Showing papers on "Oxidation state published in 1981"

Intermediates of a polynuclear manganese center involved in photosynthetic oxidation of water

Abstract: Electron paramagnetic resonance of spinach chloroplasts given a series of laser flashes, n = 0, 1,..., 6, at room temperature and rapidly cooled to -140°C reveals a signal possessing at least 16 and possibly 21 or more hyperfine lines when observed below 35 K. The spectrum is consistent with a pair of antiferromagnetically coupled Mn ions, or possibly a tetramer of Mn ions, in which Mn(III) and Mn(IV) oxidation states are present. The intensity of this signal peaks on the first and fifth flashes, suggesting a cyclic change in oxidation state of period 4. The multiline signal produced on the first flash is not affected by the electron transport inhibitor 3-(3,4-dichlorophenyl)-1,1-dimethylurea but is abolished by agents that influence the state of bound manganese, such as incubation with alkaline Tris, or dithionite, and by extraction with cholate detergent in the presence of ammonium sulfate. These results indicate that the paramagnetic signal is monitoring oxidation state changes in the enzyme involved in oxidation of water.

State of manganese in the photosynthetic apparatus. 2. X-ray absorption edge studies on manganese in photosynthetic membrane

Abstract: X-ray absorption spectra at the Manganese K-edge are presented for spinach chloroplasts, and chloroplasts which have been Tris-treated and hence unable to evolve oxygen. A significant change in the electronic environment of manganese is observed and is attributed to the release of manganese from the thylakoid membranes with a concomitant change in oxidation state. A correlation of the K-edge energy, defined as the energy at the first inflection point, with coordination charge has been established for a number of manganese compounds of known structure and oxidation state. Comparison of the manganese K-edge energies of the chloroplast samples with the reference compounds places the average oxidation state of the chloroplasts between +2 and +3. Using the edge spectra for Tris-treated membranes which were osmotically shocked to remove the released manganese, difference edge spectra were synthesized to approximate the active pool of manganese. Coordination charge predictions for this fraction are consistent with an average resting oxidation state higher than +2. The shape at the edge is also indicative of heterogeneity of the manganese site, of low symmetry, or both.

Model compounds for microbial iron-transport compounds. Part 1. Solution chemistry and Mössbauer study of iron(II) and iron(III) complexes from phenolic and catecholic systems

Abstract: The iron complexes found in the systems FeCl3–phenol, FeCl3–catechol, FeCl3-2,3-dihydroxybenzaldehyde, FeCl3–2,3-dihydroxybenzoic acid, and FeCl3–salicylic acid have been investigated by pH and conductance titrations together with Mossbauer spectroscopy. On the basis of further studies using ascorbic acid and salicylaldehyde, a mechanism for the reduction of FeIII to FeII and the reverse oxidation via a phenolic or catecholic radical is discussed. The properties of enterobactin are explored in the light of the chemistry of the model systems. The Mossbauer spectra of frozen aqueous solutions of hydroxybenzene compounds containing iron cations show that those complexes that are green or blue at acid pH contain FeII, whereas those that are purple or red contain FeIII. It is proposed that these results make the colour of the complex a good indication of the oxidation state of the iron in phenolic and catecholic systems.

Optical and magnetic properties of first-row transition metal ions in lead-silicate glass

Abstract: First-row transition metal ions in lead-silicate glasses of composition: 37.9% mol PbO, 61.8% mol SiO2 have been studied with regard to the oxidation state and the coordination by means of optical and magnetic measurements. Optical spectra have been recorded at 300 and 77 K. All the observed bands are assigned as being due to d-d transitions in Td and/or Oh fields. Magnetic moments are of the order of the spin-only values. By ESR measurements we reveal and quantify titanium, vanadium and manganese oxidation states not detectable by the other techniques. It turns out that the various metal ions have the following oxidation states: Ti3+ and Ti4+, V4+ and V5+, Cr3+ and Cr6+, Mn2+ and Mn3+, Fe3+, Co2+, Ni2+, Cu2+. The coordination is 4-fold for Ti4+ and V5+ and 6-fold for Mn3+ and Cu2+. Moreover it has been found that Fe3+, Co2+ and Ni2+ are both 4-fold and 6-fold coordinated and that Cr3+ and Cr6+ oxidation states coexist in the same sample.

