Department of Chemistry, Federal University of Lavras, P.O. Box 3037, 37200-000, Lavras, MG, Brazil.
J Phys Chem A. 2013 Feb 21;117(7):1659-64. doi: 10.1021/jp311791g. Epub 2013 Feb 7.
Some aminofluorobenzoic acids were studied to evaluate the power of the F···HO hydrogen bond and other interactions as driving forces of the conformational isomerism of these compounds. Despite the occurrence of this hydrogen bond in the 2-fluorinated derivatives, as well as attractive O/F nonbonding interactions and NH···O═C hydrogen bond, the O/O repulsion dictates the orientation of the carboxyl group. Unlike 2-fluorophenol, which is reported to not experience a F···HO hydrogen bond, 2-fluorobenzoic acid derivatives were calculated to exhibit such interaction, but it could not be monitored experimentally by means of F/H(O) coupling constant, because of the low solubility of these compounds in nonpolar solvents, the acidity of the carboxyl hydrogen, the small population of some conformers capable of exhibiting hydrogen bond, and the solute self-association in solution, which make their conformational equilibrium different from that in gas phase.
研究了一些氨基氟苯甲酸，以评估 F···HO 氢键和其他相互作用作为这些化合物构象异构的驱动力的能力。尽管在 2-氟取代衍生物中存在这种氢键，以及有吸引力的 O/F 非键相互作用和 NH···O═C 氢键，但 O/O 排斥决定了羧基的取向。与据报道不经历 F···HO 氢键的 2-氟苯酚不同，计算出 2-氟苯甲酸衍生物表现出这种相互作用，但由于这些化合物在非极性溶剂中的低溶解度、羧基氢的酸性、能够表现出氢键的一些构象体的小种群以及溶质在溶液中的自组装，使得它们的构象平衡与气相中的不同，因此无法通过 F/H(O) 偶合常数实验监测到这种相互作用。
