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1983 (1)
1982 (1)
1Author    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 
2Author    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