Oxidation state of arsenic in coal ash leachate

Abstract: D.; Prentice, B. A. Enuiron. Sci. Technol. 1979,13,455. ( 7 ) Fisher, G. L.; Prentice, B. A.; Silberman, D.; Ondov, J. M.; Ragaini, R. C.; Biermann, A. H.; McFarland, A. R.; Pawley, J. B. “SizeDependence of the Physical and Chemical Properties of Coal Fly Ash”. In Proceedings of the Division of Fuel Chemisty Symposium on Properties of Coal Ash, 2nd Joint Chemical Institute of CanadalAmerican Chemical Society Meeting, Montreal, Canada, May 1977 (reprints available from G. L. Fisher). (8) Silberman, D.; Fisher, G. L. Anal. Chim. Acta 1979,106,299. (9) McFarland, A. R.; Bertch, R. W.; Fisher, G. L.; Prentice, B. A. Enuiron. Sci. Technol. 1977,11,781. (10) Fisher, G. L.; Prentice, B. A.; Silberman, D.; Ondov, J. M.; Bierman, A. H.; Ragaini, R. C.; McFarland, A. R. Enuiron. Sci. Technol. 1978,12,447. (11) Hansen, L. D.; Fisher, G. L. Enuiron. Sci. Technol. 1978,14, 1111. (12) Hulett, L. D.; Weinberger, A. J.; Ferguson, N. M.; Northcutt, K. J.; Lyon, W. S. “Chemical Speciation Studies of Fly Ash”; Final Report to the Electric Power Research Institute, July 1979, Part 1, Section 1.4.1. (13) Wilson, A. D. Analyst (London) 1960,85,823-7. (14) Weast, R. C., Ed. “Handbook of Chemistry and Physics”, 55th

Process for the removal of selenium from aqueous systems

Abstract: A process for reducing the concentration of selenium ions in the Se(VI) oxidation state in an aqueous solution. The aqueous solution is admixed with a quantity of metallic iron. The iron reduces the selenium ions from the Se(VI) oxidation state to a lower oxidation state and then dissolves in the aqueous solution. If the pH level of the aqueous solution is above about 2.3, the selenium ions are reduced to at least the Se(IV) oxidation state and the dissolved metallic iron hydrolyses to form an iron hydroxide that precipitates. The precipitated material is separated from the aqueous solution to provide a solution having a lower concentration of selenium ions. If the pH level of the aqueous solution is below about 2.3, no iron hydrolysis is observed to occur. At least a portion of the selenium in the Se(VI) oxidation state is believed to be reduced to the elemental state. The elemental selenium then is separated from the aqueous solution to provide a solution having a lower concentration of selenium ions.

Hydrogen peroxide oxidation by chlorine compounds. Reaction dynamics and singlet oxygen formation

Abstract: The kinetics of oxidation of hydrogen peroxide by several compounds (XC1) containing chlorine in its +1 formal oxidation state have been determined. The rate law in each instance is -d[XCl]/dt = k[XCl][HO,-]. Rate constants at 25.0 OC are k = 4.4 X lo7 M-l s-I for rert-butyl hypochlorite in 0.35 M tert-butyl alcohol (p = 0.02 M), k = 1.5 X lo6 M-l s-' for N-chlorosuccinimide (p = 0.10 M), and k < 1 M-' SKI for ethanolchloramine (p = 0.10 M). Formation of molecular oxygen in its ]A, electronic excited state was detected for hydroperoxide oxidation by tert-butyl hypochlorite and Nchlorosuccinimide. The results confirm a previously proposed mechanism which identifies hydroperoxide ion and hypochlorous acid as the reactants in the corresponding singlet oxygen generating reaction between these compounds. General mechanistic features, which should be widely applicable to reactions of this type, are discussed.

Electronic solution spectra for uranium and neptunium in oxidation states (iii) to (vi) in anhydrous hydrogen fluoride

Abstract: Spectra have been recorded for solutions in anhydrous hydrogen fluoride (AHF) of uranium and neptunium in oxidation states III to VI. The spectra for U(III), Np(III), and Np(IV) in AHF are very similar to those in acidified aqueous solution, but that for U(IV) suggests that the cationic species is UF/sub 2//sup 2 +/. The AHF spectra for the elements in oxidation states V and VI are not comparable with those of the formally analogous aqueous solutions, where the elements exist as well-defined dioxo cations. However, the AHF spectra can be related to spectra in the gas phase, in the solid state, or in nonaqueous solvents for each element in its appropriate oxidation state.

