Effect of beta radiation on the crystallization of sodium chlorate from water: A new type of asymmetric synthesis

Sodium chlorate is an achiral molecule that crystallizes from water in the chiral space group P2 1 3. In the absence of chiral perturbations, a random distribution of (+) and (−) crystals is obtained. Kondepudi 2 has shown that constantly stirring an evaporating NaClO 3 solution gives mostly either (+) or (−) crystals. Repeating this experiment many times gives equal numbers of (+) and (−) sets of crystals. Herein we report that when evaporating aqueous NaClO 3 is subjected to beta particles from an Sr‐90 source, an asymmetric distribution of (+) and (−) crystals favoring the (+) crystals is obtained. The beta particles are energetic polarized electrons that are approximately 80% of left‐handed helicity. By a poorly understood mechanism, the spin polarized electrons produce chiral nucleating sites that favor formation of the (+)‐NaClO 3 crystals. Exposure of the evaporating solution instead to energetic positrons from an Na‐22 source yields mainly (−)‐NaClO 3 crystals. Polarized positrons are of predominantly right‐handed helicity. One may conclude that the chirality of the radiation is correlated with the chirality of the crystals being generated. Chirality 13:636–640, 2001. © 2001 Wiley‐Liss, Inc.