Hexacyanoferrate , oxidation with

Methyl-thiazolo[4,5-/]quinoline 19 was methylated by methyl iodide on the nitrogen atom of pyridine giving the appropriate methodide. A subsequent oxidation with potassium hexacyanoferrate in alkaline media gave the 2,6-dimethyl-7-0x0-6,7-dihydrothiazolo[4,5-/]quinoline 21 (37LA60). 

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). 

The industrial production of Prussian blue is based on the reaction in aqueous solution of sodium hexacyanoferrate(n), Na4Fe(CN)6, with iron(n) sulfate, FeS04-7H20 in the presence of an ammonium salt, which results initially in the formation of the colourless insoluble iron(n) hexa-cyanoferrate(n) (Berlin white). Prussian blue is generated by subsequent oxidation with a dichromate or chlorate. 

The effects of various metal oxides and salts which promote ignition of amine-red fuming nitric acid systems were examined. Among soluble catalysts, copperQ oxide, ammonium metavanadate, sodium metavanadate, iron(III) chloride (and potassium hexacyanoferrate(II) with o-toluidine) are most effective. Of the insoluble materials, copper(II) oxide, iron(III) oxide, vanadium(V) oxide, potassium chromate, potassium dichromate, potassium hexacyanoferrate(III) and sodium pentacyanonitrosylferrate(II) were effective. 

The fact that Prussian blue is indeed ferric ferrocyanide (Fe4in[Fen(CN)6]3) with iron(III) atom coordinated to nitrogen and iron(II) atom coordinated to carbon has been established by spectroscopic investigations [4], Prussian blue can be synthesized chemically by the mixing of ferric (ferrous) and hexacyanoferrate ions with different oxidation state of iron atoms either Fe3+ + [Fen(CN)6]4 or Fe2+ + [Fem(CN)6]3. After mixing, an immediate formation of the dark blue colloid is observed. However, the mixed solutions of ferric (ferrous) and hexacyanoferrate ions with the same oxidation state of iron atoms are apparently stable. 

In contrast to a variety of oxidizable compounds, only a few examples for the detection of strong oxidants with transition metal hexacyanoferrates were shown. Among them, hydrogen peroxide is discussed in the following section. Except for H202, the reduction of carbon dioxide [91] and persulfate [92] by Prussian blue-modified electrode was shown. The detection of the latter is important in cosmetics. It should be noted that the reduction of Prussian blue to Prussian white occurs at the lowest redox potential as can be found in transition metal hexacyanoferrates. 

The oxidative behaviour of glycolaldehyde towards hexacyanoferrate(III) in alkaline media has been investigated and a mechanism proposed, which involves an intermediate alkoxide ion. Reactions of tetranitromethane with the luminol and luminol-peroxide radical anions have been shown to contribute substantially to the tetranitromethane reduction in luminol oxidation with hexacyanoferrate(III) in aerated aqueous alkali solutions. The retarding effect of crown ethers on the oxidation of triethylamine by hexacyanoferrate(III) ion has been noted. The influence of ionic strength on the rate constant of oxidation of ascorbic acid by hexacyanofer-rate(III) in acidic media has been investigated. The oxidations of CH2=CHX (where X = CN, CONH2, and C02 ) by alkaline hexacyanoferrate(III) to diols have been studied. ... 

Manganese(IV) oxide in dichloromethane or potassium permanganate in chloroform oxidizes 2,4-disubstituted 1,2-dihydroquinazoline 3-oxides 6 to 2,4-substituted quinazoline 3-oxides 7. Potassium hexacyanoferrate(III) or iron(lll) chloride in alcohol can also be used for this oxidation, but the yields are lower. Oxidation of 2,4-disubstituted 1,2-dihydroquinazoline 3-oxidcs to 2,4-disubstituted quinazoline 3-oxides with lead(IV) acetate apparently proceeds via the corresponding nitroxides." ... 

