Unraveling the interaction between singlet state atomic oxygen O(1D) and water: toward the formation of oxywater and hydrogen peroxide

Abstract

We performed high-level quantum mechanical calculations to explore the interaction of atomic oxygen in the ground triplet state, O(³P), and the excited singlet state, O(¹D), with water. We reported the potential energy curves for a few lowest electronic states when an atomic oxygen approaches the oxygen of a water molecule. Our results predict the formation of a singlet oxywater species as the product of O(¹D) and H₂O which lies about 149.33 kJ mol⁻¹ below the total energy of a singlet oxygen atom and a water molecule. Our calculations predict that an O(³P) atom interacting with a water molecule forms a triplet oxywater complex with a shallow minimum on the triplet potential energy surfaces. We examined the transition of the singlet state oxywater species to hydrogen peroxide through the unimolecular reaction pathway, a (1,2)-hydrogen shift. We reported the structural properties, vibrational frequencies, and dipole moments of oxywater species, the transition state, and hydrogen peroxide. We also reported the energy barrier for the transition, and we provided an estimate for the respective reaction rate constant. In addition, we investigated the impact of solvents on the reaction pathway using an implicit solvation model of water. We predict that a singlet state oxywater species has a longer lifetime in a water environment than in the gas phase.