Preferential crystallization (resolution by entrainment) is a resolution without use of a resolving agent. The compound to be resolved must be a conglomerate, which means it crystallizes as enantiomeric crystals.
Major pharmaceutical companies have recently emphasized the necessity to be able to determine rapidly and accurately the crystal type of a racemate, i.e. conglomerate, racemic compound or solid solution, and to construct and analyze the phase diagrams to obtain optimal resolutions. Syncom can do this!
From careful study of the ternary phase diagram by Syncom, protocols for conglomerates can be developed based on selective seeding that allow isolation of both enantiomers in high enantiomeric purity and near the theoretical yield of 50%. Syncom has extensive experience with multi-kilo resolution of conglomerates using the entrainment process.
For the case of organics that crystallize as racemic compounds (the majority of organic compounds) careful analysis of the phase diagram also allows on occasion discovery of metastable conglomerates than can be subjected to entrainment. If the compound can be racemized in situ, resolution by grinding enhanced Ostwald ripening may produce 100% yield and 100% e.e..
Preferential crystallization service is also part of our ‘Chirality First Time Right‘ service.