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Updated: Jun 12, 2025

Spatial Separation of Molecular Conformers and Clusters
Published on: January 9, 2014
Conformational Landscapes of 2,3-, 2,4-, 2,5-, and 2,6-Difluorobenzaldehyde Unveiled by Rotational Spectroscopy
Yue Liang1, DingDing Lv1, Guanjun Wang1
1Department of Chemistry, Collaborative Innovation Center of Chemistry for Energy Materials, Shanghai Key Laboratory of Molecular Catalysis and Innovative Materials, Fudan University, Songhu Rd. 2005, Shanghai 200438, China.
Abstract:
We report the coexistence of anti-conformers and energetically unfavorable syn-conformers of 2,3-, 2,4-, 2,5-, and 2,6-difluorobenzaldehyde in the gas phase using broadband chirped-pulse Fourier transform microwave (CP-FTMW) spectroscopy. The rotational spectra of monosubstituted 13C isotopologues of the anti-conformers have also been assigned in natural abundance, which were used to derive their vibrationally averaged geometries and semi-experimental equilibrium structures. The energy differences between anti- and syn-conformations are estimated to be 10.9, 11.3, and 12.9 kJ/mol for 2,3-, 2,4-, and 2,5-difluorobenzaldehyde, respectively, at the theoretical level of DLPNO-CCSD(T)/def2-TZVP. Despite the steric repulsion caused by the close proximity between the oxygen atom of the aldehyde group and the ortho-substituted fluorine atom, our experimental results indicate the planarity of the syn-conformations. The frequencies of the large amplitude torsion between the phenyl and aldehyde groups have been estimated by experimental inertial defects, which agree with theoretical calculation results.
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