A pulse radiolysis study of the reaction of OH with I2 and the decay of I2−

1992 ◽  
Vol 70 (6) ◽  
pp. 1658-1661 ◽  
Author(s):  
A. John Elliot
Keyword(s):  
Ionic Strength ◽  
Hydroxyl Radical ◽  
Time Dependence ◽  
Rate Constant ◽  
Rate Constants ◽  
Pulse Radiolysis

The rate constant for the reaction of the hydroxyl radical with iodine was estimated to be (9.5 ± 1.0) × 109 dm3 mol−1 s−1 at 20 °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 = (4.6 ± 1.6) × 109 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) × 109 dm3 mol−1 s−1); and I with I (2k = (3.0 ± 1.0) × 1010 dm3 mol−1 s−1).

Pulse radiolysis of aqueous solutions of N-Vinylpyrrolidin-2-one and Poly(N-vinylpyrrolidin-2-one)

1981 ◽  
Vol 34 (7) ◽  
pp. 1423 ◽  
Author(s):  
JE Davis ◽  
DF Sangster ◽  
E Senogles
Keyword(s):  
Aqueous Solutions ◽  
Hydroxyl Radical ◽  
Absorption Spectra ◽  
Rate Constant ◽  
Rate Constants ◽  
Pulse Radiolysis ◽  
Kinetic Method ◽  
Transient Species ◽  
Radical Scavengers ◽  
Dilute Aqueous Solutions

The absorption spectra of transient species produced when dilute aqueous solutions of N-vinylpyrrolidin-2-one (vp) and poly(N- vinylpyrrolidin-2-one) (pvp) are subjected to pulse radiolysis in the presence and absence of radical scavengers have been obtained and compared with those obtained from analogous compounds. The precise structure of the transients has not been established. Rate constants for the reaction of the hydroxyl radical with vp and pvp have been evaluated both by a competition kinetic method and by direct observation of the build-up of transient species: k(vp+·OH) = (6.4-8.1) × 109 dm3 mol-1 s-1 and k(pvp+·OH) = (1.5-2.3) × 108 dm3 mol-1 s-1 at 25°C. The rate constant for the reaction of the hydrated electron with vp has been determined as(1.6�0.3) × 109 dm3 mol-1 s-1 at 25°C. Rate constants for decay of the transient species have also been evaluated at 25°C: 2k(vp- OH·) = (8.1�1.0)× 108 dm3 mol-1 s-1; 2k(vp-e-) = (1.7�0.2) × 109 dm3 mol-1 s-1 and 2k(pvp-OH·) = (1.5�0.2) × 108 dm3 mol-1 s-1.

Radiolysis studies on the corrosion inhibitors 1 -hexyn-3-ol, cinnamonitrile, and 1,3-diethyl-2-thiourea

1995 ◽  
Vol 73 (12) ◽  
pp. 2137-2142 ◽  
Author(s):  
A.J. Elliot ◽  
M.P. Chenier ◽  
D.C. Ouellette
Keyword(s):  
Hydrogen Atom ◽  
Hydroxyl Radical ◽  
Temperature Dependence ◽  
Rate Constant ◽  
Rate Constants ◽  
Corrosion Inhibitors ◽  
Hydrated Electron

In this publication we report: (i) the rate constants for reaction of the hydrated electron with 1-hexyn-3-ol ((8.6 ± 0.3) × 108 dm3 mol−1 s−1 at 18 °C), cinnamonitrile ((2.3 ± 0.2) × 1010 dm3 mol−1 s−1 at 20 °C), and 1,3-diethyl-2-thiourea ((3.5 ± 0.3) × 108 dm3 mol−1 s−1 at 22 °C). For cinnamonitrile and diethylthiourea, the temperature dependence up to 200 °C and 150 °C, respectively, is also reported; (ii) the rate constants for the reaction of the hydroxyl radical with 1-hexyn-3-ol ((5.5 ± 0.5) × 109 dm3 mol−1 s−1 at 20 °C), cinnamonitrile ((9.2 ± 0.3) × 109 dm3 mol−1 s−1 at 21 °C), and diethylthiourea ((8.0 ± 0.8) × 108 dm3 mol−1 s−1 at 22 °C). For cinnamonitrile, the temperature dependence up to 200 °C is also reported; (iii) the rate constant for the hydrogen atom reacting with 1-hexyn-3-ol ((4.3 ± 0.4) × 109 dm3 mol−1 s−1 at 20 °C). Keywords: radiolysis, corrosion inhibitors, rate constants.

