Experimental kinetic data related to the reaction of carbonyl compounds with peroxynitrite anion, ONOO-, in aqueous solutions was combined with estimated rate constants for the recombination of alkoxyl radicals with nitrogen dioxide. The equilibrium constants for O- transfer from ONOO- and OH transfer from ONOOH to the carbonyls were derived and the Gibbs' energies of formation of the neutral and anionic alpha-hydroxy alkoxyl radicals were calculated. By means of these data the O-H bond strengths in carbonyl hydrates as well as reduction potentials of the alkoxyl radicals were obtained.