Cerium IV oxide

Cerium(IV) oxidizes ferrous ion to ferric and the cerium ions are stable under the conditions of a molten silicate—glass bath. Furthermore, cerium itself has no absorption ia the visible region. Economical additions of cerium, as cerium concentrate, enable the efficient use of raw materials containing trace quantities of iron (26). 

Ceri-oxyd, n. ceric oxide, cerium(IV) oxide, -salz, rt. ceric salt, cerium(IV) salt. sulfat, n. ceric sulfate, cerium(IV) sulfate. 

Cerium(IV) oxide is used to coat interior surfaces of self-cleaning ovens, where it prevents the build-up of tar deposits. 

Central metal cation Monatomic metal cation to which all the ligands are bonded in a complex ion, 409 Cerium (IV) oxide, 147 Chadwick, James, 517 Chalcocite, 539... 

M sulphuric acid at 25 °C is 1.43 0.05 volts. It can be used only in acid solution, best in 0.5M or higher concentrations as the solution is neutralised, cerium(IV) hydroxide [hydrated cerium(IV) oxide] or basic salts precipitate. The solution has an intense yellow colour, and in hot solutions which are not too dilute the end point may be detected without an indicator this procedure, however, necessitates the application of a blank correction, and it is therefore preferable to add a suitable indicator. 

Determination of cerium as cerium(IV) iodate and subsequent ignition to cerium(IV) oxide Discussion. Cerium may be determined as cerium(IV) iodate, Ce(I03)4, which is ignited to and weighed as the oxide, Ce02. Thorium (also titanium and zirconium) must, however, be first removed (see Section 11.44) the method is then applicable in the presence of relatively large quantities of lanthanides. Titrimetric methods (see Section 10.104 to Section 10.109) are generally preferred. 

A detailed study of the dehydrogenation of 10.1 l-dihydro-5//-benz[6,/]azcpinc (47) over metal oxides at 550 C revealed that cobalt(II) oxide, iron(III) oxide and manganese(III) oxide are effective catalysts (yields 30-40%), but formation of 5//-dibenz[7),/]azepinc (48) is accompanied by ring contraction of the dihydro compound to 9-methylacridine and acridine in 3-20 % yield.111 In contrast, tin(IV) oxide, zinc(II) oxide. chromium(III) oxide, cerium(IV) oxide and magnesium oxide arc less-effective catalysts (7-14% yield) but provide pure 5H-dibenz[b,/]azepine. On the basis of these results, optimum conditions (83 88% selectivity 94-98 % yield) for the formation of the dibenzazepine are proposed which employ a K2CO,/ Mn203/Sn02/Mg0 catalyst (1 7 3 10) at 550 C. 

The cerium(IV) oxidation of Mn(II) has been briefly reported on by Aspray et The reaction was followed from the rate of appearance of Mn(III) at... 

Methods for determination of thiol drugs (i.e., captopril [21-25], penicillamine [26-28], hydrochlorothiazide [24, 25, 29, 30], and tiopronin [31, 32]) have been developed. These methods are based on CL from a cerium (IV) oxidation system sensitized by adequate fluorophores such as quinine and rhodamine B. By using HPLC-coupled CL-flow-injection analysis method, tiopronin and its metabolite 2-mercaptopropionic acid in human urine were sensitively determined with the detection limits of 0.8 and 1 pM, respectively [32],... 

Hohl, H., E. Werth, R. Giovanoli, and E. Posch (1985), Heterogeneous Nucleation. I. Nucleation of Calcium Fluoride on Cerium(IV) Oxide. Quoted in Schindler P.W. Grenzflachenchemie oxidi-scher Mineralien", Oster. Chem. Z. 86, 141-147. 

Chromium(III) catalyses the cerium(IV) oxidation of primary and secondary alcohols in a mixture of H2SO4 and HC104. Kinetic results have been interpreted in terms of the formation of chromium(IV) in a reversible equilibrium, which forms a complex with the alcohol. Internal oxidation-reduction occurs in a rate-determining step to give aldehyde or ketone and regenerate the catalyst in the +3 state. The oxidation of ethanol under similar conditions has also been studied. ... 

Cerium(IV) oxidations of organic substrates are often catalysed by transition metal ions. The oxidation of formaldehyde to formic acid by cerium(IV) has been shown to be catalysed by iridium(III). The observed kinetics can be explained in terms of an outer-sphere association of the oxidant, substrate, and catalyst in a pre-equilibrium, followed by electron transfer, to generate Ce "(S)Ir", where S is the hydrated form of formaldehyde H2C(OH)2- This is followed by electron transfer from S to Ir(IV) and loss of H+ to generate the H2C(0H)0 radical, which is then oxidized by Ce(IV) in a fast step to the products. Ir(III) catalyses the A -bromobenzamide oxidation of mandelic acid and A -bromosuccinimide oxidation of cycloheptanol in acidic solutions. ... 