Hydroxyl radical rate constants: comparing UV/H2O2 and pulse radiolysis for environmental pollutants

2008 ◽  
Vol 57 (6) ◽  
pp. 391-401 ◽  
Author(s):  
Michael S. Elovitz ◽  
Hilla Shemer ◽  
Julie R. Peller ◽  
K. Vinodgopal ◽  
Mano Sivaganesan ◽  
...  
Keyword(s):  
Hydroxyl Radical ◽  
Rate Constants ◽  
Pulse Radiolysis ◽  
Environmental Pollutants

Conductometric Pulse Radiolysis Study on the Reaction of the Solvated Electron with 5-Bromouracil in Aqueous Solutions at Different pH Values

1974 ◽  
Vol 29 (1-2) ◽  
pp. 86-88b ◽  
Author(s):  
Burkhard O. Wagner ◽  
Herbert Klever ◽  
Dietrich Schulte-Frohlinde
Keyword(s):  
Aqueous Solution ◽  
Hydrogen Atom ◽  
Aqueous Solutions ◽  
Hydroxyl Radical ◽  
Rate Constant ◽  
Pulse Radiolysis ◽  
Solvated Electron ◽  
Ph Values

To study the reaction of the solvated electron with 5-bromouracil an aqueous solution has been examined by conductometric pulse radiolysis at pH values between 4.68 and 8.74. Alcohol was added to scavenge the hydrogen atom and the hydroxyl radical. G(Br—) = (2.64 ± 0.08)/100 eV was found to be independent of the pH. The mobility of the bromouracil mono-anion was measured to be (2.7 ± 0.2) 10-4 cm2 V-1 s-1 at 20°C, and the rate constant of reaction (3b) was determined to be k(H+ BrUr-) = (2.3 ± 0.2) 1010 I mole-1 s-1*.

scholarly journals Formation of super-reduced Chromatium high-potential iron–sulphur protein in aqueous solution by pulse radiolysis

1980 ◽  
Vol 189 (3) ◽  
pp. 641-644 ◽  
Author(s):  
J Butler ◽  
A G Sykes ◽  
G V Buxton ◽  
P C Harrington ◽  
R G Wilkins
Keyword(s):  
Aqueous Solution ◽  
Rate Constant ◽  
Rate Constants ◽  
Pulse Radiolysis ◽  
High Potential ◽  
Single Stage ◽  
Process Rate ◽  
Stage Process ◽  
Reduced Forms

Both the oxidized and reduced forms of Hipip (high-potential iron–sulphur protein) are reduced (approx. 30% yields) by eaq.- in a single-stage process, rate constants 1.7 × 10(10) and 1.8 × 10(10) M-1 . s-1 respectively, at 25 degrees C, pH 7.0 (5 mM-phosphate). Super-reduced Hipip, which is formed in the latter case, has a spectrum which closely resembles that of reduced ferredoxin, i.e. Fe4S4 (SR)4(3-) clusters. The spectrum is stable over 2 s periods investigated. Super-reduced Hipip is reoxidized with O2, rate constant 4.8 × 10(6) M-1 . s-1 at 25 degrees C.

scholarly journals The kinetics of oxygen exchange between the sulfite ion and water

1970 ◽  
Vol 48 (13) ◽  
pp. 2035-2041 ◽  
Author(s):  
R. H. Betts ◽  
R. H. Voss
Keyword(s):  
Aqueous Solution ◽  
Ionic Strength ◽  
Rate Constant ◽  
Rate Constants ◽  
Time Rate ◽  
A Value ◽  
First Time ◽  
Kinetics Of ◽  
Sulfite Ion ◽  
Gross Rate

Oxygen of mass 18 was used as a stable tracer to measure the rate of exchange between the sulfite ion and water as a function of pH and total sulfite concentration. A value for the rate constant of hydration of SO2 in aqueous solution was determined. The gross rate constants k1 and k−1 for the overall reaction[Formula: see text]at 24.7 °C and ionic strength = 0.9 were evaluated from exchange results to be [Formula: see text]Also, for the first time, rate constants for the pyrosulfite equilibrium[Formula: see text]Were obtained[Formula: see text]at 24.7 °C and ionic strength = 0.9

Kinetics of the anation reaction of nickel(II) and 1,10-phenanthroline in methanol–water mixtures

1969 ◽  
Vol 47 (20) ◽  
pp. 3773-3778 ◽  
Author(s):  
M. L. Sanduja ◽  
W. MacF. Smith
Keyword(s):  
Ionic Strength ◽  
Rate Constant ◽  
Rate Constants ◽  
Solvent Composition ◽  
Solvent Mixtures ◽  
Methanol Content ◽  
Dependent Rate ◽  
Kinetics Of Formation ◽  
Kinetics Of ◽  
Anation Reaction

The kinetics of formation of the monophenanthroline complex of nickel(II) has been studied spectrophotometrically in water–methanol mixtures of 0 to 97 weight % of methanol, at ionic strength 0.050, at varying acidities at 25 °C. Values for the rate constants for the acid independent and acid dependent reactions together with values for the equilibrium acid ionization quotient of phenanthrolium ion over the range of solvent mixtures have been determined. The values of the acid independent rate constant show little dependence on solvent compositions up to 76% methanol, then decrease and show no correlation with trends in the ionization quotient of phenanthrolium ion. The acid dependent rate constant shows only a modest dependence on solvent composition over most of the range of solvent compositions except in the range of highest methanol content where it is not significantly different from zero.

