Chiral Symmetry Breaking During Crystallization: Complete Chiral Purity Induced by Nonlinear Autocatalysis and Recycling

We report experimental results that show a large and symmetric population of $D$ and $L$ crystals moving into complete chiral purity, with one of the enantiomers completely disappearing. The results indicate (i) a new symmetry breaking process incompatible with the hypothesis of an initial single chiral phase or “mother crystal,” (ii) that total symmetry breaking and complete chiral purity can be achieved from a system that initially includes both enantiomers, and (iii) that this is achieved through a nonlinear autocatalytic-recycling process.

Figure 1

Solutions with initial symmetric mixtures of $L$ and $D$ crystals and glass balls show total symmetry breaking and chiral crystal purity. The data show the necessary time to achieve chiral purity depending on the number of balls in the system (600 rpm).

Figure 2

Solutions with initial symmetric mixtures of $L$ and $D$ crystals and glass balls show total symmetry breaking and chiral crystal purity. The data show the necessary time to achieve chiral purity depending on the speed of agitation of the system (4 g of balls).

Figure 3

Solutions with initial 5% $L\mathrm{\text{−}}\mathrm{C}\mathrm{E}\mathrm{E}$ show 100% $L\mathrm{\text{−}}\mathrm{C}\mathrm{E}\mathrm{E}$, and solutions with initial 5% $D\mathrm{\text{−}}\mathrm{C}\mathrm{E}\mathrm{E}$ show 100% $D\mathrm{\text{−}}\mathrm{C}\mathrm{E}\mathrm{E}$ in 8 h (600 rpm).

Figure 4

Initial symmetric mixtures of $D$ and $L$ crystals and 4 g of balls show total symmetry breaking and chiral purity after 24 h (600 rpm). The handedness in this case is $L$ or $D$ randomly.