Potassium ferricyanide method

A new development is that electrochemical oxidation of ferrocyanide to ferricyanide can be coupled with AD to give a very efficient electrocatalytic process [37]. Under these conditions, the amount of potassium ferricyanide needed for the reaction becomes catalytic and Eqs. 6D.6 and 7 can be added following Eq. 6D.4. Summation of Eq. 6D.1-6D.4, 6D.6, and 6D.7 gives 6D.8, showing that only water in addition to electricity is needed for the conversion of olefins to asymmetric diols and that hydrogen gas, released at the cathode, is the only byproduct of this process. In practice, sodium ferrocyanide is used in the reaction and the amount of this reagent used in comparison with the potassium ferricyanide method mentioned above has been reduced from 3.0 equiv. to 0.15 equiv. (relative to an equivalent of olefin). 

Furoic acid has been made by oxidation of lactose followed by pyrolysis, by the oxidation of 2-acetylfuran, 2-methylfuran, or furfuryl alcohol using potassium ferricyanide in alkaline medium, and by other methods already listed. ... 

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. 

Procedure Cholinesterase activity in analyzed tissue or the matrix (biotest with immobilized AChE) is determined in the incubation media [consisting of substrate ATCh - 34 mmol maleate buffer 0.1 M, pH = 6.0- 6.5 ml sodium citrate 0.1 M - 0.5 ml CuS045H20 0.03M -1.0 ml distilled H20 (or inhibitor in variant with toxin analyzed) -1.0 ml potassium ferricyanide 0.005 M -1 ml.] Volume of incubation media in one test - 400 mcl. As a blank (control sample), a treatment of the exposure without the substrate is used. If inhibitory effects of allelochemical (or any toxin) are analyzed, before the substrate addition the sample was preliminary exposed to allelochemical inhibitor. Two methods for the AChE-biotests may be recommended (i) in microcells ( stationary conditions ) and (ii) in flowing columns-reactors ( dynamic conditions ). 

Water Direct distillation or distillation of solvent-cleaned sample at acidic pH, react with 4-amino antipyrine and potassium ferricyanide at pH 10 or extract colored complex in chloroform Spectrophotometric (ASTM Method D-1783) <5 pg/L (chloroform extract) <0.1 mg/L (direct) NG ASTM 1978... 

Benzofuroxans are far more stable than simple furoxans and are more favourable for practical applications. There are two standard methods for the synthesis of the benzofuroxan skeleton (1) treating an ortho-nitroarylamine with a mild oxidant like sodium hypochlorite and (2) either heating or irradiating an orf/to-nitroarylazide with UV light. Benzofuroxan itself has also been prepared by treating 1,2-benzoquinone dioxime with alkaline hypochlorite or alkaline potassium ferricyanide solution. ... 

The second method of making sulfamethizole consists of reacting 4-acetylaminobenzenesulfonyl chloride with thiosemicarbazone of acetaldehyde, and subsequent oxidative cyclization of the product (33.1.16) to the substituted 1,3,4-thiadiazole in the presence of potassium ferricyanide in base, along with the simultaneous removal of the protective acetyl group [16,17],... 

A new synthetic route to quinazolines from N-protected anilines 895 is available using hexamethylenetetramine (HMTA) in trifluoroacetic acid and potassium ferricyanide in aqueous ethanolic KOH. The method affords substituted quinazolines 897 with good selectivity <2006T12351>, and although only moderate yields were initially achieved, good yields have now been obtained under microwave-assisted conditions <2007TL3229>. The method has also been used to prepare benzoquinazolines <20060L255>. 

A much more useful method for the preparation of a variety of substituted thiophenes and benzo[6]thiophenes in good yield depends on the oxidative cyclization of 1,3-diene-1-thiols (3) to the substituted thiophenes (4). This reaction was first reported (13CB1903) for the oxidation of o-mercaptocinnamic acid (5) to form benzo[6]thiophene (8) in good yield, using an aqueous alkaline solution of potassium ferricyanide. The intermediacy of a sul-fenium ion (6) was suggested, in view of the quantitative loss of carbon dioxide in the final product. 

Some of the volumetric methods described above may also be adapted to the electrometric determination of arsenic. Such methods have been described for titration of arsenites with ceric sulphate,9 iodine in the presence of sodium bicarbonate,10 chloramine (p-toluene-sulphone chloramide),11 alkaline potassium ferricyanide solution,12 potassium bromate13 or potassium iodate14 in the presence of hydrochloric acid, silver nitrate15 (by applying a secondary titration with 01N alkali to maintain the desired low H+-ion concentration), and with... 

Potassium ferricyanide, 255 of silyl enol ethers and lithium enolates Iodosylbenzene, 151 Miscellaneous methods Palladium catalysts, 230 Tetrakis(trifluoroacetate)ruthenium,... 

A method is described for the determination of the preservatives SA and BA in foods (including yogurt, soft drinks, and fruit juices) based on HPLC on a hydrogen-sulfonated divinyl-benzene-styrene copolymer column, isocratic elution with 0.01 N sulfuric acid/acetonitrile (75 25) mobile phase and UV detection at 220 nm (for BA) and 258 nm (for SA). Soft drinks and fruit juices merely require dilution and filtration before injection yogurt samples require treatment with potassium ferricyanide (III) and ZnS04 before analysis. Recovery of SA from yogurt was 95-110% the detection limit was 0.01 mg/kg. The recovery of BA from soft drinks and fruit... 

