14362-44-8Relevant articles and documents
Sustained and Damped pH Oscillation in the Periodate-Thiosulfate Reaction in a Continuous-Flow Stirred Tank Reactor
Rabai, Gyula,Beck, Mihaly T.,Kustin, Kenneth,Epstein, Irving R.
, p. 2853 - 2858 (1989)
The reaction between IO4- and S2O32- exhibits a variable stoichiometry in acetate buffer.With a large excess of IO4-, the products are IO3- and SO42-.In excess thiosulfate, IO4- is reduced
The reduction of I2 by 1-hydroxyalkyl radicals in aqueous solution. A pulse radiolysis study
Ershov,Janata
, p. 195 - 198 (2003)
The one electron reduction of iodine by various 1-hydroyalkyl radicals in aqueous solution is described, which leads first to the formation of I2-, and to I- at longer times. Rate constants of 5×109, 6.5×109, or 8×109dm3 mol-1 s-1 were obtained for the reaction between iodine and the radical of methanol, ethanol or 2-propanol, respectively.
STUDIES ON THE μ-(NN')-ETHYLENEDIAMINETETRA-ACETATO-DI-μ-OXO-BIS-, 2-, COMPLEX IN AQUEOUS SOLUTIONS. FORMATION OF AN AQUO-ION AND REDOX PROPERTIES
Soares, Allan B.,Taylor, Craig R.,Sykes, Geoffrey A.
, p. 1101 - 1104 (1980)
The aquation of 2- (edta=ethylenediaminetetra-acetate) to W2O42+ (or a closely related species) proceeds to completion in HCl>=2 mol dm3-.First-order kinetics have been observed, with the rate constant (1.16*10-4 s-1 at 25 deg C) in 2 mol dm-3 HCl some 60 times less than for the corresponding reaction of 2-.With HClO4>=2 mol dm-3 aquation is accompained by oxidation to WVI.No aquation (or oxidation) has been observed with HClO4-3, under which condition redox reactions of the edta complex could be investigated.At 25 deg C, I=0.50 mol dm-3 (H-LiClO4) rate constants for the first stage of the 1:2 oxidations of 2- with 2- and 3+ (phen=1,10-phenantroline) are 6.3*105 dm3 mol-1 s-1 and >107 dm3 mol-1 s-1 respectively.For the 2- reaction activation parameters are ΔH+=5.4 kcal mol-1 s-1 and ΔS+=-13.8 cal K-1 mol-1 respectively.Rate constants (dm3 mol-1 s-1) for other oxidants, I=0.10 mol dm-3, are 3- (0.058), 3+ (2.0) (bipy=2,2'-bipyridine), and I3- (ca. 20).The complex 2- is a much stronger reducing agent than 2-.
General pathway of sulfur-chain breakage of polythionates by iodine confirmed by the kinetics and mechanism of the pentathionate-iodine reaction
Xu, Li,Csek?, Gy?rgy,Kégl, Tamás,Horváth, Attila K.
, p. 7837 - 7843 (2012)
The pentathionate-iodine reaction has been studied spectrophotometrically at T = 25.0 ± 0.1 °C and at an ionic strength of 0.5 M in both the absence and presence of an initially added iodide ion at the pH range of 3.95-5.15. It was found that the pH does not affect the rate of the reaction; however, the iodide ion produced by the reaction strongly inhibits the oxidation. Therefore, it acts as an autoinhibitor. The kinetic curves also support the fact that iodide inhibition cannot be explained by the formation of the unreactive triiodide ion, and S5O6I- along with the iodide ion has to be involved in the initiating rapid equilibrium being shifted far to the left. Further reactions of S5O6I -, including its hydrolysis and reaction with the iodide ion, lead to the overall stoichiometry represented by the following equation: S 5O62- + 10I2 + 14H2O → 5SO42- + 20I- + 28H+. A nine-step kinetic model with two fitted parameters is proposed and discussed, from which a rate equation has also been derived. A brief discussion about the general pathway of sulfur-chain breakage of polythionates supported by theoretical calculations has also been included.
Kinetics and Mechanisms of the Oxidation of Hydrazine by Aqueous Iodine
Liu, Rong Ming,Margerum, Dale W.
, p. 2531 - 2537 (1998)
Kinetics for the reactions of I2 with excess N2H5+/N2H4 and I- are measured by the loss of I3- over a wide range of acidity from pH 0.35 to 8.0 at 25.0 °C, μ = 0.50 M. Pseudo-first-order rate constants increase by factors of more than 107 with increase of pH, hydrazine, and buffer concentrations. Below pH 1, I2 reacts directly with N2H5+ which has a relative reactivity that is 2.4 × 107 times smaller than N2H4 (the dominant reactant at pH ≥ 1). Kinetic evidence for IN2H4+ as a steady-state species is found below pH 3. From pH 3.5 to 6.3, rate constants are measured by stopped-flow methods and at higher pH by pulsed-accelerated-flow methods. A multistep mechanism is proposed where I2 reacts rapidly with N2H4 to form an I2N2H4 adduct (KA = 2.0 × 104 M-1) that is present in appreciable concentrations above pH 6. The adduct undergoes general base-assisted deprotonation accompanied by loss of I- in the rate-determining step. Subsequent intermediates react rapidly with another I2 to form N2 as a final product. At high pH, hydrazine acts as a general base as well as the initial nucleophile. Rate constants for various bases (H2O, CH3COO-, HPO42-, N2H4, and OH-) fit a Br?nsted β value of 0.46. Values for the second-order rate constants (M-1 s-1) for I2N2H4 reactions with CH3COO-, HPO42-, N2H4 and OH- are 7.5 × 103, 2.0 × 105, 8.5 × 105, and 4.8 × 108, respectively.
