14998-27-7Relevant articles and documents
Electron Affinity of Chlorine Dioxide
Babcock, L. M.,Pentecost, T.,Koppenol, W. H.
, p. 8126 - 8127 (1989)
The flowing afterglow technique was used to determine the electron affinity of chlorine dioxide.A value of 2.37+/-0.10 eV was found bracketing between the electron affinities of HS and SF4 as a lower limit and that of NO2 as an upper limit.This value is in excellent agreement with 2.32 eV predicted from a simple thermodynamic cycle involving the reduction potential of the ClO2/ClO2- couple and a Gibbs hydration energy identical with that of SO2-.
OXIDATION OF TRIS(1,10-PHENANTHROLINE)IRON(II) BY CHLORINE DIOXIDE.
Lednicky,Stanbury
, p. 3098 - 3101 (1983)
The reaction of left bracket Fe(phen)//3 right bracket **2** plus with ClO//2 has been investigated in aqueous solution at 25. 0 degree C and at an ionic strength of 0. 10 M (NaCF//3SO//3). The equilibrium quotient for formation of left bracket Fe(phen)//3 right bracket **3** plus and CO//2** minus was determined spectrophotometrically to be (1. 98 plus or minus 0. 22) multiplied by 10** minus **3. Since the product ClO//2** minus is a weak base, it was possible by mass action to drive the reaction in the uphill direction in acidic media. In the reverse direction the kinetics were immeasurably rapid, but in the uphill direction the kinetics were slow enough to be measured by using a stopped-flow spectrophotometer. The kinetics were consistent with a mechanism involving reversible bimolecular electron transfer followed by protonation fo the ClO//2** minus . The rate constant for electron transfer was calculated as 4. 5 multiplied by 10**4 M** minus **1 s** minus **1. Applying the cross relationship of Marcus theory leads to an effective self-exchange rate constant of 7. 8 multiplied by 10**1 M** minus **1 s** minus **1 for the ClO//2/ClO//2** minus couple.
Chlorine dioxide reduction by aqueous iron(II) through outer-sphere and inner-sphere electron-transfer pathways
Wang, Lu,Odeh, Ihab N.,Margerum, Dale W.
, p. 7545 - 7551 (2004)
The reduction of ClO2 to ClO2- by aqueous iron(II) in 0.5 M HClO4 proceeds by both outer-sphere (86%) and inner-sphere (14%) electron-transfer pathways. The second-order rate constant for the outer-sphere reacti
Dissection of the mechanism of manganese porphyrin-catalyzed chlorine dioxide generation
Umile, Thomas P.,Wang, Dong,Groves, John T.
, p. 10353 - 10362 (2011/11/29)
Chlorine dioxide, an industrially important biocide and bleach, is produced rapidly and efficiently from chlorite ion in the presence of water-soluble, manganese porphyrins and porphyrazines at neutral pH under mild conditions. The electron-deficient manganese(III) tetra-(N,N-dimethyl)imidazolium porphyrin (MnTDMImP), tetra-(N,N-dimethyl)benzimidazolium (MnTDMBImP) porphyrin, and manganese(III) tetra-N-methyl-2,3-pyridinoporphyrazine (MnTM23PyPz) were found to be the most efficient catalysts for this process. The more typical manganese tetra-4-N-methylpyridiumporphyrin (Mn-4-TMPyP) was much less effective. Rates for the best catalysts were in the range of 0.24-32 TO/s with MnTM23PyPz being the fastest. The kinetics of reactions of the various ClOx species (e.g., chlorite ion, hypochlorous acid, and chlorine dioxide) with authentic oxomanganese(IV) and dioxomanganese(V)MnTDMImP intermediates were studied by stopped-flow spectroscopy. Rate-limiting oxidation of the manganese(III) catalyst by chlorite ion via oxygen atom transfer is proposed to afford a trans-dioxomanganese(V) intermediate. Both trans-dioxomanganese(V)TDMImP and oxoaqua-manganese(IV)TDMImP oxidize chlorite ion by 1-electron, generating the product chlorine dioxide with bimolecular rate constants of 6.30 × 10 3 M-1 s-1 and 3.13 × 103 M-1 s-1, respectively, at pH 6.8. Chlorine dioxide was able to oxidize manganese(III)TDMImP to oxomanganese(IV) at a similar rate, establishing a redox steady-state equilibrium under turnover conditions. Hypochlorous acid (HOCl) produced during turnover was found to rapidly and reversibly react with manganese(III)TDMImP to give dioxoMn(V)TDMImP and chloride ion. The measured equilibrium constant for this reaction (Keq = 2.2 at pH 5.1) afforded a value for the oxoMn(V)/Mn(III) redox couple under catalytic conditions (E′ = 1.35 V vs NHE). In subsequent processes, chlorine dioxide reacts with both oxomanganese(V) and oxomanganese(IV)TDMImP to afford chlorate ion. Kinetic simulations of the proposed mechanism using experimentally measured rate constants were in agreement with observed chlorine dioxide growth and decay curves, measured chlorate yields, and the oxoMn(IV)/Mn(III) redox potential (1.03 V vs NHE). This acid-free catalysis could form the basis for a new process to make ClO2.
