Liang Yue, Lv DingDing, Wang Guanjun, Zeng Xiaoqing, Li Weixing, Zhou Mingfei
Department 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.
J Phys Chem A. 2024 Oct 3;128(39):8305-8311. doi: 10.1021/acs.jpca.4c01960. Epub 2024 Sep 18.
We report the coexistence of -conformers and energetically unfavorable -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 C isotopologues of the -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 and 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 -substituted fluorine atom, our experimental results indicate the planarity of the -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.
