Ligand dependence in the copper-catalyzed oxidation of hydroquinones

Arch Biochem Biophys. 2005 Mar 1;435(1):21-31. doi: 10.1016/


Transition metal-mediated oxidation of hydroquinones is an important physiologic reaction, and copper(II) effectively catalyzes the reaction in phosphate-buffered saline (PBS). Studies reported herein in phosphate buffer alone demonstrate that copper(II) is an ineffective catalyst in the absence of coordinating ligands, but that 1,10-phenanthroline and histamine facilitate the copper(II)-mediated oxidation of hydroquinone and its 2,5- and 2,6-di-tert-butyl analogs to the corresponding benzoquinones. The high concentration of chloride in PBS is the key element that allows copper(II) to work in this system. Although the bis-bathocuproine disulfonate complex of Cu(II), (BC)(2)Cu(II), is a strong stoichiometric oxidant, stoichiometric amounts of copper(II) in the presence of ligands other than BC oxidize hydroquinones very slowly under anaerobic conditions. Thus, the rapid copper(II)-catalyzed reaction operating aerobically does not involve a simple ping-pong reduction of copper(II) to copper(I) by hydroquinone and reoxidation of copper(I) by O(2).

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Benzoquinones / chemical synthesis*
  • Catalysis
  • Copper / chemistry*
  • Histamine / chemistry*
  • Hydroquinones / chemistry*
  • Ligands
  • Oxidation-Reduction
  • Oxygen / chemistry*
  • Phenanthrolines / chemistry*


  • Benzoquinones
  • Hydroquinones
  • Ligands
  • Phenanthrolines
  • Copper
  • Histamine
  • Oxygen