The acid dissociation free energy values in solution are expressed through the pK a values as ∆G * acid, soln (AH) = ln (10) • RT • pK a (AH). ∆G * solv (AH) is the solvation free energy of the neutral conjugate acid. ∆G o acid, gas (AH) is the gas-phase acidity of the acid AH. The o symbol denotes an 1 atm gas-phase reference state, and the * denotes an 1 M reference state in either the gas or the solution phase. ∆G o→ * is defined as the free energy difference between the 1 atm (or 1 bar) and the 1 M reference states of an ideal gas, and is equal to 1.9 kcal mol -1 at 298 K. ∆G * solv (H + ) is the proton's solvation free energy in a solvent. The gas-phase acidity is defined as The databases we compiled are summarized in Table . In this work, we use a systematic naming convention. DISSOLVE2-ANIONS refers to the set of all physicochemical data that we compiled or computed: pK a , ∆G o acid, gas (AH), ∆G * solv (AH), ∆G * solv (A -). The prefix D2A indicates that the database is a subset of the DISSOLVE2-ANIONS data that we curated in this work.