Physics & Astronomy Faculty Publications

Document Type

Article

Publication Date

2-5-2027

Abstract

The conformational structure and nuclear quadrupole interactions of 3-bromopropionitrile were investigated using high-resolution cavity Fourier transform microwave spectroscopy and quantum chemical calculations. Potential energy scans along the Br–C–C–C dihedral angle predict two stable conformers, with the anti conformer as the global minimum and the gauche conformer lying 2.4 kJ mol-1 higher in energy at the MP2/aug-cc-pVTZ level after zero-point energy correction. The rotational spectra of both conformers were recorded in the 8–38 GHz region, and the spectra of the 79Br and 81Br isotopologues were assigned for each conformer. Improved rotational and centrifugal distortion constants were obtained for the anti conformer, while the gauche conformer was spectroscopically characterized at high resolution for the first time. The bromine nuclear quadrupole hyperfine structure was resolved for both conformers, and nitrogen quadrupole coupling constants were newly determined for 3-bromopropionitrile. The quadrupole coupling tensors show strong conformational dependence, particularly for the gauche conformer, where the large off-diagonal tensor components are consistent with a substantial rotation of the electric field gradient tensor relative to the inertial principal axes. Analysis of the diagonalized bromine quadrupole coupling tensors within the extended Townes–Dailey model indicates that the C–Br bond is predominantly σ-type, with only a small π-type anisotropic contribution and greater ionic character than that in bromoacetonitrile. The experimental constants are in good agreement with calculated values and provide a detailed conformational and hyperfine characterization of 3-bromopropionitrile.

Publication Title

Journal of Molecular Structure

DOI

10.1016/j.molstruc.2026.147589

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