Oxidation by cerium

To determine of Ce(IV) in acid soluble single crystals, a simple and sensitive method is proposed. The method is based on the reaction of tropeoline 00 oxidation by cerium(IV) in sulfuric acid solution with subsequent measurement of the light absorption decrease of the solution. The influence of the reagent concentration on the analysis precision is studied. The procedure for Ce(IV) determination in ammonium dihydrophosphate doped by cerium is elaborated. The minimal determined concentration of cerium equal to 0.04 p.g/ml is lower than that of analogous methods by a factor of several dozens. The relative standard deviation does not exceed 0.1. 

Goumont et al. exploited this kind of reactivity for the nucleophilic substitution of the hydrogen atom in position 5 by carbon nuclophiles <20030BC2192> (Scheme 18). These authors reported that 6,8-dinitrotetrazolo[l,5- ]pyr-idine 11 easily reacts with potassium nitropropenide to yield an adduct similar to those obtained with alcohols 12. This adduct when oxidized by cerium ammonium nitrate yields the nitroalkyl-substituted aromatic compound 64. 

Indirect determinations of the formal oxidation potential of Bk(IV)-Bk(III) couple in sulfuric and nitric acids have been made by tracer measurement. From the Bk(IV)/Bk(III) ratios and the corresponding Ce(IV)/Ce(III) ratios at equilibrium conditions one can calculate the oxidation potential of the Bk(IV)-Bk(III) couple. The Bk(IV)/Bk(III) ratio can be determined by extracting Bk(IV) by an appropriate organic solvent. The formal oxidation potentials of the Bk(IV)-Bk(III) couple in IN and 0.5N sulfuric acid were found to be 1.42 and 1.44 volts using trilaurylmethylammonium sulfate in carbon tetrachloride as a solvent. In 6N nitric acid the oxidation potential of the couple was found to be 1.56 volts by using 0.18M tributylphosphate. Whereas, in IN to 2N nitric acid berkelium was not oxidized by cerium(IV). 

Until very recently the evidence for the existence of the HO2 radical in a condensed phase was based lai gely on kinetic measurements. However, recently it has been reported that the NMR spectrum of the HO2 radical may be observed in ice irradiated at very low temperatures (8, 11) and at room temperature in an aqueous solution (iO), where hydrogen peroxide is being oxidized by cerium (IV). 

This reaction can also be applied to P-lactam synthesis as depicted below. Treatment of the p-K-allylcarbonyliron intermediate with benzylamine followed by oxidation by cerium(IV) yields the P-lactam framework in high yield (Scheme 10.7) [22]. 

Silva et al.[44] developed an indirect Fl-AAS method for the determination of nitrate and nitrite in meats and vegetables following liquid-liquid extraction. Nitrate forms an ion pair with bis(2,9- dimethyl-l,10-phenanthrolinato)copper(l) which is extracted into IBMK. Copper is then determined in the separated mganic phase. When the nitrite is oxidized by cerium(VI) into nitrate before the extractirm, total nitrate is determined. When nitrite is ccmverted to nitrogen with sulfamic acid, only the origina] nitrate is determined. 

On heating at 110°, the potassium octacyanomolyb-date(IV) 2-hydrate loses its water of hydration. The salt is extremely soluble in water, from which it may be crystallized in the form of yellow rhombic bipyramidal crystals, (a b c = 0.7028 1 0.3711). It is oxidized by cerium(IV) salt solution to the corresponding octacyanomolybdate(V), K3Mo(CN)g. Aqueous solutions are photosensitive and, on prolonged exposure to direct sunlight, turn red and then pale green with the evolution of hydrogen cyanide. 

Me, = H 71 %) and (208 R = H, R = Me 21.5 %) was obtained from the iron tricarbonyl complex of methylcyclo-octatetraene. Oxidation of these adducts with ceric (iv) ion gives dihydrotetracyanotriquinacenes in good yield. tcne reacts with the iron-tricarbonyl complex of unsubstituted cyclo-octatetraene to give the 1,3-adduct (208 R = R = H) which is oxidized by cerium (iv) to a dihydrotetracyano-triquinacene. ... 

An outer-sphere mechanism is suggested for the oxidation of acetylacetone giving acetic acid by Ce(C104)4 solution. The reaction is first order each in substrate and Ce(IV) and is not catalysed by H+. The oxidations of pentane-l,5-diol, octane-1,8-diol, and fra 5-cyclohexane-l,2-diol by cerium(IV) have been studied in perchloric acid solution intermediate and final products of oxidation were identified and plausible reaction mechanisms were proposed. A mechanism has been proposed for the ruthenium(Vni)-catalysed oxidation of methoxyethanol by Ce(C104)4 in HCIO4 medium, which is zero order in Ce(IV) and H+ and first order each in substrate and Ru(VIII). In oxidations by cerium(IV) perchlorate, fV,fV,-disubstituted anilines gave... 

Polycyclic ketones undergo Baeyer-VilUger oxidation with ammonium hexanitratocerate(IV) or cerium(IV) ammonium sulfate to afford lactones (Soucy et al., 1972 Mehta et al., 1976). The Baeyer-Villiger oxidation of adamantanone to the corresponding lactone is shown above in scheme 14. Camphorquinone is oxidized to a complex mixture of oxidation products (Danieli and Palmisano, 1976). Simple aliphatic ketones are not oxidized by cerium(IV) in the absence of a catalyst. In presence of ruthenium(III) chloride, cerium(IV) sulfate oxidizes 2-butanonone to acetic acid and formic acid, and 3-pentanone to a mixture of propionic acid, acetic acid and formic acid (Singh et al., 1980). 

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