Cerium Oxidation Research Articles

Microbially mediated cerium oxidation in sea water

REDOX processes influence the geochemistry of many elements in the ocean, but attributing the distribution of these elements in the water column and sediments to specific redox processes is difficult because they are also influenced by non-redox processes and by other inputs that are poorly constrained. Cerium provides an opportunity to study redox processes in the ocean1–5 because its redox chemistry leads to its enrichment or depletion ('cerium anomalies') with respect to its lanthanide neighbours. A detailed understanding of Ce geochemistry is lacking, however, because of the paucity of knowledge of the redox rates and mechanisms in natural waters. Here I report measurements of Ce(III) oxidation rates using radiotracers in seawater samples collected in the Sargasso Sea and in Vineyard Sound, Massachussetts, which are much faster than previous, indirect estimates1. The data indicate that the negative Ce anomaly in sea water is the result of microbial oxidation followed by preferential scavenging of Ce(IV); no abiotic oxidation was detectable. This suggests that inhibition by sunlight of microbial oxidation and scavenging of Ce and Mn contribute to the pronounced surface maxima observed for these elements.

Oxidation of Cerium(III) in Aqueous Carbonate Solutions

Abstract The stoichiometric composition of Cerium(III) and Cerium(IV) carbonato complexes in concentrated aqueous Na2CO3 solutions has been investigated by emf measurements based on a junctionless cell. It is found that in the range of carbonate concentration between 2.084 m and 4.00 m, the prevailing species are the tetracarbonato cerium(III) and the esacarbonato cerium(IV) complexes. There is evidence that the large negative charge on the complexes is partially neutralized by Na+ ions. The above results rest upon an account of activity coefficients (which unavoidably vary by changing carbonate concentration) |based on the Specific Interaction Theory.

The photo-oxidation of meso-tetraphenylporphyrins

The photo-oxidation of meso-tetraphenylporphyrin (TPP) dianion in methanol affords a purple benzoyl bilinone (5b) by addition of singlet oxygen, followed by ring-opening and addition of methanol; similar products (5a) and (5c) can be formed by addition of water, or ethanol, respectively. The water adduct (5a) had previously been obtained by other workers from the photo-oxidation of metallo derivatives of TPP, by cerium(IV) or thallium(III) oxidation of TPP, or by treatment of the cation radical of TPP with nitrite, but a different structure had been assigned. Our new structure(5) has been deduced from detailed NMR and mass spectral studies including decoupling and NOE measurements, as well as field desorption mass spectra at low wire currents; the presence of quaternary meso-carbon atoms in structures (5a) and (5b) has been shown by the 13C NMR spectra of the meso13C -labelled pigments. Confirmation of these assignments has been provided by photo-oxidation of the meso-tetra(4-methoxyphenyl)porphyrin and further spectral studies of the resulting bilinones (7a) and (7b), including NOE and 13C -1H shift correlated NMR spectra.

Kinetics and mechanism of the cerium(IV) oxidation of methylmalonic acid in sulfuric acid

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTKinetics and mechanism of the cerium(IV) oxidation of methylmalonic acid in sulfuric acidPeter Ruoff and Gunn NevdalCite this: J. Phys. Chem. 1989, 93, 23, 7802–7806Publication Date (Print):November 1, 1989Publication History Published online1 May 2002Published inissue 1 November 1989https://doi.org/10.1021/j100360a016RIGHTS & PERMISSIONSArticle Views117Altmetric-Citations15LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (562 KB) Supporting Info (1)»Supporting Information Supporting Information Get e-Alerts

Redox properties of cerium‐exchanged Y‐zeolites

AbstractThe oxidation of cerium(III)‐exchanged zeolite NaY (exchange level 24‐91%) with aqueous hydrogen peroxide and oxygen has been studied. The fraction of Ce(IV) produced decreases with increasing Ce content of the zeolites. Hydrogen peroxide is catalytically decomposed by the Ce(III)/Ce(IV) redox couple with formation of an equilibrium level of a Ce(IV) hydroxide species. Oxidation with oxygen at temperatures higher than 400 K yields an oxycerium(IV) complex. The latter NaCe(IV)Y zeolite effects oxidative glycol cleavage of 2,3‐dimethyl‐2,3‐butanediol to acetone. Activation in oxygen restored its oxidizing capacity. Thus, the oxygen‐activated NaCe(IV)Y zeolite is a regenerable glycol‐cleaving oxidant. The H2O2‐oxidized NaCe(IV)Y is not active in glycol‐cleavage oxidiation.