Process for preparing p-substituted benzaldehydes

Abstract: of EP00092391. A process for the preparation of a p-substituted benzaldehyde of the formula see diagramm : EP0009239,P6,F1 where R is methyl, methoxy or tertiary butyl, by vapor phase oxidation of an alkylbenzene of the formula see diagramm : EP0009239,P6,F2 where R' is alkyl, with oxygen or an oxygen-containing gas in the presence of a molybdenum-containing catalyst at temperatures of from 150 degrees to 600 degrees C, characterized in that a metal oxide catalyst is used which has a composition corresponding to the general formula Mo12 Mea-1 Meb-2 Mec-3 Mec-3 Med-4 Ox where Me**1 is one or more of the elements Bi, Co, Ni, Fe, W, Nb and Ta, Me**2 is one or more of the elements K, Rb, Cs, Tl, and In, Me**3 is one or more of the elements P, B, Sb, V, Sr and Cr, Me**4 is one or more of the elements Mn, Re, Pd, Ir, Rh, Cu, Sn, Zn, Sm, Mg, Ce, Ag, Li, As, Ba and Ca, a is a number from 0 to 24, but if W is present, is a number from 0.5 to 110, b is a number from 0.01 to 0.2, but if more than 0.5 atom of Bi, V or P is present, is a number from 0.01 to 6, c is a number from 0 to 6, but if a is 0, is a number from 0.5 to 5, d is a number from 0 to 10, and x is the number which results formally from the sum of metal atoms and phosphorus atoms present and their highest oxidation state.

Formation of chromium atoms in air-acetylene flames. Part I. Atom formation from pure chromium compounds

Abstract: A study has been made of the formation of chromium atoms from several chromium compounds in air-acetylene flames. The results indicate that the major cause of differences in the atom formation behaviour of the compounds investigated is the nature of the solid phase formed on desolvation and its subsequent thermal decomposition. Factors such as pH and oxidation state are not important per se but because they affect the nature of the solid phase formed on desolvation.

Low oxidation state, .sigma.-bonded organometallic derivatives of indium(I)

Abstract: : The organoindium compounds, NaIn(CH2SiMe3)2 and NaIn(CH2SiMe3)2. MeOC2H4OMe, whose formulas indicate indium in the +1 oxidation state, have been prepared and characterized by elemental analyses, cryoscopic molecular weight measurements in benzene solution and infrared and 1H NMR spectral data. The novel indium(I) compounds were prepared from In(CH2SiMe3)3 and NaH in the appropriate solvent by an apparent reductive elimination reaction. The nature of the specific indium(I) product was dependent on the reaction solvent. When either aromatic or hydrocarbon solvents were used, a hexameric species (NaIn(CH2SiMe3)2)6, was formed. The product from dimethoxyethane, (NaIn(CH2SiMe3)2 MeOC2H4OMe)x exhibited an association which was concentration dependent. Structures which involve indium-indium bonds are proposed to account for the observed molecular association as well as the chemical and spectral properties.

Notes. Open-shell molybdenum carbonyl complexes and the binding of π-acid ligands to higher-oxidation-state molybdenum sites

Abstract: Molybdenum sites which have a mixed-ligand tertiary phosphine and dithiocarbamate environment bind carbon monoxide at three oxidation levels, MoII and open-shell MoIII and MoIV. The complex [MoIII(CO)(S2CNEt2)2(Ph2PCH2CH2PPh2)]+ is stable in tetrahydrofuran at 0 °C and may be prepared by low-temperature controlled-potential electrolysis. The open-shell MoIII–CO and MoIV–CO complexes are new; their significance to the binding of π-acid ligands to higher-oxidation-state molybdenum sites in the nitrogenase system is briefly discussed.

ESCA study of Cu/SiO2 and Fe/SiO2 interfaces heated in high vacuum

Abstract: The reaction at the interfacial region of Cu/SiO2 and Fe/SiO2 heated in the high vacuum of an ESCA spectrometer has been studied. Copper spread slightly into SiO2 at 500–800°C in the metallic oxidation state. Cupric oxide formed on SiO2 changed to cuprous oxide or cuprous oxide plus copper metal and slightly diffused into the SiO2 by heating. Iron began to react with SiO2 at about 600°C and migrated into SiO2 in the ferrous oxidation state. This reaction was stimulated over 800°C and may be promoted by the presence of a small amount of oxygen on the iron surface.

Preparation of unsaturated acids and esters from saturated carboxylic acid derivatives and carbonyl compounds

Abstract: Promoted phosphate catalysts have been found to be effective for the vapour phase condensation of saturated monocarboxylic acids or esters with formaldehyde, to produce unsaturated carboxylic acids or esters. These catalysts have the empirical formula: wherein A is Fe, Ni, Co, Mn, Cu, Ag or mixtures thereof; a is 0.2-3.0; and x is determined by the nature and oxidation states of the other elements. The preferred catalysts have the empirical formula:- wherein A is Fe, Ni, Co, Mn, Cu, Ag or mixtures thereof; B is alkali metal, alkaline earth metal, TI or mixtures thereof; C is Se, Y, La, rare earth metal, Th, Nb, Mo, Te, Cr, Ta, U or mixtures thereof; and a = 0.2-3.0; b = 0-1.5; c = 0-2.0; and x is determined by the nature and oxidation state of the other elements.

