- Hypohalite ion catalysis of the disproportionation of chlorine dioxide
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The disproportionation of chlorine dioxide in basic solution to give ClO2- and ClO3- is catalyzed by OBr- and OCl-. The reactions have a first-order dependence in both [ClO2] and [OX-] (X = Br, Cl) when the ClO2- concentrations are low. However, the reactions become second-order in [ClO2] with the addition of excess ClO2-, and the observed rates become inversely proportional to [ClO2-]. In the proposed mechanisms, electron transfer from OX- to ClO2 (k1OBr- = 2.05 ± 0.03 M-1 s-1 for OBr-/ClO2 and k1OCl- = 0.91 ± 0.04 M-1 s-1 for OCl-/ClO2) occurs in the first step to give OX and ClO2-. This reversible step (k1OBr-/k-1OBr- = 1.3 × 10-7 for OBr-/ClO2, k1OCl-/k-1OCl = 5.1 × 10-10 for OCl-/ClO2) accounts for the observed suppression by ClO2-. The second step is the reaction between two free radicals (XO and ClO2) to form XOClO2. These rate constants are k2OBr = 1.0 × 108 M-1 s-1 for OBr/ClO2 and k2OCl = 7 × 109 M-1 s-1 for OCl/ClO2. The XOClO2 adduct hydrolyzes rapidly in the basic solution to give ClO3- and to regenerate OX-. The activation parameters for the first step are ΔH1? = 55 ± 1 kJ mol-1, ΔS1? = - 49 ± 2 J mol-1 K-1 for the OBr-/ClO2 reaction and ΔH1? = 61 ± 3 kJ mol-1, ΔS1? = - 43 ± 2 J mol-1 K-1 for the OCl-/ClO2 reaction.
- Wang, Lu,Margerum, Dale W.
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- Photoinduced reaction between chlorine dioxide and iodine in acidic aqueous solution
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Photoinduced reaction between ClO2 and I2 has been discovered under illumination with 460 nm lightband. The photochemical reaction has a variable stoichiometry in acidic aqueous solution because the induced disproportionation of ClO2 to ClO3- and Cl- competes with the oxidation of I2 to IO3- by ClO2 in the illuminated reaction mixture. The reaction rate depends on the light power of illumination and on the concentration of I2, but it is independent of the concentration of ClO2. It is also independent of the pH in the range of 0-2.0 and of the ionic strength in the range of 0.01-1.0 M. Reversible dissociation of I2 has been identified as the primary photochemical process and rate-determining step in the mechanism. Reactive I atoms are considered to initiate fast reaction steps, leading to the formation of products through reactive intermediates such as IClO2, ClO, IO, and HOCl. This mechanism is proposed for explaining the photoresponses of the CDIMA oscillatory reaction system to the illumination with visible light.
- Rabat, Gyula,Kovacs, Klara M.
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- New pathways for chlorine dioxide decomposition in basic solution
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The product distribution from the decay of chlorine dioxide in basic solution changes as the ClO2 concentration decreases. While disproportionation reactions that give equal amounts of ClO2- and ClO3- dominate the stoichiometry at millimolar or higher levels of ClO2, the ratio of ClO2- to ClO3- formed increases significantly at micromolar ClO2 levels. Kinetic evidence shows three concurrent pathways that all exhibit a first-order dependence in [OH-] but have variable order in [ClO2]. Pathway 1 is a disproportionation reaction that is first order in [ClO2]. Pathway 2, a previously unknown reaction, is also first order in [ClO2] but forms ClO2- as the only chlorine-containing product. Pathway 3 is second order in [ClO2] and generates equal amounts of ClO2- and ClO3-. A Cl2O4 intermediate is proposed for this path. At high concentrations of ClO2, pathway 3 causes the overall ClO3- yield to approach the overall yield of ClO2-. Pathway 2 is attributed to OH- attack on an oxygen atom of ClO2 that leads to peroxide intermediates and yields ClO2- and O2 as products. This pathway is important at low levels of ClO2.
- Odeh, Ihab N.,Francisco, Joseph S.,Margerum, Dale W.
