- Protein-Template-Driven Formation of Polynuclear Iron Species
-
Ferritins are iron-storage proteins capable of holding up to 4500 Fe 3+ ions within a single water-soluble protein shell made from 24 polypeptide chains. The Glu128Arg/Glu135Arg mutants of Escherichia coli and Rhodobacter capsulatus bacterioferritins are unable to associate into 24-meric structures, with dimers of polypeptide chains being their stable forms. The aerobic addition to these of up to 8-10 or 14-20 Fe2+ ions per dimer, respectively, results in the oxidation of the added Fe2+ to Fe 3+. Gel permeation chromatography and sedimentation equilibrium studies confirm that the Fe3+ ions are associated with the polypeptide dimer, and the lack of intense EPR signals from magnetically isolated Fe3+ ions confirms the formation of one or more antiferromagnetically coupled clusters of Fe3+ ions. The effect of Fe3+ chelators on iron-loaded subunit dimers is to remove the Fe 3+ from the protein, but to do so slowly, consistent with it not being merely adventitiously associated with protein. These data provide experimental support for the presence of nucleation centers for the mineral cores in bacterioferritins and indicate that these proteins are not simply acting as vessels in which hydrolysis of Fe3+ occurs independent from the protein surface. From analyses of X-ray structures and amino acid sequence comparisons, possible nucleation sites are identified.
- Malone, Simon A.,Lewin, Allison,Kilic, Mehmet A.,Svistunenko, Dimitri A.,Cooper, Chris E.,Wilson, Michael T.,Le Brun, Nick E.,Spiro, Stephen,Moore, Geoffrey R.
-
-
Read Online
- Characterisation of chemically lithiated heat-treated electrolytic manganese dioxide
-
Heat treated manganese dioxide is partially lithiated using butyl-lithium to determine the changes in crystal structure, chemical composition and morphology upon reduction, as a means of simulating its discharge behaviour in a non-aqueous battery cathode. As reduction proceeds, and lithium ions are inserted into the heat treated electrolytic manganese dioxide (EMD) structure, the material undergoes a phase transition to LiMn2O4. This new phase is further reduced to Li2Mn2O4. Reduction initially results in a 56% decrease in the surface area of the material; however, at higher degrees of reduction a slight increase in this value is observed, as a consequence of the strain placed on the lattice through continued lithium insertion.
- Dose, Wesley M.,Lehr, Joshua,Donne, Scott W.
-
-
Read Online
- Redox processes in water, initiated by electric discharge over its surface
-
The yields of oxidation and reduction in a flash corona discharge between a solid cathode and the water surface are compared. As the cathode was used a system of five aluminum electrodes. As the gas medium were tested air, oxygen, and nitrogen. The models of processes in the discharge suggest formation of atomic hydrogen in water vapor: H2O → H + OH. However, the reduction yield is equal to the Faraday value irrespective of the gas composition. In the presence of oxygen, oxidation prevails. The yield of Fe2+ oxidation in oxygen is about 190 reaction events per electron passed in the circuit; in air it is lower by a factor of 2, and in nitrogen the yield is equal to the Faraday value.
- Piskarev
-
-
Read Online
- On the highest oxidation states of plutonium in alkali solutions in the presence of ozone
-
During ozonation of Pu(VI) alkaline solutions, the highest oxidation state of Pu is formed in an oscillatory reaction. This plutonium species is reduced with Pu(VI) or Fe(III). Ferrate ion is also reduced with Pu(VI). It was assumed that in alkali solutio
- Nikonov,Gogolev,Tananaev,Myasoedov
-
-
Read Online
- Drosophila multicopper oxidase 3 is a potential ferroxidase involved in iron homeostasis
-
Multicopper oxidases (MCOs) are a specific group of enzymes that contain multiple copper centers through which different substrates are oxidized. Main members of MCO family include ferroxidases, ascorbate oxidases, and laccases. MCO type of ferroxidases is key to iron transport across the plasma membrane. In Drosophila, there are four potential multicopper oxidases, MCO1–4. No convincing evidence has been presented so far to indicate any of these, or even any insect multicopper oxidase, to be a ferroxidase. Here we show Drosophila MCO3 (dMCO3) is highly likely a bona fide ferroxidase. In vitro activity assay with insect-cell-expressed dMCO3 demonstrated it has potent ferroxidase activity. Meanwhile, the ascorbate oxidase and laccase activities of dMCO3 are much less significant. dMCO3 expression in vivo, albeit at low levels, appears mostly extracellular, reminiscent of mammalian ceruloplasmin in the serum. A null dMCO3 mutant, generated by CRISPR/Cas9 technology, showed disrupted iron homeostasis, evidenced by increased iron level and reduced metal importer Mvl expression. Notably, dMCO3-null flies phenotypically are largely normal at normal or iron stressed-conditions. We speculate the likely existence of a similar iron efflux apparatus as the mammalian ferroportin/ferroxidase in Drosophila. However, its importance to fly iron homeostasis is greatly minimized, which is instead dominated by another iron efflux avenue mediated by the ZIP13-ferritin axis along the ER/Golgi secretion pathway.
- Wang, Xudong,Yin, Sai,Yang, Zhihao,Zhou, Bing
-
-
Read Online
- Solvent extraction of some trace metals and iron with N-octyl-N,N- bis(dihexylphosphinylmethyl)amine
-
The processes were studied of the solvent extraction of the ions of triply-charged trace elements including scandium, indium, gallium, and yttrium, as well as iron, with N-octyl-N,N-bis(dihexylphosphinylmethyl)amine solution in toluene, chloroform or methylene chloride from hydrochloric, nitric or perchloric acids aqueous solutions. The metals extraction dependence on the acid concentration showed that the best results were reached using perchloric acid. The calculation of partition coefficients of metals allowed us to reveal a high selectivity of the scandium extraction. The prospects of using the investigated bisphosphinylamine in the technology of extraction, concentration and separation of the trace metals ions was concluded. Pleiades Publishing, Ltd., 2011.
- Cherkasov,Garifzyanov,Bazanova,Leont'eva
-
-
Read Online
- Kinetics and mechanism of oxidation of Fe2+ by the tris(biguanide)manganese(IV) ion in aqueous acid media
-
Tris(biguanide)manganese(IV), [Mn(LH2)3]4+ (LH2 = biguanide, C2N5H7), quantitatively oxidises Fe2+ to Fe3+ and is itself reduced to Mn2+ with almost quantitative (> 95%) release of biguanide, The reaction rate strongly depends on added Fe3+; in the presence of externally added Fe3+, the reaction shows a clear first-order dependence in [MnIV], whereas in the absence of any added Fe 3+, an initial quick loss of MnIV is associated with a subsequent very sluggish decay. Two consecutive one-electron transfer inner-sphere steps are proposed for the entire redox process where [Mn(LH 2)3]3+, the initial one-electron-reduced product of MnIV, is believed to be a steady-state intermediate. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004.
