Structural differences in solutions derived from polymorphic modifications of aspirin

Abstract

Differences in the structure of solutions derived from two polymorphic modifications of aspirin were demonstrated through differences in apparent pKa values. The apparent pKa's were determined in dimethylformamide using tetrabutyl-ammonium hydroxide as the titrant. The pKa differences were ascribed to differences in intra- and intermolecular hydrogen bonding of the solute.