Sarel and co-workers have examined some reactions of alkynylcyclopropanes with iron carbonyl compounds [1]. Treatment of cyclopropylacetylene (5) with iron pentacarbonyl under photolytic conditions gives, after cerium(IV) oxidation, isomeric quinones 6 and 7, derived from two molecules of 5 and two carbonyls with both cyclopropane rings intact [6]. Furthermore, the photoreaction of dicyclopropylacetylene (8) with iron carbonyl gives some ten different products depending on the reagents and the reaction conditions, and some of them have the cyclopentenone skeleton formed by the opening of cyclopropane ring coupled with carbonyl insertion [7] (Scheme 2). 

Cerium(IV) oxide may be obtained by heating cerium oxalate, carbonate or other salts at elevated temperatures ... 

Cerium(IV) sulfate is prepared by heating cerium(IV) oxide, Ce02 with con-... 

A diene system with unsymmetrical 1,4-disubstitution is converted to the iron carbonyl complex 1 which is resolved into its enantiomers. The aldehyde function is conformationally locked in the transoid position and is diastereofacially shielded from the bottom face. Nucleophiles attack from the top face with high selectivity. Alternatively, chain elongation leads to the triene 2 which is reacted with diazomethane. Cerium(IV) oxidation removes the metal and furnishes the substituted cyclopropane 3. 

Thus, for the conditions where second-order behavior is observed, the chemical circumstances indicate the cerium(IV) oxidation of each chromium complex will involve a rate-determining one-equivalent oxidation of the complex ion (or a species in rapid equilibrium with the complex ion) to an intermediate, followed by the rapid one-equivalent oxidation of the intermediate. Without reference to the role of water coordinated to the chromium, the most obvious mechanism in accord with these specifications is ... 

It is of interest to compare the influence of cerium(III) on the cerium(IV)-ar-Cr(OH2)2(0204)2" reaction with the similar retarding action by cerium(III) which Tong and King (43) found in their careful kinetic investigation of the cerium(IV) oxidation of Cr(OH2)6+3 in acidic-sulfate media. The observed rate law for the latter reaction may be written in the form... 

Continuous analysis of highly fluorinated materials can present problems, primarily caused by the corrosiveness of hydrogen fluoride which is liberated from all of them during combustion. Hydrogen fluoride will react with the permanently bound hydroxy groups on the surface of the cooler parts of combustion tube walls and catalysts. The effect can lead to erratic hydrogen values and so the installation of some type of oxide [magnesium oxide, alumina, or cerium (IV) oxide] trap in the combustion tube to prevent its escape is recommended. 11... 

The cerium(IV) oxidation of lactyllactic acid49 and of 4-oxopentanoic acid50 in aqueous nitric acid solutions shows first-order dependence of the reaction on both cerium(IV) and substrate. A 1 1 complex formation between manganese(III) and amine, which later decomposes in the rate-limiting step, best explains the kinetics of oxidation of aliphatic amines by cerium(IV) in nitric acid medium in the presence of manganese(II).51 The kinetics of oxidation of naphthalene, 2-methyhiaphthalene, and a-naphthol with cerium(IV) in perchloric acid solutions have been studied.52 Use of a 50-fold molar excess of cerium(IV) perchlorate results in complete oxidation of fluorophenols to CO2, HCO2H, and HF in 48 h at 50 °C.53... 

The cerium(IV) oxidation reaction of many organic acids provides a sensitive and selective method for HPLC analysis of these compounds [116,117]. The oxidation of specific classes of organic compounds with cerium(lV), and the effects on the reaction of temperature, acidity, anion and catalyst, have been studied extensively [118-120]. The reaction produces cerium(HI) which is fluorescent and can be measured spectrofluori-metrically. The method has been applied successfully to the post-column reaction and detection of nmole amounts of organic acids by HPLC. 

Fig.4.71. Separation of some chlorophenols by cerium(IV) oxidation and fluorimetric detection. Column Corasil-C, 0.61 m X 4.83 mm I.D. Gradient elution from water to 36% acetonitrile-64% water. Peaks 1 = phenol (18.4 ppb) 2 = o-chlorophenol (22.S ppb) 3 = p-chlorophenol (20.2 ppb) 4 2,4-dichlorophenol (52.2 ppb) 5 = 2,4,6-trichlorophenol (42.6 ppb) S = solvent.

The HPLC analysis of phenols and related pollutants of the environment may be made by use of the cerium(IV) oxidation technique mentioned earlier (Section 4.2.1.6.2) [195]. The limits of detection of many phenols are ca. 0.4 ppb (parts per 109) in environmental samples. The detector shows good linearity in the region 10-230 ppb of phenol. 

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