Conformational analysis, stereoelectronic interactions and NMR properties of 2-fluorobicyclo[2.2.1]heptan-7-ols

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Four diastereoisomers of 2-fluorobicyclo[2.2.1]heptan-7-ols were computationally investigated by using quantum-chemical calculations, and their relative energies were analyzed on the basis of stereoelectronic interactions, particularly the presence or otherwise of the F center dot center dot center dot HO intramolecular hydrogen bond in the syn-exo isomer. It was found through NBO and AIM analyses that such an interaction contributes to structural stabilization and that the (1h)J(F),(H(O)) coupling constant in the syn-exo isomer is modulated by the n(F)->sigma*(OH) interaction, i.e., the quantum nature of the F center dot center dot center dot HO hydrogen bond.812271232Fundação de Amparo à Pesquisa do Estado de Minas Gerais (FAPEMIG)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

Theoretical and infrared studies on the conformations of monofluorophenols

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Theoretical calculations for the isolated state indicate the presence of two conformers (A and B) for 2- and 3-fluorophenols, while a single form exists for 4-fluorophenol, as it is well known. The conformer with the hydroxyl hydrogen directed toward the fluorine atom (A) in 2-fluorophenol is calculated to be significantly more stable than the second form, while similar behavior is not obtained for the meta isomer. The infrared C-F stretching intensities confirm these findings in cyclohexane solution, where internal hydrogen bonding in 2-fluorophenol is supposed to be a stabilizing effect of A, but the figure changes in acetonitrile solution and neat liquid, where the most polar conformer B is preferred and intermolecular hydrogen bonding seems to take place, as confirmed by the broadening and shifting of the O-H stretching band. In fact, the strong solvent effect in 2-fluorophenol suggests that conformer A is the most stable form in the isolated state and nonpolar solution predominantly due to dipolar repulsion in B. (C) 2011 Elsevier B.V. All rights reserved.1009SI1115Fundação de Amparo à Pesquisa do Estado de Minas Gerais (FAPEMIG)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq