Controlling the Effect of Chiral Impurities on Viedma Ripening

Abstract

Spontaneous symmetry breaking and chiral amplification by means of Viedma ripening by definition should result in complete deracemization of a racemic conglomerate into either one of the enantiomers with equal probability. In practice, however, chiral impurities influence Viedma ripening and one enantiomer is obtained in preference over the other. Here, we show that by increasing the attrition intensity during Viedma ripening, the effect of chiral impurities is suppressed and deracemization does yield either enantiomer with equal probability. The reason for this is that the resulting smaller crystals lead to such a low surface density of chiral impurities that they no longer inhibit the crystal growth sufficiently to determine the chiral outcome. Furthermore, we show that even for low attrition intensities, the effect of chiral impurities can be canceled by using the right amount (10 ppm) of chiral additives.