Crystallization in polymorphic systems: The solution-mediated transformation beta to alpha glycine

The crystallization and subsequent polymorphic transformation from the beta to the alpha form of glycine has been studied using optical microscopy, X-ray diffraction, and Fourier transform infrared spectroscopy techniques. The crystal structure and morphology of beta glycine have been determined, and the influence of solvent, solubility, and process scale on its solvent-mediated transformation to the alpha form was quantified. It is concluded that for the low solubility environments used in this study, the rate-determining step in the transformation process is the dissolution rate of the metastable beta polymorph.