Datensatz

Zusammenfassung

Abstract By far the most systems of enantiomers exhibit compound formation. Crystallization is one powerful thermodynamic process to resolve chiral compounds by crystallization from enantiomerically enriched solutions. The different separation techniques like preferential crystallisation require detailed knowledge of the regions of existence of the desired phases. The shape of the relevant ternary phase diagrams can be classified by the intersection of the solubility isotherms of the enantiomer und the racemic compound. Reference works prove that multicomponent gE models can be suitable tools to reduce experimental work [1]. We apply and evaluate these models in this study. Upon the results derived for two very different systems, strategies for chiral resolution are proposed and experimentally confirmed. Experiments and Modelling The ternary phase diagram of the chiral systems of Propanol-Hydrochloride/ water and Serine/ water have been determined by classical isothermal equilibrium experiments for several temperatures. Liquid and solid phase analyses were performed be means of chiral HPLC, polarimetry and XRPD. We apply activity coefficient models as Margules/Wohl and NRTL to limit the amount of experimental work to obtain necessary but not measured isotherms of different temperatures for the two model systems. Results Depending on the determined shape of the two ternary phase diagrams, different separation methods for compound forming systems were applied experimentally. The chosen systems show significant differences with respect to the eutectic composition. Thus, the most promising separation technique varies. In the case of Propanolol-Hydrochloride preferential crystallization [2] was chosen as suitable resolution method since the eutectic composition is close to 50:50. Serine will be enantiomerically enriched in the liquid phase due to its exceptional high enantiomeric ratio at eutectic composition. The compound will be dried subsequently by concurrent removal of hydrates. The obtained purities for each separation technique are comparable. We have found that due to differences in the temperature dependency of the solubility of the racemic compound and the enantiomers, the eutectic composition may be varied in favourable manner by a change in crystallization temperature. This conference contribution will exemplify methods of how to benefit from the phase behaviour and provides a guideline to the choice of chiral resolution techniques based on the present phase diagram of systems of enantiomers. A simplification to access the necessary knowledge of the phases will be presented by means of gE models.