- Reaction Kinetics in a Microemulsion Medium IV. Hexacyanoferrate(III)-Iodide Reaction in Water/Aerosol-OT/Heptane Microemulsion and Mixed Solvents
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The kinetics of the reaction between [Fe(CN)6]3- and I- was studied in a W/O microemulsion (Water/AOT/Heptane at different [Water]/[Amphiphile] mole ratios) and in mixed water-organic media (water-formamide, water-ethylene glycol, and water-dioxane). The pseudo-first-order rate constants were observed to radically increase in microemulsion media with a [Water]/[AOT] mole ratio below 6. At a mole ratio of 5.4, the rate constant was found to be about 20-fold greater than that in water. At a constant mole ratio, the rate constant was witnessed to be independent of [AOT]. In all mixed media, the rate decreased with increasing proportion of the nonaqueous solvent. The ionic-strength effect on the reaction did not obey either the modified Bronsted-Bjerrum or Bronsted-Bjerrum-Pitzer relations in the studied nonaqueous media, except for ethylene glycol. This disagreement is very prominent in the studied W/O microemulsion medium at [Water]/[AOT] ω = 9.1. The activation parameters for the pseudo-first-order reaction in all of the studied media suggested distinct difference of the microemulsion from other solvents. A reasonable compensation between ΔH? and ΔS? i.e., the isokinetic effect, was observed.
- Mukherjee, Kallol,Mukherjee, Dulal Chandra,Moulik, Satya Priya
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- Halogenated Peroxyl Radicals as Multi-Electron Oxidants: Pulse Radiolysis Study on the Reaction of Trichloromethyl Peroxyl Radicals with Iodide
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CCl3OO radicals are shown to oxidize three equivalents of iodide ions to yield one I2 molecule (showing up as I3- in aqueous solution) and one I-radical atom (showing up as I2-radical anion per peroxyl unit; the mechanism is considered to proceed via a protonated CCl3OO-radical/I- adduct radical as the primary intermediate and subsequent nucleophilic (SN2) attack by a second iodide accompanied by electron localization in the hydroperoxide moiety leads to I2 and CCl3O-radical with the latter being responsible for the oxidation of the third iodide.
- Bonifacic, Marija,Schoeneich, Christian,Asmus, Klaus-Dieter
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- Sequential flow injection determination of iodate and periodate with spectrophotometric detection.
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A flow injection (FI) system is described for the sequential determination of periodate and iodate based on their reaction with iodide at pH 3.5. Two sample plugs were injected into the same carrier stream sequentially. One injection is for the iodate determination and the other for the sum of iodate and periodate determination. For iodate determination, molybdate solution buffered at pH of 3.5 was used for selective masking of periodate. The influences of reagent concentrations were studied by a univariable method and the influence of FI manifolds was studied using univariable and simplex method. Periodate and iodate can be determined in the range of 0.050-5.0 and 0.050-10 microg/ml, respectively. The 3 sigma limit of detection was 0.030 and 0.050 microg/ml for periodate and iodate, respectively. The proposed method has been applied for the sequential determinations of periodate and iodate in water samples.
- Ensafi, Ali A,Chamjangali, M Arab
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- Effect of acetylacetone on morphology and crystalline structure of nanostructured TiO2 in titanium alkoxide aqueous solution system
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Network structure of single-crystal-like TiO2 nanowires with anatase phase was synthesized at low temperature by the "oriented attachment" mechanism. The most important factor for synthesis of network structure of the TiO2 nanowires
- Nakagawa, Keizo,Wang, Fumin,Murata, Yusuke,Adachi, Motonari
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- Photolysis of triiodide studied by femtosecond pump-probe spectroscopy with emission detection
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The photodissociation of triiodide into diiodide and iodine in ethanol solution was studied by a novel femtosecond pump-probe technique. The dispersed emission of the triiodide sample was recorded as a function of the delay between a 407 nm pump pulse and
- Gilch, Peter,Hartl, Ingmar,An, Qingrui,Zinth, Wolfgang
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- α-cyclodextrin-I3- host-guest complex in aqueous solution: Theoretical and experimental studies
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UV-vis spectroscopic studies on aqueous solutions of iodine, potassium iodide, and α-cyclodextrin (αCD), (C6H10O5)6, suggest that a complex forms with the composition of αCD2I3-. Semiempirical quantum mechanical PM3 calculations suggest that two major host-guest isomer types exist for this complex. The most stable isomer has the I3- ion oriented almost parallel to the plane of one of the αCD molecules and sandwiched between two αCD molecules. The second sandwich isomer is less stable than the above isomer by about 5 kcal/mol (20.9 kJ/mol) and has the I3- ion oriented vertically (along the vertical axis) between two αCD molecules. The formation constant (Kf) of the complex is determined to be around 7.0 × 108 M-2 for both 15 and 25°C.
- Minns, Jason W.,Khan, Arshad
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- Mechanisms of oxidation reactions of iodide and hexacyanoferrate(II) ions, induced by the reaction between phosphinate ion and molecular oxygen in an aqueous solution
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When an I- solution was mixed with a PH2O2- solution which had been kept standing for given times of 5-40 min m the presence of molecular oxygen (O2), the I2 (or I3-)
- Kimura,Ieyama,Matsumoto,Shimada,Tsukahara
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- snorkelling : Vs. diving in mixed micelles probed by means of a molecular bathymeter
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A photoactive bathymeter based on a carboxylic acid moiety covalently linked to a signalling methoxynaphthalene (MNP) fluorophore has been designed to prove the concept of snorkelling vs. diving in mixed micelles (MM). The carboxylic acid floats on the MM surface, while the MNP unit sinks deep in MM. The rate constants of MNP fluorescence quenching by iodide, which remains basically in water, consistently decrease with increasing spacer length, revealing different regions. This is associated with the distance MNP should dive in MM to achieve protection from aqueous reactants. Unequivocal proof of the exergonic photoinduced electron transfer was obtained from the UV-visible spectral signature of I3- upon steady-state photolysis. The applicability of the bathymeter was examined upon testing a family of MNP derivatives. The obtained results were validated by comparison with different lipophilicity tests: (i) a modified version of the Kow partition coefficient and (ii) the retention factor on thin layer chromatography. This concept could potentially be extended to test drugs or pharmacophores exhibiting any photoactive moiety.
- Rodriguez-Mu?iz, Gemma M.,Gomez-Mendoza, Miguel,Nuin, Edurne,Andreu, Inmaculada,Marin, M. Luisa,Miranda, Miguel A.