The Lead Dioxide Anode. I. A Kinetic Study of the Electrolytic Oxidation of Cerium(III) and Manganese(II) in Sulfuric Acid at the Lead Dioxide Electrode

The electrolytic oxidation reactions of cerium(III) and manganeseII) in sulfuric acid have been used as probes to investigate the mechanism of the lead dioxide anode. The kinetics observed for such reactions at the lead dioxide surface provide no direct support for the proposal that the lead dioxide anode functions by a sequential 'two-step' mechanism (heterogeneous chemical oxidation of solution species followed by electrochemical oxidation of the reduced lead dioxide surface); rather the kinetics show characteristics similar to those observed previously for the oxidation of cerium(III) and manganese(II) at the platinum electrode, suggesting that the lead dioxide surface functions as a simple, 'inert' electron-transfer agent.

Regioselective introduction of a methoxy group at the benzylic position of isochromane derivatives by cerium(IV) oxidation in methanol.

The oxidation of methoxy-isochromans and -isochromanones with ceric ammonium nitrate in methanol introduced a new methoxy group regioselectively at a benzylic position para to the methoxy function on the aromatic nucleus.

The Lead Dioxide Anode. II. The Kinetics and Participation of the Lead Dioxide Electrode in Electrochemical Oxidation Reactions in Sulfuric Acid

Lead dioxide is a strong oxidizer in sulfuric acid, consequently electrochemical oxidation of solution species at a lead dioxide anode may occur by a two-step, C-E process (chemical oxidation of solution species by PbO2 followed by electrochemical regeneration of the reduced lead dioxide surface). The maximum rate of each step has been determined in sulfuric acid for specified lead dioxide surfaces and compared with the rates observed for the electrochemical oxidation of cerium(III) and manganese(II) on the same electrode surfaces. While the rate of electrochemical oxidation of a partially reduced PbO2 surface may be sufficient to support the observed rates of CeIII and MnII oxidation at the lead dioxide anode, the rate of chemical reaction between PbO2 and the reducing species is not. Hence it is concluded that the lead dioxide electrode functions as a simple, 'inert' electron-transfer agent during the electrochemical oxidation of CellI and MnII in sulfuric acid. In general, it will most probably be the rate of the chemical step which determines the feasibility or otherwise of the C-E mechanism.

A Comparative Kinetic Study of lridium(III) Catalysis in H2SO4 and HClO4 Media in the Cerium(IV) Oxidation of Diacetone Alcohol

A Comparative Kinetic Study of lridium(III) Catalysis in H2SO4 and HClO4 Media in the Cerium(IV) Oxidation of Diacetone Alcohol

Kinetics of cerium(IV) oxidation of macrocyclic complexes of chromium(III) and fate of chromium(IV) intermediates

AbstractKinetics and mechanism of the cerium(IV) oxidation of Cr(III) complexes of a series of macrocyclic (or pseudomacrocyclic) ligands with [14]‐membered intraligand ring‐sizes have now been investigated at I = 1.0 M (LiClO4) Temp. 30°C. The complexes of the formulation Cr(macrocycle)(X)(H2O) where X = CHCl2 and H2O, n = 0 or 1 undergo oxidation to Cr(VI) with the formation of chromium(IV) intermediates. The observed kinetic parameters for the Ce(IV) oxidation of Cr(III) macrocyclic complexes have been discussed in terms of changes brought about by the macrocyclic ligands on the Cr(III)—Cr(IV) redox potentials and in specific rates for Cr(IV)—Cr(V) conversion. On the basis of this study, it has been suggested that the trapping of Cr(IV) is easier when a macrocyclic ligand having a symmetrical intra‐ligand ring size and unsaturation in the cyclic structure is coordinated equatorially. Cyclic voltammetric studies indicate the formation of Cr(IV) transient in the case of electrochemical oxidation of trans‐Cr(Me4[14]tetraene)(H2O).

Chromium(III)-catalysed cerium(IV) oxidation of arsenic(III) in aqueous sulphuric acid

The chromium(III)-catalysed cerium(IV) oxidation of arsenic(III) studied in aqueous sulphuric acid follows the rate law (i) where the right-hand side represents the catalysed path. In equation (i), the –d[CeIV]//dt–ku[AsIII][CeIV]=2kakcβ4KIP[CeIV][CrIII][AsIII][SO42–]3[HSO4–]2[H+]2//(1 +β1[SO42–]+β2[SO42–]2+β3[SO42)]2[HSO4–]+β4[SO42–]2[(HSO4–]2[H+])(1 +KIP[SO42–])×{kbK5[CeIII][SO42–]3//(1 +K5[SO42–]3)+kc[AsIII][H+]}–1(i)β's are the stability constants of the different cerium(IV) sulphate complexes and KIP and K5 are the equilibrium constants of the species Cr3+SO42– and Ce(SO4)33– respectively. A chromium(IV) species is involved in the catalysed path. Increasing sulphuric acid concentrations effect rate increases of both the uncatalysed and catalysed paths and the active oxidant is understood to be the species H3Ce(SO4)4–.