- Dhar, Basab Bijayi,Mukherjee, Ritam,Mukhopadhyay, Subrata,Banerjee, Rupendranath
-
-
Read Online
- The special features of the kinetics of oxidation of divalent iron during sulfuric acid leaching of pyrrhotine with the participation of nitrous acid
-
The kinetics of oxidation of divalent iron ions with molecular oxygen during pyrrhotine leaching in sulfuric acid solutions with the participation of nitrous acid as an activator was studied. The oxidation of Fe2+ to Fe3+ only occurr
- Markovich
-
-
Read Online
- Iron(II) sulfate oxidation with oxygen on a Pt/C catalyst: A kinetic study
-
The kinetics of iron(II) sulfate oxidation with molecular oxygen on the 2% Pt/Sibunit catalyst was studied by a volumetric method at atmospheric pressure, T = 303 K, pH 0.33-2.4, [FeSO4] = 0.06-0.48 mol/l, and [Fe 2(SO4)3] = 0-0.36 mol/l in the absence of diffusion limitations. Relationships were established between the reaction rate and the concentrations of Fe2+, Fe3+, H+, and Cl- ions in the reaction solution. The kinetic isotope effect caused by the replacement of H2O with D2O and of H+ with D+ was measured. The dependence of Fe2+ and Fe 3+ adsorption on the catalyst pretreatment conditions was studied. A reaction scheme is suggested, which includes oxygen adsorption, the formation of a Fe(II) complex with surface oxygen, and the one-electron reduction of oxygen. The last step can proceed via two pathways, namely, electron transfer with H+ addition and hydrogen atom transfer from the coordination sphere of the iron(II) aqua complex. A kinetic equation providing a satisfactory fit to experimental data is set up. Numerical values are determined for the rate constants of the individual steps of the scheme suggested.
- Okhlopkova,Kuznetsova
-
-
Read Online
- Modeling the anodic half-cell of a low-temperature coal fuel cell
-
(Graph Presented) Mined over matter: The partial oxidation of sub-bituminous coal by FeIII ions in 5 M H2SO4 at 100°C was used in the anodic compartment in a prototype coal fuel cell, with a solution of VO2+/VO2+ in 5 M H 2SO4 in the cathodic compartment (see scheme). The cell operated without loss of performance for 1000 h at 100°C, with a maximum current density of 5 A L-1 and a power density of 0.6 W L -1.
- Weibel, Douglas B.,Boulatov, Roman,Lee, Andrew,Ferrigno, Rosaria,Whitesides, George M.
-
-
Read Online
- Kinetics of Oxidation of Aquairon(2+) by Iodate in Dilute Perchloric Acid Solution
-
The kinetics of oxidation of aquairon(2+) by iodate in dilute perchloric acid have been studied at 35 degC in the presence of allyl alcohol, thus avoiding catalysis by the molecular iodine normally formed in this reaction.Overall, the reaction is 4Fe(2+)
- Higginson, William C. E.,McCarthy, Davina A.
-
-
Read Online
- Modeling the kinetics of Fe(II) oxidation in the presence of citrate and salicylate in aqueous solutions at pH 6.0-8.0 and 25°C
-
The kinetics of Fe(II) oxidation in the presence of low concentrations of citrate and salicylate have been investigated in aqueous solutions over the pH range 6.0-8.0 using colorimetry. A kinetic model has been developed to describe the oxidation of Fe(II) with specific attention given to the oxidation of inorganic Fe(II), formation and dissociation of Fe(II) complexes and the oxidation of these complexes. At low concentrations of salicylate, both experimental data and model show that the common approach to modeling Fe(II) oxidation that assumes pre-equilibrium between metal and ligand prior to their oxidation is not valid. Complexation of Fe(II) by salicylate is found to be relatively slow, and oxidation of the complex formed occurs rapidly. Citrate, on the other hand was found to be in rapid equilibrium with Fe(II) but the complex formed was oxidized slowly. Both citrate and salicylate complexes are found to dissociate at a rate much faster than previously thought. A model of the oxidation kinetics of Fe(II) species that incorporates the formation and dissociation kinetics of Fe(II) and Fe(III) complexes of citrate and salicylate as well as the reactions of these species with oxygen and reduced oxygen species including superoxide and hydrogen peroxide provides an excellent description of data obtained over a wide range of concentration and pH conditions.
- Pham, A. Ninh,Waite, T. David
-
-
Read Online
- Redox reactions of K3[Fe(CN)6] during mechanochemically stimulated phase transitions of AlOOH
-
Thermally induced redox reactions of K3[Fe(CN)6] (1) were investigated for a broad temperature range by thermal methods and structure analytical methods (ESR and M??bauer spectroscopy, X-ray Powder diffraction and XANES). Based on the influence of the mechanically activated and transforming matrices 2 and 3, redox processes can be tuned to form doped Al2O3 systems which contain either isolated Fe3 centres or redox active phases and precursors like (Al1-xFe x)2O3 (4), (Al3-xFe x)O4 (5), Fe3O4, Fe 2O3 and Fe0. The phase Fe3C and the chemically reactive C-species were detected during the reaction of 1. The final composition of the doped products of α-Al2O3 is mainly influenced by the chemical nature of the Fe doping component, the applied temperature and time regime, and the composition of the gas phase (N 2, N2/O2 or N2/H2). From the solid state chemistry point of view it is interesting that the transforming matrix (2 and 3) possesses both oxidative and protective properties and that the incorporation of the Fe species can be performed systematically.
- St??er, Reinhard,Feist, Michael,Patzwaldt, Kerstin,Menzel, Michael,Emmerling, Franziska
-
-
Read Online
- Sequential one-electron reduction of Fe(V) to Fe(III) by cyanide in alkaline medium
-
The reduction of Fe(V) by cyanide has been studied anaerobically in alkaline media (pH 10.55-12.10) by using a premix pulse radiolysis technique. The results demonstrated for the first time the spectroscopic evidence for sequential one-electron reductions of Fe(V) to Fe(IV) to Fe(III) in aqueous media. Rates for reductions decrease with an increase in pH and appeared to be related to deprotonation of Fe(V) and Fe(IV) species. The reactivity of the three ferrates (Fe(VI), Fe(V), and Fe(IV)) with cyanide showed that Fe(V) and Fe(IV) are approximately four- and two-orders of magnitude more reactive than Fe(VI), respectively. These rates suggest that Fe(VI) oxidations of compounds may be accelerated if reactions are performed in the presence of one-electron or two-electron reducing substrates.
- Sharma, Virender K.,O'Connor, Donald B.,Cabelli, Diane E.
