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1984 (1)
1983 (1)
1Author    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 
2Author    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