Spontaneous deracemizations

Spontaneous deracemizations is a challenging, multidisciplinary subject in current chirality research. In the absence of any chiral inductors, an achiral substance or a racemic composition is driven into an enantioenriched or even homochiral state through a selective energy input, e.g., chemical potential, photoirradiation, mechanical grinding, ultrasound waves, thermal gradients, etc. The most prominent examples of such transformations are the Soai reaction and the Viedma deracemization. In this review, we track the most recent developments in this topic and recall that many other deracemizations have been reported for solutions from mesophases to conglomerate crystallizations. A compiled set of simply available achiral organic, inorganic, organometallic, and MOF compounds, yielding conglomerate crystals, should give the impetus to realize new experiments on spontaneous deracemizations. Taking into account thermodynamic constraints, modeling efforts have shown that structural features alone are not sufficient to describe spontaneous deracemizations. As a guideline of this review, particular attention is paid to the physicochemical origin and symmetry requirements of such processes.J.C., D.H., and J.M.R. acknowledge the coordinated research project CTQ2017-87864-C2-1(2)-P(MINECO) Spain and are grateful to Albert Moyano and Oriol Arteaga for many discussions related to the topics covered in this review. J.-C.M. and T.B. acknowledge support by the French-Mexican International Laboratory (LIA) LCMMC. The authors thank Prof. Bart Kahr for the historical remarks about chirality and stereochemistry