2,6-Difluorobenzoic acid

Abstract

In the title compound, C7H4F2O2, the dihedral angle between the benzene ring and the carboxyl­ate group is 33.70 (14)°. In the crystal structure, inversion dimers linked by pairs of O—H⋯O hydro­gren bonds occur, generating R 2 2(8) loops. The dimers are linked into sheets lying parallel to (102) by C—H⋯F hydrogen bonds.

Structural Aspects of the Ortho Chloro- and Fluoro- Substituted Benzoic Acids: Implications on Chemical Properties

“…Table 11 presents the values of the ring C-C bond lengths for the isolated molecule, as calculated in the present study, and those obtained experimentally for the crystals [ 20 , 21 , 22 , 23 , 24 , 30 ]. For both situations, the less aromatic rings are present in the mono-substituted compounds due to pronouncedly different nature of the ortho substituents, with 2CBA being the compound exhibiting the smaller HOMA index.…”

“…The crystal structures for all the compounds investigated here have been previously reported [ 20 , 21 , 22 , 23 , 24 , 30 ]. Table 8 summarizes the crystal data, while Figure 18 , Figure 19 and Figure 20 depict the crystal packing schemes observed for the different compounds.…”

“…The different intrinsic characteristics of the fluorine versus chlorine substituent atoms have also been shown to be major factors in determining the structures of the conformers of the corresponding isolated molecules of the ortho -halogen substituted benzoic acids [ 16 , 17 , 18 , 19 ]. Likewise, they play a key role in defining other properties of the compounds, as for example relative acidities, cell volumes in crystalline phase, dipole moments, spectroscopic data, and melting points [ 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 ].…”

“…The structures of the relevant conformers of the molecules are also discussed in comparative terms, and used to rationalize experimental data obtained for the isolated molecules of the compounds, in particular, the compounds in the gas phase and isolated in low-temperature inert matrices. The structures of the crystals reported previously in the literature [ 20 , 21 , 22 , 23 , 24 , 30 ] are revisited and discussed in a comparative basis. Particular emphasis is given to the analysis of the intermolecular interactions in the different crystals and to their correlation with thermodynamic data.…”

“…Crystal packing for 26DFBA (left) and 2C6FBA (right) as viewed from the (a) (top), (b) (middle) and (c) (bottom) crystallographic axes. Data from[22], and[24], respectively.…”