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- Kinetics and mechanism of catalytic decomposition and oxidation of chlorine dioxide by the hypochlorite ion
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The oxidation of ClO2 by OCl-is first order with respect to both reactants in the neutral to alkaline pH range: -d[ClO2]/dt = 2kOCl[ClO2][OCl-]. The rate constant (T = 298 K, μ = 1.0 M NaCl
- Csordas,Bubnis,Fabian,Gordon
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- Spontaneous decomposition of industrially manufactured sodium hypochlorite solutions
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Spontaneous decomposition of industrially manufactured aqueous solutions of sodium hypochlorite was studied. The rate constants of the decomposition reactions were calculated for different pH values.
- Sizeneva,Kondrashova,Val'tsifer
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- Bromite ion catalysis of the disproportionation of chlorine dioxide with nucleophile assistance of electron-transfer reactions between ClO2 and BrO2 in basic solution
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The rate of ClO2 conversion to ClO2- and ClO3- is accelerated by BrO2-, repressed by ClO2-, and greatly assisted by many nucleophiles (Br- > PO43- > HPO42- > CO32- > Cl- ~ OH- > CH3COO- ~ SO42- C5H5N ? H2O). The kinetics (at p[H+] = 9.3-12.9) show that the first step of the mechanism is an electron transfer between ClO2 and BrO2- (k1 = 36 M-1 s-1) to give ClO2- and BrO2. This highly reversible reaction (k1/k-1 = 1 × 10-6) accounts for the observed inhibition by ClO2-. The second step is an electron transfer between ClO2 and BrO2 to regenerate BrO2- and form ClO3-. A novel aspect of the second step is the large kinetic contribution from nucleophiles (kNu) that assist the electron transfer between ClO2 and BrO2. The kNu (M-2 s-1) values at 25.0 °C vary from 2.89 × 108 for Br- to 2.0 × 104 for H2O.
- Wang, Lu,Nicoson, Jeffrey S.,Huff Hartz, Kara E.,Francisco, Joseph S.,Margerum, Dale W.
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- Concerted dismutation of chlorite ion: Water-soluble iron-porphyrins as first generation model complexes for chlorite dismutase
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Three iron-5,10,15,20-tetraarylporphyrins (Fe(Por-Ar4), Ar = 2,3,5,6-tetrafluro-N, N, N-trimethylanilinium (1), N, N, N-trimethylanilinium (2), and p-sulfonatophenyl (3)) have been investigated as catalysts for the dismutation of chlorite (CIO
- Zdilla, Michael J.,Lee, Amanda Q.,Abu-Omar, Mahdi M.
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- Two-dimensional cluster catalysts with superior thermal stability and catalytic activity for AP
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The preparation of catalysts with small particle size, large specific surface area and high atomic utilization has always been the focus of research in the field of catalysis. As for energetic materials, catalysts are always used to improve the thermal decomposition performance of ammonium perchlorate (AP) as it has significant effect on the power of engine. In this work, a two-dimensional metal clusters catalyst has been successfully prepared by solvothermal and heat treatment to improve thermal decomposition performance of AP. In detail, the transition metal ions were supported on the graphene oxide (GO) surface by organic ligands linking, followed by heat treatment to obtain two-dimensional rGO based metal clusters catalyst. The morphology and structure of the catalysts at different temperatures and their effect on AP decomposition were studied, the results show that catalyst at 300 °C has a particle size of 20 nm and uniformly distributed on rGO. The catalyst promotes the high temperature decomposition of AP by 73.7 °C with improved stability, and increases the heat release from 652.73 J/g to 1392.11 J/g. This may be attributed to good conductivity of GO and the strong gain-loss electron ability of the metal clusters. The presence of GO increased the active sites for cluster catalysis, additional, the metal clusters have a positive synergistic effect with GO. Thus, the thermal decomposition performance of AP was enhanced meanwhile thermal stability can also be improved.
- Guo, Yanli,Liang, Taixin,Liu, Wei,Song, Ruidong,Wang, Chao,Xiao, Fei,Zhang, Jiangbo
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- Kinetics and mechanism of the chromium(VI) catalyzed decomposition of hypochlorous acid at elevated temperature and high ionic strength
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An important reaction step in the industrial production of NaClO3 (electrochemical chlorate process) is the thermal decomposition of HOCl/OCl- to yield ClO3- and Cl-. It is widely accepted that this reaction is accelerated by aqueous chromium(vi) species. A detailed kinetic study was conducted under industrially relevant conditions, i.e. at high ionic strength (6.0 M) and elevated temperature (80 °C), to investigate this phenomenon. The decomposition of hypochlorous acid was followed in the presence of Cr(vi) or phosphate (PO43-) or without any additive. In addition to the beneficial pH buffering effect of Cr(vi), the CrO42- form of chromium(vi) was found to slightly catalyze the decomposition of hypochlorous acid. The overall rate of HOCl decomposition can be expressed as -dcHOCl/dt = kdec[HOCl]2[OCl-] + kcat[HOCl]2[CrO42-]. The corresponding rate constants were determined, kdec = 9.4 ± 0.1 M-2 s-1 and kcat = 4.6 ± 0.8 M-2 s-1, and mechanistic interpretation of the catalytic rate law is given. The contribution of the catalytic path to the overall rate of decomposition changes from ca. 30% at pH = 8 to ca. 70% at pH = 6.