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- Heterogeneous Catalysis in Solution. Part 18. The Catalysis by Carbons of Oxidation-Reduction Reactions
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A mechanism of electron-transfer-through-the-solid is proposed to account for the widespread catalysis by carbons of redox reactions in solution.Charcoal catalysis of the aqueous reaction between Fe(3+) and I(-) ions was predicted, found, and studied kinetically.The activation energy of the heterogeneous process was only 24 kJ mol-1 compared with 100 kJ mol-1 for the homogeneous reaction.The (3-) + I(-) reaction in water was found to be catalysed by carbons as well as by several phthalocyanines.Neither reaction was catalysed by solids such as SiO2 or Ba which do not conduct electronically.
- Austin, Jack M.,Groenewald, Theo,Spiro, Michael
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- Microemulsion as a Medium in Chemical Kinetics: The Persulfate-Iodide Reaction
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Rate constants are reported for the oxidation of iodide ions by persulfate in sodium bis(2-ethylhexyl)sulfosuccinate (aerosol OT or AOT)/decane/water microemulsions.The rate law is in the form v = k2->2->, where both concentrations are referred to the aqueous phase.The reaction rate is higher in microemulsions than when it takes place in a conventional aqueous medium.Results show that when the AOT concentration remains constant, the reaction rate decreases when increasing the molar ratio w = /, appearing to asymptotically approach the rate in bulk water as the amount of water in the microemulsions increases.For a given w value, the reaction rate shows no dependence on the surfactant concentration.
- Moya, Maria Luisa,Izquierdo, Carmen,Casado, Julio
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- Syntheses, crystal structures, reactivity, and photochemistry of gold(iii) bromides bearing N-heterocyclic carbenes
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Gold(i) complexes bearing N-heterocyclic carbenes (NHC) of the type (NHC)AuBr (3a/3b) [NHC = 1-methyl-3-benzylimidazol-2-ylidene (= MeBnIm), and 1,3-dibenzylimidazol-2-ylidene (= Bn2Im)] are prepared by transmetallation reactions of (tht)AuBr (tht = tetrahydrothiophene) and (NHC)AgBr (2a/2b). The homoleptic, ionic complexes [(NHC)2Au]Br (6a/6b) are synthesized by the reaction with free carbene. Successive oxidation of 3a/3b and 6a/6b with bromine gave the respective (NHC)AuBr3 (4a/4b) and [(NHC)2AuBr2]Br (7a/7b) in good overall yields as yellow powders. All complexes were characterized by NMR spectroscopy, mass spectrometry, elemental analysis and single crystal X-ray diffraction. Reactions of the Au(iii) complexes towards anionic ligands like carboxylates, phenolates and thiophenolates were investigated and result in a complete or partial reduction to a Au(i) complex. Irradiation of the Au(iii) complexes with UV light yield the Au(i) congeners in a clean photo-reaction.
- Hirtenlehner, Christa,Krims, Charlotte,Hoelbling, Johanna,List, Manuela,Zabel, Manfred,Fleck, Michel,Berger, Raphael J. F.,Schoefberger, Wolfgang,Monkowius, Uwe
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- High electron transfer of TiO2nanorod@carbon layer supported flower-like WS2nanosheets for triiodide electrocatalytic reduction
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WS2-based nanomaterials have been extensively studied due to their unique catalytic properties. However, it is still a great challenge to prepare WS2-based electrocatalysts with both maximally active edge sites exposure and high electronic conductivity. In this work, we have engineered a 1D-2D multidimensional nanostructured TiO2 nanorod@carbon layer supported flower-like WS2 nanosheets (TNRs@C@WS2) electrocatalyst with abundant exposed active edge sites as well as high electron transfer abilities. The TNRs@C@WS2 was explored as a good catalyst for the triiodide reduction reaction. The assembled dye-sensitized solar cell achieves a high photoelectric conversion efficiency (7.15%) and comparable to that (7.18%) of Pt. This unique 1D-2D multidimensional nanostructure may open up new opportunities for a variety of applications in clean energy and catalysis.
- Wang, Wei,Liu, Tianyu,Ding, Chuan,Wang, Min,Bai, Jirong,Zhang, Jintao,Bi, Hengchang,Sun, Yueming,Wang, Yuqiao
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- A Thioether-Ligated Cupric Superoxide Model with Hydrogen Atom Abstraction Reactivity
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The central role of cupric superoxide intermediates proposed in hormone and neurotransmitter biosynthesis by noncoupled binuclear copper monooxygenases like dopamine-β-monooxygenase has drawn significant attention to the unusual methionine ligation of the CuM ( CuB ) active site characteristic of this class of enzymes. The copper-sulfur interaction has proven critical for turnover, raising still-unresolved questions concerning Nature's selection of an oxidizable Met residue to facilitate C-H oxygenation. We describe herein a model for CuM, [(TMGN3S)CuI]+ ([1]+), and its O2-bound analog [(TMGN3S)CuII(O2?-)]+ ([1·O2]+). The latter is the first reported cupric superoxide with an experimentally proven Cu-S bond which also possesses demonstrated hydrogen atom abstraction (HAA) reactivity. Introduction of O2 to a precooled solution of the cuprous precursor [1]B(C6F5)4 (-135 °C, 2-methyltetrahydrofuran (2-MeTHF)) reversibly forms [1·O2]B(C6F5)4 (UV/vis spectroscopy: λmax 442, 642, 742 nm). Resonance Raman studies (413 nm) using 16O2 [18O2] corroborated the identity of [1·O2]+ by revealing Cu-O (446 [425] cm-1) and O-O (1105 [1042] cm-1) stretches, and extended X-ray absorption fine structure (EXAFS) spectroscopy showed a Cu-S interatomic distance of 2.55 ?. HAA reactivity between [1·O2]+ and TEMPO-H proceeds rapidly (1.28 × 10-1 M-1 s-1, -135 °C, 2-MeTHF) with a primary kinetic isotope effect of kH/kD = 5.4. Comparisons of the O2-binding behavior and redox activity of [1]+ vs [2]+, the latter a close analog of [1]+ but with all N atom ligation (i.e., N3S vs N4), are presented.
- Bhadra, Mayukh,Transue, Wesley J.,Lim, Hyeongtaek,Cowley, Ryan E.,Lee, Jung Yoon C.,Siegler, Maxime A.,Josephs, Patrick,Henkel, Gerald,Lerch, Markus,Schindler, Siegfried,Neuba, Adam,Hodgson, Keith O.,Hedman, Britt,Solomon, Edward I.,Karlin, Kenneth D.
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- Ruthenium Dioxide Hydrate: Is it a Hydrogen Catalyst?
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RuO2*xH2O needs to be reduced quite substantially before it can function as a hydrogen catalyst; without reduction, RuO2*xH2O is a strong oxidant, capable of oxidising MV+., I(-), Br(-), Cl(-), Ru(bpy)3(2+), and Fe(phen)3(2+) (bpy= 2,2'-bipyridine and phen = 1,10-phenanthroline).
