Universal Trends between Acid Dissociation Constants in Protic and Aprotic Solvents

Abstract

pKa values in non-aqueous solvents are of critical importance in many areas of chemistry. Our knowledge is, despite their relevance, still limited to the most fundamental properties and few pKa values in the most common solvents. Taking advantage of a recently introduced computationally efficient procedure we computed the pKa values of 182 compounds in 21 solvents. This data set is used to establish for the first time universal trends between all solvents. Our computations indicate, that the total charge of the molecule and the charge of the acidic group combined with the Kamlet-Taft solvatochromic parameters are sufficient to predict pKa values with at least semi-quantitative accuracy. We find, that neutral acids such as alcohols are strongly affected by the solvent properties. This is contrasted by cationic acids like ammonium ions whose pKa is often almost completely independent from the choice of solvent.[a

Exploring the Mechanism of the Electrochemical Polymerization of CO2 to Hard Carbon over CeO2(110)

“…The second deprotonation step has an even higher p K a value of 45.3. The trend toward significantly increased p K a values in DMF compared to water for neutral acids is in good agreement with the significantly lower stability of protons and other charged species in aprotic nonaqueous solvents. ,, Overall, this clearly shows that only CO 2 is a possible reactant for the CO 2 RR in DMF.…”

Exploring the Mechanism of the Electrochemical Polymerization of CO2 to hard carbon over CeO2 (110)

“…The trend towards significantly increased pK a values in DMF compared to water for neutral acids is in good agreement with the significantly lower stability of protons and other charged species in aprotic non-aqueous solvents. 84,85,93 Overall, this clearly shows that only CO 2 is a possible reactant for the CO 2 RR in DMF.…”

Density functional theory and machine learning for electrochemical square-scheme prediction: an application to quinone-type molecules relevant to redox flow batteries

“…increase the p K a ). 61 Therefore, compounds in QH 2 2+ and QH − states represent the strongest and weakest acids, respectively. Those with negative p K a are unstable in normal solutions and they release proton into the solution even at pH = 0.…”

“…, and E 0 estimations. 43,53,[60][61][62] When compared to the experiments, the predictability of the DFT-calculated E red. and E 0 is very good.…”