Chiral Symmetry Breaking in Stirred Crystallization of 1,1‘-Binaphthyl Melt

As a supercooled melt at 150 °C, the chiral compound 1,1‘-binaphthyl racemizes rapidly. The melt solidifies as a conglomerate of crystals, each consisting exclusively of either R -(−)- or S -(+)-enantiomer. We find that crystallization performed with a 2.00 g sample with constant stirring produces a large enantiomeric excess (mean 77%) in almost every crystallization. The predominance of R -(−) or S -(+) was random. Unstirred 2.00 g samples of binaphthyl produce a much lower enantiomeric excess (mean 20%) with optical activity centered around zero similar to an earlier report. 1 Thus, chiral symmetry breaking can be realized in crystallization from a melt by the mere act of stirring, as it can be in crystallization from a solution.