- Mills, Andrew,Williams, Geraint
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- Synthesis and spectroscopic characterization of ternary copper(ii) complexes containing nitrogen and oxygen donors as functional mimics of catechol oxidase and phenoxazinone synthase
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Two ternary copper(ii) complexes 1 [(Cu2Me4en)4(EDTA)] and 2 [(CuMe4en)2(MIDA)] containing the mixed ligand system of 1,1′,4,4′-tetramethylethylenediamine (Me4en) (L) and N-methyliminodiace
- Abdel-Rahman, Adel A.-H.,Al-Harbi, Sami A.,Ibrahim, Mohamed M.,Omar, Walid,Ramadan, Abd El-Motaleb M.,Sallam, Shehab A.,Shaban, Shaban Y.
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- Acid-induced mechanism change and overpotential decrease in dioxygen reduction catalysis with a dinuclear copper complex
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Catalytic four-electron reduction of O2 by ferrocene (Fc) and 1,1′-dimethylferrocene (Me2Fc) occurs efficiently with a dinuclear copper(II) complex [CuII2(XYLO)(OH)] 2+ (1), where XYLO is a m-xylene-linked bis[(2-(2-pyridyl)ethyl) amine] dinucleating ligand with copper-bridging phenolate moiety], in the presence of perchloric acid (HClO4) in acetone at 298 K. The hydroxide and phenoxo group in [CuII2(XYLO)(OH)] 2+ (1) undergo protonation with HClO4 to produce [Cu II2(XYLOH)]4+ (2) where the two copper centers become independent and the reduction potential shifts from -0.68 V vs SCE in the absence of HClO4 to 0.47 V; this makes possible the use of relatively weak one-electron reductants such as Fc and Me2Fc, significantly reducing the effective overpotential in the catalytic O 2-reduction reaction. The mechanism of the reaction has been clarified on the basis of kinetic studies on the overall catalytic reaction as well as each step in the catalytic cycle and also by low-temperature detection of intermediates. The O2-binding to the fully reduced complex [CuI2(XYLOH)]2+ (3) results in the reversible formation of the hydroperoxo complex ([CuII2(XYLO)(OOH)] 2+) (4), followed by proton-coupled electron-transfer (PCET) reduction to complete the overall O2-to-2H2O catalytic conversion.
- Das, Dipanwita,Lee, Yong-Min,Ohkubo, Kei,Nam, Wonwoo,Karlin, Kenneth D.,Fukuzumi, Shunichi
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- Photocatalytic activity of titanium dioxide modified with thiourea under the action of visible light
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Photocatalyst powders were synthesized from nanosized titanium dioxide crystals modified by sintering with thiourea (TU). The powders contained anatase crystals of various sizes. TU-TiO2 powders absorbed visible light to produce an oxidizer (oxidizing iodide) and a reducing agent (reducing tetranitromethane). The activity of TU-TiO2 correlated with the size of nanocrystals. The photocatalytic activity of TU-TiO2 was suggested to be related to impurity states appearing during modification in the forbidden band of TiO2.
- Chubukov,Denisov,Gorenberg,Shilov,Kozlov,Groznov,Nadtochenko
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- Time-Resolved Reaction of O2(1Δ) with I- in Aqueous Solution
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The rate constant for quenching of O2(1Δ) by I- in room temperature aqueous solution has been determined by time-resolved measurement of the O21Δ -> 3Σ- emission at 1.3 μm as (8.7 +/- 0.2) * 105
- Braathen, Geir,Chou, Pi-Tai,Frei, Heinz
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- Direct and Indirect Oxidations by Peroxynitrite
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The mechanism of oxidation of iodide, Ni(II)cyclam, and ferrocyanide byperoxynitrite has been studied in detail. The results demonstrate that the oxidative chemistry of peroxynitrite is highly pH dependent and can take place either directly by the peroxynitrous acid, as in the case of iodide and Ni(II)cyclam, or indirectly by secondary reactive intermediates formed via the self-decomposition of peroxynitrous acid, as in the case of ferrocyanide. The rate constants of the oxidation of I(1-) and Ni(II)cyclam by ONOOH have been determined to be (2.3 .+-. 0.1) x 10**4 M**-1 s**-1 and (3.25 .+-. 0.15) x 10**4 M**-1 s**-1, respectively. In the indirect pathway, about 60% of ONOOH isomerizes to nitric acid and about40% is converted into a highly reactive oxidant which directly oxidizedferrocyanide via the formation of NO2.cntdot. as an intermediate without the involvement of hydroxyl radicals in this process.
- Goldstein, Sara,Czapski, Gidon
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- KINETIC STUDIES OF THE POLYIODIDE COMPLEX FORMATION IN THE IODINE-IODIDE SOLUTIONS.
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A relaxation obviously different from that due to the triiodide complex formation was observed by the temperature-jump experiments in the iodine-iodide solution. On the basis of the dependences of the relaxation time on the concentration of iodine and iodide and on the temperature, the relaxation was assigned to the complex formation of I//6**2** minus . The rate constants of the reaction were estimated to be 2. 2 multiplied by 10**5 M** minus **1 s** minus **1 and 5. 3 multiplied by 10**5 s** minus **1 for forward and backward processes, respectively.
- Sano,Hori,Yamamoto,Yasunaga
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- Copper catalysis of the oxidation of iodide by [FeIII(bpy) 2(CN)2]+ in acetonitrile
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Because of its potential relevance to the Graetzel photoelectrochemical cell, we have investigated the oxidation of iodide by [Fe(bpy) 2(CN)2]+ in acetonitrile solution at 25 °C. The reaction occurs on the stopped-flow time scale and is highly sensitive to catalysis by Cu2+, to the degree that, under typical conditions, the impurity levels of Cu2+ are sufficient to dominate the reaction. 2,2′-Bipyridine is a very effective inhibitor of the Cu2+ catalysis, and 1 μM Cu2+ can accelerate the rates by as much as a factor of 280, relative to the bpy-inhibited reaction.
- Wang, Xiaoguang,Stanbury, David M.
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- Radical Scavenging in the Sonolysis of Aqueous Solutions of I-, Br-, and N3-
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Iodide and bromide solutions are sonolyzed under pH conditions, where reactions of the products, i.e. hydrogen peroxide and iodine (or bromine), do not occur.The total yield of the products as well as the hydrogen yield is independent of solute concentration.The results are understood in terms of the competition of the OH + OH and the OH + solute reactions.A local concentration of 4*10-3 M of the OH radicals in an interfacial region between the cavitation bubbles and the liquid is derived from the data obtained.The sonolysis of azide solutions is also investigated.The main product is nitrogen, which is formed in the reaction of N3- with OH radicals in the millimolar concentration range.At higher azide concentrations, additional nitrogen is formed as hydrogen atoms are also scavenged.Ammonia and hydrazine are minor products of the N3- sonolysis.
