The hydroxylation of the salicylate anion by a Fenton reaction and T-radiolysis: a consideration of the respective mechanisms

Free Radic Biol Med. 1990;8(2):153-62. doi: 10.1016/0891-5849(90)90088-z.


The yield of 2,3- and 2,5-dihydroxybenzoates (dHB's) from the reaction of .OH radicals with salicylate (SA) ions has been measured as a function of pH and in the presence of oxidants. Under steady-state radiolysis conditions, the production of these products occurs via the reactions .OH + SA----HO-SA. (radical adduct) HO-SA. H+.OH+----2-carboxyphenoxyl radical (SA.) + H2O HO-SA. + SA.----2,3-/2,5-dHB + SA The addition of the oxidants O2, Fe3+ edta, or Fe(CN)63- increases the relative yield of 2,5-dHB/2,3-dHB from about 0.2 to 1. A model to account for this effect is presented. Steady-state radiolyses of 3- and 4-hydroxybenzoate give dihydroxybenzoate products consistent with the phenol group being an ortho-para director in the electrophilic attack of the hydroxyl radical on the aromatic ring. A comparison of product distributions from the reaction of ferrous edta with hydrogen peroxide using salicylate as a scavenger strongly suggests that the same hydroxyl radical adducts are formed as in the radiation experiments.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Azides / analysis
  • Chemical Phenomena
  • Chemistry
  • Edetic Acid / pharmacology
  • Free Radicals
  • Gamma Rays
  • Gentisates*
  • Hydrogen Peroxide*
  • Hydrogen-Ion Concentration
  • Hydroxybenzoates / analysis
  • Hydroxylation
  • Iron*
  • Kinetics
  • Oxidation-Reduction
  • Salicylates / analysis*
  • Salicylates / radiation effects


  • Azides
  • Fenton's reagent
  • Free Radicals
  • Gentisates
  • Hydroxybenzoates
  • Salicylates
  • 2,3-dihydroxybenzoic acid
  • Edetic Acid
  • Hydrogen Peroxide
  • Iron
  • 2,5-dihydroxybenzoic acid