scholarly journals Pulse Radiolysis Study of Reaction of OH Radicals with Triose Reductone

1986 ◽  
Vol 59 (3) ◽  
pp. 721-724 ◽  
Author(s):  
Hideo Horii ◽  
Yasuo Abe ◽  
Setsuo Taniguchi
Keyword(s):  
Pulse Radiolysis ◽  
Oh Radicals

Reactions of OH Radicals with Acetylacetone in Aqueous Solution. A Pulse Radiolysis and Electron Spin Resonance Study

1982 ◽  
Vol 37 (3) ◽  
pp. 368-375 ◽  
Author(s):  
R. K. Broszkiewicz ◽  
T. Söylemez ◽  
D. Schulte-Frohlinde
Keyword(s):  
Double Bond ◽  
Pulse Radiolysis ◽  
Visible Region ◽  
Alkaline Condition ◽  
Main Reaction ◽  
Electron Spin Resonance Study ◽  
Oh Radicals ◽  
Oh Radical ◽  
Keto Form ◽  
Optical Absorbance

Abstract Pulse radiolysis experiments monitoring optical absorbance as well as conductivity and in-situ ESR radiolysis studies show that the OH radical reacts with the enol (k=8.6 x 109 M-1 s-1) and the enolate (k = 7.4 X 109 M-1 s-1) forms of acetylacetone by addition to the C = C double bond in aqueous N2O saturated solution. The OH reaction with enol leads to equal amounts of two radicals, CH3COCHOHCOHCH3 (2) and CH3COCHC(OH)2CH3 (4), as determined by scavenger reactions. At pH less than 1 the radical CH3COCHCOCH3 (1) is observed by ESR spectroscopy showing that radical 2 and/or 4 eliminate water by proton catalyzed reactions. Under alkaline condition the OH adducts to the enolate eliminate OH -with rate constants larger than 105 s-1 leading to radical 1. G(OH-) is determined to be 5.6 showing that addition is the main reaction of OH with enolate. To a much smaller degree the OH radical is proposed to abstract an H atom from that CH3 group which is attached to the C -C double bond in enol and enolate, producing substituted allyl radicals which absorb in the visible region. The reaction of OH with the keto form has not been observed indicating that the rate constant of this reaction is significantly smaller than those with enol and enolate.

Pulse Radiolysis of Cycloserine in Aqueous Solutions. One-Electron Oxidation by OH Radicals

1984 ◽  
Vol 57 (12) ◽  
pp. 3403-3407 ◽  
Author(s):  
Masako Tanaka ◽  
Hiroshi Sakuma ◽  
Osamu Kohanawa ◽  
Seijun Fukaya ◽  
Meiseki Katayama
Keyword(s):  
Aqueous Solutions ◽  
Pulse Radiolysis ◽  
Oh Radicals

A pulse radiolysis study of solvated electrons in tert-butanol/water solutions

1986 ◽  
Vol 64 (8) ◽  
pp. 1548-1552
Author(s):  
Joanna Cygler ◽  
Norman V. Klassen ◽  
Carl K. Ross
Keyword(s):  
Experimental Data ◽  
Pulse Radiolysis ◽  
Oh Radicals ◽  
Solvated Electrons ◽  
Secondary Electrons ◽  
Water Solutions ◽  
Tert Butanol

Many solutes, added to water in amounts of a few mol%, cause an increase in the yield of solvated electrons (es−) measured by pulse radiolysis. A pulse radiolysis study of tert-butanol (tBuOH) in D2O has been carried out to investigate this phenomenon. Detailed measurements of the yield, measured as Gεmax(es−), and the deeay of solvated electrons were made at 6, 25, and 46 °C over the range 0–5mol% tBuOH. The maximum Gεmax(es−) occurs at about 1 mol% tBuOH, but the exact concentration depends on the temperature of the sample and the time after the pulse at which the measurement is made. Three factors are examined as contributing to the increased Gεmax(es−) in the presence of tBuOH and certain other solutes. They are (i) the change in viscosity produced by the added solute, (ii) the scavenging of OH radicals by the solute, thereby reducing the reaction of OH with es− and (iii) the possibility that the addition of the solute leads to an increase in the thermalization distance of the secondary electrons. It is concluded that effects (i) and (ii) are sufficient to explain the existing experimental data.

Site of H Atom Attack on Uracil and Its Derivatives in Aqueous Solution

1985 ◽  
Vol 40 (3-4) ◽  
pp. 292-294 ◽  
Author(s):  
Suresh Das ◽  
David J. Deeble ◽  
Clemens von Sonntag
Keyword(s):  
Aqueous Solution ◽  
Double Bond ◽  
Pulse Radiolysis ◽  
Hydrogen Abstraction ◽  
Methyl Groups ◽  
Oh Radicals ◽  
Hydrogen Atoms ◽  
Sugar Moiety ◽  
Reducing Properties

Hydrogen atoms from the radiolysis of water at pH 1.6 add to the 5,6-double bond of pyrimidines. The preferen­tial site of attack is the C(5) position (values in brackets) in the case of 6-methyluracil (87%), 1,3-dimethyluracil (71%), uracil (69%) and poly(U) (60%). This reaction yields a radical of reducing properties which can be monitored by its reaction with tetranitromethane in a pulse radiolysis experiment. In thymine (37%), thymidine (32%) and 1,3-dimethylthymine (25%) H-addition no longer pre­ferentially occurs at C(5), but addition is now mainly at C(6). Hydrogen abstraction from the methyl groups or the sugar moiety is negligible (≦ 5.5%). A comparison is made with literature values for the equivalent reactions of OH radicals.