- Gutierrez, Maritza,Henglein, Arnim,Ibanez, Fernando
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- The effect of hydroxycinnamic acids on oxy-radical generating iodide-hydrogen peroxide reaction
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The influence of hydroxycinnamic acids (HCA) on the oxy-radical generated system, potassium iodide/hydrogen peroxide, was investigated through the enhancement of triiodide (I3-) yield. Caffeic acid, chlorogenic acid, and p-coumaric acid were used as typical representatives of HCA. A linear correlation, with positive slopes, was found between absorption maximum of I3- at 351 nm and HCA concentration in all cases. The magnitude of enhanced I3- production was found to increase in the following order: p-coumaric acid A reaction mechanism, which includes negative influence of oxygen-centered free radicals on the I3- yield, was proposed. The enhanced production of I3- by HCA is attributed to their radical scavenging activity. Supported by literature data, results obtained in this study have showed the correlation between radical scavenging activities of HCA and their ability to enhanced I3- generation.
- Milenkovi, Maja C.,Potkonjak, Neboja I.
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- Heterogeneous Catalysis in Solution. Part 23.-Kinetics of a Redox System Showing Complete Mass-transport Control: The Hexacyanoferrate(III)+Iodide Reaction at a Rotating-platinum-disk Catalyst
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The rate of the reaction between Fe(CN)63- and I- has been measured from 5 to 30 deg C in 1 mol dm-3 aqueous KNO3 solution both homogenously and in the presence of a large anodically preconditioned platinum-disk catalyst rotating from 100 to 2000 rev. min-1.The catalytic rate agreed quantitatively with the mixture current (converted to a rate) at the point where the current-voltage curves of the two separate couples intersected; the mixture potential at this point also agreed well with the potential adopted by the catalysing disk, This confirmed the electrochemical mechanism of the platinum catalysis.That the catalytic process become wholly mass-transport controlled was shown by the fact that the catalytic rates always varied proportionately with the square root of the angular velocity (ο) of the disk, while the catalyst potential remained independent of ο.Other predictions of the theory in the preceeding paper to be fulfilled within experimental error were kinetic orders of the heterogeneous reaction, the marked changes in these orders on adding the product Fe(CN)64- to the initial mixture, and the negative Arrhenius activation energy associated with the catalytic rate constant.
- Freund, Paul L.,Spiro, Michael
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- Polyiodine and polyiodide species in an aqueous solution of iodine + KI: Theoretical and experimental studies
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In the presence of KI, iodine crystals dissolve rapidly in an aqueous solution forming triiodide ions (I3-) and other neutral species. The experimental evidence does not support the formation of polyiodide ions such as I5-, I7-, etc. in the solution. However, there is a strong evidence suggesting the formation of polyiodine species, I2x where x = 2, 3, etc., stabilized by H+ ions in the solution. Ab initio results are presented for structures and energies of some of these species with an x value of up to 4. Each geometry optimization was done at the HF/LANL2DZ level followed by a single-point energy calculation at the MP2/LANL2DZ level. These calculations suggest that the isolated polyiodine species are not stable and, among the complexed species, the protonated clusters are most stable.
- Calabrese, Vincent T.,Khan, Arshad
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- Kinetics and mechanism of the copper(II)-catalyzed oxidation of the iodide ion to iodine by the vanadium(V) ion in an aqueous solution
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The vanadium(V) ion, which is described as Vv herein, could hardly oxidize the iodide ion to iodine at pH 2.8; however, the oxidation reaction occurred catalytically upon adding traces of copper(II) ion. When a copper(II) solution of 10-8 - 10-5 M (M = mol dm-3) was mixed with an iodide solution, after a rapid formation of iodine, the iodine concentration remained constant. After such iodine formation had occurred, if a Vv solution was added into the reacting mixture, the iodine began to form again in accordance with a rate law of 2(d[I2]/dt) = -d[Vv]/dt = k[CuI][Vv], in which [CuI] is a steady-states' concentration in a chain cycle CuI+/CuI. The reaction rate was independent of the time to add the Vv ion, and the formation of iodine I2 (or triiodide ion I3-) stopped at the time when all of the Vv was consumed, indicating the stoichiometry to be 2I-+2VV→I2+2VIV. The initial rate (Vi) after Vv addition was proportional to the concentrations of not only the added Vv over the range 10-6 - 10-5 M, but also the added copper(II) ion. Although a self-inhibiting effect did not appear over the pH range 2.8 - 3.6, it occurred at pH > 3.6. It was found that such a retarding effect was caused by the vanadium(IV) ion (denoted as VIV herein), which was the reduced product of Vv; the VIV inhibiting effect was extremely dependent on the pH in the reacting solution. The mechanisms for the retardation reaction as well as iodine formation are discussed in terms of accounting for the obtained results.
- Kimura, Masaru,Shiga, Yuko,Tsukahara, Keiichi
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- Heterogeneous Catalysis in Solution. Part 19. The Effect on Oxidation-Reduction Reactions of Certain Sparingly Soluble Salts and Other Solids
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The addition of various semiconducting solids (silicon and metal sulphides) and of two ionically conducting solids appeared either to catalyse or inhibit the rate of iodine formation by the reactions (3-) + I(-) in aqueous solution.The curious effect of CuI on the latter reaction was investigated in more detail.Adsorption experiments demonstrated that (3-) and I3(-) chemically attacked these solids.Their chemical instability in the presence of the oxidants or the reaction mixtures was confirmed by thermodynamic calculations and the observed kinetic effects could then be explained.Only silica and silver(I) iodide did not affect the rates of the reactions; adsorption tests and thermodynamic calculations showed that these two solids were stable under the experimental conditions.The catalytic effect produced by a solid is therefore genuine only if kinetic and/or thermodynamic evidence has established its chemical stability in the reaction mixture.
- Groenewald, Theo,Austin, Jack M.,Spiro, Michael
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- Peptide-induced hierarchical long-range order and photocatalytic activity of porphyrin assemblies
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Long-range structural order and alignment over different scales are of key importance for the regulation of structure and functionality in biology. However, it remains a great challenge to engineer and assemble such complex functional synthetic systems with order over different length scales from simple biologically relevant molecules, such as peptides and porphyrins. Herein we describe the successful introduction of hierarchical long-range order in dipeptide-adjusted porphyrin self-assembly by a thermodynamically driven self-orienting assembly pathway associated with multiple weak interactions. The long-range order and alignment of fiber bundles induced new properties, including anisotropic birefringence, a large Stokes shift, amplified chirality, and excellent photostability as well as sustainable photocatalytic activity. We also demonstrate that the aligned fiber bundles are able to induce the epitaxially oriented growth of Pt nanowires in a photocatalytic reaction.
