A comparison between different approaches to estimate the aqueous pKa values of several non-steroidal anti-inflammatory drugs

Two different approaches, one involving the experimental pK determination in an organic or hydro-organic solvent and the other using the program SPARC, have been tested to estimate the aqueous pKa values of several α-arylpropionic acids with anti-inflammatory properties. In the first approach, isopropyl alcohol seems to be a very suitable solvent because of its good solvation properties and also because it avoids the preferential solvation shown by the binary solvents that affects each solute to a different degree. The results obtained using isopropyl alcohol agree very well with those obtained by means of the SPARC program, based on the analysis of the chemical structure.