Density functional theory and ab initio study of oxywater isomerization into hydrogen peroxide

Density functional theory (DFT) methods have been applied to study the stability of the oxywater molecule through its 1,2-hydrogen shift to hydrogen peroxide. All 12 DFT methods found oxywater molecules to be a minimum on the potential energy surfaces (PESs) for the isomerization reaction. The computed activation energies were between 1.5 and 4.8 kcal mol(-1). The best estimation was the one obtained with G2 and hybrid DFT methods with a zero-point energy correction. It was estimated that the activation barrier was around 4 kcal mol(-1) and that oxywater lies above hydrogen peroxide by 46 kcal mol(-1). In this way, the existence of oxywater molecules was confirmed. Furthermore, it was demonstrated that hybrid DFT methods could accurately compute the PESs for low barrier, highly exothermic reactions. The energies obtained were in qualitative agreement with experimental results. (C) 1997 Elsevier Science B.V.