D. Chopra, T. Row
Aug 19, 2005
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Journal
Crystal Growth & Design
Abstract
4-Fluoro-N-(2-fluorophenyl) benzamide, a prochiral molecule, exhibits dimorphic behavior. This feature has been analyzed in terms of morphology, X-ray single-crystal structure analysis, differential thermal analysis, and measurement of second harmonic generation (SHG) in both forms, which crystallize in noncentric space groups. The dimorphs have different morphologies, a major form as needles and a minor form as thin plates, occurring concomitantly in the same crystallization setup. The plates crystallize in the monoclinic space group $P2_1$, while the needles are in the orthorhombic space group $Pca2_1$. Strong N-H \cdot\cdot\cdot O hydrogen bonds and weak but highly directional C-H \cdot\cdot\cdot F interactions acting cooperatively are responsible for the observed symmetry steering the molecules to pack in noncentric environments.