- Liu, Kai,Xing, Ruirui,Chen, Chengjun,Shen, Guizhi,Yan, Linyin,Zou, Qianli,Ma, Guanghui,M??hwald, Helmuth,Yan, Xuehai
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- The Kinetics and Mechanism of the Chlorine Dioxide - Iodide Ion Reaction
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The oxidation of iodide ion by chlorine dioxide has been studied by stopped-flow techniques at I = 1.0 M (NaClO4). The following two-term rate law was confirmed for the reaction: -d[ClO2]/dt = kI[ClO2][I-/
- Fábián, István,Gordon, Gilbert
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- Radiolysis of Concentrated Solutions. 2. Pulse and γ-Radiolysis Studies of Direct and Indirect Effects in Lithium Iodide Solutions
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In the preceding study of the radiolysis of concentrated aqueous LiCl solutions (ref 6), one of the hypotheses used to explain the apparent inefficacy of Cl2(1-) formation by the direct effect was that molecular chlorine, not detectable by spectrophotometry, could be formed during the early stages of water radiolysis.Such an hypothesis is confirmed here for pulse and γ-radiolysis of concentrated aqueous neutral LiI solutions.Indeed, it is shown that, 10 ns after the pulse, molecular iodine, detected as I3(1-), is formed with a yield that increases with the LiI concentration.The experimental results yields values of 4.8 and 7.3 respectively for the indirect and direct effects of total oxidation GI2(1-) + 2GI3(1-).This last high value is discussed.
- Hadjadj, A.,Julien, R.,Pucheault, J.,Ferradini, C.,Hickel, B.
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- Photoredox decomposition of tin(II), lead(II), antimony(III) and bismuth(III) iodide complexes in solution
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The main group metal complexes SnI3- , PbI3- , SbI4- and BiI4- display long-wavelength absorption bands which are assigned to sp/ LMCT transitions. The photochemistry of these complexes is determined by the CT character of their lowest-energy excited state. The photolysis in acetonitrile leads to a photoredox decomposition which yields I3- and the elemental metals as final products. The results of the continuous photolysis are supplemented by observations on the flash photolysis of PbI3-.
- Oldenburg, Karin,Vogler, Arnd,Miko, Ildiko,Horvath, Otto
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- Kinetics and Mechanisms of the Vanadium(IV)-Catalyzed Oxidation of Iodide Ion in the Presence of Molecular Oxygen in an Acid Solution
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The kinetics of the oxidation of iodide ion to iodine by molecular oxygen catalyzed by VO2+ ions were studied in sulfuric acid solutions in the dark.After an induction period during which time the I2-radical anion forms, the rate of formation of iodine increased due to catalysis by VO2+ ions.The rate of reaction depended on the concentrations of VO2+, H+, and I-, and was independent of the ionic strength.The reaction was inhibited by either radical scavengers or the complex-forming substances of ethylenediaminetetraacetic acid and chloride ions.A chain mechanism containing I2-radical anion/I2, VO2+/V3+, and O2/HO2-radical redox cycles is presented.
- Kimura, Masaru,Hara, Tomoko,Tsukahara, Keiichi
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- Enhancing the photocatalytic efficiency of the BiOCl/Bi3O4Cl composite modified with WO3for environmental purification under visible light
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Covering the BiOCl/Bi3O4Cl composite with a monolayer of WO3resulted in a significant increase in the photocatalytic activity of WO3/BiOCl/Bi3O4Cl in the presence of visible light (?= 420 nm). The decomposition of gaseous isopropyl alcohol (IPA) and aqueous salicylic acid (SA) in the presence of visible light was maximized when 0.2 mol% of WO3was attached to the surface of BiOCl/Bi3O4Cl. However, while the amount of WO3on the surface of BiOCl/Bi3O4Cl was less or more than 0.2 mol%, the photocatalytic activity was found to be abruptly reduced. At this composition, WO3/BiOCl/Bi3O4Cl demonstrated 2.1 and 5.2 times better activity than the BiOCl/Bi3O4Cl composite and Degussa P25 (TiO2nanoparticle) for evolving CO2from the decomposition of IPA in gas phase under the identical conditions. These results suggest that 0.2 mol% WO3/BiOCl/Bi3O4Cl was the optimized composition to achieve the highest photocatalytic activity covering of BiOCl/Bi3O4Cl through the formation of a monolayer by molecular WO3. On the surface of BiOCl/Bi3O4Cl, the function of WO3is to offer increasing OH-, H2O or organics towards WO3/BiOCl/Bi3O4Cl by increasing the adsorption affinity of WO3/BiOCl/Bi3O4Cl. Furthermore, the chemical durability of BiOCl/Bi3O4Cl was increased due to the covering of BiOCl/Bi3O4Cl with WO3. Considering the above findings, the role of WO3in enhancing the photocatalytic efficiency of BiOCl/Bi3O4Cl has been explained in detail.
- Chakraborty, Ashok Kumar,Ganguli, Sumon,Bera, Sandipan
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p. 17617 - 17629
(2021/10/04)
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- Preparation of CdS/BiOCl/Bi2O3 double composite system for visible light active photocatalytic applications
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An efficient visible-light-harvesting (λ ≥ 420 nm) three component system heterojunction photocatalyst, CdS/BiOCl/Bi2O3 was prepared by anchoring of CdS nanoparticles on the surface of BiOCl/Bi2O3 composite. The effect of CdS nanoparticles on the surface of BiOCl/Bi2O3 composite photocatalyst had been justified in enhancing photocatalytic activity towards the degradation of organic pollutants in gas as well as aqueous phase. With the loading of CdS on to the BiOCl/Bi2O3 heterojunction composite photocatalyst, the photocatalytic activity of the CdS/BiOCl/Bi2O3 composite structure has been appreciably improved for the decomposition of 2-propanol (IPA) in gas phase and salicylic acid (SA) in aqueous phase under visible light irradiation (λ ≥ 420 nm). The amount of loading of CdS nanoparticles was optimized to 2 mol% CdS/BiOCl/Bi2O3. Compare to bare BiOCl/Bi2O3 photocatalyst, CdS/BiOCl/Bi2O3 heterojunction demonstrated 2 times decomposition of IPA in gas phase and 1.8 times of SA in aqueous phase after 120 min. of visible light irradiation. At the same time, with this composition the evolution of CO2 from degradation of IPA was 1.9 times higher than that of BiOCl/Bi2O3 composite. The enhanced photocatalytic efficiency is deduced from the electron (eˉ) and hole (h+) transfer among the component semiconductor nanoparticles Bi2O3, BiOCl and CdS due to their relative energy band positions. Several experimental evidences were also provided to confirm the electron-hole transfer among the semiconductors and a mechanistic way has been proposed.
