Structural Studies of Enantiomers, Racemates, and Quasiracemates. 2-(2,4,5-Trichloroanilino)propanoic Acid and 2-(2,4,5-Trichlorophenoxy)propanoic Acid

Cocrystallization of equimolar quantities of (S)-2-(2,4,5-trichloroanilino)propanoic acid and (R)-2-(2,4,5-trichlorophenoxy)propanoic acid yields molecular crystals with approximate centrosymmetric frameworks.
Such molecular assemblies, termed quasiracemates, are constructed of pairs of isosteric molecules that differ in
handedness and chemical composition. Despite the different hydrogen-bonding possibilities of the anilino −NH−
and phenoxy −O− groups, the principal quasiracemate components align via topological influences to form molecular
architectures nearly indistinguishable from the “true” racemic structures. The relation of molecular shape to crystal
packing is examined in light of the complete family of structures (i.e., quasiracemate, racemates, and enantiomers)
and the imposed −NH− and phenoxy −O− structural differences.