- Kalmár, József,Szabó, Mária,Simic, Nina,Fábián, István
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p. 3831 - 3840
(2018/03/21)
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- Kinetics and Mechanism of the Chlorite-Periodate System: Formation of a Short-Lived Key Intermediate OClOIO3 and Its Subsequent Reactions
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The chlorite-periodate reaction has been studied spectrophotometrically in acidic medium at 25.0 ± 0.1 °C, monitoring the absorbance at 400 nm in acetate/acetic acid buffer at constant ionic strength (I = 0.5 M). We have shown that periodate was exclusive
- Baranyi, Nóra,Cseko, Gy?rgy,Valkai, László,Xu, Li,Horváth, Attila K.
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p. 2436 - 2440
(2016/03/19)
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- Catalytic reactions of chlorite with a polypyridylruthenium(ii) complex: Disproportionation, chlorine dioxide formation and alcohol oxidation
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cis-[Ru(2,9-Me2phen)2(OH2) 2]2+ reacts readily with chlorite at room temperature at pH 4.9 and 6.8. The ruthenium(ii) complex can catalyze the disproportionation of chlorite to chlorate and chloride, the oxidation of chlorite to chlorine dioxide, as well as the oxidation of alcohols by chlorite. The Royal Society of Chemistry 2012.
- Hu, Zongmin,Du, Hongxia,Man, Wai-Lun,Leung, Chi-Fai,Liang, Haojun,Lau, Tai-Chu
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p. 1102 - 1104
(2012/02/17)
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- Effect of chloride ion on the kinetics and mechanism of the reaction between chlorite ion and hypochlorous acid
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The effect of chloride ion on the chlorine dioxide formation in the ClO2--HOCl reaction was studied by following ?ClO2 concentration spectrophotometrically at pH 5-6 in 0.5 M sodium acetate. On the basis of the earlier experimental data collected without initially added chloride and on new experiments, the earlier kinetic model was modified and extended to interpret the two series of experiments together. It was found that the chloride ion significantly increases the initial rate of ?ClO2 formation. At the same time, the ?ClO2 yield is increased in HOCl but decreased in ClO2- excess by the increase of the chloride ion concentration. The two-step hydrolysis of dissolved chlorine through Cl2 + H2O ? Cl 2OH- + H+ and Cl2OH- ? HOCl + Cl- and the increased reactivity of Cl 2OH- compared to HOCl are proposed to explain these phenomena. It is reinforced that the hydrolysis of the transient Cl 2O2 takes place through a HOCl-catalyzed step instead of the spontaneous hydrolysis. A seven-step kinetic model with six rate parameters (constants and/or ratio of constants) is proposed on the basis of the rigorous least-squares fitting of the parameters simultaneously to 129 absorbance versus time curves measured up to ~90% conversion. The advantage of this method of evaluation is briefly outlined.
- Kormanyos, Balazs,Nagypal, Istvan,Peintler, Gabor,Horvath, Attila K.
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p. 7914 - 7920
(2009/02/08)
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- Kinetics and mechanism of the oxidation of sulfite by chlorine dioxide in a slightly acidic medium
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The sulfite-chlorine dioxide reaction was studied by stopped-flow method at I = 0.5 M and at 25.0 ± 0.1 °C in a slightly acidic medium. The stoichiometry was found to be 2 SO32- + 2-ClO2 + H2O → 2SO42- + Cl- + ClO 3- + 2H+ in ClO2 excess and 6SO 32- + 2·ClO2 → S2O 62- + 4SO42- + 2Cl- in total sulfite excess ([S(IV)] = [H2SO3] + [HSO 3-] + [SO32-]). A nine-step model with four fitted kinetic parameters is suggested in which the proposed adduct SO3C1O22- plays a significant role. The pH-dependence of the kinetic traces indicates that SO32- reacts much faster with ClO2 than HSO3- does.