- Chakraborty, Ashok Kumar,Ganguli, Sumon,Bera, Sandipan,Lee, Wan In
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p. 159 - 168
(2018/06/14)
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- Synthesis, structural and magnetic characterizations of a dinuclear copper(II) complex with an (N,S,O) donor ligand: Catecholase and phenoxazinone synthase activities
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A new dinuclear Cu(II) complex (1) was synthesized and crystallographically characterized. Each of the Cu(II) centres has penta coordination and been found to adopt square pyramidal geometry. Variable temperature magnetic measurements showed that there is weak ferromagnetic interaction between the Cu(II) centres in 1. 1 shows catecholase as well as phenoxazinone synthase activities in different solvents. The turn over numbers for the catecholase activity were 4.02 × 103 h?1 (MeOH) and 9.57 × 103 h?1 (MeCN), and that of phenoxazinone synthase activity were 1.065 × 103 h?1 (MeOH), 2.13 × 102 h?1 (MeCN) and 2.844 × 103 h?1 (DCM).
- Ghosh, Ayon Kanti,Ali, Anzar,Singh, Yogesh,Purohit, Chandra Shekhar,Ghosh, Rajarshi
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p. 156 - 163
(2018/02/20)
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- Mechanism and scope of the base-induced dehalogenation of (E)-diiodoalkenes
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A wide range of nucleophiles have induced the elimination of iodine from (E)-diiodoalkenes to form alkynes under surprisingly mild conditions. The iodide anion is particularly efficient, and can drive the reaction to completion in less than 1 hour at room temperature in a polar aprotic solvent. Detailed investigations have suggested the reaction has a bimolecular polar mechanism. The deiodination reaction can be driven to completion with 1 equiv. of nucleophile and is partially catalytic with substoichiometric amounts of deiodinating reagent. Kinetic analysis of the stoichiometric iodide-induced reaction indicated an overall pseudo-first-order behavior. The reaction exhibited strong solvent effects, with much slower reactions observed in protic solvents than in polar aprotic solvents. The substrate dimethyl (2E)-2,3-diiodo-butene-2-dioate demonstrated orthogonal reactivity for either elimination or hydrolysis, depending on the solvent and nucleophile used. This reaction is a major pathway for all the diiodoalkenes examined, and represents a challenge and an opportunity for using these substrates in organic synthesis.
- Resch, Daniel,Lee, Chang Heon,Tan, Siew Yoong,Luo, Liang,Goroff, Nancy S.
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p. 730 - 737
(2015/01/30)
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- On the complexity of kinetics and the mechanism of the thiosulfate- periodate reaction
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The thiosulfate-periodate reaction has been studied spectrophotometrically in a slightly acidic medium at 25.0 ± 0.1 °C in an acetate/acetic acid buffer by monitoring the absorbance in the 250-600 nm wavelength range at a constant ionic strength adjusted by the buffer component sodium acetate. In agreement with a previous study, we found that the reaction cannot be described by a single stoichiometric equation, tetrathionate and sulfate are simultaneously formed, and its ratio strongly depends on the pH. As expected at certain initial concentration ratios of the reactants, the reaction behaves as a clock reaction, but after its appearance, iodine is slowly consumed mainly because of the moderate tetrathionate-iodine reaction. It is also enlightened that the initial rate of the reaction is completely independent of the pH, which apparently contradicts a previous study, which postulates a "supercatalytic" behavior of the hydrogen ion on the title reaction. Significant buffer assistance that may change the absorbance-time profiles was also observed. On the basis of the kinetic data, a robust 28-step kinetic model with 22 fitted parameters is proposed and discussed to explain adequately all of the important characteristics of the kinetic curves.
- Rauscher, Evelin,Cseko, Gyoergy,Horvath, Attila K.
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p. 5793 - 5802
(2011/07/29)
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- Acid-catalysed chlorine transfer from N-chloramines to iodide ion: Experimental evidence for a predicted change in mechanism
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Rate constants for acid catalysis of the reactions of N-chlorodimethylamine (1), N-chloro-2,2,2-trifluoroethylamine (2) and N,N-dichlorotaurine (3) with iodide ion were determined in H2O at 25°C and I = 0.5 (NaClO 4). The failure to detect significant catalysis by general acids of chlorine transfer from 1 to the nucleophile, together with the observed inverse solvent deuterium isotope effect on the hydronium ion-catalysed reaction (k H/kD = 0.37), indicates that this process occurs by protonation of 1 in a fast equilibrium step, followed by rate determining chlorine transfer to iodide ion. The appearance of general acid catalysis for the reactions of 2 and 3 shows that increasing the leaving group ability leads to a change to a concerted mechanism, which is suggested to be enforced by the absence of a significant lifetime of the protonated chloramine intermediate in the presence of iodide ion.
- Calvo, Paula,Crugeiras, Juan,Rios, Ana
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p. 4137 - 4142
(2010/10/19)
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- One- versus two-electron oxidation with peroxomonosulfate ion: reactions with iron(II), vanadium(II), halide ions, and photoreaction with cerium(III)
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The kinetics of the redox reactions of the peroxomonosulfate ion (HSO 5-) with iron(ll), vanadium(IV), cerium(lll),chloride, bromide, and iodide ions were studied. Cerium(lll) is only oxidized upon illumination by UV light and cerium
- Lente, Gabor,Kalmar, Jozsef,Baranyai, Zsuzsa,Kun, Aliz,Kek, IIdikoe,Bajusz, David,Takacs, Marcell,Veres, Lilla,Fabian, Istvaen
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p. 1763 - 1773
(2009/06/17)
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- Mechanism of enhancement of sonochemical-reaction efficiency by pulsed ultrasound
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The enhancement of sonochemical-reaction efficiency by pulsed ultrasound at 152 kHz has been studied experimentally through absorbance measurements of triiodide ions from sonochemical oxidation of potassium iodide at different liquid volumes to determine
- Tuziuti, Toru,Yasui, Kyuichi,Lee, Judy,Kozuka, Teruyuki,Towata, Atsuya,Iida, Yasuo
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p. 4875 - 4878
(2009/03/11)
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- Kinetics and mechanisms of the oxidation of iodide and bromide in aqueous solutions by a trans-dioxoruthenium(VI) complex
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The kinetics and mechanisms of the oxidation of I- and Br - by trans-[RuVI(N2O2)(O) 2]2+ have been investigated in aqueous solutions. The reactions have the following stoichiometry: trans-[RuVI(N 2O2)(O)2]2+ + 3X- + 2H+ → trans-[RuIV(N2O2)(O) (OH2)]2+ + X3- (X = Br, I). In the oxidation of I- the I3- is produced in two distinct phases. The first phase produces 45% of I3- with the rate law d[I3-]/dt = (ka + k b[H+])[RuVI][I-]. The remaining I3- is produced in the second phase which is much slower, and it follows first-order kinetics but the rate constant is independent of [I-], [H+], and ionic strength. In the proposed mechanism the first phase involves formation of a charge-transfer complex between Ru VI and I-, which then undergoes a parallel acid-catalyzed oxygen atom transfer to produce [RuIV(N2O 2)(O)(OHI)]2+, and a one electron transfer to give [RuV(N2O2)(O)(OH)]2+ and I .. [RuV(N2O2)(O)(OH)]2+ is a stronger oxidant than [RuVI(N2O2)(O) 2]2+ and will rapidly oxidize another I- to I.. In the second phase the [RuIV(N2O 2)(O)(OHI)]2+ undergoes rate-limiting aquation to produce HOI which reacts rapidly with I- to produce I2. In the oxidation of Br- the rate law is -d[RuVI]/dt = {(k a2 + kb2[H+]) + (ka3 + A b3[H+]) [Br-]}[RuVI][Br -]. At 298.0 K and I = 0.1 M, ka2 = (2.03 ± 0.03) × 10-2 M-1 s-1, kb2 = (1.50 ± 0.07) × 10-1 M-2 s-1, k a3 = (7.22 ± 2.19) × 10-1 M-2 s-1 and kb3 = (4.85 ± 0.04) × 102 M-3 s-1. The proposed mechanism involves initial oxygen atom transfer from trans-[RuVI(N2O2)(O) 2]2+ to Br to give trans-[RuIV(N 2O2)(O)(OBr)]+, which then undergoes parallel aquation and oxidation of Br-, and both reactions are acid-catalyzed.
