Metastability in Supersaturated Solution and Transition towards Chirality in the Crystallization of NaClO3

摘要

Reports on spontaneous deracemization of crystal mixtures of achiral or racemizing compounds (Viedma deracemization) are arousing strong interest not only because of their potential applications but also for understanding spontaneous emergence of chirality in chemical scenarios. The systems that may undergo such deracemizations involve compounds that crystallize as enantiopure crystals (racemic conglomerates) but are achiral or racemize rapidly in solution. The experimental conditions that promote such deracemizations are wet grinding of a racemic conglomerate in contact with its saturated solution and, if necessary, addition of a catalyst to accelerate racemization of the compound in the liquid phase. The results cannot be explained by dynamic kinetic resolution, because the assumption of a single parent crystal does not apply when a mixture of enantiomeric crystals is ground. Moreover, they cannot be explained by a second-order dynamic kinetic resolution process, nor by enantioselective inhibition of crystal growth under the influence of a chiral minor component, because of the absence of a second chiral compound.