The reduction of ferrideuteroporphyrin by a-hydroxyisopropyl radicals is investigated in acidic 2-propanol and acidic 2-propanol-water mixtures by means of steady-state and pulse radiolysis. The rate constant of the reaction is much higher (k N 1.3 X log M-'8-l) than that reported for neutral solutions emphasizing the effect of the positive charge carried by the ferric porphyrin in acidic solutions (due to protonation of the alkoxide ligand). Competition ...