Evaluation of the interchangeability of C–H and C–F groups: insights from crystal packing in a series of isomeric fluorinated benzanilides

Abstract

A series of mono-and difluorinated benzanilides have been synthesized and characterized to unravel the importance of interactions involving organic fluorine. The effect of fluorine substitution on the molecular conformation and the solid-state organization of the molecules in the crystalline lattice have been discussed in terms of changes in molecular conformation and the supramolecular aggregation. It is noteworthy that the meta-and para-isomers (mono and difluorinated) are isostructural, with the ortho-isomers possessing minor conformational variations. Furthermore, the molecular conformation as obtained by theoretical DFT calculations is different from the solid-state conformation highlighting the importance of co-operative features brought by N-H … O and C-H … O hydrogen bonds, along with weak intermolecular interactions involving organic fluorine and aromatic C-H … p contacts in the solid state.

Understanding of Noncovalent Interactions Involving Organic Fluorine

“…[83]. b cisoid-conformation of but-2-yne-1,4-diylbis(pentafluorophenylcarbonate) stabilized by the presence of short C-H···F-C hydrogen bonds in the crystal packing [84] Further, the capability of organic fluorine as H-bond acceptor was also studied extensively in the presence of strong hydrogen bond donor [87][88][89][90][91][92][93]. The importance of such C-H···F interactions being weak and cooperative in nature has been realized in the crystal structure analysis of fluorinated N-(2-Chloropyridin-4-yl)-N′-phenylureas ( Fig.…”

Synthesis, structural and conformational analysis of a 3 × 3 isomer grid based on nine methyl-N-(pyridyl)benzamides

“…[1][2][3] A 3×3 isomer grid of nine Methyl-N-(pyridyl)benzamides (C 13 H 12 N 2 O) as Mxx (x = para-/meta-/ortho-) has been synthesised and characterised to evaluate and correlate structural relationships from both solid-state (Table 1, Figs. 1,2,4) and ab initio calculations (Fig.…”

Intramolecular N-H···X (X = F, Cl, Br, I, and S) Hydrogen Bonding in Aromatic Amide Derivatives - The X-Ray Crystallographic Investigation

“…The crystal structures of many N-(2-fluorophenyl)amides are also available, which usually exhibit the intramolecular five-membered N−H⋅⋅⋅F H-bonding. As examples, the structures of 6 and 7 are provided in Figure 2 (Chopra & Row, 2005;Buyukgungor & Odabasoglu, 2008). It is worthy to note that no intramolecular N−H⋅⋅⋅F H-bonding is generated by the 2-fluorobenzenamine cation of 7.…”

“…The structures of compounds 4 and 5 are shown in Figure 2 as examples (Chopra & Row, 2008. The crystal structures of many N-(2-fluorophenyl)amides are also available, which usually exhibit the intramolecular five-membered N−H⋅⋅⋅F H-bonding.…”