Overall stability for the ibuprofen racemate: experimental and topological results leading to the pressure-temperature phase relationships between its racemate and conglomerate

Abstract

Enantiomer resolution is much sought after for pharmaceutical applications, because many optically active drug molecules have only one pharmaceutically active enantiomer. Although it is always possible to force separation, it will come at a cost. The present method, based on thermodynamics, provides a relatively easy approach to investigate whether separation can be thermodynamically spontaneous. A topological phase diagram of the binary enantiomer system at 0.5 mol-fraction is constructed as a function of temperature and pressure after analysis of pressure and heat related quantities. It is demonstrated that for ibuprofen, an optically active analgesic, the racemate is the only stable solid form; the phase relationship between the racemate and the conglomerate is analogous to dimorphism with overall monotropy in pure chemical compounds.