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  • Title: Peculiar structure of the HOOO(-) anion.
    Author: Kraka E, Cremer D, Koller J, Plesnicar B.
    Journal: J Am Chem Soc; 2002 Jul 17; 124(28):8462-70. PubMed ID: 12105928.
    Abstract:
    The HOOO(-) anion (1) can adopt a triplet state (T-1) or a singlet state (S-1), where the former is 9.8 kcal/mol (DeltaH(298) = 10.3 kcal/mol) more stable than the latter. S-1 possesses a strong O-OOH bond with some double bond character and a weakly covalent OO-OH bond (1.80 A) according to CCSD(T)/6-311++G(3df,3pd) calculations (the longest O-O bond ever found for a peroxide). In aqueous solution, S-1 adopts a geometry closely related to that of HOOOH (OO(O), 1.388 A; (O)OO(H), 1.509 A; tau(OOOH), 78.3 degrees ), justifying that S-1 is considered the anion of HOOOH. Dissociation into HO anion and O(2)((1)Delta(g)) requires 15.4 (DeltaH(298) = 14.3; DeltaG(298) = 8.9) kcal/mol. Structure T-1 corresponds to a van der Waals complex between HO anion and O(2)((3)Sigma(g)(-)) having a binding energy of 2.7 (DeltaH(298) = 2.1) kcal/mol. Modes of generating S-1 in aqueous solution are discussed, and it is shown that S-1 represents an important intermediate in ozonation reactions.
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