In situ growth of mirror-like platinum as highly-efficient counter electrode with light harvesting function for dye-sensitized solar cells
Zhang, Nan Nan,Zhang, Bo,Li, Yu Hang,Hou, Yu,Yang, Shuang,Zhong, Ju Hua,Yang, Hua Gui
, p. 1641 - 1646 (2014)
In this work, we prepared a continuous nanostructured Pt-mirror film with metallic lustre and good adhesion to the F-doped tin oxide conducting glass (FTO) substrate through a simple in situ growth method, which retains a good catalytic activity and more importantly, exhibits significant light reflection for light-harvesting. The dye-sensitized solar cells (DSCs) fabricated with Pt-M CE exhibited superior photovoltaic performance compared with the conventional Pt CE. The enhancements of the short-circuit current density and energy conversion efficiency are 15.3% and 18.5%, respectively. Such significant enhancement of the short-circuit current density was found to be related to the excellent light reflection and high catalytic activity of the Pt-M CE. This has been proved by ultraviolet and visible reflection spectra (UV/Vis), electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV).
Electron transfer. 144. Reductions with germanium(II)
Babich, Olga A.,Gould, Edwin S.
, p. 4119 - 4122 (2000)
Solutions 0.2-0.4 M in Ge(II) and 6 M in HCl, generated by reaction of Ge(IV) with H3PO2, are stable for more than 3 weeks and can be diluted 200-fold with dilute HCl to give GeCl3- preparations to be used in redox studies. Kinetic profiles for the reduction of Fe(III) by Ge(II), as catalyzed by Cu(II), implicate the odd-electron intermediate, Ge(III), which is formed from Cu(II) and Ge(II) (k = 30 M-1 s-1 in 0.5 M HCl at 24 °C) and which is consumed by reaction with Fe(III) (k = 6 x 102 M-1 s-1). A slower direct reaction between Ge(II) and Fe(III) (k = 0.66 M-1 s-1) can be detected in 1.0 M HCl. The reaction of Ge(II) with I3- in 0.01-0.50 M iodide is zero order in oxidant and appears to proceed via a rate-determining heterolysis of a Ge(II)-OH2 species (k = 0.045 s-1) which is subject to H+-catalysis. Reductions of IrCl62- and PtCl62- by Ge(II) are strongly Cl--catalyzed. The Ir(IV) reaction proceeds through a pair of 1e- changes, of which the initial conversion to Ge(III) is rate-determining, whereas the Pt(IV) oxidant probably utilizes (at least in part) an inner-sphere Pt(IV)-Cl-Ge(II) bridge in which chlorine is transferred (as Cl+) from oxidant to reductant. The 2e- reagent, Ge(II), like its 5s2 counterpart, In(I), can partake in 1e- transactions, but requires more severe constraints: the coreagent must be more powerfully oxidizing and the reaction medium more halide-rich.
Kinetics and Mechanism of Oxidation of Hydrazine by Tri-iodide Ion in Aqueous Acidic Media
Radhakrishnamurti, Patapati Subbu,Rath, Nabeen Kumar,Panda, Rama Krushna
, p. 1189 - 1192 (1986)
The kinetics of oxidation of hydrazine (L) by I3- follows a pseudo-first-order rate law in aqueous acid-sulphuric acid media in the range +> 2.0-1.58 x 10-3 mol dm-3.The pseudo-first-order rate constants (kobs.) exhibit: (1) at +>=0.9 mol dm-3 a linear dependence on 0 at low 0, with a tendency to a limiting value at high relative 0; (2) a decreasing and complex trend in -> and in +>; (3) a decreasing trend with decreasing dielectric constant of the medium; and (4) negligible dependence on the ionic strength of the medium, on added Cu2+(aq), and on added ethylenediaminetetra-acetate.The results are interpreted in terms of a mechanism which envisage (a) negligible reactivities of I3- and of HL+ predominant in the medium, (b) an inner-complex mechanism of electron transfer (i.e. a 1:1 ?-charge-transfer co-ordination prior to the electron transfer) involving I2 and L, and (c) an encounter reaction between IOH and L.Mechanistic ambiguities of some earlier reports of the same reaction are explained.
Complex kinetics of a landolt-type reaction: The later phase of the thiosulfate-iodate reaction
Horvath, Attila K.,Varga, Denes,Nagypal, Istvan
, p. 5752 - 5758 (2010)
The thiosulfate-iodate reaction has been studied spectrophotometrically in slightly acidic medium at 25.0 ± 0.1 °C in acetate/acetic acid buffer by monitoring the absorbance at 468 nm at the isosbestic point of iodine-triiodide ion system. The formation of iodine after the Landolt time follows a rather complex kinetic behavior depending on the pH and on the concentration of the reactants as well. It is shown that the key intermediate of the reaction is I2O2, its equilibrium formation from the well-known Dushman reaction along with their further reactions followed by subsequent reactions of HOI, HIO2, S2O3OH -, and S2O3I- adequately accounts for all the experimentally measured characteristics of the kinetic curves. A 19-step kinetic model is proposed and discussed with 13 fitted and 7 fixed parameters in detail.
The Oscillatory Landolt Reaction. Empirical Rate Law Model and Detailed Mechanism.
Gaspar, Vilmos,Showalter, Kenneth
, p. 4869 - 4876 (1987)
The iodate oxidation of sulfite and ferrocyanide when carried out in a continuous flow stirred tank reactor exhibits large-amplitude oscillations in pH accompanied by an almost constant concentration of iodide.A description of the reaction in terms of component processes and associated empirical rate laws is used to model the dynamical behavior.Limitations and potential refinements of the empirical rate law model are discussed.A detailed mechanism consistent with the component process description is presented.
