Iodide, oxidation

Brines. About 65% of the iodine consumed in the world comes from brines processed in Japan, the United States, and the former Soviet Union (see Chemicals frombrine). The predorninant production process for iodine from brines is the blow-out process, which was first used in Japan. Iodine is present in brines as iodide, and its concentration varies from about 10 to 150 ppm. As shown in Figure 3, the recovery process can be divided into brine clean-up, iodide oxidation to iodine followed by air blowing out and recovery, and iodine finishing. 

The induced oxidation of iodide reveals that some intermediate is more kinetically competent toward iodide oxidation than either HCr04 or VOJ. The stoichiometric coefficients in Eq. (5-2) suggest that chromium(V) is the species responsible. 

Phosphonium iodide See Phosphonium iodide Oxidants See other metal halides, oxidants... 

Another important example of catalytic oxidation of inorganic compounds by peroxidases is the catalysis of iodide oxidation by TPO. TPO is involved in the biosynthesis of thyroid hormone and catalyzes the reactions of iodination and coupling in the thyroid gland. Magnusson et al. [215] considered two possible pathways of iodination the formation of enzyme-bound hypoiodite and the formation of free hypoiodide (Reactions (17) and (18)) ... 

Efficient operation of these cells requires, inter alia, that the M(III) species (obtained by electron injection) be reduced by 1 in solution preferentially to recombination with the electrons that were injected into the Ti02.To probe this competition, both recombination rates and iodide oxidation rates were determined. Recombination rates were investigated by monitoring the recovery of the characteristic ground-state M(II) MLCT bands in the visible region. These recovery rates were found to obey a rate law having two second-order terms, as in Eq. (22). 

The above results indicate the great progress being made in understanding the electron-transfer behavior in these sensitizer/semiconduc-tor assemblies. They also highlight the need for further work to establish the full rate laws for iodide oxidation, to obtain better resolution of site heterogeneity in the recombination process, and to define better the nature of the sites for the injected electrons. 

At a level of 1000 ppm in the diet of rats, significant enlargement of the thyroid could be detected as early as 3 days. At a dietary level of 60 or 120 ppm, there was enlargement of the thyroid within 2 weeks. Morphologic changes were noted in the thyroid of rats fed 10 or 50 mg/kg amitrole for 11-13 weeks. Amitrole is thought to interfere with the formation of thyroxine by inhibiting the peroxidase-dependent iodide oxidation in the thyroid. Suppression of thyroid function leads to further stimulation by the pituitary, with resultant hyperplasia and tumor formation. 

The HRP-catalyzed oxidation of 2-hydroxy-l-naphthaldehyde salicylhydrazone (116) with H2O2, at pH 8.5, is finished in about 10 min, and the fluorescent product (A-ex = 296 nm, A-a = 414 nm) persists for 1 h. The results compare well with those obtained by iodide oxidation. LOD is 0.7 nM and LOQ is 2.5 nM. The influence of various factors on flnorescence development was investigated . 

In the case of phosphine, the active catalyst is presumably either bisphosphine dicarbonyl or the phosphine tricarbonyl complex. Kinet-ically the bis-phosphine nickel complex cannot be the predominant species. However, in the presence of very high phosphine concentration it may have an important role in the catalyst cycle. After ligand loss and methyl iodide oxidative addition, both complexes presumably give the same 5 coordinate alkyl species. 

Iodine may be employed as a mediator to achieve a-hydroxylation of carbonyl compounds. In basic methanolic solution containing iodide, oxidation was reported to lead to a-iodo ketones, which further reacted to give a-hydroxy ketals [171]. The electrolysis of alkylidenemalonates in the presence of iodide as a mediator has been shown to yield cyclopropane derivatives [172]. 

Henglein, A. and Gutierrez, M., Effects of continuous and pulsed ultrasound a comparative study of polymer degradation and iodide oxidation,. Phys. Chem., 94, 5169-5172, 1990. 

In this section we discuss five different materials as examples with different charging mechanisms mercury, silver iodide, oxides, mica, and semiconductors. Mercury is one example of an inert metal. Silver iodide is an example of a weakly soluble salt. Oxides are an important class of minerals. For most biological substances like proteins or lipids a similar charging process dominates. Mica is an example for a clay mineral. In addition, it is widely used as a substrate in surface force measurements and microscopy. We also included a general discussion of semiconductors because the potential in the semiconductor can be described similarly to the diffuse layer in electrolytes and there is an increasing effort to make a direct contact between a liquid or a living cell and a semiconductor. 

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