Sulphur compounds: Part 149. Structures, relative stabilities and vibrational spectra of several isomeric forms of sulphoxylic acid (H 2SO 2) and its anion (HSO 2'−): an ab initio study

Abstract

The ground state geometries, energies, atomic charges, dipole moments, and vibrational wavenumbers of four isomeric forms of H 2SO 2 and two isomere of HSO 2 − have been calculated at the HF and MP2 levels of theory using 6-31G ∗ basis sets. The correlation energy has also been included up to the fourth order of Møller-Plesset perturbation theory (MP4). The two most stable isomers of H 2SO 2 are two retamers of the chain-like HOSOH structure of C 2, and C 8 symmetry, the C 8 conformer being less stable by about 8 kJ mol −1. The sulphuric acid structure HS(O)OH was found to be less stable by about 56 kJ mol −1. The geometries obtained are compared to known structures of organic derivatives of H 2SO 2. The anion HSO 2 − containing an SH bond is more stable than the HOSO − isomer by 23 kJ mol −1. The calculated vibrational wavenumbers are discussed in terms of recent experimental data.