-
-
Read Online
- Kinetics of stepwise hydrolysis of ferrioxamine B and of formation of diferrioxamine B in acid perchlorate solution
-
Kinetic and thermodynamic parameters for the hydrolysis of ferrioxamine B, Fe(HDFB)+ + 3H+ ? Fe3+ + H4DFB+, in 0.005-11.0 M acid at 25°C and ionic strength 2.0 M (NaClO4/HClO4) have been obtained by stopped-flow and rapid-scan spectral methods. Four stages can be separated. These consist of (a) Fe(HDFB)+ + H+ ? Fe(H2DFB)2+, (b) transformation of Fe(H2DFB)2+ to another form Fe(H2DFB)2+* without H+ change, (c) Fe(H2DFB)2+* + H+ ? Fe(H3DFB)3+, and (d) Fe(H3DFB)3+ + H+ ? Fe3+ + H4DFB+. The equilibrium constants for each stage were determined by rapid-scan spectral methods and the rate laws by stopped-flow methods. The kinetics of stage d were checked by examining the reverse direction. Agreement between equilibrium constants determined by spectral means and from the kinetics was fair to good. The results were compared with those of previous investigators. The kinetics of formation and decomposition of the binuclear complex Fe2(HDFB)4+ from Fe3+ and Fe(HDFB)+ were also determined at 25°C and ionic strength 2.0 M (NaClO4/HClO4). A relationship between the hydrolysis and the formation of the dimer was shown.
- Birus, Mladen,Bradic, Zdravko,Krznaric, Gordana,Kujundzic, Nikola,Pribanic, Marijan,Wilkins, Patricia C.,Wilkins, Ralph G.
-
-
Read Online
- Hydrogen ion dependence of the oxidation of iron(II) with peroxydisulfate in acid perchlorate solutions
-
The title reaction has been studied in the [H+] range of 0.01-1.0 M at different ionic strengths and temperatures. Unlike previous reports, the rate is dependent on the concentration of the hydrogen ions, if it is larger than 0.2 M. The rate laws are d[Fe(III)]/dt = 2k1[S2O82-][Fe(II)] for [H+] 1 + k2K[H+])[S2O82-][Fe(II)] for [H+] >0.4 M. In the [H+] range of 0.4-1.0 M and at I ≈ 1.0 M, k1 (M-1 s-1) and k2K (M-2 s-1) were found to be 25 ± 1.2 and 83 ± 8, 18 ± 1.2 and 63 ± 4, and 11.5 ± 0.6 and 55 ± 4 at 40, 35, and 30°C, respectively. A plot of log kobsd (second-order rate constant) vs. I1/2 for I a straight line with a slope of -3.83. The slope decreases numerically with the increase in the range of ionic strength investigated. The energy of activation (kcal mol-1) was found to be 14.7 ± 1 and 7.6 ± 2 for the k1 and k2 paths, respectively. The value for the k1 path is dependent on the ionic strength showing ion pairing.
- Gupta,Gupta
-
-
Read Online
- Kinetic Studies of the Electron Transfer Reaction in Iron(II) and Iron(III) Systems. X. The Electron Transfer Reaction between Iron(II) and Iron(III) in the Presence of Pyridine in Aqueous Solution
-
When pyridine is added to the reaction system of the electron transfer between Fe(II) and Fe(III) in aqueous solution at constant 0, the apparent rate constant k grows rapidly with 0 at 0 0, while k suddenly diminishes to a small and constant value at 0 > 0.The predominant paths of the reaction will be discussed.
- Wada, Goro,Kawauchi, Aiko
-
-
Read Online
- Reactivity of ferrate(V) (FeV O43 -) with aminopolycarboxylates in alkaline medium: A premix pulse radiolysis
-
A premix pulse radiolysis technique was used to study the reaction between Fe(V) and APCs. Fe(V) reactions with glycine, IDA, NTA, EDTA and DTPA were measured at pH 12.5. Spectral results showed that Fe(V) is reduced to Fe(III); therefore, the reaction of Fe(V) with APCs proceeds via a concerted two-electron oxidation, which converts Fe(V) to Fe(III). The rate law for the oxidation of these APCs by Fe(V) is first-order with respect to each reactant at this pH. Fe(V) reactivity with APCs at pH 12.5 was found to increase in the order of tertiary 2 M-1 s-1 to 1.4 × 104 M-1 s-1. Both EDTA and DTPA reacted faster than NTA with Fe(V) and Fe(VI). The order of reactivity of amines with Fe(V) suggests that FeO43 - attacks at the nitrogen atom sites of the APCs, which leads to large differences in the rate constants. In addition, Fe(V) is approximately three- to five-orders of magnitude more reactive than Fe(VI). The reaction of Fe(V) with EDTA was studied as a function of pH (9.0-12.5). The rate constants increased as the pH decreased. The speciation of EDTA and Fe(V) were used to fit the data.
- Noorhasan, Nadine N.,Sharma, Virender K.,Cabelli, Diane
-
-
Read Online
- Generation and reactivity of rhodium(IV) complexes in aqueous solutions
-
At pH = 1 and 25 °C, the Fenton-like reactions of Feaq2+ with hydroperoxorhodium complexes LRhIIIOOH2+ (L = (H2O)(NH3)4, k = 30 M-1 s-1, and L = L2 = (H2O)(meso-Me6-[14]aneN4), k = 31 M-1 s-1) generate short-lived, reactive intermediates, believed to be the rhodium(IV) species LRhIVO2+. In the rapid follow-up steps, these transients oxidize Feaq2+, and the overall reaction has the standard 2:1 [Feaq2+]/[LRhOOH2+] stoichiometry. Added substrates, such as alcohols, aldehydes, and (NH3)4(H2O)RhH2+, compete with Feaq2+ for LRhIVO2+, causing the stoichiometry to change to 3)4RhO2+ toward CH3OH (1), CD3OH (0.2), C2H5OH (2.7), 2-C3H7OH (3.4), 2-C3D7OH (1.0), CH2O (12.5), C2H5CHO (45), and (NH3)4RhH2+ (125). The kinetics and products suggest hydrogen atom abstraction for (NH3)4RhO2+/alcohol reactions. A short chain reaction observed with C2H5CHO is consistent with both hydrogen atom and hydride transfer. The rate constant for the reaction between TIaqIII and L2Rh2+ is 2.25 × 105 M-1 s-1.
- Pestovsky, Oleg,Bakac, Andreja
-
-
Read Online
- Generalized Two-Pseudophase Model for Ionic Reaction Rates and Equilibria in Micellar Systems. Hexachloroiridate(IV)-Iron(II) Electron-Transfer Kinetics in Cationic Micelles
-
A general phenomenological approach based on (i) the two-pseudophase approximation, (ii) a proper definition of the transfer constants between the pseudophases in term of molar fractions, (iii) an explicit hypothesis that relates the number of bound molecules or ions to the surfactant concentration, and (iv) a semiempirical calculation of the activity coefficients of bound charged species at the micellar surface permits prediction of the reactivity as a function of micelle and added salt concentrations.The application of this approach to limiting cases leads to the equations already known in the literature.Kinetic experiments were designed to test the model through simplification of the proper formulas.Good prediction of the observed rates for the reaction of hexachloroiridate(IV)-iron(II), in the presence of hexadecyltrimethylammonium (CTA) chloride and sulfate, is obtained, and the dissociation degree of the micelle is found comparable with literature values.
