Beta irradiation may induce stereoselectivity in the crystallization of optical isomers

A novel approach has been introduced to detect the manifestation of symmetry breaking weak interactions at molecular level. In the racemic conglomerate crystallization of D,L-sodium-ammonium tartrate the effect of 32P irradiation was studied by measuring the weight and optical purity of the crystalline phase as well as the size distribution of the crystallites. The high number of independent experiments (over 1000) permitted statistical analysis of the results. The following observations have been made: 1. Beta irradiation influences the crystallization process, irradiated samples yield more crystalline material. 2. The effect involves presumably crystal seed formation because from the irradiated solutions more and smaller crystallites are formed. 3. The presence of beta particles induces stereoselective crystallization, the crystalline phase shows optical activity characteristic of the "unnatural" L-isomer. 4. The above changes are attributed to the beta irradiation as the magnitude of the effects depends on the amount of added radioactivity. Optically active contaminants are highly unlikely sources of the differences between irradiated and control series. 5. In the absence of 32P the tartrate enantiomers have equal probability to form crystals, i.e., the contribution of mixing of weak interaction into the electromagnetic one is not measurable in this system.