Determination of Acid Dissociation Constants (pK_𝑎) of Bicyclic Thiohydantoin-Pyrrolidine Compounds in 20% Ethanol-Water Hydroorganic Solvent

Table 2

The calculated 𝐻_𝑓, TE and PA values with AM1 and PM3 methods for ligand and its monoprotonated forms.

Species	AM1
	TE (kcal/mol)	𝐻𝑓 (kcal/mol)	PA
H	−59403.18	−87.83	—
1 O–H^+	−59545.75	84.41	194.96
2 S–H^+	−59560.21	69.95	209.42
3 N–H^+	−59546.16	83.99	195.38
4 O–H^+	−59513.86	116.30	163.07
Species	PM3
	TE (kcal/mol)	𝐻𝑓 (kcal/mol)	PA
H	−54070.31	−101.20	—
1 O–H^+	−54238.82	83.77	182.23
2 S–H^+	−54265.61	57.08	208.92
3 N–H^+	−54242.16	80.53	185.47
4 O–H^+	−54219.39	103.29	167.71