A parity plot of predicted versus experimental pK a data is shown in Fig. . The dashed line indicates a tolerance of 1.0 pK a unit, and for most of the considered amines the error is less than 1.0 pK a unit, equivalent to an error of ≈ 5.7 kJ•mol -1 in the reaction free energy at T=298.15 K. Table summarizes the numerical values of the protonation constant of the 77 studied amine at 298.15 K, along with the carbamate formation constant of the primary and secondary amines obtained in this work. The experimental pK a data were taken from the literature. Using the developed H 3 O + FF, we found an average absolute deviation (AAD) of 0.72 pK a units for a set of 77 amines. Our results show that the pK a values of amines with multiple hydroxyl groups are underestimated and those of alkyamines (amines with no hydroxyl group) are overestimated.