- Minero, Claudio,Pramauro, Edmondo,Pelizzetti, Ezio
-
-
Read Online
- OXIDATION EQUILIBRIUM OF IRON IN BOROSILICATE GLASS.
-
The purpose of this study is to characterize the dependence of the ferrous/ferric equilibrium on temperature, oxygen partial pressure, and glass composition for borosilicate glass used in the fiberglass industry. The stability of amber coloration, which a
- Goldman
-
-
Read Online
- The fenton reaction. Dependence of the rate on pH
-
The pH dependence of the evolution of O2 in the Fenton reaction has been studied by using an indirect method for measuring [O2]. The results confirmed observations of previous workers, namely, that the evolution of O2 diminished as the pH was lowered. A quantitative analysis of the dependence of [O2] and [Fe2+] during the reaction as a function of time showed that the pH dependence of the course of the reaction can be accounted for by assuming an acid base reaction of the active intermediate: FeO2+ + H+ ? = FeOH3+ FeOH3+ is the active entity in the reaction with Fe2+ to produce Fe3+ ions, while the other form FeO2+ is involved in reactions leading to O2 evolution.
- Kremer, Mordechai L.
-
-
Read Online
- Oxidation of phosphorus centers by ferrate(VI): Spectral observation of an intermediate
-
The kinetics and mechanism for the oxidation of phosphite, hypophosphite, phenylphosphite, and trimethylphosphite by ferrate(VI) are reported. Hypophosphite is rapidly oxidized to phosphite which is slowly oxidized to phosphate, trimethylphosphite is oxidized to trimethylphosphate, and phenylphosphite is oxidized phenylphosphate. 18O induced shifts of the 31P NMR signals support oxygen transfer from ferrate(VI) to the phosphorus center during the oxidation process. Deuteration of the hydridic hydrogens in hypophosphite and phosphite resulted in significant kinetic isotope effects on the reaction rates. It is proposed that ferrate(VI) acts as a two-electron oxidant in conjunction with oxide transfer coupled with phosphorus hydrogen bond breaking for phosphite and hypophosphite and simple oxygen transfer for trimethylphosphite and phenylphosphite.
- Hightower, Shaun M.,Lorenz, Bret B.,Bernard, Jonathan G.,Johnson, Michael D.
-
-
Read Online
- X-ray crystallographic and photophysical properties of rhodamine-based chemosensor for Fe3+
-
A fluorescent sensor for Fe3+, 2-[3′,6′-bis(ethylamino)-2′,7′-dimethyl-3-oxospiro[1H-isoindole-1,9′-[9H]xanthen]-2-((2-aminoethyl) methyl)]phenol, has been synthesized and characterized by 1H NMR, 13C NMR and X-ray crystal
- Zhang, Lizhu,Fan, Jiangli,Peng, Xiaojun
-
p. 398 - 402
(2009/07/18)
-
- Ozone reactions with sodium lignosulfonate in the presence of iron ions
-
The kinetics of ozonization of aqueous solutions of sodium lignosulfonate (LS) was studied in a bubbling reactor in the presence of iron(II) and iron(III) ions. The effective rate constants and ozone consumption in the reaction with LS were estimated. The introduction of iron(III) ions was shown to have no effect on the rate of destruction of aromatic rings in LS, but the total ozone consumption increased from 1.7 to 7.4 as the concentration of trivalent iron grew. The addition of iron(III) ions influenced the rate of oxidation of carboxylic acids formed in the ozonization of LS. In the presence of iron(II), not only the total ozone consumption in the reaction but also the initial rate of the process increased. Copyright
- Ksenofontova,Mitrofanova,Pryakhin,Lunin
-
p. 1033 - 1036
(2007/10/03)
-
- Release of NO from reduced nitroprusside ion. Iron-dinitrosyl formation and NO-disproportionation reactions
-
The kinetics and mechanism of the thermal decomposition of the one-electron reduction product of [Fe(CN)5NO]2- (nitroprusside ion, NP) have been studied by using UV-vis, IR, and EPR spectroscopy and mass-spectrometric and electrochemical techniques in the pH range of 4-10. The reduction product contains an equilibrium mixture of [Fe(CN)4NO] 2- and [Fe(CN)5NO]3- ions. The first predominates at pH 5NO]3-, which, in turn, is the main component at pH >9-10. Both nitrosyl complexes decay by first-order processes with rate constants around 10-5 s-1 (pH 6-10) related to the dissociation of NO. The decomposition is enhanced at pH 4 by 2 orders of magnitude with protons (and also metal ions) favoring the release of cyanides from the [Fe(CN)4NO]2- ions and the ensuing rapid delivery of NO. At pH 7, an EPR-silent intermediate I1 is detected (VNO, 1695 and 1740 cm-1) and assigned to the trans-[FeII(CN) 4(NO)2]2- ion, an {Fe-(NO)2} 8 species. At pH 6-8, I1 induces a disproportionation process with formation of N2O and the regeneration of nitroprusside in a 1:2 molar ratio. At lower pHs, I1 leads, competitively, to a second paramagnetic (S = 1/2) dinitrosyl intermediate I2, [Fe(CN)2(NO)2]1-, a new member of a series of four-coordinate {Fe(L)2(NO)2} complexes (L = thiolates, imidazole, etc.), described as {Fe(NO)2}9. Other decomposition products are hexacyanoferrate(II) or free cyanide, depending on the pH, and precipitates of the Prussian-Blue type. This study throws light on the conditions favoring rapid release of NO, to promote vasodilatory effects upon NP injection, and describes new processes related to dinitrosyl formation and NO disproportionation, which are also relevant to the diverse biological processes associated with NO and N2O processing.
- Roncaroli, Federico,Van Eldik, Rudi,Olabe, Jose A.
-
p. 2781 - 2790
(2008/10/09)
-
- Effect of ultrasound on the redox reactions of iron (II) and (III)
-
The standard electrode potential of Fe3+/Fe2+ (+0.77V) is very close to the mid-point value of 0.8V in the electrode potential series. The oxidation and reduction of iron from oxidation state II to III and vice versa is therefore possible theoretically with equal ease. This has been examined experimentally and the phenomenon of cavitation, generated through ultrasound, is found to facilitate both oxidation and reduction reactions of iron. Under ultrasonic field a solution of Fe(II) oxidizes to Fe(III) and forms a pink coloured complex of [Fe(SCN)6]3+, whereas Fe(III) reduces to Fe(II) and complexes with K3[Fe(CN)6] to form a prussian blue solution. A possible mechanism for inter-conversion has also been discussed.
