Rotational spectra and conformer geometries of 2-fluorophenol and 3-fluorophenol

Abstract

The ground states of 2-fluorophenol (2FPh) and 3-fluorophenol (3FPh) and their 13C isotopologues were investigated using Fourier transform microwave (FTMW) spectroscopy in the range of 6–26GHz. Two planar conformers were observed for 3FPh, corresponding to cis and trans orientations of OH relative to F, while only the cis conformer of 2FPh was detected. The rotational constants determined were used to derive substitution (rs) and effective ground state (r0) structures of the lowest energy conformer of each compound: cis-2FPh and trans-3FPh. Geometry optimization at the MP2/6-311++G(2d,2p) level provided equilibrium (re) structures which are in close agreement with the experimental parameters. The derived structures along with results from natural bond orbital (NBO) calculations provide evidence of an intramolecular interaction in cis-2FPh between the fluorine atom and OH moiety that stabilizes this conformer by 0.73kcal/mol.