Structure determination of 2,5-difluorophenol by microwave spectroscopy

• Published in: Journal of molecular structure Vol. 1321; p. 139971
• Main Authors: Nair, K.P. Rajappan, Lengsfeld, Kevin G., Buschmann, Philipp, Koziol, Kenneth J., Esselman, Brian J., Grabow, Jens-Uwe, Nguyen, Ha Vinh Lam
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 05.02.2025
• Subjects: Difluorophenol; Microwave spectroscopy; Molecular structure; Rotational spectroscopy; Difluorophenol; Molecular structure; Rotational spectroscopy; Microwave spectroscopy
• ISSN: 0022-2860
• DOI: 10.1016/j.molstruc.2024.139971

•Supersonic jet Fourier-transformed microwave spectra in the ground vibrational state of the parent, 13C, 18O, and OD species.•Only the syn conformer is observed due to the presence of strong hydrogen bonding interaction.•Semi-experimental equilibrium structure determinations with very high accuracy.•Fluorine slightly enlarges the CC-C angle at the substituted position with its σ-electron withdrawing (–I effect).•The OH bond is shortened when the second fluorine atom is in the para position with respect to the hydroxyl group. 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. [Display omitted]