cg0341353_si_001.cif (79.27 kB)

Structural Studies of Enantiomers, Racemates, and Quasiracemates:  N-(4-Methylbenzoyl)methylbenzylamine and N-(4-Nitrobenzoyl)methylbenzylamine

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posted on 07.01.2004, 00:00 by Mukta S. Hendi, Paul Hooter, Raymond E. Davis, Vincent M. Lynch, Kraig A. Wheeler
Cocrystallization of equal portions of (R)-N-(4-methylbenzoyl)-α-methylbenzylamine and (S)-N-(4-nitrobenzoyl)-α-methylbenzylamine yields bimolecular crystals that exhibit quasiracemic behavior. Derived from a slight chemical modification of one component of the “true” racemate, this quasiracemate compound extends the current knowledge base of structural features responsible for the construction of quasiracemic molecular arrays. A crystallographic comparison of the quasiracemate structure with its enantiomeric components and racemic counterpartsa total of five structuresdemonstrates the importance of molecular shape to the self-assembly of crystalline architectures. Inspection of the quasiracemate structure reveals local molecular packing that closely mimics the centrosymmetric alignment of the racemates. Unlike our prior investigations of the quasiracemate phenomena, however, the current set of enantiomeric, racemic, and quasiracemic compounds lacks any prominent long-range isostructural correlation as indicated by their relevant crystal structure information (i.e., space groups, unit cell parameters, and packing patterns). The absence of any clear preferences in crystal packing for this set of diarylamides emphasizes the practical importance of the quasiracemate approach, for which the generation of predictable molecular assemblies is not restricted by any single molecular feature as is often the case with design methods based solely (or nearly so) on hydrogen bonding patterns.