Inclusion in the reaction of a cooxidant serves to return the osmium to the osmium tetroxide level of oxidation and allows for the use of osmium in catalytic amounts. Various cooxidants have been used for this purpose historically, the application of sodium or potassium chlorate in this regard was first reported by Hofmann [7]. Milas and co-workers [8,9] introduced the use of hydrogen peroxide in f-butyl alcohol as an alternative to the metal chlorates. Although catalytic cis dihydroxylation by using perchlorates or hydrogen peroxide usually gives good yields of diols, it is difficult to avoid overoxidation, which with some types of olefins becomes a serious limitation to the method. Superior cooxidants that minimize overoxidation are alkaline t-butylhydroperoxide, introduced by Sharpless and Akashi [10], and tertiary amine oxides such as A - rn e t h y I rn o r p h o I i n e - A - o x i d e (NMO), introduced by VanRheenen, Kelly, and Cha (the Upjohn process) [11], A new, important addition to this list of cooxidants is potassium ferricyanide, introduced by Minato, Yamamoto, and Tsuji in 1990 [12]. 

The total phenolic compounds in an aqueous sample can be determined by a colorimetric method using 4-aminoantipyrine. This reagent reacts with phenolic compounds at pH 8 in the presence of potassium ferricyanide to form a colored antipyrine dye, the absorbance of which is measured at 500 nm. The antipyrine dye may also be extracted from the aqueous solution by chloroform. The absorbance of the chloroform extract is measured at 460 nm. The sample may be distilled before analysis for the removal of interfering nonvolatile compounds. The above colorimetric method determines only ortho- and meta-substituted phenols and not all phenols. When the pH is properly adjusted, certain para-substituted phenols, which include methoxyl-, halogen-, carboxyl-, and sulfonic acid substituents, may be analyzed too. 

Another method reported by Souza (3 ) for the determination of several phenols including salicylamide and aminopyrazoles in pharmaceutical products, where a solution of 2% potassium ferricyanide gives a colored indo-phenol derivative which is measured at 500 nm. 

Since L-sorbose is a reducing sugar a number of methods for its determination, based on this property, have been reported. Titration with the ceric sulfate, potassium ferricyanide reagent showed a fructose to sorbose ratio of 1.1,86 Cupric citrate87 as well as cupric tartrate87 reagents appear to be equally useful. 

Mahrous et al. [27] described the colorimetric determination of mefenamic acid with potassium ferricyanide in NaOH medium. The orange product is measured at 464 nm, and the molar absorptivity is 1.9 x 103 L/mol cm. The method was applied successfully to the determination of mefenamic acid in capsules. Garcia et al. [28] reported a flow injection spectrophotometric method for the determination of mefenamic acid in bulk samples and pharmaceuticals, also based on the reaction of mefenamic acid with potassium ferricyanide in NaOH media. The absorbance of the product obtained was measured at 465 nm, and the corresponding calibration graph was linear over the range of 1.00-100 mg/L, with a limit of detection of 0.18 mg/L. 

A simple photometric method in the visible region was described by Babu et al. [33] for the determination of mefenamic acid in its pharmaceutical dosage forms. The method is based on the reaction of the drug with 4-aminophenazone and potassium ferricyanide to yield a reddish-green colored chromophore, which exhibits an absorption maximum at 590 nm. The chromophore is stable for 40 min, and Beer s law is obeyed over the concentration range of 0.5-4 pg/mL. 

The usual method of synthesis of this system is by condensation of a diketone with 3,4-diamino-oxadiazoles (151). The alternative use of butyllithium followed by a bis-chlorooxime leads to the formation of the derivative (152) <91JHC1677> which can be cyclized to a bis(oxadiazolo)pyrazine (Equation (20)). Tetrahydro derivatives are formed from the bis-oximes (153) which give either the furoxan derivatives (155) (70-98%) by oxidation with potassium ferricyanide or the oxadiazoles (154) (55-70%) on heating (Scheme 14) <85JOC5l23>. 

As a consequence of the development of the N-methylmorpholine N-oxide (NMO) and later the potassium ferricyanide cooxidant systems the amounts of osmium tetroxide and chiral ligand used in the reaction could be considerably reduced. However, the method remains problematic for large-scale applications. The cooxidants for Os(VI) are expensive and large amounts of waste are produced (Table 5). Lately, several groups have addressed this problem and new reoxidation processes for osmium(VI) species have been developed. 

Azine approach. Oxidative cyclization of iV-thioacetyl derivatives of anilines is a common method for the preparation of benzothiazoles. The reaction may also be applied to the azine analogues, but may proceed less readily because of the decreased nucleophilidty of the ring. In the cyclization of the pyridazine (439) the oxidizing agent is alkaline potassium ferricyanide (75JHC337). 

Benzofurazan oxide has been prepared by a thermal decomposition of o-nitrophenylazide 4-8 by oxidation of the dioxime of o-benzoquinone by dilute nitric acid or potassium ferricyanide in alkaline solution 4 and by oxidation of o-nitroaniline with sodium hypochlorite.9 The present synthesis is a modification of the methods of Noelting and Kohn 8 and of Zincke and Schwarz.4... 

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