ROLE OF THE HIGH-AFFINITY PENTASACCHARIDE IN HEPARIN ACCELERATION OF ANTITHROMBIN III INHIBITION OF THROMBIN AND FACTOR Xa

1987 ◽  
Author(s):  
Steven T Olson ◽  
Ingemar Bjork ◽  
Paul A Craig ◽  
Joseph D Shore ◽  
Jean Choay
Keyword(s):  
Ionic Strength ◽  
Conformational Change ◽  
Rate Constant ◽  
Rate Constants ◽  
Antithrombin Iii ◽  
Factor Xa ◽  
Order Conditions ◽  
Bimolecular Rate Constant ◽  
High Affinity ◽  
Inhibition Of Thrombin

The high-affinity heparin pentasaccharide (H5) and an 8000 Mr high-affinity heparin (H26) have been compared with respect to their interaction with antithrombin III (AT) and their accelerating effect on AT inhibition of thrombin (T) and factor Xa by rapid kinetic and equilibrium binding studies at pH 7.4, 25°C. Kds of .068 μM at I 0.15 and 0.57 μM at I 0.3 were determined for tne AT-H5 interaction, which were 5 and 2.5-fold weaker, respectively, than affinities determined for H26. Comparison of the kinetics of binding of H5 and H26 to AT at I 0.15 under pseudofirst order conditions ([H]o>> [AT]o) demonstrated a saturable dependence of the observed rate constant for both reaction with indistinguishable limiting rate constants of 700 +/-120 s-1 and 520 +/-90 s-1 , but somewhat different Kds for the initial binding interaction of 20 and 29 μM for H5 and H26, respectively. These results indicate that H5 induces the same conformational change in AT as the larger heparin, but that the rate of reversal of this conformational change is greater for H5 which is the basis for its weaker AT affinity. Bimolecular rate constants for neutralization of factor Xa and thrombin by AT-H5 and AT-H26 complexes were determined by p-aminobenzamidine displacement under pseudo-first order conditions([AT-H] >> [T]o or [Xa]o). I-in-dependent values of .62 μM-1 s-1 were obtained for Xa inhibition by AT-H5 at I 0.15 and 0.3, compared to I-dependent values of 1.4 and 0.91 μM-1 s-1 for AT-H26. For thrombin inhibition by AT-H5, and I-independent enhancement of 1.6-fold in the bimolecular rate constant from .0098 to .016 μM-1 s-1 was observed, in sharp contrast to the marked I-independent enhancement by AT-H26 of the bimolecular rate constant ranging from 4000 to 200-fold at I 0.15 and 0.3, respectively. These results are consistent with a primary ionic strength-independent contribution of the AT conformational change to heparin enhancement of factor Xa but not thrombin neutralization by AT, with an ionic strength-dependent component for both reactions, compatible with a differential role for a protease-heparin interaction. Supported by grant HL-30237

DECOMPOSITION OF SODIUM HYPOCHLORITE: THE UNCATALYZED REACTION

1956 ◽  
Vol 34 (4) ◽  
pp. 465-478 ◽  
Author(s):  
M. W. Lister
Keyword(s):  
Sodium Chloride ◽  
Ionic Strength ◽  
Rate Constant ◽  
Sodium Hypochlorite ◽  
Rate Constants ◽  
Bimolecular Reaction ◽  
Activation Energies ◽  
Unimolecular Reaction ◽  
Uncatalyzed Reaction ◽  
Catalytic Effects

The decomposition of sodium hypochlorite has been re-examined. The results show that Foerster and Dolch’s mechanism of the decomposition to chlorate and chloride is correct; they postulated a slow bimolecular reaction to chlorite and chloride, followed by a faster reaction of chlorite with more hypochlorite. Values of the rate constants of both steps are reported; they make the activation energies 24.8 kcal./gm-molecule for the first step and 20.8 kcal./gm-molecule for the second. The rates are such that at 40 °C. a solution of sodium hypochlorite will contain about 1% as much chlorite as hypochlorite. The rate is strongly affected by changing ionic strength; at low ionic strengths it is nearly constant or falls slightly; above about 0.8, the rate rises and at high ionic strengths the rise is quite rapid. No signs of specific catalytic effects of sodium chloride, hydroxide, or carbonate could be observed, and it seems probable that earlier reports of this were due to variations in ionic strength. The decomposition to chloride and oxygen has been measured and is a unimolecular reaction, which is possibly, but not certainly, uncatalyzed. Values of its rate constant are reported; they also are much altered by changing the ionic strength.

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