Ferricyanide study

Fig. 3. Flash-induced absorption changes in the Photosystem I core protein. (A) Absorption transient in the native-Fx Photosystem I core protein. (B) Absorption transient in the apo-Fx Photosystem core protein prepared by oxidative denaturation with 3 M urea and 5 mM potassium ferricyanide. Studies at a faster digitizing rate showed that the P700 absorption transient had approximately the same magnitude with a half-time of 5 xs (not shown). (C) Absorption transient in the reconstituted-Fx Photosystem I core protein prepared by incubation of apo-Fx with inorganic iron and sulfide in the presence of 6-mercaptoethanol. All measurements were performed at 5 jxg Chl/ml in 50 mM Tris buffer, pH 8.3, containing 1.7 mM ascorbate and 0.033 mM DCPIP.

Marazano and co-workers have also applied the reactions of tryptamine with various Zincke salts, including 115 (Scheme 8.4.39), in the synthesis of pyridinium salts such as 116. This type of product is useful for further conversion to dihydropyridine or 2-pyridone derivatives. For example, in a different study, Zincke-derived chiral pyridinium salts could be oxidized site-selectively with potassium ferricyanide under basic conditions as a means of chiral 2-pyridone synthesis (117 —> 118, Scheme 8.4.40). 

Treverton, J. A. and Davies N. C. XPS Studies of a Ferricyanide Accelerated chromate Paint PretreatmenI Film on an Aluminium Surface , Surf. Interfacial Ana ., 3, 194-200 (1981)... 

Manganese(III)-promoted radical cyclization of arylthioformanilides and a-benzoylthio-formanilides is a recently described microwave-assisted example for the synthesis of 2-arylbenzothiazoles and 2-benzoylbenzothiazoles. In this study, manganese triacetate is introduced as a new reagent to replace potassium ferricyanide or bromide. The 2-substituted benzothiazoles are generated in 6 min at 110°C imder microwave irradiation (300 W) in a domestic oven with no real control of the temperature (reflux of acetic acid) (Scheme 15). Conventional heating (oil bath) of the reaction at 110 °C for 6 h gave similar yields [16]. 

The application of modified electrodes for the assay of antibodies in senun preparations using redox indicators encapsuled into antigene marked liposomes attached to an electrode surface was suggested First model studies towards this goal make use of ferricyanide ions entrapped in synthetic vesicles. 

An (emf) study of the ferricyanide oxidation of phloroglucinol revealed kine-... 

The theoretical approach by Samec based on the ion-free compact layer model established that the true apparent transfer coefficient is obtained after correction for concentration polarization effect [1] [see Eq. (14)]. Subsequent studies by Samec and coworkers on the ferricyanide-Fc system provided values of a smaller than the expected 0.5. Preliminary attempts to rationalize this behavior were based on defining effective interfacial charges and separation distance between reactants [79]. The inconclusive trends reported in these studies were ascribed to complications arising from ion pairing of the ferro/ferricyanide ions. Later analysis of the same system appeared to show that k i is... 

Skinner, W. A. Alaupovic, P. Oxidation products of vitamin E and its model, 6-hydroxy-2,2,5,7 8-pentamethyl-chroman. V. Studies of the products of alkaline ferricyanide oxidation. J. Org. Chem. 1963, 28, 2854—2858. 

For forced-convection studies, the cathodic reaction of copper deposition has been largely supplanted by the cathodic reduction of ferricyanide at a nickel or platinum surface. An alkaline-supported equimolar mixture of ferri- and ferrocyanide is normally used. If the anolyte and the catholyte in the electrochemical cell are not separated by a diaphragm, oxidation of ferrocyanide at the anode compensates for cathodic depletion of ferricyanide.3... 

Cryokinetic studies of the plastocyanin-ferricyanide redox reactions in 50 50 v/v MeOH + H2O, pH = 7.0, p = 0.1 M reveal an Eyring plot shown for the second-order rate constant k from 25 °C to -35°C. The reaction is irreversible over the whole temperature range and there is no evidence for a change in the Cu(I) active site. Recalling that these reactions may involve consecutive steps, explain the deviation from a linear Eyring plot. F. A. Armstrong, P. C. Driscoll, H. G. Ellul, S. E. Jackson and A. M. Lannon, J. Chem. Soc. Chem. Communs. 234 (1988). 

