CSD- and PDB-wide
surveys of CF3-containing compounds
have identified very divergent rates of isostructrality between CH3/CF3 analogues and a variety of behaviors for the
CF3 groups ranging from nucleophilic to electrophilic.
We present 13 crystal structures containing the 4-trifluorotoluenesulfonamide
(F3TsN) moiety and then analyze these structures and 10
pairs of CF3/CH3 toluenesulfonamide analogues
using PIXEL-calculated lattice energies, Hirshfeld surfaces, ratios
of frequencies, and electrostatic potential energy maps. The F3TsN group is directly and representatively interesting from
a pharmaceutical context, given its strong additional intermolecular
forces (H bonding and π stacking). Unsurprisingly, many C–F···F
angles correspond to type I halogen–halogen interactions, with
several presenting at distances shorter than the sum of the van der
Waals radii. Only 1 of 10 pairs in our study are isostructural, likely
resulting from numerous but individually weak F···H
and F···C intermolecular interactions. A ratio of frequencies
analysis shows that C[unsat]–F contacts occur much more frequently
in F3Ts structures than in the general population of fluorinated
structures. We suggest that a detailed analysis of increasing pools
of structural data for specific moieties can complement database-wide
surveys and lead to more definitive conclusions and eventually design
principles.
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