Packing similarities in organic crystals with C–H/C–F exchange: a database analysis of CH3/CF3 pairs

Abstract

The prediction of packing motifs in organofluorine compounds is relevant to crystal engineering, drug design and materials chemistry. A Cambridge Structural database analysis of 50 CH₃/CF₃ organic crystal structures has been carried out, that is pairs of molecules in which a methyl group is replaced with trifluoromethyl. These 50 CH₃/CF₃ hits are classified into four categories: identical organisation in the crystals (24 hits), different packing modes (6 hits), perfluorination (6 hits) and a miscellaneous category with 14 hits. Identical packing may be expected in crystal structures stabilised by robust, cyclic supramolecular synthons (hydrogen bonding) or in molecules with a large, rigid, polycyclic carbon skeleton (van der Waals interactions).