Enantiopolar crystal

C. Topochemical Reactions in Enantiopolar Crystals Cinnamide-Cinnamic... 

V. ABSOLUTE CONFIGURATION FROM CHEMICAL REACTIVITY IN POLAR AND ENANTIOPOLAR CRYSTALS... 

In principle, an anisotropic reaction performed on a crystal of polar symmetry may fix the absolute direction of the polar axis. In the case of an asymmetric reaction carried out in a centrosymmetric (enantiopolar) crystal, one may establish the absolute configuration of the chiral product. The degree of reliability of the assignment will depend on knowledge of the various states of the reaction pathway. Here we briefly describe some heterogeneous reactions in polar and enantiopolar crystals that illustrate this approach. 

Fig. 54a-b. The chiral bilayer effect a chiral micellar cylinders rearrange slowly to enantiopolar crystals b the hydrophobic bilayer of achiral micellar cylinders is retained in the crystal. Crystallization is fast [373]... 

The observed structures were explained by a chiral bilayer effect mechanism proposing that only the enantiomerically pure compounds can lead to the formation of helical fibers which in turn slowly rearrange to enantiopolar crystal layers (Scheme 7.1). Within the micellar fibers, the polar head groups are oriented toward the aqueous environment and must therefore go through an energetically unfavourable -slow- dehydration followed by a 180 ° to form the enantiopolar crystals. 

Figure 7.20 K-Ala adds to the (010) face and prevents the growth of the glycine crystal along the +b-axis. The (010) face becomes dominant because growth along the other faces is faster now. S-Ala has the same effect in the — b direction R,S-v4/a in b directions. Enantiopolar crystals of achiral glycine add S-alanine to pro-S crystal faces and R-alanine to pro-R faces ". ...

Addadi, L., Berkovitch-Yellin, Z., Weissbuch, 1., Lahav, M., Leiserowitz, L., and Weinstein. S. The use of enantiopolar directions in centrosymmetric crystals for direct assignment of absolute configuration of chiral molecules application to the system serine/threonine. J. Amer. Chem. Soc. 104, 2075-2077 (1982). 

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