Redox systems perchloric acid

Only the obvious studies of aqueous plutonium photochemistry have been completed, and the results are summarized below. The course of discussion will follow the particular photochemical reactions that have been observed, beginning with the higher oxidation states. This discussion will consider primarily those studies of aqueous plutonium In perchloric acid media but will include one reaction in nitric acid media. Aqueous systems other than perchlorate may affect particular plutonium states by redox reactions and complex formation and could obscure photochemical changes. Detailed experimental studies of plutonium photochemistry in other aqueous systems should also be conducted. 

Dining preparation of iron(II) perchlorate, a mixture of iron sulfate and perchloric acid was being strongly heated when a most violent explosion occurred. Heating should be gentle to avoid initiating this redox system. 

Hence, there are convincing reasons to expect strong chemical effects on the 5f2 system Pu(VI) known from PuOj2 and PuF6. Unfortunately, the electron transfer bands are lower (though broader) in the visible than the 5 f2 internal transitions. Two candidates for the lowest wave-number of such an electron transfer band in PuO 2 253 are situated at 17000 or 19200 cm"1. The spectroscopic difference that MOj does not seem to have electron transfer spectra in the visible is accompanied by a maximum chemical stability of NpOj. However, the rate of lsO exchange at 23 °C in 1M perchloric acid is 0.31 s"1 in NpOj (PuOj is much slower, UOj much more rapid) but below 6 10"7 s"1 in NpOj2231. Much of the reported chemistry of transuranium elements is influenced by redox reactions, due to products of the intense radioactivity. Thus, lg of the uranium... 

Redox processes involving 178 have also been studied.Anodic oxidation of thianthrene has been eifected in a wide variety of solvents. Use of trifluoracetic acid gives stable solutions of 178 and, if perchloric acid is included, the solid perchlorate salt may be isolated on evaporation of the solvent after electrolysis. Dichloromethane at low temperatures has been used and, at the opposite extreme, fused aluminum chloride-sodium chloride mixtures. " Propylene carbonate permits the ready formation of 178, whereas the inclusion of water in solvent mixtures gives an electrochemical means of sulfoxidizing thianthrene. Reversible oxidation of 178 to thianthrenium dication may be brought about in customary solvents such as nitriles, nitro compounds, and dichloromethane if the solvent is treated with neutral alumina immediately before voltammetry addition of trifluoracetic anhydride to trifluoracetic acid equally ensures a water-free medium. The availability of anhydrous solvent systems which permit the reversible oxidation and reduction of 178 has enabled the determination of the equilibrium constants for the disproportionation of the radical and for its equilibria with other aromatic materials. ... 

The redox system Ce 7Ce is diluted in perchloric acid. Excercise 9.6... 

From quantum yield measurements it has been shown that the photoactive species in these reactions are Ce dimers, and that the reduced Ce " ion deactivates the reactive states of these dimers. It is possible that these dimers act as two-electron acceptors in the redox reaction. The reduced Ce " ion undergoes a photoreaction in aqueous perchloric acid that results in the formation of hydrogen. It is plausible therefore to use aqueous cerium ion solutions for the photosplitting of water into hydrogen and oxygen. Since such a system requires both the Ce and Ce ions to be involved in the photoredox process, it is necessary that the experimental conditions can be controlled to independently effect each reaction. 

Although the redox potentials favour electron transfer between cerium(iv) and thallium(i), the reaction is very slow. Catalysis by osmium(vm) has, however, been observed in both sulphate and perchloric acid media. In the latter system, although perchlorate complexing is not completely ruled out, the reactive species is considered to be the hydrolysed cerium(iv) ion, the mechanism... 

Barek J, Berka A, Pokorna A (1979) Oxidation of organic substances with manganese(lll). Compounds XII. Oxidation of citric acid hexaaquamanganese(II) ion in a noncomplex perchloric acid medium. Coll Czechoslov Chem Comm 44 2603-2611 Prasad G (1965) A kinetic study of redox system containing citric acid and manganic acetate. Bull Chem Soc Jpn 38 882-883... 

Insoluble 3-methylPT with incorporated copper(II)salt arising from CuCl2 used during chemical polymerization as co-promoter pressed as pellets has been used as both anode and cathode of a very stable battery cell with 0.1M aqueous sodium perchlorate solution with perchloric acid as supporting electrolyte at pH 1.5. The charge-discharge process has an efficiency of 0.31, but it is unknown if the charge capacity is within the copper redox system or within the PT redox system [99]. 

The efficiency of the cyclohexanone/Mn redox system for the polymerization of acrylonitrile and methyl methacrylate in perchloric acid and sulfuric acid media was investigated [81]. It was found that the rate of polymerization was independent of the oxidant concentration and varied linearly with the monomer and reducing agent concentration. Complex formation and termination mechanism was found to be different in two acidic media. In perchloric media, the termination is effected by the oxidant, whereas in sulfuric acid, primary radicals terminate growing chains. 

Similar results were obtained by Hartley and Wilson [28] during investigation of the reduction of flavinomononucleotide (ester of phosphoric acid and riboflavin). In 0.1 N perchloric acid this compound gives a polarographic curve with a prewave. The electrocapillary curves of flavinomononucleotide show that both the oxidized and the reduced forms of the redox system are adsorbed under the conditions mentioned above. The surface concentration of the oxidized form varies between 0.6 and 1.53-10 mole/cm depending on the extrapolation method and the volume concentration. 

Farage and Janjic (1982-1 and 2) observed oscillations in the concentrations of bromide and redox potentials during the uncatalyzed oxidation of 1,4-cyclohexane-dione by bromate in sulfuric, nitric (1982-1), perchloric and orthophosphoric (1982-2) acid solutions. The system does not require a catalyst such as the redox couple Ce(IV)/Ce(III) or Mn(III)/Mn(II) of the B-Z reaction. Experimenting with this system Farage and Janjic (1982-3) observed that temperature, stirring and oxygen affect the frequency or amplitude of oscillations. 

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