Lead ferricyanide

Hydrogen ferricyanide, Ferricyanic acid, H3[Fe(CN)6], maybe obtained as crystalline brown needles by the action of dilute sulphuric acid upon lead ferricyanide and subsequent concentration of the... 

Lead ferricyanide, Pb3[Fe(CN)6]2.16H20, is obtained by double decomposition of lead nitrate with potassium ferricyanide. It yields dark reddish brown crystals. 

Lead ferricyanide nitrate, Pb3[Fe(CN)6]2.Pb(N03)2.12H20, and Lead potassium ferricyanide, PbK[Fe(CN)6].3H20, have been described.3... 

Methylpyridinium quaternary salts, such as (12), undergo oxidation in alkaline solution in the presence of potassium ferricyanide to give 2-pyridones, eg, A/-methyl-2-pyridone [694-85-9] (16). Frequendy nucleophilic attack at position 2 by excess hydroxide leads to ring opening this and synthetically useful recycli2ations have been reviewed (17). 

The most suitable oxidizing agent is potassium ferricyanide, but ferric chloride, hydrogen peroxide ia the presence of ferrous salts, ammonium persulfate, lead dioxide, lead tetraacetate or chromate, or silver and cupric salts may be useful. Water mixed, eg, with methanol, dimethylformamide, or glycol ethers, is employed as reaction medium. 

A weighed amount of sample is dissolved in a mixture of propanone and ethanoic acid and titrated potentiometrically with standard lead nitrate solution, using glass and platinum electrodes in combination with a ferro-ferricyanide redox indicator system consisting of 1 mg lead ferrocyanide and 0.5 ml 10% potassium ferricyanide solution. The endpoint of the titration is located by graphical extrapolation of two branches of the titration plot. A standard solution of sodium sulfate is titrated in the same way and the sodium sulfate content is calculated from the amounts of titrant used for sample and standard. (d) Water. Two methods are currently available for the determination of water. 

A few data exist on the oxidation by ferricyanide. This is simple second-order (in oxidant and neutral hydrazine), and leads to quantitative production of nitrogen in accordance with scheme (71)-(74) with A 4 k and A i. No scrambling occurs during oxidation of N-labelled N2H4 indicating that all N2 is formed via di-imine" Di-imine so prepared is capable of hydrogenating added unsaturated compounds, for example, phenylpropiolic acid gives m-cinnamic acid" " . 

Ferricyanide oxidation of 1,5-disubstituted thiocarbazones (116) give the mesoionic tetrazolium salts (117) under mild conditions (Eq. 21).190 This is in contrast to the strongly alkaline oxidation of carbazides leading to mercapto formazans as shown in Eq. 8 (Section 7.3.1.4). The heterocyclic triazine (118), obtained by the action of a diazonium salt on 2-... 

The reaction may be characterized by slow surface kinetics, leading to shortening of the plateau. Compare, for example, ferricyanide reduction and copper deposition at a rotating disk (shown in Fig. 3a and b). 

Except for deposition of Prussian blue from the mixture of ferric and ferricya-nide ions, its electrosynthesis from the single ferricyanide solution is reported [13]. Ferricyanide ions are not extremely stable even in aqueous solution, which is noticed in the change of color after a few days of storage. Thus, the coordination sphere can be destroyed also in the course of electrochemical reactions. The mentioned processes may lead to formation of ferric-ferricyanide complex or free ferric ions. The reduction of the resulting mixture leads to the formation of Prussian blue. 

The dehydrogenation of dioximes symmetrically substituted (17, R=Ri, Scheme 6.4) with a variety of oxidants, including potassium ferricyanide, halogens, hypohalides, nitric acid, nitrogen dioxides, and lead tetracetate, is a common route to symmetrically substituted furoxans. 

Marchand and co-workers reported a synthetic route to TNAZ (18) involving a novel electrophilic addition of NO+ NO2 across the highly strained C(3)-N bond of 3-(bromomethyl)-l-azabicyclo[1.1.0]butane (21), the latter prepared as a nonisolatable intermediate from the reaction of the bromide salt of tris(bromomethyl)methylamine (20) with aqueous sodium hydroxide under reduced pressure. The product of this reaction, A-nitroso-3-bromomethyl-3-nitroazetidine (22), is formed in 10% yield but is also accompanied by A-nitroso-3-bromomethyl-3-hydroxyazetidine as a by-product. Isolation of (22) from this mixture, followed by treatment with a solution of nitric acid in trifluoroacetic anhydride, leads to nitrolysis of the ferf-butyl group and yields (23). Treatment of (23) with sodium bicarbonate and sodium iodide in DMSO leads to hydrolysis of the bromomethyl group and the formation of (24). The synthesis of TNAZ (18) is completed by deformylation of (24), followed by oxidative nitration, both processes achieved in one pot with an alkaline solution of sodium nitrite, potassium ferricyanide and sodium persulfate. This route to TNAZ gives a low overall yield and is not suitable for large scale manufacture. 

Nesvadba and Kuthan (80TL3727 83CCC511) observed another contraction of the pyridinium ring leading to 2-acylpyrroles 129 on treatment of pyridinium salts 128 with alkaline ferricyanide under vigorous conditions (82CCC1494). If an additional 3-alkyl substituent is present as in 130, two... 

H-NMR spectral studies. Moreover, the mechanism of ferricyanide oxidation of 166 has been established (78JOC1132). The rate-determining abstraction of hydride ion by ferricyanide leads to isoquinolone 169 and a species [HFe(CN)6] that rapidly reacts with a second ferricyanide ion to give two ferrocyanide ions. This mechanism is contrary to the results in the pyridine series (cf Section 1I,A,2 and II,A,3). 

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