Synthesis, crystal structure and Hirshfeld surface analysis of...

The title phenytoin analog 2-(2,5-dioxo-4,4-di-phenyl-imidazolidin-1-yl)-N-(4-fluoro-phen-yl)acetamide, C₂₃H₁₈FN₃O₃, was synthesized by alkyl-ation of phenytoin with 2-chloro-N-(4-fluoro-phen-yl)acetamide under phase-transfer catalysis conditions and crystallized as colorless blocks in the monoclinic space group P2₁/c. In the mol-ecular structure, the imidazolidine ring shows a slight departure from planarity, adopting a twist conformation, while the two phenyl substituents are markedly inclined to the mean plane of the heterocyclic ring. The N-substituted 4-fluoro-phenyl-acetamide fragment projects away from the imidazolidine core, with its conformation partly consolidated by an intra-molecular C-H⋯O contact. In the crystal packing, pairs of inversion-related mol-ecules are linked through N-H⋯O hydrogen bonds to form dimers, which are further connected by additional N-H⋯O inter-actions into layers extending parallel to the bc plane. These layers stack along the a-axis direction through normal van der Waals contacts. Hirshfeld surface analysis was used to qu-antify the inter-molecular inter-actions, showing that H⋯H contacts give the largest contribution to the crystal packing, followed by C⋯H/H⋯C and O⋯H/H⋯O contacts, the latter being associated with the classical N-H⋯O hydrogen bonds. F⋯H/H⋯F inter-actions also contribute to the packing, mainly through contacts between adjacent mol-ecular layers.