Radiolysis of Tertiary Butyl Hydroperoxide in Aqueous Solution. Reductive Cleavage by the Solvated Electron, the Hydrogen Atom, and, in Particular, the Superoxide Radical Anion

Abstract

The reactions of the solvated electron, the H atom, the OH radical and the superoxide radical anion with t-butylhydroperoxide (t-BuOOH) have been studied in aqueous solutions using γ-radiolysis and pulse radiolysis to generate these radicals. The solvated electron reacts rapidly with t-BuOOH (k = 5 × 109 dm3 mol-1 s-1) yielding t-BuO and OH in a ratio of 4:1. The yield of t-BuO has been determined by measuring its fragmentation product, acetone. The H atom reacts more slowly with t-BuOOH (k = 5× 107 dm3 mol-1 s-1). There is very little H-abstraction from the methyl and the hydroperoxyl groups (about 3%), the main reaction again being the scission of the hydroperoxyl function with a branching ratio t-BuO/OH of about unity. The OH radical reacts with t-BuOOH considerably more slowly (k = 8 × 107 dm3 mol-1 s-1) than with t-butanol (k = 5 × 108 dm3 mol-1 s-1) with an approximate preference of 8:1 of abstracting a methyl hydrogen over a hydroperoxyl hydrogen atom. The carbon-centered radical undergoes γ-cleavage (k ≈ 102 s-1) thereby reforming an OH radical. The resulting chain reaction is rather short (maximum yield G(2-methyl-1,2-epoxypropane), 26 × 10-7 mol J-1 at low dose rate) due to H-abstraction at the hydroperoxyl function of t-BuOOH by the OH radical. The superoxide radical anion also reacts with t-BuOOH by cleaving the hydroperoxyl function. Its reactivity is, however, rather low (k = 5 dm3 mol-1 s-1). © 1990, Walter de Gruyter. All rights reserved.