Molecular Recognition in the Formation of Conglomerate Crystal. The Role of Cinnamic Acid in the Conglomerate Crystals of 1-Phenylethylamine and 1-(4-Isopropylphenyl)ethylamine Salts

The Crystal structures of (+)-1-phenylethylamine·cinnamic acid salt and (+)-1-(4-isopropylphenyl)ethylamine·cinnamic acid salt were determined by X-ray analysis. The crystal structures of these two salts provided for the first time some insights into the mechanism of the formation of a conglomerate crystal. In each crytal, two amine components and two acid components form a helical column by hydrogen bonds. On the basis of this similarity in the molecular arrangements, the role of cinnamic acid, an achiral acid, is discussed, and the criteria for the choice of an achiral acid in the transformation of the racemic modification of an amine into a conglomerate crystal is proposed.