2,3-disubstituted benzo[b]furans <06TL595>. 

As shown in Figure 14.3, this process involved thirteen unit operations. Apart from colloidal iodate/manganate waste, significant aqueous waste was also generated. Additionally, the usage of multiple solvents (t-butanol, dichloromethane, water, and petroleum ether) in the reaction and isolation makes the synthesis, presented in Scheme 14.11, less attractive and more eco-unfriendly. 

Details of the oxidation and rearrangement of tabersonine (126) to (+)-14,15-dehydrovincamine (127) and (+)-14,15-dehydro-16-cp/-vincamine (128), which were previously recorded only in the patent literature, have now been published.90 A minor product in this sequence of reactions was formulated as (129), since hydrogenation, hydrolysis, and decarboxylation afford a hydroxy-amide (130), which can be reduced to rhazinilam (131) (Scheme 18). The reaction of 14,15-dehydrovincamine (127) with iodine and potassium iodate results in the formation of a dehydro-derivative (not isolated), followed by closure of the tetrahydrofuran ring. The product is the iodo-compound (132), which, as an iodo-enamine, loses its iodine when treated with acid, with formation of the alkaloid criocerine (133).90... 

The efficiency of mixing is usually determined by a standard chemical method, the so-called Dushman reaction.Mixing of a strong acid (FICl) and a solution of I , lOs , and CFi3C02Na (sodium acetate) leads to a combination of an ultrafast reaction (neutralization of the acid) and a fast reaction (I2 formation by an acid promoted redox reaction between iodide ions and iodate ions) as shown in Scheme 7.1. These two reactions having H as a common reaction component compete in a parallel way. If the mixing is very fast, the ultrafast process masks the slower second... 

Compound 199 is also synthesized from 177 via a series of reactions including silylation, condensation, saponification, ketal formation, iodation, hydrogenolysis, and hydrolysis, giving the product with overall yield of 55% (Scheme 12.40). ... 

Reaction of the methyl ester of cyclodopa 84 with potassium iodate, followed by reduction and acetylation gives the 7-iodo derivative 95 (R = Me) in good yield (Scheme 21) (77JOC4153). Under acidic conditions, the aromatic proton at position C-7 of cyclodopa 78 exchanges with deuterium (68HCA1476). 

Kirschning and coworkers have also reported the preparation of reagent systems generated in situ from (diazidoiodo)benzene and tetraalkylammonium halides [51], Particularly useful is a sfable polymer-bound bis(azido)iodate (30), which can be readily prepared by the reaction of polystyrene-supported iodide 28 with (diazidoiodo)benzene generated in situ from (diacetoxyiodo)benzene and azidotrimethylsilane (Scheme 5.17) [51]. 

The determination of iodide, after preceding oxidation to 10 i and reaction of the iodate formed with an excess of I, is an example of direct valency exchange process. Scheme 1 summarizes the experimental procedure involved. 

Bromination of organic compounds and subsequent reaction with iodide provides an indirect amplification based on the extraction of the iodine liberated, reduction to iodide, and iodometric titration of the iodate formed by Scheme 1. By this method phenol is ampfified 12 times and resorcinal and phloroglucinol 24 times. Other compounds, such as sahcylic acid, acetylsalicylic acid, and p-hydro-xybenzoic acid, have been also amplified. 

The first systematic design of a chemical oscillator had been achieved There remained some ambiguity, however. Since two autocatalytic reactions had been employed, it was not immediately clear which constituted the fundamental autocatalytic reaction and which provided the feedback in the model scheme. Historically, the arsenite-iodate system had been chosen for the former role, since its bistable behavior had been established first. More careful investigation revealed that, in fact, it was the chlorite-iodide reaction that provides the essential dynamical features of this system. The evidence comes in two forms. First, the chlorite-iodide reaction is also bistable in a CSTR (Dateo et al., 1982) and the relaxation to its steady states is more rapid than the relaxation behavior of the arsenite iodate system. According to our theory,... 

The same reaction is the basis of a brine electrolysis scheme for the mass production of sodium chlorate in which chlorine and hydroxide are mixed together as they are produced. Bromates and iodates can also be made on a small scale by oxidizing the halide to the halate with hypochlorite. [See, for example. Equation (18.37).] Iodic acid is easily prepared from the oxidation of iodine with hot nitric acid, as shown in Equation (18.41) ... 

In 1980, Szantay found that tetraethylammonium[di(acylo3q )iodate(i)] derivatives effectively promote the CDC reaction of 92 to give 93 (Scheme 8.43). ... 

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