Reactions of Mn(II) and Mn(III) with alkyl, peroxyalkyl, and peroxyacyl radicals in water and acetic acid.

The kinetics of oxidation of Mn(II) with acylperoxyl and alkylperoxyl radicals were determined by laser flash photolysis utilizing a macrocyclic nickel complex as a kinetic probe. Radicals were generated photochemically from the appropriate ketones in the presence of molecular oxygen. In both acidic aqueous solutions and in 95% acetic acid, Mn(II) reacts with acylperoxyl radicals with k = (0.5-1.6) x 10(6) M(-1) s(-1) and somewhat more slowly with alkylperoxyl radicals, k = (0.5-5) x 10(5) M(-1) s(-1). Mn(III) rapidly oxidizes benzyl radicals, k = 2.3 x 10(8) M(-1) s(-1) (glacial acetic acid) and 3.7 x 10(8) M(-1) s(-1) (95% acetic acid). The value in 3.0 M aqueous perchloric acid is much smaller, 1 x 10(7) M(-1) s(-1). The decarbonylation of benzoyl radicals in H(2)O has k = 1.2 x 10(6) s(-1).