- Pankaj,Chauhan, Manju
-
p. 2098 - 2101
(2007/10/03)
-
- A series piezoelectric quartz crystal response model for ferrous ion oxidation in the presence of T. ferrooxdians
-
A novel and simple method, series piezoelectric quartz crystal (SPQC) has been used to monitor ferrous ion oxidation in the presence of T. ferrooxidans. By combination of a general SPQC response model with the kinetics of the bacterial growth, a SPQC response model for ferrous ion oxidation in the presence of T. ferrooxidans has been built. The response model can describe the bacterial growth process well. Some important kinetic parameters, such as μm(the maximum specific growth rate of bacterium), K (saturation constant, i.e., the ferrous iron concentration at which the half-maximal growth rate occurs), Xo/Y (ratio of initial bacterial concentration to cell yield coefficient), have been obtained by fitting the model to the experimental curves.
- Chai,Bao,Yao,Wei
-
p. 939 - 942
(2007/10/03)
-
- Organometallic color chemistry: Studies on [FcCH=CHC5H4NCH2C6H 4(tBu)]X (X = BPh4-, ClO4-)
-
The title dyes, [FcCH=CHC5H4NCH2C6H 4(tBu)]X (X = BPh4-, ClO4-), developed for rapid screening of catalysts, are intensely colored, but bleach on exposure to visible light in solution. Detailed study shows that on irradiation these alkene dyes first undergo a trans-cis isomerization, then give an irreversible bleaching via decomposition. Both dyes show color dependence on the nature of the anion as a result of ion-pairing, which affects the intensity and position of the visible absorption. NMR, MS and EPR data are also reported.
- Diéguez, Montserrat,Collomb, Marie-No?lle,Crabtree, Robert H.
-
p. 146 - 152
(2007/10/03)
-
- Photocatalytic destruction of organic pollutants in a Pt/TiO2 semiconductor particulate system
-
Photo-oxidation of phenol, chlorophenol and trichloroethylene in water has been studied by using Pt/TiO2 semiconductor photocatalyst in presence of FeCl3. After 5 h of irradiation with a 50 W tungsten lamp, over 80-90 % degradation of pollutants is achieved. A working mechanism involving the formation of a hydroxyl radical is proposed.
- Chatterjee, Debabrata,Bhattacharya, Chandan
-
p. 1256 - 1258
(2007/10/03)
-
- Kinetics of silver(I) catalysed oxidation of sulphur(IV) by peroxodisulphate
-
Silver(I) catalysed oxidation of sulphur(IV) by peroxodisulphate yields sulphate as the only product and the kinetics are consistent with the experimental rate law (i) in acetate buffered medium - d[S(IV)]/dt=k[PDS]Ag(1)]. The value of k has been found to be (7.0 ± 0.2) x 10-2 dm3 mol-1 s-1 at I = 0.14 mol dm-3 and 40°C. The mechanism of the reaction, in the light of known chemistry of oxysulphur radicals, is discussed.
- Gupta,Bhargava,Manoj
-
p. 692 - 697
(2007/10/03)
-
- Oxidation of Fe2+ and formation of hydrogen peroxide during electric discharges between a liquid electrolyte surface and an electrode above it
-
Oxidation of Fe2+ and formation of H2O2 have been investigated in course of spark electric discharges (I = 0.5 mA) between a liquid electrolyte surface and an electrode above it. Yields have been calculated by assuming that active radicals (OH, H), created in the discharge, interact with solution components in surface layer having thickness 0.1 mm (with positive discharge electrode) and thickness 0.05 mm (with negative discharge electrode). Additional active particles are created in the liquid by energised positive ions of water accelerated in cathode drop of the discharge. Experimental data are reasonably reproduced by calculation model. Some new features for chemical effects of electric discharge at small current compared to well known GDE at higher current have been noted.
- Piskarev
-
p. 280 - 285
(2007/10/03)
-
- Simple electrochemical procedure for measuring the rates of electron transfer across liquid/liquid interfaces formed by coating graphite electrodes with thin layers of nitrobenzene
-
A simple, new method is described that allows the rates of electron transfer across liquid/liquid interfaces to be measured with unprecedented ease. The method takes advantage of thin layers of organic liquids that adhere to the surface of pyrolytic graphite electrodes. The method was applied to the nitrobenzene/water interface. Redox reactants dissolved in the nitrobenzene included decamethylferrocene and zinc tetraphenyl-porphyrin. Reactants in the adjoining aqueous phase were multiply charged anions, including Fe(CN)63-/4-, Ru(CN)64-, Mo(CN)84-, and IrCl62-. Rate constants for cross-phase electron transfer were evaluated and compared with those obtained in recent studies that employed the scanning electrochemical microscope that was invented and developed by A. J. Bard and co-workers.
- Shi, Chunnian,Anson, Fred C.
-
p. 9850 - 9854
(2007/10/03)
-
- Determination of reaction energy values for biological pyrite oxidation by calorimetry
-
The reaction energy values for pyrite oxidation by chemolithotrophic leaching bacteria (pure cultures of Thiobacillus ferrooxidans, Leptospirillum ferrooxidans, and mixed cultures of L. ferrooxidans and T. thiooxidans) were calorimetrically measured in batch experiments. The obtained data were compared with the nonconservative values for the corresponding abiotic processes that were calculated from standard enthalpies and chemical analyses of the leaching products. Due to the different abilities of the investigated species to oxidize the sulphur moiety of pyrite, the measured reaction energy values ranged from - 1100 to - 1600 kJ/mol with an accuracy of 4-16%. In samples with T. ferrooxidans and with the mixed cultures, no significant difference between the calorimetric and theoretical reaction energy values occurred. In contrast, pure cultures of L. ferrooxidans exhibited measured values which were up to 200 kJ/mol lower than the theoretical ones. It is highly unlikely that this difference may be explained by a higher energy conservation efficiency of L. ferrooxidans compared to the one of T. ferrooxidans or T. thiooxidans. Besides use in efficiency studies, the collected data can be used to determine the activity of leaching bacteria in natural biotopes by calorimetric measurements.
- Rohwerder, Thore,Schippers, Axel,Sand, Wolfgang
-
-
- Comparative Studies of Autoxidation of Ferrous Ions in Corn-starch Gel with those of the Haemoglobins in Human Red Blood Cells
-
The observed increase in the relaxivity of FeII ions in its ethylenediaminetetraacetic acid (EDTA) complex solution over that in ferrous sulphate solution is rationalised. Spin-lattice (T1) and spin-spin (T2) relaxation times of haemoglobin (Hb) solutions are recorded. The extents of the respective decreases of the T1s and T2s in packed red blood cell (PRBC) samples during the autoxidations of their Hb-iron contents are compared with those of the FeII ions in corn-starch gel samples during the periods of the respective chemical changes. The continued decreases of both T1s and T2s in two samples of a freshly prepared corn-starch gel have been monitored for a shorter experimental period from the time of preparation of the gel.
