The Redox Thermodynamics for Dioxygen Species (O2, O2-·, HOO·, HOOH, and HOO-) and Monooxygen Species (O, O, ·OH, and -OH) in Water and Aprotic Solvents

  • Donald T. Sawyer
Part of the Basic Life Sciences book series (BLSC, volume 49)


Biological systems activate dioxygen (O2) by reduction via electron transfer and H-atom transfer to give intermediates that may be further activated by transition metals in proteins and metabolic co-factors. The reaction thermodynamics for these processes are influenced by the solution matrix and its acidity. Thus, the redox thermodynamics of O2 are directly dependent upon proton activity, O2 + 4H+ + 4e- → 2 H2O E°’ (1) which in turn depends upon the reaction matrix. Table 1 summarizes the pKa’ values for a series of Br0nsted acids in several aprotic solvents and water.1 In acetonitrile the activity values for pKa’ range from -8.8 for (H3O)ClO4 to 30.4 for H2O. This means that the formal potential (E°’) for reaction 1 in acetonitrile (MeCN) is +1.75 V vs. NHE in the presence of 1M(H3O)ClO4 and -0.56 V in the presence of IM (Bu4N)OH.


Methyl Viologen Aprotic Solvent Anhydrous Acetonitrile Aprotic Medium Allylic Hydrogen 
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Copyright information

© Plenum Press, New York 1988

Authors and Affiliations

  • Donald T. Sawyer
    • 1
  1. 1.Department of ChemistryTexas A&M UniversityCollege StationTexasUSA

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