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 P2₁3. In the absence of chiral perturbations, a random distribution of (+) and (-) crystals is obtained. Kondepudi² has shown that constantly stirring an evaporating NaClO₃ 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 NaClO₃ 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 (+)-NaClO₃ crystals. Exposure of the evaporating solution instead to energetic positrons from an Na-22 source yields mainly (-)-NaClO₃ 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.