Thermodynamic cycles and the calculation of pKa

Boric acid, “carbonic” acid, and N-containing oxyacids in aqueous solution: Ab initio studies of structure, pKa, NMR shifts, and isotopic fractionations

“…In their analysis of this data Stumm and Morgan (1981) treat this as essentially a pK a , with an activity for water given as 1, rather than using the molarity of ϳ55. This raises a question very similar to that involved in the controversy between da Silva et al (2003) and Pliego (2003) over the proper way to count (without double counting) the molarity of liquid water in the calculation of pK a . For the gas-phase reaction…”

“…Pliego (2003) has discussed the possible reasons for this failure, but controversy about the proper theoretical approach continues (da Silva et al, 2003). While accurate determination of the various contributions to the free energy can be difficult for Eqn.…”

Acid–base properties of a goethite surface model: A theoretical view

“…Similar to reactions in the gas phase the proper standard state has to be considered for species in liquid phase. Detailed discussions to this point can be found, e.g., in works by Ben-Naim and Marcus (1984), Da Silva et al (1999), Pliego (2003), or by Camaioni and Schwerdtfeger (2005). However, the bare proton represents an enormous problem for theoretical calculations of its solvation free energy (Pliego, 2003).…”

“…Detailed discussions to this point can be found, e.g., in works by Ben-Naim and Marcus (1984), Da Silva et al (1999), Pliego (2003), or by Camaioni and Schwerdtfeger (2005). However, the bare proton represents an enormous problem for theoretical calculations of its solvation free energy (Pliego, 2003). Usually, the experimental values of the absolute solvation free energy of the H + instead of the calculated one were used in the calculations of the pK a values (e.g., Liptak and Shields, 2001).…”

Experimental and Theoretical Studies of Oxalic Acid Dissociation in Water-Ethanol Solvents

“…Many publications [10]- [13]have shown a theoretical relationship between pKa and the structural property, bond valences methods and bond lengths, pKa correlations with highest occupied molecular orbital (HOMO) energies and frontier molecular orbitals, and artificial neural networks. The gas-phase free energy calculation [14] is the lowest source of error in pKa calculations.…”