- Horvath, Attila K.,Nagypal, Istvan
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p. 4753 - 4758
(2008/10/09)
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- Three autocatalysts and self-inhibition in a single reaction: A detailed mechanism of the chlorite-tetrathionate reaction
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The chlorite-tetrathionate reaction has been studied spectrophotometrically in the pH range of 4.65-5.35 at T = 25.0 ± 0.2°C with an ionic strength of 0.5 M, adjusted with sodium acetate as a buffer component. The reaction is unique in that it demonstrates autocatalysis with respect to the hydrogen and chloride ion products and the key intermediate, HOCl. The thermodynamically most-favorable stoichiometry, 2S4O6 2- + 7ClO2- + 6H2O → 8SO 42- + 7Cl- + 12H+, is not found. Under our experimental conditions, chlorine dioxide, the chlorate ion, or both are detected in appreciable amounts among the products. Initial rate studies reveal that the formation of chlorine dioxide varies in an unusual way, with the chlorite ion acting as a self-inhibitor. The reaction is supercatalytic (i.e., second order with respect to autocatalyst H+). The autocatalytic behavior with respect to Cl- comes from chloride catalysis of the chlorite-hypochlorous acid and hypochlorous acid-tetrathionate subsystems. A detailed kinetic study and a model that explains this unusual kinetic behavior are presented.
- Horvath, Attila K.,Nagypal, Istvan,Epstein, Irving R.
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p. 9877 - 9883
(2008/10/09)
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- Kinetics and mechanisms of the reactions of hypochlorous acid, chlorine, and chlorine monoxide with bromite ion
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The reaction between BrO2- and excess HOCl (p[H +] 6-7, 25.0 °C) proceeds through several pathways. The primary path is a multistep oxidation of HOCl by BrO2- to form ClO3- and HOBr (85% of the initial 0.15 mM BrO 2-). Another pathway produces ClO2 and HOBr (8%), and a third pathway produces BrO3- and Cl - (7%). With excess HOCl concentrations, Cl2O also is a reactive species. In the proposed mechanism, HOCl and Cl2O react with BrO2- to form steady-state species, HOClOBrO - and ClOClOBrO-. Acid facilitates the conversion of HOClOBrO- and ClOClOBrO- to HOBrOClO-. These reactions require a chainlike connectivity of the intermediates with alternating halogen-oxygen bonding (i.e. HOBrOClO-) as opposed to Y-shaped intermediates with a direct halogen-halogen bond (i.e. HOBrCl(O)O -). The HOBrOClO- species dissociates into HOBr and ClO2- or reacts with general acids to form BrOClO. The distribution of products suggests that BrOClO exists as a BrOClO·HOCl adduct in the presence of excess HOCl. The primary products, ClO 3- and HOBr, are formed from the hydrolysis of BrOClO·HOCl. A minor hydrolysis path for BrOClO·HOCl gives BrO3- and Cl-. An induction period in the formation of ClO2 is observed due to the buildup of ClO 2-, which reacts with BrOClO·HOCl to give 2 ClO2 and Br-. Second-order rate constants for the reactions of HOCl and Cl2O with BrO2- are k1HOCl = 1.6 × 102 M-1 s -1 and k1Cl2O = 1.8 × 105 M-1 s-1. When Cl- is added in large excess, a Cl2 pathway exists in competition with the HOCl and Cl2O pathways for the loss of BrO2-. The proposed Cl 2 pathway proceeds by Cl+ transfer to form a steady-state ClOBrO species with a rate constant of k1Cl2 = 8.7 × 105 M-1 s-1.
- Nicoson, Jeffrey S.,Perrone, Thomas F.,Huff Hartz, Kara E.,Wang, Lu,Margerum, Dale W.
