Experimental and Theoretical Study of the Emergence of Single Chirality in Attrition-Enhanced Deracemization

The single-handedness of biological molecules has fascinated scientists since Pasteur’s first painstaking physical separation of the mirror-image crystals of a tartrate salt. The emergence of single chirality requires sustaining and propagating a small imbalance induced by the initial symmetry breaking in a presumably racemic prebiotic environment.  Viedma’s striking demonstration that a racemic mixture of enantiomorphic crystals of the achiral salt NaClO­₃ under dynamic phase equilibrium evolves inexorably to crystals of a single solid enantiomorph when mechanically stirred in the presence of glass beads has sparked considerable research into what is now known as "Viedma Ripening" or attrition-enhanced deracemization. Experimental studies help to deconvolute the driving forces for crystal growth during attrition-enhanced deracemization, demonstrating an interplay between crystal size and crystal number in the emergence of homochirality. A modified population balance model is presented based on considerations of the solubility driving force, as outlined by the Gibbs-Thomson rule, and the total interfacial surface area between solid crystals and the solution phase.