Dihydroquinazolines 8 are easily oxidized with molecular oxygen,2,3-dichloro-5,6-dicyano-l,4-benzoqiiinone or potassium hexacyanoferrate(IIl) ° to the... 

Thus, dihydro-1,2,4-triazines are obtained by addition of a Grignard reagent or other carbanions to aromatic 1,2,4-triazines and the thus formed dihydro-1,2,4-triazines are oxidized with potassium hexacyanoferrate(III) or potassium permanganate (see p 627). 

Thiamine Pharmaceutical formulation Oxidation with hexacyanoferrate(lll)... 

The possible role of soot and water in the atmospheric oxidation of SO2 has been explored by studying the catalytic oxidation of SO2 by O2 on carbon in aqueous suspensions/ " A complex rate law was obtained, which was interpreted in terms of several equilibria involving the adsorption of O2 and S(IV) and the formation of C c 02-2S(IV), which reacts to give Q + 2S(VI). The oxidation of thiocyanate to sulfate and cyanate by alkaline hexacyanoferrate(III) with OSO4 catalyst has been discussed briefly/ ... 

Yao and Wasa [41] used hexacyanoferrate(III) as a mediator for oxidation of NADH with an oxidation potential of 0.4 V versus Ag/AgCl. To catalyze this reaction, a well-known diaphorase compound was immobilized on a platinum electrode with bovine serum albumin. The current produced by hexacyanoferrate oxidation was proportional to the LA concentration. For the LA determination, a flow injection system was used with a sample splitting zone after injection (10 J.L) in a carrier stream containing NAD / Fe(CN) . After the split, each sample plug passed through one of the immobilized enzyme reactors (l-LDH and d-LDH). After the enzymatic reactor, each part of the sample containing of NADH, moved by different residence time, were proportioned by coil... 

Manganese(II) can be titrated directly to Mn(III) using hexacyanoferrate(III) as the oxidant. Alternatively, Mn(III), prepared by oxidation of the Mn(II)-EDTA complex with lead dioxide, can be determined by titration with standard iron(II) sulfate. 

Probably the most extensively applied masking agent is cyanide ion. In alkaline solution, cyanide forms strong cyano complexes with the following ions and masks their action toward EDTA Ag, Cd, Co(ll), Cu(ll), Fe(ll), Hg(ll), Ni, Pd(ll), Pt(ll), Tl(lll), and Zn. The alkaline earths, Mn(ll), Pb, and the rare earths are virtually unaffected hence, these latter ions may be titrated with EDTA with the former ions masked by cyanide. Iron(lll) is also masked by cyanide. However, as the hexacy-anoferrate(lll) ion oxidizes many indicators, ascorbic acid is added to form hexacyanoferrate(ll) ion. Moreover, since the addition of cyanide to an acidic solution results in the formation of deadly... 

Hexa.cya.no Complexes. Ferrocyanide [13408-63 ] (hexakiscyanoferrate-(4—)), (Fe(CN) ) , is formed by reaction of iron(II) salts with excess aqueous cyanide. The reaction results in the release of 360 kJ/mol (86 kcal/mol) of heat. The thermodynamic stabiUty of the anion accounts for the success of the original method of synthesis, fusing nitrogenous animal residues (blood, horn, hides, etc) with iron and potassium carbonate. Chemical or electrolytic oxidation of the complex ion affords ferricyanide [13408-62-3] (hexakiscyanoferrate(3—)), [Fe(CN)g] , which has a formation constant that is larger by a factor of 10. However, hexakiscyanoferrate(3—) caimot be prepared by direct reaction of iron(III) and cyanide because significant amounts of iron(III) hydroxide also form. Hexacyanoferrate(4—) is quite inert and is nontoxic. In contrast, hexacyanoferrate(3—) is toxic because it is more labile and cyanide dissociates readily. Both complexes Hberate HCN upon addition of acids. 

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