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p. 5818 - 5824
(2008/10/08)
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- Kinetics and mechanisms of the ozone/bromite and ozone/chlorite reactions
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Ozone reactions with XO2- (X = Cl or Br) are studied by stopped-flow spectroscopy under pseudo-first-order conditions with excess XO2-. The O3/XO2- reactions are first-order in [O3] and [XO2-], with rate constants k1Cl = 8.2(4) × 106 M-1 s-1 and k1Br = 8.9(3) × 104 M-1 s-1 at 25.0 °C and μ = 1.0 M. The proposed rate-determining step is an electron transfer from XO2- to form XO2 and O3-. Subsequent rapid reactions of O3- with general acids produce O2 and OH. The OH radical reacts rapidly with XO2- to form a second XO2 and OH-. In the O3/CIO2- reaction, CIO2 and CIO3- are the final products due to competition between the OH/CIO2- reaction to form CIO2 and the OH/CIO2 reaction to form CIO3-. Unlike CIO2, BrO2 is not a stable product due to its rapid disproportionation to form BrO2- and BrO3-. However, kinetic spectra show that small but observable concentrations of BrO2 form within the dead time of the stopped-flow instrument. Bromine dioxide is a transitory intermediate, and its observed rate of decay is equal to half the rate of the O3/BrO2- reaction. Ion chromatographic analysis shows that O3 and BrO2- react in a 1/1 ratio to form BrO3- as the final product. Variation of k1X values with temperature gives ΔH?Cl = 29(2) kJ mol-1, ΔS?Cl = -14.6(7) J mol-1 K-1, ΔH?Br = 54.9(8) kJ mol-1, and ΔS?Br = 34(3) J mol-1 K-1. The positive ΔS?Br value is attributed to the loss of coordinated H2O from BrO2- upon formation of an [O3BrO2-]? activated complex.
- Nicoson, Jeffrey S.,Wang, Lu,Becker, Robert H.,Hartz, Kara E. Huff,Muller, Charles E.,Margerum, Dale W.
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p. 2975 - 2980
(2008/10/08)
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- General-acid-catalyzed reactions of hypochlorous acid and acetyl hypochlorite with chlorite ion
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The rate of oxidation of ClO2- by HOCl is first order in each reactant and is general-acid catalyzed. In the initial steps of the proposed mechanism, a steady-state intermediate, HOClOClO-, forms (k1 = 1.6 M-1 s-1) and undergoes general-acid (HA)-catalyzed reactions (k2(HA)) to generate a metastable intermediate, ClOClO. Values of k2(HA)/k-1 are 1.6 x 104 M-1 (H3O+), 20 M-1 (HOAc), and 8.5 M-1 (H2PO4-). Subsequent competitive reactions of ClOClO with ClO2- (k3) to give 2ClO2 and with OH- (k4(OH)) and other bases (k5(B)) to give ClO3- are very rapid. The relative yields of these products give k4(OH)/k3 = 1.3 x 105, k5(HPO)4/k3 = 0.20, and k5(OAc)/k3 = 0.06. At low pH and low buffer concentrations, the apparent yield of ClO2, based on 2ClO2 per initial HOCl, reaches 140%. This anomaly is attributed to the induced disproportionation of ClO2- by ClOClO to give ClO3- and additional HOCl. A highly reactive intermediate, ClOCl(O)OClO-, is proposed that can undergo Cl - O bond cleavage to give 2ClO2 + Cl- via one path and ClO3- + 2HOCl via another path. The additional HOCl recycles in the presence of excess ClO2- to give more ClO2. Ab initio calculations show feasible structures for the proposed reaction intermediates. Acetic acid has a second catalytic role through the formation of acetyl hypochlorite, which is much more reactive than HOCl in the transfer of Cl+ to ClO2- to form ClOClO.
- Jia, Zhongjiang,Margerum, Dale W.,Francisco, Joseph S.
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p. 2614 - 2620
(2008/10/08)
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- Oxygen-Transfer Reactions of Methylrhenium Oxides
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Methylrhenium dioxide, CH3ReO2 (or MDO), is produced from methylrhenium trioxide, CH3ReO3 (or MTO), and hypophosphorous acid in acidic aqueous medium. Its mechanism is discussed in light of MTO's coordination ability and the inverse kinetic isotope effect (kie): H2P(O)OH, k = 0.028 L mol-1 s-1; D2P(O)OH, k = 0.039 L mol-1 s-1. The Re(V) complex, MDO, reduces perchlorate and other inorganic oxoanions (XOn-, where X = Cl, Br, or I and n = 4 or 3). The rate is controlled by the first oxygen abstraction from perchlorate to give chlorate, with a second-order rate constant at pH 0 and 25°C of 7.3 L mol-1 s-1. Organic oxygen-donors such as sulfoxides and pyridine N-oxides oxidize MDO to MTO as do metal oxo complexes: V(aq)2+, VO2+(aq), HOMoO2+(aq), and MnO4-. The reaction between V(aq)2+ with MTO and the reduction of VO2+ with MDO made it possible to determine the free energy for MDO/MTO. Oxygen-atom transfer from oxygen-donors to MDO involves nucleophilic attack of X-O on the electrophilic Re(V) center of MDO; the reaction proceeds via an [MDO-XO] adduct, which is supported by the saturation kinetics observed for some. The parameters that control and facilitate the kinetics of such oxygen-transfer processes are suggested and include the force constant for the asymmetric stretching of the element-oxygen bond.
