Reaction of Dihydroxymethyl Radical with Molecular Oxygen in Aqueous Solution

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Abstract
Dihydroxymethyl radical (1) was found to react with oxygen diffusion controlled (k = 4.5 x 109 M-1 s-1). The final products of the reaction are formic acid and 1/2 hydrogen peroxide. The precursor of H2O2 was shown to be O2 ·- which is formed with G(O2 ·-) = 6.3 (a value which includes the O2 ·- formed by H atoms and oxygen (G(H) = 0.55)). If it is assumed that dihydroxymethylperoxyl radicals are formed as intermediates the rate constant of O2 ·- formation must be ≥ 106 s-1 . A bimolecular reaction of two dihydroxy-methylperoxyl radicals forming tetroxides does not occur at the dose rates used. The rate constants for the establishment of the equilibrium have been determined at pH 5.7 and 19 °C to be k3=1.9x 10-2 M-1 s-1 and k-3 = 1.5 X 10-6 M-1 s-1 in aqueous solution.