Journal of Physical Chemistry A, Vol.117, No.7, 1659-1664, 2013
Conformational Analysis and Intramolecular Interactions in Aminofluorobenzoic Acids
Some aminofluorobenzoic acids were studied to evaluate the power of the F center dot center dot center dot 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 center dot center dot center dot 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 center dot center dot center dot 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.