The self-reaction of hydroperoxyl radicals: ab initio characterization of dimer structures and reaction mechanisms
نویسندگان
چکیده
The global potential energy surfaces of singlet and triplet H2O4 systems have been searched at the B3LYP/ 6-311G(d, p) level of theory; their relative energies have been calculated at the G2M(CC5)// B3LYP/6-311G (d, p) level. The results show that the most stable intermediate out of the 11 open-chain and cyclic dimers of HO2 is the singlet HO4H chain-structure with C1 symmetry which lies 19.1 kcal mol 21 below the reactants. The transition states for the production of H2O2 z O2 (singlet and triplet), H2O z O3 and H2 z 2O2 have been calculated at the same level of theory. The results show that the most favored product channel, producing H2O2 z O2, occurs by the formation of a triplet six-member-ring intermediate through head-to-tail association with a dual hydrogen-bonding energy of 9.5 kcal mol. The intermediate fragments to give H2O2 z O2 via a transition state, which lies below the reactants by about 0.5 kcal mol. There are four channels over the singlet surface which can produce O2; all the transition states associated with these channels lie above the reactants by 2.8–5.6 kcal mol at the G2M level. Similarly, the O3 and H2 formation channels also occur over the singlet surface with high energy barriers, 5.2 and 74.2 kcal mol, respectively; their formation is kinetically unimportant.
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