The acidity of carbon acids in aqueous solutions: correlations with theoretical descriptors

The acidity of 32 carbon acids in water, with pKa values ranging from 25.6 to −6.2, was correlated with a two-parameter equation, involving the theoretical descriptors ΔE and ∑ΔqX, calculated with the HF/3-21G//HF/3-21G and the B3LYP/6-31G(d)//HF/3-21G methods, with regression coefficients r≥0.95. The acid deprotonation energy (ΔE) was associated with its intrinsic, or gas-phase acidity, whereas the total charge variation at the hard centers (∑ΔqX) was a measure of the contributions of aqueous solvation to its acid behavior in water.