As described, other nucleophilic reactions in the anthraquinone series also involve the production of anion-radicals. These reactions are as follows Hydroxylation of 9,10-anthraquinone-2-sulfonic acid (Fomin and Gurdzhiyan 1978) hydroxylation, alkoxylation, and cyanation in the homoaromatic ring of 9,10-anthraquinone condensed with 2,1,5-oxadiazole ring at positions 1 and 2 (Gorelik and Puchkova 1969). These studies suggest that one-electron reduction of quinone proceeds in parallel to the main nucleophilic reaction. The concentration of anthraquinone-2-sulfonate anion-radicals, for example, becomes independent of the duration time of the reaction with an alkali hydroxide, and the total yield of the anion-radicals does not exceed 10%. Inhibitors (oxygen, potassium ferricyanide) prevent formation of anion-radicals, and the yield of 2-hydroxyanthraquinone even increases somewhat. In this case, the anion-radical pathway is not the main one. The same conclusion is made in the case of oxadiazoloanthraquinone. 

Theis,T.L. Iyer, R. Kaul, L.W. (1988) Kinetic studies of cadmium and ferricyanide adsorption on goethite. Envir. Sci. Technol. 22 1013-1021... 

Some experimentation afforded improvements to the process. For example, in the case of the AD reaction, both the osmium and chiral concentrations could be reduced to a level of 0.05 mol % and 0.25 mol %, respectively, or one-fourth the levels in the commercial AD-mix formulation, without compromising the yield and enantiomeric excess of the etude product. The volume of liquid was also reduced to one-fourth of the quantities reported (1.5 L of water and 1 L tert-butyl alcohol per mole of substrate versus 5 L of water d 5 L of tert-butyl alcohol per mole of substrate). Under these conditions the reaction mixture is a slurry, but the potassium ferricyanide dissolves as it reacts. Reducing the catalyst concentration had the effect of doubling the reaction time from 1 day to 2 days. Interestingly, a study on the use of reduced amounts of osmium in the AD reaction of 1-phenyl-1-cyclohexene concluded that reducing the quantity of osmium by half (to 0.1 mol %), doubled the reaction time without affecting the yield, but that further reductions h osmium content made the reaction too sluggish to be useful. ... 

The oxidation of l,r-dialkyl diquaternary salts of 4,4 -bipyridine has also been studied. With potassium ferricyanide they give bipyridinones of types 96 and 97. i3.96o gjjjjiiar results were obtained on air oxidation of paraquat at Pyrolysis of paraquat results in demethylation to 4,4 -... 

The oxidation of phenols forming aryloxyl radicals was first recognized by Pummerer and Frankfurter in 1914," who reacted 2,2 -dihydroxy-l,l -binaphthyl with ferricyanide, and isolated dimers and trimers of the radical 20 (equation 8), which was later observed by ESR." Many further examples were studied by Goldschmidt, Muller, and others," and an X-ray crystal structure confirmed dimer formation with C—O bonding at the 4-position for 3-bromo-2,4,6-triphenylphenoxyl. ... 

Abramovitch and Vinutha (71JCS(B)131) reported a semiquantitative study of substituent effects on the rates of ferricyanide oxidation of 3 (R = Me = H, Me, CN, C02Me). On the basis of product ratios 4/5 being the same for the oxidation of the 2- and 6-deuterio isomers of 3 (R = R = Me), they concluded that the formation of a complex 7 is the ratedetermining step compound. 7 then reacts with additional ferricyanide, oxidation taking place within a second complex 8 to give the pyridone (Scheme I). Meanwhile this hypothesis has been confirmed by Russian authors... 

In a study concerning the kinetics and mechanism of osmium tetroxide-catalyzed ferricyanide oxidation of pyridinium and quinolinium salts it was found that the rates of reaction are first order with respect to substrate, alkali, and catalyst, but zero order with respect to ferricyanide concentration (82IJC(A)517). 

Bunting and Kauffman (84CJC729) studied both the kinetics and mechanism of disproportionation and ferricyanide oxidation of 154 in aqueous base. Ferricyanide ion oxidation is kinetically first-order in each of ferricyanide ion... 

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). 

P700 can be created by light or chemical oxidation (ferricyanide) in PS I. To learn more about the electronic structure of this species different groups studied P 7o0 by EPR at different mw frequency to resolve the g tensor components.191 195 The results were compared with those obtained for monomeric Chi a +.195,196 it could be shown that the g-tensor could only be fully resolved at very high mw frequency (> 300 GHz)193 unless fully deuterated material was used.191 Another possibility is the investigation of P7J0 in PS I single crystals, which in addition yields information on the g-tensor principal axes in the molecular frame.192,197... 

Substrates in the second grouping may be subdivided into those (hydrogen peroxide, ferricyanide, and nitrobenzene) undergoing catalytic reduction only when added to the catalyst in less than stoichiometric quantities in the presence of additional alkali, and those (benzoquinone and benzaldehyde) undergoing catalytic reduction when added in excess quantities in the presence of alkali. Of all these substrates, only hydrogen peroxide has not been studied in the absence of added alkali. Ferricyanide, benzoquinone, and benzaldehyde could be reduced only when alkali was added. Nitrobenzene underwent partial reduction and anthraquinone was quantitatively reduced without requiring additional alkali. 

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