Structure determination of 2,5-difluorophenol by microwave spectroscopy

Abstract

The Fourier transform microwave spectrum of 2,5-difluorophenol has been obtained in the centimeter wave range, revealing only one conformer stabilized by an intramolecular interaction where the hydrogen atom of the OH group is in a syn orientation to the fluorine atom at the 2-ring position. The heavy atom backbone structure was obtained from the rotational constants of the 13C and 18O isotopologues whose spectra were measured in natural abundance. The spectrum of the OD isotopologue obtained by deuterium enrichment was also measured, and the nuclear quadrupole hyperfine structures arising from deuterium were analyzed. The semi-experimental equilibrium structure (reSE) was determined by correcting the experimental rotational constants with the vibration-rotation interaction constants obtained via an anharmonic force field. Quantum chemical calculations at various levels of theory were used to support results from the experiments.