- Abu-Omar, Mahdi M.,Appelman, Evan H.,Espenson, James H.
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p. 7751 - 7757
(2008/10/09)
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- Iron(III)-catalyzed decomposition of the chlorite ion: An inorganic application of the quenched stopped-flow method
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The kinetics and mechanism of the iron(III)-catalyzed decomposition of the chlorite ion have been investigated by using conventional batch, stopped-flow, stopped-flow-rapid-scan spectrophotometric, and quenched stopped-flow methods at 25°C and in 1.0 M NaClO4. The concentration vs time profiles were determined for chlorite ion, chlorine dioxide, and, in a few cases, chloride ion in the 40 ms-several minute interval. It was confirmed that the stoichiometry can be given as the appropriate combination of the following reactions: 4HClO2 = 2ClO2 + ClO3- + Cl- + 2H+ + H2O; 5HClO2 = 4ClO2 + Cl- + H+ + 2H2O. The proposed mechanism postulates that the catalytic decomposition is initiated by the formation of the FeClO22+ complex and the rate-determining step is the redox decomposition of this species. The mechanism was validated by model calculations based on the GEAR algorithm. The measured and calculated kinetic curves are in excellent agreement under a variety of experimental conditions. It was shown that the overall stoichiometry is kinetically controlled and ultimately determined by fast secondary reactions between various chlorine species. This work represents the first totally inorganic application of the quenched stopped-flow method. Several aspects of this technique are discussed.
- Fábián, István,Gordon, Gilbert
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p. 2144 - 2150
(2008/10/08)
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- The Primary Process ClO3- (+hν) ClO- + O2 in the Photolysis of Aqueous ClO3- Solutions
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The quantum yield, Φ1, in the primary process ClO3- (+hν) ClO- + O2 (1) and the sum of the quantum yields Φ1 + Φ2 in the primary processes ClO3- (+hν) ClO2 + O- (2) and ClO3- ClO2- + O(3P) (3) were measured in the steady state photolysis of aqueous ClO3- solutions at 214 and 229 nm.The ratio of the yields of ClO- and ClO3- in the reactions ClO2 ClO- + O2 and ClO2 + O- ClO3- (4) was determined by γ-radiolysis of aqueous solutions of ClO2 at varying pH.The finding that the ratio between the yields of ClO- and ClO3- in reactions 4 equals the ratio between Φ1 and the quantum yield, Φ0 = 1 -Φ1 - Φ2 - Φ3, for ClO3- returning to the ground state is taken as evidence that process 1 results from a cage-back reaction.This result combined with recent studies of the radiolysis of KClO3 crystals suggest that the primary processes in the photolysis of aqueous ClO3- originate in a common process by which O- is expelled from ClO3- upon photoexcitation.The expelled O- may escape the solvent cage containing ClO2 (process 2), or react in cage-back reaction (process 0 and 1).During the expulsion of O- the photoproducts may convert to ClO2- and O(3P) (process 3).
- Klaening, U. K.,Sehested, K.
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p. 740 - 743
(2007/10/02)
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- MASS-SPECTROMETRIC AND QUANTUM-CHEMICAL INVESTIGATION OF THERMOCHEMICAL CHARACTERISTICS OF CHLORINE OXIDES
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An electron impact technique has been used for the direct determination of the ionization potential (IP) of the ClO3 radical and the electron affinity (EA) of the ClO3 and ClO4 radicals.By means of quantum-chemical calculations taking into account configu
- Alekseev, V. I.,Zyubina, T. S.,Zyubin, A. S.,Baluev, A. V.
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p. 2092 - 2096
(2007/10/02)
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- Cinetique et mecanisme des reactions bromate-chlorite et bromate-dioxyde de chlore
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In an acidic solution, containing initially chlorous ac id and bromate in excess, two consecutive reactions are observed, the oxidation of chlorous acid to chlorine dioxide followed by the oxidation of chlorine dioxide: BrO3- + 4ClO2 + 2H2O = 4ClO3- + 3H+ + HOBr.The kinetics of this reaction has been studied and a mechanism proposed.It agrees with the one accepted for the related reaction between bromate and Ce(III).Extended by reactions of chlorous acid, the mechanism reproduces the experimental curves of chlorine dioxode evolution in chlorous acid - bromate solutions.The values of the equilibrium and kinetic constantes are discussed.
