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1984 (1)
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1Author    W. A. Prütz, S. VogelRequires cookie*
 Title    Specific Rate Constants of Hydroxyl Radical and Hydrated Electron Reactions Determined by the RCL Method  
 Abstract    Relative rate constants of OH radical and eaq~ reactions have been determined by comparing, under steady x-irradiation, the effect of various solutes upon the radiation-induced chemiluminescence (RCL) of aqueous dye (DH) solutions, [DH + -OH] + eaq --> DH* + OH -. The results abundantly confirm other published data. RCL changes upon addition of phosphates indicate prototropic reactions with the oxidized dye, D'-f^PO^ ^ DH-+ + HPO4 2-, promoting or inhibiting the formation of semioxidized dye (DH-+) as the most efficient RCL precursor. The RCL enhancement commonly observed upon addition of halides and pseudo halides is discussed at some length on the base of previous and present results in order to focus attention to the possible correlation between such RCL enhancement and the effect of halogen-sensitization in radiobiology. RCL results suggest that the halide transients formed from OH radicals, X -+ -OH X 1 -f OH -, are very powerful oxidizing agents reacting with aromatics by electron-abstraction rather than by addition or H-abstraction. The common application of I -and SCN -as competitors for the estimation of OH radical reactivities is being commented in the context. 
  Reference    (Z. Naturforsch. 31b, 1501—1510 [1976]; received July 12 1976) 
  Published    1976 
  Keywords    Hydrated Electron, Hydroxyl Radical, Luminescence, Radiation Chemistry, Rate Constants 
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 TEI-XML for    default:Reihe_B/31/ZNB-1976-31b-1501.pdf 
 Identifier    ZNB-1976-31b-1501 
 Volume    31 
2Author    Nien Man, Clemens Schuchmann, Von SonntagRequires cookie*
 Title    Determination of the Rate Constants of the Reactions C02 -f-OH~ -> HC03 — and Barbituric Acid -> Barbiturate Anion + Using the Pulse Radiolysis Technique  
 Abstract    The kinetics of the reactions of CO2 + OH --»HCO3 -(i) and barbituric acid ^barbi-turate anion -j-H + (ii) have been remeasured using as a new approach the pulse radiolysis technique with optical and conductivity detection. The rate constants obtained in the present study, ki (21 °C) = 6900 ± 700 M^s" 1 and ku (19 °C) = 22 ± 2s-1 agree within experimental errors with values obtained earlier by other methods. 
  Reference    Z. Naturforsch. 37b, 1184—1186 (1982); received March 29 1982 
  Published    1982 
  Keywords    Fast Reaction Kinetics, Pulse Conductometry, Peroxyl Radicals, Radiation Chemistry 
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 TEI-XML for    default:Reihe_B/37/ZNB-1982-37b-1184.pdf 
 Identifier    ZNB-1982-37b-1184 
 Volume    37 
3Author    Eberhard Bothe, Nien Man, Dietrich Schuchmann, Schulte-Frohlinde, Clemens Von SonntagRequires cookie*
 Title    Hydroxyl Radical-Induced Oxidation of Ethanol in Oxygenated Aqueous Solutions. A Pulse Radiolysis and Product Study  
 Abstract    y-Radiolysis of N20-saturated water or photolysis of aqueous H2O2 provided a source of OH radicals. These radicals react with ethanol by preferentially abstracting an H atom at C-l. In the presence of oxygen these radicals are converted into the corresponding peroxyl radicals. The a-hydroxyethylperoxyl radicals decay by first order kinetics (k = ki + k2 [OH -]) acetaldehyde and H02/H+ + 01 being the products (ki (20 °C) = 50 ± 10 s" 1 , Ea = 66 ± 7 kJ-mol -1 , k2= (4± 1) X 10 9 M -1 s -1). In competition (favoured by low pH, low tem-perature and high dose rate) they also decay by second order kinetics (2k3 = (7 ^ 2) x 10 8 M~ 1 s _1). The most important route in the bimolecular decay leads to acetaldehyde, acetic acid and oxygen (ca. 75%). This route might largely be concerted (Russell mech-anism), but there might also be a contribution from the disproportionation of oxyl radicals within the solvent cage. There is also a concerted route that leads to two molecules of acetic acid and to hydrogen peroxide (ca. 10%). Another pathway (ca. 15%) yields two oxyl radicals and oxygen. The former may either decompose into formic acid and methyl radicals (ca. 5%) or rearrange into 1,1-dihydroxyethyl radicals (ca. 10%). These radicals add oxygen and the resulting peroxyl radicals rapidly decompose into acetic acid and HO2. The reaction of a-hydroxyethylperoxyl radicals with H02/02 radicals appears to be slow (k» 10 7 M-is-i). 
  Reference    Z. Naturforsch. 38b, 212—219 (1983); received September 28 1982 
  Published    1983 
  Keywords    Pulse Conductometry, Peroxyl Radicals, Oxyl Radicals, Radical Rearrangements, Radiation Chemistry 
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 TEI-XML for    default:Reihe_B/38/ZNB-1983-38b-0212.pdf 
 Identifier    ZNB-1983-38b-0212 
 Volume    38 
4Author    Heinz-Peter Schuchmann, Clemens Von SonntagRequires cookie*
 Title    Methylperoxyl Radicals: A Study of the y-Radiolysis of Methane in Oxygenated Aqueous Solutions  
 Abstract    A product study has been made of the y-radiolysis of aqueous methane solutions that also contained nitrous oxide and oxygen. Formaldehyde (G = 2.8), hydrogen peroxide (G = 2.1), methanol (G = 1.5), methylhydroperoxide (G = 0.8), formic acid (G = 0.3), and dimethylper-oxide (G = 0.1) were found. In alkaline solutions (pH 8, 10-3 M phosphate buffer), the formal­ dehyde yield rises to G = 3.2, while the formic acid yield falls to almost zero (G = 0.05). The initial precursor of the carbon-containing products is the methylperoxyl radical. The methyl­ peroxyl radicals decay through a short-lived tetroxide along various pathways. The most promi­ nent one leads to formaldehyde, methanol and oxygen. Methoxyl radicals (and oxygen) are also formed and, after rearrangement into hydroxymethyl radicals and their conversion into hy-droxymethylperoxyl radicals, eventually yield formic acid and probably further formaldehyde. A route to formaldehyd and hydrogen peroxide is also envisaged. Methylhydroperoxide is formed in the reaction of methylperoxyl radicals with H 0 2 / 0 27 radicals (from radiolytic H atoms and the unimolecular decay of the hydroxymethylperoxyl radical). 
  Reference    Z. Naturforsch. 39b, 217 (1984); received September 19 1983 
  Published    1984 
  Keywords    Autoxidation, Peroxyl Radicals, Oxyl Radicals, Radical Rearrangements, Radiation Chemistry 
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 TEI-XML for    default:Reihe_B/39/ZNB-1984-39b-0217.pdf 
 Identifier    ZNB-1984-39b-0217 
 Volume    39