The reactivity of OH radicals with ferro-ferricyanide, formate, ethanol and amino acids in irradiated solutions

Aqueous solutions containing ferro- and ferricyanide were used in the pH range 2.5-10.5 to investigate the reactions of OH radicals produced by ionizing radiations. In the presence of added organic substrates: ethanol, formic acid-formate, glycine or alanine, the rate constant ratio k _{OH+ferrocyanide}/k_OH+RH2 could be determined. As the ferro-ferricyanide system does not change with pH in this range the respective reactivities of the different ionic forms of the organic substrates with OH radicals could be derived. The results are compared with the reactions of OH radicals in other systems. Indications are obtained and discussed of the increased reactivity of OH radicals in aqueous solution compared with the gas phase.