- Schmitz, Guy,Rooze, Henri
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p. 231 - 235
(2007/10/02)
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- Mecanisme des reactions du chlorite et du dioxyde de chlore. 3. La dismutation du chlorite
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The disproportionation of chlorite was studied in 0.01 to 1 M perchloric acid solutions at 25 deg C and an ion strengs of 1 M.The results suggest at least three reaction paths.The first is catalysed by Cl- ions, the second gives a second-order rate law, and the third is catalysed by iron.Its rate law is d/dt = 3+>->/(1.39 + 0.11/+>) This can be interpreted by the reversible reaction ClO2- + Fe3+ = ClO2 + Fe2+ followed by two rate-determining reactions Fe2+ + HClO2 -> products, Fe2+ + ClO2--> products.From this study and the former, made with added ortho-tolidine, we conclude that the second-order reaction proceeds by a radical chain mechanism.
- Schmitz, Guy,Rooze, Henri
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p. 975 - 980
(2007/10/02)
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- Photolysis of Solid KClO4 at l85 nm Studied by Chemical Analysis, Electron Spin Resonance and Optical Spectroscopy
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O2 and ClO3(1-) have been established as primary products in the photolysis of KClO4, at l85 nm, whereas Cl(1-) is the dominant product of secondary photolysis.The primary photolysis resembles the radiolysis of KClO4, with the exception that Cl(1-) is a primary product in radiolysis but not in photolysis.It is proposed that the primary photolytic process is photoionization, in which an electron is transferred between adjacent anions.The resulting charge-transfer complex may account for the observed transient optical absorptions.
- Klaening, Ulrik K.,Bjerre, Nis,Byberg, Jorgen R.
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p. 1835 - 1840
(2007/10/02)
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- Disproportionation of chlorous acid. I. Stoichiometry
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The disproportionation of chlorous acid was studied at an ionic strength of 2.0 M under a variety of hydrogen ion conditions from 1.2 × 10-3 to 2.0 M and with up to 0.1 M added chloride ion. In the absence of added chloride ion, in 1.2 and 2.0 M perchloric acid at 25°, the stoichiometry can be approximated as: 4HClO2 → 2ClO2 + ClO3- + Cl- + 2H+ + H2O. At the beginning of the reaction less chlorine dioxide than that predicted by the above equation is formed, and, as the reaction proceeds, the relative amount of chlorine dioxide produced increases. The relative amount of chlorine dioxide produced also varies with the hydrogen ion concentration. Chloride ion catalyzes the disproportionation of chlorous acid and also alters the stoichiometry to approximately 5HClO2 → 4ClO2 + Cl- + H+ + 2H2O. As the reaction proceeds in the presence of initial chloride ion, less chlorine dioxide than that predicted by the second equation is formed. Also, as the initial concentration of chloride ion is decreased, the relative amount of chlorine dioxide formed decreases. A mechanism which is consistent with these observations is proposed.
- Kieffer, Robert G.,Gordon, Gilbert
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p. 235 - 239
(2008/10/08)
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- Disproportionation of chlorous acid. II. Kinetics
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Kinetic data are presented for the disproportionation of chlorous acid at an ionic strength of 2.0 M under a variety of hydrogen ion conditions from 1.2 × 10-3 to 2.0 M and with up to 0.1 M added chloride ion concentration. At 1.2 and 2.0 M hydrogen ion concentrations and at 25°, the rate law is -d[HClO2] / dt = k1 [HClO2]2 + k2[HClO2][Cl-]2 / K + [Cl-] The parameters k1 and K are independent of the hydrogen ion concentration and correspond to 1.17 × 10-2 M-1 sec-1 and 0.0012 M, respectively. In solutions which contain 1.2 M HClO4, k2 is 1.57 × 10-2 M-1 sec-1, and in 2.0 M HClO4, k2 is 3.00 × 10-2 M-1 sec-1. The results are discussed in terms of a detailed mechanism.
- Kieffer, Robert G.,Gordon, Gilbert
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p. 239 - 244
(2008/10/08)
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