Nucleophile Assistance of Electron-Transfer Reactions between Nitrogen Dioxide and Chlorine Dioxide Concurrent with the Nitrogen Dioxide Disproportionation
Becker, Robert H.,Nicoson, Jeffrey S.,Margerum, Dale W.
, p. 7938 - 7944 (2008/10/09)
The reaction of chlorine dioxide with excess NO2- to form ClO2- and NO3- in the presence of a large concentration of ClO2- is followed via stopped-flow spectroscopy. Concentrations are set to establish a preequilibrium among ClO2, NO2-, ClO2-, and an intermediate, NO2. Studies are conducted at pH 12.0 to avoid complications due to the ClO2-/NO2- reaction. These conditions enable the kinetic study of the ClO2 reaction with nitrogen dioxide as well as the NO2 disproportionation reaction. The rate of the NO2/ClO2 electron-transfer reaction is accelerated by different nucleophiles (NO2- > Br- > OH- > CO32- > PO43- > ClO2- > H 2O). The third-order rate constants for the nucleophile-assisted reactions between NO2 and ClO2 (kNu, M -2 s-1) at 25.0 °C vary from 4.4 × 10 6 for NO2- to 2.0 × 103 when H2O is the nucleophile. The nucleophile is found to associate with NO2 and not with ClO2 in the rate-determining step to give NuNO2+ + ClO2-. The concurrent NO2 disproportionation reaction exhibits no nucleophilic effect and has a rate constant of 4.8 × 107 M-1 s -1. The ClO2/NO2/nucleophile reaction is another example of a system that exhibits general nucleophilic acceleration of electron transfer. This system also represents an alternative way to study the rate of NO2 disproportionation.
New pathways for chlorine dioxide decomposition in basic solution
Odeh, Ihab N.,Francisco, Joseph S.,Margerum, Dale W.
, p. 6500 - 6506 (2008/10/08)
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.
Bromite ion catalysis of the disproportionation of chlorine dioxide with nucleophile assistance of electron-transfer reactions between ClO2 and BrO2 in basic solution
Wang, Lu,Nicoson, Jeffrey S.,Huff Hartz, Kara E.,Francisco, Joseph S.,Margerum, Dale W.
, p. 108 - 113 (2008/10/08)
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.
Hypohalite ion catalysis of the disproportionation of chlorine dioxide
Wang, Lu,Margerum, Dale W.
, p. 6099 - 6105 (2008/10/08)
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.
Kinetics and mechanism of catalytic decomposition and oxidation of chlorine dioxide by the hypochlorite ion
Csordas,Bubnis,Fabian,Gordon
, p. 1833 - 1836 (2008/10/08)
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
Kinetics and mechanism of the reaction between thiosulfate and chlorine dioxide
Horvath, Attila K.,Nagypal, Istvan
, p. 7267 - 7272 (2007/10/03)
The reaction between thiosulfate and chlorine dioxide in slightly alkaline medium has been studied by stopped- flow techniques. The reaction cannot be studied under pseudo-first-order condition, thus a new approach based on the improved calibration and use of stopped-flow spectrophotometers was applied. The reaction starts with irreversible formation of ?S2O3ClO22- radical. The main path of the reaction produces tetrathionate and chlorite through the formation of light absorbing tetrathionate radical (?S4O63-). Any of the reactant present in excess slightly modifies the 1:1 stoichiometry, and sulfate as well as chloride ions are also formed. A detailed mechanism based on a rigorous simultaneous fitting of the experimental data is proposed.
