ETAL INDUCED RADICAL REACTIONS

Competition between metal ion-induced and radical-induced decompositions of alkyl hydroperoxides is affected by several factors. First, the competition is influenced by the relative concentrations of the metal complex and the hydroperoxide. At high concentrations of the hydroperoxide relative to the metal complex, alkoxy radicals will compete effectively with the metal complex for the hydroperoxide. Competition is also influenced by the nature of the solvent (see above). Contribution from the metal-induced reaction is expected to predominate at low hydroperoxide concentrations and in reactive solvents. The contribution from the metal-induced decomposition to the overall reaction is readily determined by carrying out the reaction in the presence of free radical inhibitors, such as phenols, that trap the alkoxy radicals and, hence, prevent radical-induced decomposition.129,1303 Thus, Kamiya etal.129 showed that the initial rate of the cobalt-catalyzed decomposition of tetralin hydroperoxide, when corrected for the contribution from radical-induced decomposition by the... 

Methyl-l-phenyl-2-pyrazolin-5-one (MCI-186) is a potent scavenger of hydroxyl radicals inhibiting not only hydroxyl radicals but iron-induced per-oxidative injury (Watanabe etal. 1988, Muroto et al. 1990). After the reaction with peroxy radicals, MCI-186 changes into 2-oxo-3-(phenylhydrazone)-butanoic acid (Yamamoto et al. 1996, Kawai et al. 1997). In a thrombotic rat distal middle cerebral artery occlusion model, 3-methyl-l-phenyl-2-pyrazolin-5-one (3 mg/kg) significantly P < 0.05) decreased the size of the cerebral infarct 1 day after artery occlusion (Kawai et al. 1997). 

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