Geometric conformation of the oxirane hydrogen halide dimers from Ab initio calculations

Abstract

The dimers formed between oxirane (ethylene oxide) and HX, where X = F and Cl, have been studied using restricted Hartree–Fock and Møller–Plesset second-order type wavefunctions and a double zeta plus polarization basis set. The global minima are found to be pyramidal with C_s symmetry, with the C_2v structures being saddle points (D₀= 448 cm^–1, X = F and D₀= 775 cm^–1, X = Cl). Good agreement is found between the MP2/DZP and experimental geometries for both dimers. The MP2 intermolecular O…X distances and pyramidal angles are: 2.58 Å, 71.4°, and 3.05 Å, 71.7°, for X = F and Cl, respectively. The hydrogen bond is also predicted to be significantly non-linear.