Preparation and characterization of stable ruthenium(IV)-oxo complexes that contain tertiary phosphine ligands

The chemistry of high-valent ruthenium-oxo complexes has received much attention recently due to the potential applications of these complexes as oxidation catalysts and as oxygen atom transfer agents. In contrast, tertiary phosphine ligands have been primarily utilized in the syntheses of low-valent organometallic complexes, including those that have been used as both homogeneous and heterogeneous catalysts. Through the combination of these two dissimilar types of chemistry, the authors wish to report the first successful syntheses and characterization of ruthenium(IV)-oxo complexes that contain tertiary phosphine ligands in a position cis to the oxo ligand. In the syntheses of these phosphine-ruthenium(IV)-oxo complexes, oxidation of the tertiary phosphine ligand by the ruthenium(IV)-oxo moiety is avoided by initial generation of the ruthenium(II)-aquo-phosphine species, followed by cerium(IV) oxidation to the phosphine-ruthenium(IV)-oxo species. In this manner, no free tertiary phosphine ligand is exposed to a ruthenium(IV)-oxo complex, which would result in rapid phosphine oxidation. In addition, the coordinated phosphine ligands do not undergo any intramolecular or intermolecular oxidation upon formation of the ruthenium(IV)-oxo species. Notably, the reactivity of these complexes as oxidants toward organic substrates is substantially affected by simple variation of the substituents on the cis-phosphine ligand. 12 references, 1 figure.

Ruthenium tris chelates with O,S-siderophores: synthesis, oxidation state, and electronic structure

N-methylthiohydroxamic acids (RC(S)N(OH)Me), abbreviated HmeR (R = pH, p-C/sub 6/H/sub 4/OMe, CH/sub 2/Ph), react with RuCl/sub 3/ x 3H/sub 2/O in aqueous ethanol affording the green tris chelates Ru/sup III/(meR)/sub 3/. Cerium(IV) oxidation of these complexes in perchlorate media furnishes reddish pink Ru/sup IV/ (meR)/sub 3/ClO/sub 4/ x H/sub 2/O. The ruthenium(IV)-ruthenium(III) formal potential (E/sup 0//sub 298/) determined cyclic voltammetrically is approx. 0.4 V vs SCE. E/sub 298//sup 0/ of the ruthenium(III)-ruthenium(II) couple is approx. -1.0 V. Both redox couples are nearly reversible, suggesting the same gross stereochemistry for the three oxidation states. On the basis of comparative X-ray powder and IR data it is concluded that Ru(meR)/sub 3/ has facial stereochemistry. The Ru(meR)/sub 3/ complexes are low spin (S = 1/2; t/sub 2//sup 5/) and have rhombic EPR spectra. The EPR spectrum of Ru(ph)/sub 3//sup 3 -/ is rhombic but the three g values are closely spaced near 2 compatible with large net distortion. Two descriptions, viz. the ruthenium(IV)-stabilized ligand radical complex Ru/sup IV/(ph)/sub 2/(ph.)/sup -/ and the ruthenium(V) complex Ru/sup V/(ph)/sub 3//sup -/, are examined. The EPR spectrum is not incompatible with either description, but the Ru/sup v/(ph)/sub 3//sup -/ description has more favorable features. The thiohydroximate ligandmore » appears to be able to span all oxidation states of ruthenium from +2 to +5. 58 references, 4 figures, 5 tables.« less

Surface oxidation of cerium and lanthanum

Surface oxidation of cerium and lanthanum

Surface oxidation of cerium and lanthanum

The surface oxidation of Ce and La with oxygen and water vapour has been studied by electron energy loss spectroscopy (EELS), electron stimulated desorption (ESD) and work function measurements on polycrystalline film surfaces and on a Ce(001) single crystal surface. The changes in electronic structure during oxidation reaction have been successfully probed by ELS, and similar oxidation behaviour is deduced for Ce and La up to the sesquioxide stoichiometry. On Ce surfaces, a CeO 2-like oxide phase is detected under heavy oxidation conditions; this phase is characterised by a sharp loss feature due to valence band → 4 f excitations. With water vapour, only trivalent sesquioxide phases are observed, in which the terminal groups are surface hydroxyl species. ESD time-of-flight experiments from the hydroxylated Ce(001) surface reveal H + as the dominant ion; on the well-ordered surface the H + ion yield as a function of H 2O dose exhibits a maximum followed by a decrease, which is interpreted in terms of a cooperative effect within the surface OH layer.

