Complexes of bivalent iron stabilized in the FeZSM-5 zeolite matrix (alpha-sites) are known to be able to decompose nitrous oxide stoichiometrically to form oxygen anion radicals, O-, bound to iron (alpha-oxygen), (Fe-II)(alpha) + N2O -> (Fe-III-O-)(alpha) + N-2. Similar to O- radicals on V and Mo oxides, alpha-oxygen is highly reactive in respect to CO, H-2, methane and other hydrocarbons. It participates in catalytic oxidation of benzene to phenol by nitrous oxide, providing selectivity close to 100%. In this work, adsorption measurements, IR spectroscopy, TPD, and isotope methods were used to describe an earlier unknown reaction of O- species with water, which proceeds at 5200 degrees C via the hydrogen abstraction mechanism according to the equation 2(Fe-III-O-)(alpha) + H2O -> 2(Fe-III-OH-)(alpha) + (1/2)O-2. The reaction leads to the hydroxyl groups formed on alpha-sites, and equivalent amount Of 02 evolves into the gas phase from water. Desorption of the hydroxyl groups occurs at above 400 degrees C via their recombination into water and dioxygen, resulting in the reactivation of alpha-sites, 2(Fe-III-OH-)(alpha) -> 2(Fe-II)(alpha) + H2O + (1/2)O-2. High sensitivity of alpha-oxygen to water admixtures may be an important factor explaining some contradictory results reported in the literature on the behavior of alpha-oxygen. Because alpha-oxygen is a typical representative of anion radicals O-, this reaction may be relevant not only to the conventional oxidation catalysis over zeolites and metal oxides, but also to photocatalytic processes, where formation of O- is well documented. (c) 2007 Elsevier Inc. All rights reserved.