- Lam, William W. Y.,Man, Wai-Lun,Wang, Yi-Ning,Lau, Tai-Chu
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p. 6771 - 6778
(2009/02/06)
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- Freezing halide ion solutions and the release of interhalogens to the atmosphere
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The effect of freezing on a variety of acidified and neutral, nitrite ion and halide-containing mixtures has been investigated using UV/vis spectroscopy. Several trihalide ions were formed and monitored, including I2Cl -, I2Br-, ICI2- and IBr2-. A mechanism to explain the observations is given in terms of steps involving INO and the nitroacidium ion, [H2ONO] +. The transformation of sea salt components to specific trihalide ions by freezing represents a potentially important process in a polar atmospheric context. This is because the dichloro- and dibromo-trihalide ions can release chlorine- and bromine-containing gases, which are key intermediates in ozone destruction.
- O'Driscoll, Paul,Lang, Kathrin,Minogue, Nicholas,Sodeau, John
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p. 4615 - 4618
(2008/10/09)
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- Oxidation of iodide by a series of Fe(III) complexes in acetonitrile
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The oxidations of iodide by [FeIII(bpy)2(CN) 2]NO3, [FeIII(dmbpy)2(CN) 2]NO3, [FeIII(CH3Cp) 2]PF6, and [FeIII(5-Cl-phen) 2-(CN)2]NO3 at 25°C, ionic strength of 0.10 M in acetonitrile, are catalyzed by trace levels of copper ions. This copper catalysis can be effectively masked with the addition of 5.0 mM 2,2′-bipyridine (bpy), which permits the rate law of the direct reactions to be determined: -d[Fe(III)]/dt = 2(k1[1-] + k 2[l-]2)[Fe(III)]. According to 1H NMR and UV-vis spectra, the products of the reaction are I3 - and the corresponding Fe(II) complexes, with the stoichiometric ratio (Δ[I3-] /Δ[Fe(II)]) of 1:2. Linear free-energy relationships (LFERs) are obtained for both log k1 and log k2 vs E1/2 with slopes of 16.1 and 13.3 V -1, respectively. A mechanism is inferred in which k1 corresponds to simple electron transfer to form I. plus Fe(II), while k2 leads directly to I2-.. From the mild kinetic inhibition of the k1 path by [FeII(bpy) 2(CN)2] the standard potential (E°) of l ./l- is derived: E° = 0.60 ± 0.01 V (vs [Fe(Cp)2]+/0).
- Wang, Xiaoguang,Stanbury, David M.
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p. 3415 - 3423
(2008/10/09)
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- Pulse radiolysis study of I- oxidation with radical anions Cl2.- in an aqueous solution
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Radiation-chemical transformations of chloride solutions in the presence of iodide additives were studied by pulse radiolysis. Radical anion Cl 2.- oxidize I- ion, while in the secondary reactions Cl2 reacts with I- to form a mixed trihalide ion ICl2-. A reaction model that satisfactorily describes the experimental data was proposed.
- Ershov,Janata,Gordeev
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p. 1378 - 1382
(2007/10/03)
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- Two- and three-body photodissociation of gas phase I3 -
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The photodissociation dynamics of gas phase I-3 by using a fast beam photofragment translational spectrometer was examined. It was stated that the photofragment translational spectrometer was coupled to a coincidence imaging detector that enabled the direct detection and analysis of two and three neutron or anion fragments from single dissociation events. The three-body dissociation yielding I-+2I(2P3/2) photofragments was also seen throughout the energy range probed. Analysis shows that the three-body decay dynamics was dominated by synchronous concerted dissociation.
- Hoops, Alexandra A.,Gascooke, Jason R.,Faulhaber, Ann Elise,Kautzman, Kathryn E.,Neumark, Daniel M.
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p. 7901 - 7909
(2007/10/03)
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- Photochemistry of trimethyltin iodide in polar media: Orbital parentage and observed reactivity
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(CH3)3Snl exists as individual tetrahedral molecules in hexane but reacts with the silanol moieties present on the surface of porous glass and with the hydroxyl group of ethanol and hexanol to form five-coordinate adducts. With the exception of slight shifts to higher energy, formation of the adduct has little effect on the electronic spectrum of the complex, and the wavelength and O2 dependencies of the quantum yield of (CH3)3Snl disappearance indicate that the photochemistry of the complex initiates from the ligand-to-metal charge-transfer (LMCT) state populated on absorption in each medium. Nevertheless, 254 nm excitation in hexane leads to l2 and ((CH3)3Sn)2, whereas excitation of the five-coordinate adduct on the glass surface leads to l2, l3-, ((CH3)3Sn)2, and (CH3)3Sn-OSi≡ (OSi≡ represents a surface siloxyl), while in ethanol, l3- is the only detectable product. Regardless of the medium, the ground state is polarized and population of the LMCT state creates a more uniform charge distribution from which homolytic cleavage of the (CH3)3Sn-l bond is the dominant reaction pathway in each medium. In hexane, the (CH3)3Sn? and l? radicals couple to form ((CH3)3Sn)2 and l2, whereas adsorbed onto the glass, a fraction of the radical pairs thermalize via electron transfer to form l3- and a surface-bound (CH3)3Sn-OSi≡ species. In ethanol, excitation of the solvent adduct (CH3)3Sn-OHC2H5 leads to homolytic cleavage and l2 formation, which reacts thermally with (CH3)3Sn-OHC2H5 to form an [(CH3)3Sn+, l3-] ion pair.