Kinetics and Mechanism of Cerium(IV) Oxidation of Dextrose and Sorbose in Aqueous Sulphuric Acid Medium

Kinetics and Mechanism of Cerium(IV) Oxidation of Dextrose and Sorbose in Aqueous Sulphuric Acid Medium

Kinetics of the redox reactions between ceric sulfate and lactic and atrolactic acids in the medium HClO4‐Na2SO4‐NaClO4

AbstractThe kinetics of the oxidation of lactic and atrolactic acids by ceric sulfate have been studied in the medium HClO4‐Na2SO4‐NaClO4 at 25.0°C and ionic strength 2.0 mol dm−3 over a wide range of organic substrate (HL), hydrogen and bisulfate ion concentrations. The redox reactions proceed significantly through three simultaneous paths involving intermediate complexes between the reactive cerium(IV) species and the organic substrate according to the following expression where kobs indicates the observed pseudo‐first‐order rate constant, b and c are rate constants relative to that for the path associated with the term [H+] in the numerator, and A' is a quantity depending on the [H+] and [HSO] concentrations. Moreover, three equilibria involving cerium(IV) and HSO (or SO) ions are important from a kinetic point of view, the cumulative equilibrium constants being in the ratios β1: β2: β3 = d1: e1: f1. The present data are compared with those obtained previously for the cerium(IV) oxidation of glycolic acid and the substituent effects discussed.

Regio- and stereocontrolled functionalization of the seven-membered ring using organomanganese chemistry

Reaction of enolate nucleophiles with cycloheptatriene-Mn(CO) 3, hexafluorophosphate gives substituted cycloheptadienyl-Mn(CO) 3, complexes, which can be decomplexed with concomitant oxygenation of the cycloheptane ring either by direct cerium(IV) oxidation or by a novel cycloetherification procedure.

ChemInform Abstract: KINETICS AND MECHANISM OF THE CERIUM(IV) OXIDATION OF METHYLMALONIC ACID AND OF ETHYLMALONIC ACID IN ACID MEDIA

Chemischer InformationsdienstVolume 14, Issue 46 Preparative Organic Chemistry ChemInform Abstract: KINETICS AND MECHANISM OF THE CERIUM(IV) OXIDATION OF METHYLMALONIC ACID AND OF ETHYLMALONIC ACID IN ACID MEDIA F. TISCHLER, F. TISCHLERSearch for more papers by this authorJ. I. MORROW, J. I. MORROWSearch for more papers by this author F. TISCHLER, F. TISCHLERSearch for more papers by this authorJ. I. MORROW, J. I. MORROWSearch for more papers by this author First published: November 15, 1983 https://doi.org/10.1002/chin.198346115AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume14, Issue46November 15, 1983 RelatedInformation

ChemInform Abstract: COMPLEX RATE LAW FOR THE CERIUM(IV) OXIDATION OF GLYCOLIC ACID IN THE MEDIUM PERCHLORIC ACID‐SODIUM SULFATE‐SODIUM PERCHLORATE

Chemischer InformationsdienstVolume 14, Issue 37 Preparative Organic Chemistry ChemInform Abstract: COMPLEX RATE LAW FOR THE CERIUM(IV) OXIDATION OF GLYCOLIC ACID IN THE MEDIUM PERCHLORIC ACID-SODIUM SULFATE-SODIUM PERCHLORATE G. CALVARUSO, G. CALVARUSOSearch for more papers by this authorF. P. CAVASINO, F. P. CAVASINOSearch for more papers by this authorC. SBRIZIOLO, C. SBRIZIOLOSearch for more papers by this authorR. TRIOLO, R. TRIOLOSearch for more papers by this author G. CALVARUSO, G. CALVARUSOSearch for more papers by this authorF. P. CAVASINO, F. P. CAVASINOSearch for more papers by this authorC. SBRIZIOLO, C. SBRIZIOLOSearch for more papers by this authorR. TRIOLO, R. TRIOLOSearch for more papers by this author First published: September 13, 1983 https://doi.org/10.1002/chin.198337104AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume14, Issue37September 13, 1983 RelatedInformation