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1Author    Horst-Dieter Försterling, Szilvia Murányi, Helmut SchreiberRequires cookie*
 Abstract    In the Belousov-Zhabotinsky system bromine species of oxidation states — 1 to 5 are important for the start and for the inhibition of the autocatalytic reaction steps. Especially, the reaction of Br~ with HBr02 competes with the oxidation of Ce3+ by BrOz formed from HBrO, and HBr03. In our investigation the reaction of Br with HBr02 (solvent 1 M sulfuric acid) is followed spectroscopi-cally in a mixture of bromine and hypobromous acid, which system works as a buffer for bromide. Including experiments on the hydrolysis of Br2 and on the solubility product of AgBr in 1 M sulfuric acid solution direct information about the rate constant kl of the Br~/HBrO, reaction is obtained (fc, = 2.5 x 106 M"2 s"1 at 20 C and 4x 106 M"2 s"1 at 25°C, which values are valid in the range of 0.01 to 1 M sulfuric acid). R a te o f th e B ro m o u s A c i d -B r o m i d e R e a c tio n 
  Reference    Z. Naturforsch. 44a, 555 (1989); received March 15 1989 
  Published    1989 
  Keywords    Belousov-Zhabotinsky reaction, Bromous acid Bromide, Bromine hydrolysis, Bromate, Dual wavelength spectroscopy 
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 TEI-XML for    default:Reihe_A/44/ZNA-1989-44a-0555.pdf 
 Identifier    ZNA-1989-44a-0555 
 Volume    44 
2Author    Horst-Dieter Försterling, Szilvia MurányiRequires cookie*
 Title    Contribution of Malonyl Radical Control in the Classical Belousov-Zhabotinsky Reaction  
 Abstract    In the original theory of the Belousov-Zhabotinsky reaction it is assumed that the oscillations are exclusively controlled by bromide ions. From uv/vls and ESR experiments on BZ systems started with Ce 4+ we conclude that malonyl radicals play an important role as additional intermediates. The experiments are in agreement with calculations based on the Radicalator model. 
  Reference    Z. Naturforsch. 45a, 1259—1266 (1990); received July 15 1990 
  Published    1990 
  Keywords    Belousov-Zhabotinsky reaction, Cerium, Malonic acid, Bromate, Bromide, Feedback, Malonyl radicals 
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 TEI-XML for    default:Reihe_A/45/ZNA-1990-45a-1259.pdf 
 Identifier    ZNA-1990-45a-1259 
 Volume    45 
3Author    Thomas Buhse, Wolfram ThiemannRequires cookie*
 Title    Chiral Intermediates and the Oscillatory Effect of Circular Dichroism in the Belousov -Zhabotinskii Type Reaction of L-Ascorbic Acid  
 Abstract    Investigating the Belousov-Z habotinskii (BZ) type reaction of an acidic L-ascorbic acid (AA) / potassium brom ate / cerous sulfate system, an oscillatory effect of circular dichroism is detectable at A = 300 nm. HPLC analysis o f the oscillatory mixture and spectroscopic experi­ ments indicate that this effect is caused by 3,4,5-trihydroxy-2-oxo-L-valeraldehyde (TVA) -a C5 oxidation fragment of AA. Because of the bromide ion production occurring before the metal catalyst addition the AA system shows no preoscillatory phase and a rather short entire length of oscillation up to a maximum of 20 min. Since AA is not brom inated but oxidized by bromine which is formed by the Landolt typ "clock reaction" o f AA with acidic brom ate, par­ tially bromine-hydrolysis-controlled (BHC) oscillations are discussed for the overall mecha­ nism of this BZ system. 
  Reference    Z. Naturforsch. 46b, 1406—1414 (1991); received 
  Published    1991 
  Keywords    M arch 1, 1991 Chemical Oscillations, CD Spectra, L-Ascorbic Acid, B elousov-Z habotinskii Reaction, Bromate 
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 TEI-XML for    default:Reihe_B/46/ZNB-1991-46b-1406.pdf 
 Identifier    ZNB-1991-46b-1406 
 Volume    46