- Dong, Jinquan,Devi, P. Sujatha,Sunil,Mendoza, Edgar,Gafney, Harry D.
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- CO2-Catalyzed One-Electron Oxidations by Peroxynitrite: Properties of the Reactive Intermediate
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In neutral bicarbonate-containing solutions, the predominant pathway for peroxynitrite decomposition was CO2-catalyzed formation of nitrate ion; that is, CO2 was regenerated in the process. When nitrite ion was present HCO3- also formed during ONO2- decomposition. The data could be reproduced by a kinetic model wherein a reactive intermediate formed from ONO2- and CO2 oxidizes NO2- to ?NO2, which subsequently hydrolyzes in a bimolecular reaction to form NO3- and regenerate NO2-. Carbon dioxide catalyzed one-electron oxidations of Fe(CN)64-, Mo(CN)4-, Os(bpy)32+, Fe(bpy)32+, Ru(bpy)2-, and I- were also observed, establishing that the reactive intermediate is capable of oxidizing compounds whose reduction potentials are as great as 1.3 V. The maximal product yields, measured for reactions with NO2-, Fe(CN)-4-, and Mo(CN)84-, were all ~35% of the added peroxynitrite, suggesting that they were oxidized by a common intermediate. On the basis of the reactivity characteristics revealed, the intermediate is suggested to be carbonate radical formed by homolytic decomposition of an ONO2CO2- adduct.
- Lymar, Sergei V.,Hurst, James K.
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p. 294 - 301
(2008/10/08)
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- Reactivity of Peroxynitric Acid (O2NOOH): A Pulse Radiolysis Study
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Peroxynitrate (O2NOOH/O2NOO-) is formed within less than 2 ms after pulse irradiation of aerated solutions containing relatively low concentrations of formate and nitrate. The pKa for peroxynitric acid was determined to be 5.9 ± 0.1 both from the pH-dependent absorbance of the anion at 310 nm and from the dependence of the decay kinetics on pH. An absorption spectrum was measured for the anion giving εmax(290) = 1500 ± 100 M-1 cm-1. This method of generation of peroxynitrate is very useful for studying the mechanism of the oxidation of various substrates by peroxynitrate. The oxidation by peroxynitrate can take place either directly or indirectly. In the direct oxidation pathway, the reaction is first order in peroxynitrate and first order in the substrate, whereas in the indirect oxidation pathway, the reaction is zero order in the substrate. In both cases, the observed rate constants are highly pH-dependent. The results show that the direct oxidation pathway takes place through O2NOOH. We suggest that the indirect oxidation takes place through reactive intermediates that are formed during the decomposition of peroxynitrate. In the presence of sufficient concentrations of the substrates, the oxidation yields approach 100% through the direct and indirect oxidation pathways.
- Goldstein, Sara,Czapski, Gidon
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p. 4156 - 4162
(2008/10/09)
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- Spontaneous reactions and reduction by iodide of peroxynitrite and peroxynitrate: mechanistic insight from activation parameters
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Thermal and pressure activation parameters are reported for the decomposition of peroxynitrate, isomerization of peroxynitrite, and their reduction by iodide in aqueous solutions. The spontaneous decomposition reactions are characterized by activation ent
- Goldstein,Meyerstein,van Eldik,Czapski
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p. 7114 - 7118
(2007/10/03)
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- Kinetics and Mechanism of the Oxidation of Iodide by trans-Dioxoruthenium(VI)
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The kinetics of reduction of trans-(2+) (tmc = 1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane) by iodide has been studied in aqueous acidic solution.The reaction has the following stoichiometry: trans-(2+) + 3I(1-) + 2H(1+) --> trans-(2+) + I3(1-).The rate low is -d/dt = (ka + kb) with ka = 0.041 +/- 0.013 dm3 mol-1 s-1 and kb = 18.5 +/- 0.2 dm6 mol-2 s-2 at 25.0 deg C and 0.1 mol dm-3 ionic strength.For ka ΔH(excit.) = 42.9 +/- 9.4 kJ mol-1 and ΔS(excit.) = -131 +/- 40 J K-1 mol-1, while for kb, ΔH(excit.) = 36.9 +/- 2.9 kJ mol-1 and ΔS(excit.) = -97 +/- 10 J K-1 mol-1.A mechanism involving oxygen-atom transfer from Ru(VI) to iodide is consistent with the data.
- Lau, Tai-Chu,Lau, Kent W. C.,Lau, Keung
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p. 3091 - 3094
(2007/10/02)
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- A new type of oxyhalogen oscillator: The bromite-iodide reaction in a continuous flow reactor
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The reaction between bromite and iodide ions in a flow reactor shows two steady states and sustained oscillations in pH, redox potential, and [I-]. The oscillatory behavior is extremely sensitive to the inflow ratio [BrO2-]/[I-], the flow rate, the initial pH of the input solutions, and the stirring rate. Batch experiments suggest that the system behaves in several respects like the analogous chlorite-iodide oscillator. The bromite-iodide system, however, is also a pH oscillator and is the first oxyhalogen oscillator to oscillate in the neutral and basic pH range.
- Orbán, Miklós,Epstein, Irving R.
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p. 1252 - 1256
(2007/10/02)
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- A pulse radiolysis study of the reaction of OH with I2 and the decay of I2-
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The rate constant for the reaction of the hydroxyl radical with iodine was estimated to be (9.5 +/- 1.0) * 10-9 dm3 mol-1 s-1 at 20 deg C from fitting the time dependence of the decrease in the absorption of iodine at 460 nm.A number of rate constants associated with the decay of I2- that were required for this fitting process were also determined.They were the reaction of I2- with I2- (2k = (4.60 +/- 0.05) * 10-9 dm3 mol-1 s-1) at an ionic strength of 1.2 * 10-2 mol dm-3; I2- with I (k = 4.6 +/- 1.6) * 10-9 dm3 mol-1 s-1); and I with I (2k = (3.0 +/- 1.0) * 10-10 dm3 mol-1 s-1).
- Elliot, A. John
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p. 1658 - 1661
(2007/10/02)
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- Kinetic estimation of aminopolycarboxylic acids using their catalytic effect on chromium(VI)-iodide reaction
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Aminopolycarboxylic acids NTA, HEDTA and DTPA catalyse the chromium (VI)-iodide reaction.Based on this a kinetic spectrophotometric method for the determination of microgram quantities of NTA (5 to 70 μg/ml), HEDTA (19 to 138 μg/ml) and DTPA (5 to 52 μg/ml) has been developed.
- Satyanarayana, Tatakuntla,Mushini, Ramakrishna,Anipindi, Nageswara Rao
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p. 936 - 937
(2007/10/02)
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