Reactivity properties of the HOSO and HSO2 isomers in liquid medium: A sequential Monte-Carlo/Quantum-Mechanics Study

Abstract

Understanding the atmospheric sulfur cycle is fundamental in developing actions to mitigate its effects on acid rain formation. Solvation of HOSO and HSO2 species has been indicated as a possible pathway in sulfur acid formation. To observe differences in the behavior of these isomers in the water medium, electrical and reactivity properties - electronic chemical potential (μ), chemical hardness (η), and electrophilicity (ϵ)- have been obtained. Once the respective first solvation shells (15H2O for HSO2 and 23 H2O for HOSO) are considered, an increase of 25% in the dipole moment of HSO2 was observed, while the dipole moment of HOSO decreases in 11%. Both solvated isomers become softer (η decreases) compared to gas phase. Methods: HOSO and HSO2 radicals in the presence of water are investigated through a sequential Monte Carlo/ Quantum Mechanics methodology. There, the intermolecular interactions are described by the Lennard-Jones plus the Coulomb potentials. For this, the DICE program was employed. The quantum calculations were performed at CASPT2/aug−cc− pV(T+d)Z level of theory through MOLPRO computational package.