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*.

Forms of H and OH produced in the radiolysis of aqueous system

1962 ◽  
Vol 267 (1331) ◽  
pp. 443-463 ◽  
Keyword(s):  
Aqueous Solution ◽  
Nitrous Oxide ◽  
Hydrogen Atom ◽  
Hydroxyl Radical ◽  
Ground State ◽  
Ferrous Sulphate ◽  
Aqueous System ◽  
Ferrous Ions ◽  
Ph Values ◽  
Ionic Dissociation

As the pH of an aqueous solution of nitrous oxide is increased from 0.1 to 4, G (N 2 ) for the γ -irradiated system increases sigmoidally from 0.75 to 3.1 and G (O 2 ) from 0.1 ± 0.1 to 1.23 while G (H 2 ) decreases from 0.45 to 0.2 and G (H 2 O 2 ) decreases slightly. At all higher pH values G (H 2 ) is constant, but G (N 2 ) and G (O 2 ) are constant only up to pH 11.2 when G (N 2 ) increases suddenly by about one unit and G (O 2 ) possibly undergoes a small increase. These data and the effect of pH on G (Fe 3+ ), G (N 2 ) and G (H 2 ) for N 2 O-containing, de-aerated solutions of ferrous sulphate are explicable in terms of a primary act for γ -irradiated aqueous system s represented by the equation 4.5 H 2 O → 0.45 H 2 + (0.8 - 0.015 pH ) H 2 O 2 + (2.05 + 0.03 pH )OH + 2.75 H a + 0.75 H 2 0*, where H a is an entity, stoiehiometrically equivalent to a hydrogen atom, which can react with N 2 O ultimately forming N 2 and an entity stoichiometrically equivalent to a hydroxyl radical. H a reacts with H + to form H b which reacts with N 2 O much more slowly than H a . H 2 O* is an excited water molecule which can revert to the ground state (lifetime > 10 -9 s) or react with sulphuric acid to form OH or its equivalent and H c , equivalent to a hydrogen atom and which can react with N 2 O in a manner similar to H a . All three species, H a , H b and H c can oxidize ferrous ions and reduce ceric ions in a stoichiometrically equivalent manner. Their possible identities are discussed and it is concluded that probably H a = e aq ., H b = H and H c = H + 2 . The postulated existence of H 2 O* gives a rational description of the hitherto unexplained increases in G OH and ‘conventional’ G H which occurs at pH < 3.5. The ‘step’ in the curve of G (N 2 ) against pH at 11.2 is attributed to ionic dissociation of the hydroxyl radical (→ H + + O - ) and the reaction O - + N 2 O → (N 2 O 2 - ) → 1/2N 2 + NO - 2 .

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.

scholarly journals Kinetics of thiamin cleavage by sulphite

1969 ◽  
Vol 113 (4) ◽  
pp. 611-615 ◽  
Author(s):  
J. Leichter ◽  
M. A. Joslyn
Keyword(s):  
Aqueous Solutions ◽  
Rate Constant ◽  
Sulphur Dioxide ◽  
First Order ◽  
Ph Values ◽  
Rate Of Reaction ◽  
Kinetics Of

Results are presented on the rate of thiamin cleavage by sulphite in aqueous solutions as affected by temperature (20–70°), pH(2·5–7·0), and variation of the concentration of either thiamin (1–20μm) or sulphite (10–5000μm as sulphur dioxide). Plots of the logarithm of percentage of residual thiamin against time were found to be linear and cleavage thus was first-order with respect to thiamin. At pH5 the rate was also found to be proportional to the sulphite concentration. In the pH region 2·5–7·0 at 25° the rate constant was 50m−1hr.−1 at pH5·5–6·0, and decreased at higher or lower pH values. The rate of reaction increased between 20° and 70°, indicating a heat of activation of 13·6kcal./mole.

scholarly journals Comparison of hydrogen atom and hydroxyl radical reactions with simple aromatic molecules in aqueous solution

2020 ◽  
Vol 534 ◽  
pp. 110754 ◽  
Author(s):  
Renáta Homlok ◽  
Viktória Mile ◽  
Erzsébet Takács ◽  
Gábor Járvás ◽  
Szabolcs Góger ◽  
...  
Keyword(s):  
Aqueous Solution ◽  
Hydrogen Atom ◽  
Hydroxyl Radical ◽  
Radical Reactions ◽  
Aromatic Molecules
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