- Ghosh, Binay Kumar
-
-
- Kinetics of retardation in persulphate-Fe3+-bisulphite initiated polymerization of acrylamide
-
The kinetics of persulphate-Fe3+-bisulphite initiated polymerization has been studied at 30±0.2°C in oxygen atmosphere. It has been found that the polymerization kinetics is significantly altered by Fe3+ concentration. At lower concentration (2.0 × 10-4 mol dm-3) of Fe3+ the rate of polymerization follows the rate equation Rp ∝ , [monomer] [S2O82-] while at higher concentration (8.0 × 10-4 mol dm-3) the rate equation becomes Rp ∝ [M][HSO3-]. Besides affecting the polymerization kinetics Fe3+ also decreases the molecular weight of the resulting polymers. The effects of added salts and temperature on the polymerization process have also been investigated and energy of activation is calcualted to be 42.6 kJ mol-1. Retarding effect of various aliphatic alcohols, nitro compounds and nitrophenols has been studied in terms of retardation constants.
- Bajpai,Sharma
-
p. 1091 - 1096
(2007/10/03)
-
- Some observations in the aqueous polymerizations of vinyl acetate initiated by potassium persulphate and ferrous ammonium sulphate at 30°C in nitrogen atmosphere
-
The heterogeneous aqueous polymerization of vinyl acetate (VA) has been detected by the instantaneous appearance of a bluish haze when freshly prepared ferrous ammonium sulphate (FAS) solution (saturated with pure N2 gas) is injected into the reactor containing aqueous solution of monomer (M) and potassium persulphate (KPS) in N2 atmosphere at 30°C. The colloidal latex solution gradually becomes yellowish above 10°C, but it is milky white at or below 10°C. The reactions are found to be very fast, the conversion of monomer to polymer being about 66.0% in 5 minutes at 30°C when VA is 0.1625 mol dm-3, [FAS] = [KPS]=10-3 mol dm-3. The time average rate of polymerization, (V′p), i.e. V′p = % conversion in time t/time t, may be written as: V′p[VA]x[FAS]y[KPS]z where x = 1.5. The order plots of FAS and of KPS have been found to be curved lines, y=0.50 to (-) 0.15, and z = 2.0 to 0.40, in the concentration ranges of VA from 0.0975 to 0.195 mol dm-3, and of initiators [KPS] = [FAS]= 10-3 to 5 × 10-5 mol dm-3. The values of y and z are found to vary with molar ratio(r) of [KPS]/[FAS]. When (1/r) = 0.05 to 0.10 y = 0.50 and y=(-) 0.15. when (1/r)=1.0 to 5.0, z = 0.40 when r = 0.1 to 1.0, and z = 1.5 to 2.0, when r = 0.05. Reaction (2), viz. Fe2+ + SO4- → Fe3+ + SO42 , which decreases polymerization rates at higher [FAS], is possibly responsible partly for these abnormal reaction orders of the initiators. V′p is found to decrease with increase in ionic strength (μ) of the medium. NaF, when added at the outset of polymerization, makes the latex solution colourless, decreases the colloidal stability (CS), and marginally increases the polymerization rates (V′p). H2SO4 acid (1.0 to 2.0 N) enhances V′p and also the final % conversion. Polyvinyl acetate (PVA) does not dissolve in common solvents. It seems that at 30°C, the polymerization of VA under the experimental conditions in the KPS-VA-FAS system is a case of 'dead-end polymerization'.
- Mitra, Subhash C.,De, Niharendu,Guchhait, Sukumar,Konar, Ranajit S.
-
p. 566 - 575
(2007/10/03)
-
- Kinetics and mechanisms of the redox reactions of the hydroperoxochromium(III) ion
-
The reactions of the hydroperoxochromium(III) ion, (H2O)5CrO2H2+ (CrO2H2+), with Fe2+, VO2+, V2+, Cu+, Ti3+, Co([14]aneN4)2+, Co(Me6[14]aneN4)2+, Co(tim)2+, and [Ru(NH3)6]2+ have been studied in acidic aqueous solution. The reactions are accompanied by large negative entropies of activation, -110 J mol-1 K-1 for Fe2+ and -85 J mol-1 K-1 for Ti3+. All the reactions studied follow an isokinetic relationship in that ΔH? is a linear function of ΔS?. The same is true for the analogous reactions of H2O2. It is proposed that the reactions of CrO2H2+ take place by an inner-sphere, Fenton-type process yielding pentaaquaoxochromium(IV), (H2O)5CrO2+ (CrO2+), as an intermediate. The reactivity of CrO2H2+ as an oxygen transfer reagent is about 20 times greater than that of H2O2. For example, the reactions with (en)2CoSCH2CH2NH22+ to yield (en)2CoS(O)CH2CH2NH22+ have rate constants 20.5 ± 0.4 M-1 s-1 (CrO2H2+) and 1.36 M-1 s-1 (H2O2), both in 0.1 M HClO4 at 25°C. The chromyl ion, CrO2+, oxidizes CrO2H2+ to CrO22+ with a rate constant of (1.34 ± 0.06) × 103 M-1 s-1 in 0.10 M HClO4 in H2O and 266 ± 10 M-1s-1 in D2O.
- Wang, Wei-Dong,Bakac, Andreja,Espenson, James H.
-
p. 5034 - 5039
(2008/10/08)
-
- Effects of Temperature and Wavelength on the Primary Process in the Photo-oxidation of Iron(II) Ion
-
Experiments at 253.7 and 228.8 nm, each over a range of ca. 45 K, demonstrate that the primary quantum yield of photo-oxidation in deoxygenated acidic iron(II) solutions increases only very slightly with temperature, but that at the lower wavelength it is ca. 1.36 times greater.It is suggested that the excitation process involves the transfer of an electron to a shallow trap among the neighbouring solvent molecules, such that recombination of the electron with its geminate iron(III) ion is highly probable.It appears that temperature has little effect on the quantum yield because electron escape and recombination both depend on temperature to very similar extents and that the use of a higher-energy photon increases the quantum yield because then more and more distant traps are accessible for electron transfer.
- Logan, S. R.