Notizen: Pulse Radiolysis of Selenium Containing Compounds: Selenomethionine

1974 ◽  
Vol 29 (7-8) ◽  
pp. 571-572 ◽  
Author(s):  
Maurizio Tamba ◽  
Sergio Bonora ◽  
Roberto Badiello
Keyword(s):  
Optical Absorption ◽  
Aqueous Solutions ◽  
Absorption Spectra ◽  
Pulse Radiolysis ◽  
Oh Radicals ◽  
Optical Absorption Spectra ◽  
Transient Species ◽  
Decay Kinetics ◽  
Kinetics Of

The pulse radiolysis of aqueous solutions of selenomethionine has been studied under both neutral and acid conditions and the transient optical absorption spectra have been observed. The reactivities of both eāq and OH radicals have been measured as well as the formation and the decay kinetics of the transient species.

scholarly journals The Reactions of Hydroxyl Radicals with 1,4-and 1,3-Cyclohexadiene in Aqueous Solution

1988 ◽  
Vol 43 (9) ◽  
pp. 1201-1205 ◽  
Author(s):  
Xian-Ming Pan ◽  
Eugenie Bastian ◽  
Clemens von Sonntag
Keyword(s):  
Hydroxyl Radicals ◽  
Pulse Radiolysis ◽  
Hydrogen Abstraction ◽  
Material Balance ◽  
Oh Radicals ◽  
Oh Radical ◽  
Product Analysis ◽  
Γ Irradiation ◽  
Abstraction Reaction ◽  
G Value

Abstract The reactions of radiolytically generated hydroxyl radicals and H atoms with 1,4- and 1,3-cyclohexadiene were studied by pulse radiolysis and product analysis. Hydrogen abstraction from these substrates by the OH radical yields the cyclohexadienyl radical (ε (310 nm) = 4400 dm3 mol-1 cm-1 from the reaction of the H atom with benzene) with an efficiency of 50% (0.29 ,μmol J-1) in the case of 1,4-cyclohexadiene and 25% (0.15 ,μmol J-1) in the case of 1,3-cyclohexadiene as determined by pulse radiolysis. The remaining OH radicals add to the olefin. In 1.4-cyclohexa- diene the yield of the resulting adduct radicals has been determined in a steady-state 60Co-γ-irradiation experiment by reducing it with added 1.4-dithiothreitol (DTT) to 4-hydroxycyc- lohexene. There are two sites of OH radical attack in the case of 1.3-cyclohexadiene, and only the alkyl radical is reduced quantitatively by DTT (G(3-hydroxycyclohexene) = 0.15 ,μmol J-1). From material balance considerations it is concluded that the allylic radical must be formed with a G value of 0.28 ,μmol J-1 but largelv escapes reduction by DTT (G(4-hvdroxycyclohexene) = 0.03 ,μmol J-1). H atoms add preferentially to the double bonds of 1,4- and 1,3-cyclohexadiene (78% and 93%, respectively), while the O.- radical (the basic form of the OH radical) undergoes mainly H- abstraction (92% and 83%, respectively). The radicals formed in these systems decay bimolecularly (2k = 2.8 x 109 dm3 mol-1 s-1). In their combination reactions the cyclohexadienyl radicals form the four possible dimers in propor­tions such that the dienyl radical moiety shows a 2:1 preference to react from its central (1a) rather than from a terminal carbon atom (1b). Cyclohexadienyl radicals and the OH- and H-adduct radicals also cross-tcrminate by disproportionation and dimerization. Material balance has been obtained for the 1,4-cyclohexadiene system in N2O-Saturated solution (10-2 mol dm-3) at a dose rate of 0.14 Gy s-1, the products (G values in ,μmol J-1) being: benzene (0.085), 4-hydroxycyclohexene (0.25), cyclohexadienyl-dimers (0.144). cvclohexadienyl-OH-adduct- dimers (0.02), OH-adduct-dimers (0.02). Some of the 4-hydroxycyclohcxene is formed in an H-abstraction reaction by the OH-adduct radical from 1,4-cyclohexadiene.

The UV Absorption Spectra of the C(5) and C(6) OH Adduct Radicals of Uracil and Thymine Derivatives. A Pulse Radiolysis Study

1985 ◽  
Vol 40 (11-12) ◽  
pp. 925-928 ◽  
Author(s):  
David J. Deeble ◽  
Clemens von Sonntag
Keyword(s):  
Absorption Spectra ◽  
Pulse Radiolysis ◽  
Uv Spectra ◽  
Uv Absorption ◽  
Oh Radicals ◽  
Uv Absorption Spectra

Abstract Using pulse radiolysis the UV spectra of the C(6) OH adduct radicals of 1,3-dimethyluracil and 1,3-dimethylthy-mine were obtained by reacting the formate radical with the corresponding 5-bromo-5,6-dihydro-6-hydroxy derivatives. In the reaction of the pyrimidines with OH radicals a mixture of C(5) and C(6) OH adduct radicals is formed. From the known ratios in which these two radicals are formed and the spectra of the C(6) OH adduct radicals, the spectra of the C(5) OH adducts were calculated.

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