Oxidants iodine cyanide

The Ag2 S ISE has Nemstian response dE/d log a( = 0.0296 V in the sulphide concentration range 10" to 10" M and silver ions from 10 to 10 M if the solutions are prepared from pure salts, as a further concentration decrease is prevented by adsorption on the glass (see p. 76 and [87, 163]). After prolonged use, the limit of the Nemstian behaviour shifts to about 10" m [130] as a result of formation of mixed potentials on accumulation of metallic silver in the membrane surface. An analogous deterioration in the membrane function in the presence of iodine results from surface oxidation [23]. Cyanide interferes only at large concentrations the equilibrium constant of the reaction... 

Miranda MA, Perez-Prieto J, Font-Sanchis E, Scaiano JC (2000) Five-membered-ring 9-1-2 radicals direct detection and comparison with other hypervalent iodine radicals. Org Lett 1 1587-1589 Muiioz F, Schuchmann MN.OIbrich G, von Sonntag C (2000) Common intermediates in the OH-radi-cal-induced oxidation of cyanide and formamide. J Chem Soc Perkin Trans 2 655-659 Nagarajan V, Fessenden RW (1985) Flash photolysis of transient radicals. 1. X2" with X = Cl, Br, I, and SCN. J Phys Chem 89 2330-2335... 

Lang found that, in the presence of cyanide, iodine is oxidized quantitatively to iodine cyanide. The standard potential of the half-reaction... 

Potassium periodate has been used in place of iodate for various titrations involving the iodine-chloride, iodine-bromide, and iodine-cyanide end points. Reaction of periodate with iodide involves transfer of an oxygen atom rather than an electron, followed by rearrangement of the structure of the IO4" ion. In the oxidation of the active oxidant appears to be 104 . An intermediate... 

Gregory et al. (16) and Humphries et al. (95) have examined the effect of A -ethylmaleimide (NEM) and BDC-OH on pig heart m-MDH and have obtained evidence in each case for the modification of two essential thiol groups per enzyme molecule. Both modifications were inhibited by coenzyme. Sensitivity of m-MDH to thiol modification has also been demonstrated by means of thyroxine, iodine cyanide, and molecular iodine, all of which cause oxidation of thiol groups accompanied by inactivation in this enzyme (103). 

Salicylates, magnesium salts, cuprum oxide, iodine, hydrogen peroxide, cyanides, sulfamides... 

The examination of the titration reactions shows, without any ambiguity, that iodine plays the part of an oxidizing species. Cyanide ions, at the global oxidation number -I, become oxidized into the species CN -K, as stoichiometry shows. The global redox reaction may be divided into the following two half-redox reactions ... 

Another methodology consists of operating in the presence of cyanide ions. Iodine is quantitatively oxidized into iodine cyanide (which may also be called cyanogen iodide). The half-redox reaction is... 

Grundnes, J., Klaeboe, P. and Plahte, E. (1967) Spectroscopic studies of charge transfer complexes. XV. Triphenyl arsine oxide with iodine and iodine cyanide. Sel. Top. Struct. Chem., 265-275. 

Nucleophilic aromatic substitutions involving loss of hydrogen are known. The reaction usually occurs with oxidation of the intermediate either intramoleculady or by an added oxidizing agent such as air or iodine. A noteworthy example is the formation of 6-methoxy-2-nitrobenzonitrile from reaction of 1,3-dinitrobenzene with a methanol solution of potassium cyanide. In this reaction it appears that the nitro compound itself functions as the oxidizing agent (10). 

The nitration of l,2,5-selenadiazolo[3,4-/] quinoline 77 with benzoyl nitrate affords the 8-nitro derivative 78, whereas methylation with methyl iodide or methyl sulfate afforded the corresponding 6-pyridinium methiodide 79 or methosulfate 80, respectively (Scheme 29). The pyridinium salt 80 was submitted to oxidation with potassium hexacyanoferrate and provided 7-oxo-6,7-dihydro derivative 81 or, by reaction of pyridinium salt 79 with phenylmagnesium bromide, the 7-phenyl-6,7-dihydro derivative 82. Nucleophilic substitution of the methiodide 79 with potassium cyanide resulted in the formation of 9-cyano-6,9-dihydroderivative 83, which can be oxidized by iodine to 9-cyano-l,2,5-selenadiazolo [3,4-/]quinoline methiodide 84. All the reactions proceeded in moderate yields (81IJC648). 

Cyanide and thiocyanate anions in aqueous solution can be determined as cyanogen bromide after reaction with bromine [686]. The thiocyanate anion can be quantitatively determined in the presence of cyanide by adding an excess of formaldehyde solution to the sample, which converts the cyanide ion to the unreactive cyanohydrin. The detection limits for the cyanide and thiocyanate anions were less than 0.01 ppm with an electron-capture detector. Iodine in acid solution reacts with acetone to form monoiodoacetone, which can be detected at high sensitivity with an electron-capture detector [687]. The reaction is specific for iodine, iodide being determined after oxidation with iodate. The nitrate anion can be determined in aqueous solution after conversion to nitrobenzene by reaction with benzene in the presence of sulfuric acid [688,689]. The detection limit for the nitrate anion was less than 0.1 ppm. The nitrite anion can be determined after oxidation to nitrate with potassium permanganate. Nitrite can be determined directly by alkylation with an alkaline solution of pentafluorobenzyl bromide [690]. The yield of derivative was about 80t.with a detection limit of 0.46 ng in 0.1 ml of aqueous sample. Pentafluorobenzyl p-toluenesulfonate has been used to derivatize carboxylate and phenolate anions and to simultaneously derivatize bromide, iodide, cyanide, thiocyanate, nitrite, nitrate and sulfide in a two-phase system using tetrapentylammonium cWoride as a phase transfer catalyst [691]. Detection limits wer Hi the ppm range. 

Taurog et al. [216] showed that contrary to previous suggestions, both iodination and coupling are catalyzed by the oxoferryl porphyrin Tr-cation radical of TPO Compound I and not the oxoferryl protein radical. HRP catalyzed the oxidation of bisulfite to sulfate with the intermediate formation of sulfur trioxide radical anion S03 [217] HPO, MPO, LPO, chloroperoxidase, NADH peroxidase, and methemoglobin oxidized cyanide to cyanyl radical [218],... 

The most common reactions involving nucleophiles and porphyrin systems take place on the metalloporphyrin 77-cation radical (i.e. the one-electron oxidized species) rather than on the metalloporphyrin itself. One-electron oxidation can be accomplished electrochemi-cally (Section 3.07.2.4.6) or by using oxidants such as iodine, bromine, ammoniumyl salts, etc. Once formed, the 77-cation radicals (61) react with a variety of nucleophiles such as nitrite, pyridine, imidazole, cyanide, triphenylphosphine, thiocyanate, acetate, trifluoroace-tate and azide, to give the correspondingly substituted porphyrins (62) after simple acid catalyzed demetallation (79JA5953). The species produced by two-electron oxidations of metalloporphyrins (77-dications) are also potent electrophiles and react with nucleophiles to yield similar products. 

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