-
p. 615 - 617
(2007/10/02)
-
- Kinetics of the Reactions of the SO4- Radical with SO4-, S2O82-, H2O and Fe2+
-
The sulphate radical anion, SO4-, is known to be a key intermediate in the aqueous aerobic oxidation of SO2 initiated by free radicals.The absorption spectrum of SO4- has been obtained following photolysis of K2S2O8 solutions at 248 nm.Kinetic spectrophotometric techniques have been employed to investigate the decay of SO4- in the presence of S2O82- and FeII.Several rate constants have been determined at 293 K: 2k(SO4- + SO4-) = (8.9+/-0.3) * 108 dm3 mol-1 s-1 (at infinite dilution), k(SO4- + S2O82-) = (6.1+/-0.6) * 105 dm3 mol-1 s-1 (at infinite dilution) and k(SO4- + H2O) = (500+/-60) s-1.The reaction of SO4- with FeII proceeds via a rapid equilibration step followed by electron transfer, which is rate-determining .Values of k1, k-1 and k2 at 293 K are (3.0+/-1.9) * 108 dm3 mol-1 s-1, (4.8+/-3.0) * 104 s-1 and (6.5+/-2.1) * 103 s-1 respectively.The implications of these results for current cloud and precipitation chemistry models are discussed.
- McElroy, W. J.,Waygood, S. J.
-
p. 2557 - 2564
(2007/10/02)
-
- Kinetic study of the formation of the oxo diperoxo complexes of molybdenum(VI) and tungsten(VI) and their reduction by iron(II), europium(II), the methyl viologen radical cation, and the dithionite ion
-
The rate law for the formation of MoO(OH)(O2)2- from Mo(VI) and H2O2 is rate = kf[Mo(VI)][H2O2] at [H+] ≤ 0.0030 M. The values of kf at 25°C and I = 0.10 M are (6.7 ± 0.3) × 103, (2.0 ± 0.1) × 103, and 8.6 ± 0.8 M-1 s-1 in 0.0030 M HClO4, at pH 4.0 (acetic acid, acetate buffer), and at pH 7.0 (MOPS buffer), respectively. The value of kf for WO(OH)(O2)2- is 3.0 ± 0.4 M-1 s-1 at pH 7.0. At [H+] ≥ 0.10 M, the rate law is second order with respect to H2O2 for the formation of MoO(O2)2; the transition from a first- to a second-order peroxide dependence was observed at 0.0090 and 0.014 M H+. Formation constants were determined at pH 4.0 and 6.1-7.8 for MoO(OH)(O2)2- and pH 6.1-7.7 for WO(OH)(O2)2-. The formation of an intermediate tentatively formulated as M(VI)-(O22-)-Fe(III) was detected in the iron(II) systems. The formation kinetics of the intermediate and iron(III) for the Mo(VI) system were determined at an isosbestic at 255 nm and obey the following rate expression: -d[H2O2]/dt = [Fe2+]{((2.8 ± 0.1) × 104 M-1 s-1)[MoO(O2)2] + ((5.6 ± 0.2) × 104 M-1 s-1)[MoO(OH)(O2)2-] + (63 ± 1 M-1 s-1)[H2O2]} at 25°C. A partial spectrum and the first-order decay kinetics of the intermediate were determined for the Mo(VI) system. The rate law for the reaction of WO(OH)(O2)2- and Eu2+ in 0.0050 M HClO4, at I = 0.10 M, and at 25°C is -d[H2O2]/dt = [Eu2+]{((2.8 ± 0.4) × 104 M-1 s-1)[WO(OH)(O2)2-] + (1.9 ± 0.1 M-1 s-1)[H2O2]}. The Mo(VI) system is complicated by competitive reduction of traces of uncomplexed Mo(VI). Second-order rate constants for the Eu2+ reduction of MoO(O2)2, MoO(OH)(O2)2-, and Mo(VI) were derived from the kinetic data. The ratio k{O2-Eu(II)}/k{H2O2-Eu(II)} was determined to be ca. 3 × 104. The rate laws for the dithionite systems were half-order with respect to [S2O42-], consistent with SO2- as the reactive reductant. Second-order rate constants (M-1 s-1) for the reduction of WO(OH)(O2)2-, MoO(OH)(O2)2-, and H2O2 by SO2- were 8.0 × 105, 1.7 × 105, and 2.9 × 103, respectively, at 25°C and pH 7.0. Second-order rate constants (M-1 s-1) for the reduction of Mo(VI), MoO(O2)2 + MoO(OH)(O2)2-, and H2O2 by the methyl viologen radical cation at 25°C in 0.010 M HClO4 were determined to be (2.9 ± 0.1) × 105, (6 ± 1) × 104, and 3.0 ± 0.2, respectively. The rate enhancements for the oxo diperoxo complexes of Mo(VI) and W(VI) relative to hydrogen peroxide are substantial (60-13000) and fall within the range observed previously for several reductants that undergo oxygen atom transfer from peroxide. We propose that all the present substrates react by an inner-sphere, one-electron reduction of the peroxo ligand to produce a hydroxyl radical intermediate. The hydroxyl radical can oxidize the remaining peroxo ligand in the oxo diperoxo complex to form a superoxo Mo(VI) or W(VI) intermediate, which is rapidly reduced to peroxide by the reductant. We also conclude that Mo(VI) and W(VI) are versatile catalysts for reduction of hydrogen peroxide at least over the pH range 0-7.
- Schwane, Lisa M.,Thompson, Richard C.
-
p. 3938 - 3946
(2008/10/08)
-
- Kinetics and mechanism of the oxidation of 2,3-dihydroxybenzoic acid by iron(III)
-
The kinetics of the oxidation of 2,-3-dihydroxybenzoic acid (DHB) by aqueous iron(III) have been studied in aqueous acid with [Fe(III)] ? [DHB]. The initial complexation reaction of Fe(OH2)63+ and DHB was studied previously. The iron(III)-DHB complex is oxidized by iron(III) with a rate law that is first order in iron(III) and has terms that are inverse first order in [H+] and inverse second order in [Fe(OH2)62+]. It is shown that the oxidation does not proceed by simple intramolecular electron transfer within the iron(III)-DHB complex. A mechanism is proposed in which the latter complex reacts first by substitution on free iron(III) followed by two reversible electron-transfer steps to give the quinone product.
- Xu, Jinhuang,Jordan
-
p. 4563 - 4566
(2008/10/08)
-
- KINETICS AND EQUILIBRIUM OF THE Ru3O2(NH3)14(7+)-Fe(II) REACTION IN ACID MEDIUM
-
The kinetics and equilibrium of the one-electron redox reaction Ru3O2(NH3)14(7+) + Fe(II) Ru3O2(NH3)14(6+) + Fe(III) has been investigated spectrophotometrically using conventional and stopped-flow technique.At 25 deg C, at an ionic strength of 0.500 mol dm-3 (HClO4) and reagents concentrations in the range: =(1.91-15.3) X 1E-6 mol dm-3 (sulphate salt), =(3.59-10.8) X 1E-4 mol dm-3 (perchlorate salt), the second order rate constants kf and kr, and the equilibrium constant Q are: 7.67 +/- 0.45 mol-1 dm3 s-1, 74 +/- 15 mol-1 dm3 s-1 and 0.10 +/- 0.02, respectively.In addition to the rate-accelerating effect of ionic strength the increase of ability to electron transfer with decrease in the positive charge of iron(II) and iron(III) complexes in the presence of chloride and sulphate anions have been observed.
