Structural studies of enantiomers, racentates, and quasiracemates. N-(2-chlorobenzoyl)methylbenzylamine and N-(2-bromobenzoyl)methylbenzylamine

Recrystallization of equimolar quantities of (R)-N-(2-chlorobenzoyl)methylbenzylamine (1) and (S)-N-(2-bromobenzoyl)methylbenzylamine (2) forms quasiracemic crystals (3) with approximately centrosymmetric molecular frameworks. The molecular recognition behavior observed for the principal quasiracemate diarylamide components follows a best-fit scenario controlled by topological influences. The relation of molecular shape to crystalline architectures is supported by a systematic structural study of the complete family of quasiracemate, racemate, and enantiomer structures, including two polymorphic forms of enantiomeric 1. Each of the enantiomeric, racemic, and quasiracemic compounds crystallizes to form molecular scaffolds linked by C(4) N-(HO)-O-... interactions. Although this typical hydrogen bond motif of the trans amide moiety provides a common structural theme for these diarylamides, significant variations in crystal packing arise due to the orientation of molecules within the catemeric hydrogen bond motif and the alignment of neighboring C(4) chains.