Quantitative Investigation of Halogen and Hydrogen Bonding in 2‐Chloro, 4‐X‐Benzoic Acids

Abstract

AbstractThe crystal structure, Hirshfeldsurface analysis, topological analysis of the electron density and total interaction energies of four compounds, 2‐Chloro, 4‐X‐Benzoic Acids (where X=I, Br, Cl and F) have been analysed. The packing similarity was evaluated in all compounds using theXPacanalysis. The qualitative information about intermolecular interactions is derived from the crystal structure and Hirshfeld surface analyses whereas quantitative information are determined by the QTAIM analysis as well as total interaction energies fromCrystalExplorer. The topological properties are estimated for all compounds in both crystal geometry and gas phase usingTOPONDandAIMALL, respectively. The carboxylic acid O−H⋅⋅⋅O HB dimers, C−H⋅⋅⋅O HBs and Cπ⋅⋅⋅Cπaromatic stacking interactions are found to be common interactions in all compounds. The topological properties and bond paths demonstrate them as non‐covalent stabilizing interactions in the crystalline state. The hierarchy of interactions concerning their strength is observed in the following order such that O−H⋅⋅⋅O HB dimers>Cπ⋅⋅⋅Cπaromatic stacking interactions>C−H⋅⋅⋅O HBs>Type II X⋅⋅⋅Cl interactions and C−H⋅⋅⋅Cl HBs>Type I homo‐halogen X⋅⋅⋅X interactions in all compounds. Additionally, the strength of Type I homo‐halogen X⋅⋅⋅X interactions vary in the order: I⋅⋅⋅I>Br⋅⋅⋅Br>Cl⋅⋅⋅Cl>F⋅⋅⋅F. The hierarchy of interactions is further supported by molecular electrostatic potential surfaces associated with both positive and negative potential regions.