- Banas, Bogdan
-
-
- Reactions of the superoxochromium(III) ion with transition-metal complexes
-
The reactions of the superoxochromium(III) ion, CrO22+, with a number of one-electron-reducing agents have been examined in acidic aqueous solutions at 25°C and 0.10 M ionic strength. The results are consistent with an outer-sphere mechanism for Ru(NH3)62+ (k = 9.5 × 105 M-1 s-1), Co(sep)2+ (8.5 × 105 M-1 s-1), and V(H2O)62+ (2.3 × 105 M-1 s-1). The reactions with Fe(H2O)62+, Co([14]aneN4)(OH2)22+, and Co([15]aneN4)(OH2)22+ take place by an inner-sphere mechanism characterized by the formation and subsequent decomposition of binuclear intermediates. The rate constants for these reactions have values 4.5 × 103, ~7 × 106, and 6.2 × 105 M-1 s-1, respectively.
- Brynildson, Mark E.,Bakac, Andreja,Espenson, James H.
-
p. 2592 - 2595
(2008/10/08)
-
- Sonochemistry of Aqueous Solutions: H2-O2 Combustion in Cavitation Bubbles
-
Water was insonated with 300-kHz ultrasound under H2-O2 mixtures of various compositions and the rates of gas consumption and of H2O2 formation were measured.These rates have pronounced maxima at H2:O2 ratios of 1:3 and 2:1 in the solution.The chain length of the combustion reaction is only about 10.This is explained by the high ratio of surface to volume of the tiny cavitation bubbles as intermediate radicals rapidly reach the interface where they no longer propagate the chains.The rate of Fe2+ oxidation in the absence and presence of Cu2+ ions was also investigated as well as the formation of carbon dioxide in dilute formate solution.The yields of OH, HO2, and H2O2 in the bulk solution were derived from these scavenger experiments.Fe3+ ions are not reduced when a solution is insonated under pure H2, and it is concluded that H atoms do not move to a substantial extent from the gas bubbles into the solution.The number of chemically active cavitation events is estimated as 1E9 L-1 min-1.
- Hart, Edwin J.,Henglein, Arnim
-
p. 3654 - 3656
(2007/10/02)
-
- Kinetics of the Dissociation and Kinetic Stability of Iron(III) Complexes of Tetraphenylporphin and Its Derivatives
-
The kineticas of the dissociation of the complexes L(FeT(X)4 of Fe3 with tetraphenylporphin (T) and its derivatives containing substituents X = Cl, Br, OCH3, NO2, or NH2 in the benzene ring have been investigated in proton-donating solvents as a function of the nature of the acido-ligand L = Cl-, CH3COO-, or SCN-.Conclusions have been reached about the mechanisms of the electronic influences of the functional groups and the acido-ligands on the kinetic stability of the Fe3+ complex.
- Lomova, T. N.,Shormanova, L. P.,Berezin, B. D.,Antonova, S.V.
-
p. 350 - 352
(2007/10/02)
-
- Kinetics of the Permanganate-Iron(II) Reaction in Aqueous Acid Medium
-
The kinetics of the permanganate-iron(II) redox reaction has been studied in aqueous perchloric acid at 20 deg C by using stopped-flow techniques.The disappearance of permanganate was followed at 525 nm, with use of excess iron, and consisted of two consecutive first-order decays.A mechanism consistent with the data is MnO4- + Fe2+ O3MnOFe+ (k1, k-1), O3MnFe+ -> Mn(VI) + Fe(III) (k2).The rate constants are k1 = 9.97E4 M-1 s-1, k-1 = 16.4 s-1, and k2 = 12.9 s-1.No dependence on H+ or salt was observed in either step.
- Sutter, John R.,Park, Kee B.
-
p. 770 - 772
(2007/10/02)
-
- Kinetics of Silver(II) Oxidation of Metal Cations
-
The oxidation of Fe2+, Mn2+, Co2+, Ce3+, and VO2+ by silver(II) has been investigated with a stopped-flow technique.The reactions of Mn2+ and Ce3+ occur through two competitive paths involving Ag2+ and AgOH+.For the other cations a single pathway with Ag2+ as oxidant has been observed.An inner-sphere interaction mechanism is proposed and discussed with reference to the electron configuration of the reductant and to the behaviour predicted by the Marcus cross relation.
- Arselli, Patrizia,Baiocchi, Claudio,Mentasti, Edoardo,Coe, John S.
-
p. 475 - 478
(2007/10/02)
-
- Direct Observation of Hydrated Electrons in the U.V. Photo-oxidation of 2+
-
Hydrated electrons are involved as intermediates in the photo-oxidation of 2+ to FeIII species in water at 265 nm.
- Sloper, Robert W.,Braterman, Paul S.,Cairns-Smith, A. Graham,Truscott, T. George,Craw, Marjory
-
p. 488 - 489
(2007/10/02)
-
- Kinetics of dissociation of tris-(1,10-phenanthroline)-iron(III)sulphate in water-acetone solvent medium
-
The kinetics of dissociation of tris-(1,10-phenanthroline)-iron(III) in aqueous acetone medium has been studied as a function of H(1+).The reaction is first order in ferrin and second order in acetone and further the reaction rate is inverse dependent on H(1+).A probable mechanism has been proposed invoking steady-state hypothesis.
- Sriramam, K.,Sarma, B. S. R.,Sastry, N. Ramabrahma,Kalidas, K.
-
p. 155 - 160
(2007/10/02)
-
- QUANTUM YIELDS OF Fe(2+)aq, Fe(2+)SO4(2-) AND Fe(2+)H(+)SO4(2-) AND *Fe(3+) -> Fe(2+) ENERGY TRANSFER IN THE PHOTOCHEMICAL OXIDATION OF IRON(II) IONS IN FeSO-H2SO4-H2O SYSTEMS
-
In a study of the photo-oxidation of iron(II) ions in sulfuric acid solution, individual quantum yields for the species Fe(2+)aq, Fe(2+)SO4(2-) and Fe(2+)H(+)SO4(2-) have been determined.By means of appropriate models, the occurence of the energy transfer process *Fe(3+) -> Fe(2+) has been shown to be highly probable.The experimental technique and method of calculation used in this work are suitable for the elucidation of finer details of photochemical processes which involve several photoactive particles in one system.
- Vincze, L.,Kraut, B.,Horvath, A.,Papp, S.
-
p. 183 - 190
(2007/10/02)
-