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

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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 × 109dm3mol-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 × 10 7 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 × 10 7 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)

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