Recovery of vanadium

Abstract: The present invention relates to recovering vanadium from solution and, especially, to the oxidation of vanadium to the pentavalent oxidation state (V) in aqueous acidic solution employing Caro's Acid, preferably in a high mole ratio of peroxomonosulphuric acid to hydrogen peroxide and, especially, of at least 8:1. By using preferred Caro's Acid solutions, the reaction does not exhibit an induction period, thereby enabling the reaction to be readily controlled by monitoring the electropotential of the treated-vanadium-solution and in response thereto regulating the introduction of the Caro's Acid solution. The vanadium oxidised to the pentavalent oxidation state (V) can readily be removed by contact with tertiary amines or ion exchange resins.

Synthetic method of alkane polyol

Abstract: PURPOSE: To obtain an alkane polyol, particularly ethylene glycol, etc in high yield even at a relatively low pressure, by reacting CO with H 2 in the presence of a catalytic system consisting of a ruthenium compound, an iron compound and an alkali metallic compound CONSTITUTION: CO is reacted with H 2 in the presence of a catalytic system consisting of a ruthenium compound, an iron compound and an alkali metallid compound, preferably in an organic solvent at 150W300°C and 300kg/cm 2 G for 01W 24hr to give an alkane polyol A ruthenium compound complexed with CO or complexed with CO and H 2 or one or more organic ligands is preferred as the ruthenium compound A negatively charged or zero-valent iron compound in the oxidation state is preferred as the iron compound An alkali metallic iodide is preferred as the alkali metallic compound COPYRIGHT: (C)1982,JPO&Japio

Synthesis and X-ray structural characterization of [Mo2O(S2CNEt2)6]BF4,a µ-oxo-bridged mixed oxidation state complex of molybdenum

Abstract: The reaction of [MoO(S2CNEt2)3]BF4 and PPh3 in methanol under anaerobic conditions results in the formation of [Mo2O(S2CNEt2)6]BF4, an X-ray crystal structur of which shows a new type of µ-oxo-bridging between two molybdenum atoms each having a formal oxidation state of 4·5.

Xps and xrd study of thermal oxidation and decomposition of poly (vinylferrocene)

Abstract: The thermal oxidation process of PVFc was investigated in detail by means of XPS in combination with XRD and XFS. The study of XPS indicated obvious increase in the oxidation state of iron after the thermal oxidation and the intensity change of the Fe 2p_(3/2) spectra showed that some intermediate stages occurred during the oxidation of film surface. XFS analysis demonstrated that the content of iron remained unchanged which proved that the above mentioned change occurred only on a very thin surface layer. It was shown from the XPS investigation that the obvious oxidation of iron began at 170～180℃ and the XRD result showed that the early stage of oxidation did not produce crystalline α-Fe_2O_3 until the oxidation temperature had reached about 380℃.

Continuous Determination of the Oxidation State in a Soda‐Lime‐Silica Glassmelt During Refining

Abstract: Influences on the oxidation state of glassmelts can be studied by using an electrochemical oxygen sensor which allows in-situ measurements at melting temperatures. The action of fining agents such as arsenic and sodium sulfate was investigated. The behavior of arsenic (i.e. release and uptake of oxygen) and the decomposition of sodium sulfate with and without carbon additions can be seen electrochemically.

Electron paramagnetic resonance spectra of erbium(III), dysprosium(III), and gadolinium(III) in yttrium and lanthanum hydrides

Abstract: The present research was undertaken to confirm the oxidation state of the metal and the hydridic nature of the hydrogen in metal hydrides by obtaining electron paramagnetic resonance (EPR) parameters sensitive to the oxidation state of the metal and to the sign of the charge on the hydrogen for representative lanthanides (Er, Dy, and Gd) diluted in the nonmagnetic host materials YHx and LaHx. In addition, for hydride compositions near x = 2.0, the environment of the dopant metal ion should be cubic for the majority of the ions present, thus providing a convenient situation for determining the oxidation state and electronic ground state of the ion in question so as to distinguish between protonic and hydridic crystalline electric fields.

Preparation of the solvated iron(ii) cation in acetonitrile using high oxidation-state fluorides and its reaction with trimethyl phosphite

Abstract: The cation [Fe(NCMe)6]2+ is formed from reactions in acetonitrile of iron metal with WF6, MoF6, PF5, or the NO+ cation and from the reaction of iron(II) fluoride with PF5. Oxidation to FeIII is not observed using binary fluorides or NO+, but [Fe(NCMe)6]2+ is oxidised by chlorine in MeCN to give the tetrachloroferrate(III) anion. The MeCN co-ordinated to FeII is replaced by trimethyl phosphite giving [Fe(NCMe){P(OMe)3}5]2+ as the final product at room temperature. Some of the intermediate complexes in this reaction have been identified in solution by 31P{1H} n.m.r. spectroscopy.