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Keywords:

  • oxidation;
  • catalysis;
  • hexacyanoferrate(III);
  • ruthenium(III);
  • ruthenium(VI);
  • alcohols;
  • 2-methyl-2,4-pentanediol

Abstract

The oxidation reactions of 2-methyl-2,4-pentanediol upon treatment with alkaline hexacyanoferrate(III) using Ru(III) or Ru(VI) as catalysts are governed by two quasi-identical experimental rate equations, which show that both catalysts are equally effective for the oxidation of alcohols by equation image. The reaction mechanism proposed involves the oxidation of 2-methyl-2,4-pentanediol by the catalyst, a process that occurs through the formation of a substrate–catalyst complex. The decomposition of this complex yields Ru(IV) and a protonated ketone (owing to a hydride transfer from the α-C—H bond of the alcohol to the oxoligand of ruthenium) in the case of Ru(VI), but a ketyl radical and Ru(II) (hydrogen transfer) for Ru(III). The role of the co-oxidant, equation image, is to regenerate the catalyst. For both oxidation reactions, the rate constants of complex decomposition and catalyst regeneration have been determined. Copyright © 2004 John Wiley & Sons, Ltd.