Acidity constants of some sulfur oxoacids in aqueous solution using CCSD and MP2 methods

Abstract

The calculations of the acidity constants (pK_a) of a series of sulfur oxoacids including H₂SO_n (n = 1–5) and H₂S₂O_n (n = 1, 3, 4, 6 and 7) are presented for the first time. The calculations were performed using two expensive correlated levels of theory including MP2/6-311++G(3df,3pd) and CCSD/6-311++G(d,p) in both gas and aqueous phases. The new continuum solvation model, SMD, based on the quantum mechanical charge density of a solute molecule interacting with a continuum description of the solvent, used to account the solvent effects. The calculated pK_as were corrected using the different correlation equations (Zimmermann and Tossell, J. Phys. Chem. A, 2009, 113, 5105–5111) to improve the accuracy of results. Also, the calculated results showed the effect of the intramolecular hydrogen bonding on the acidity strength.