Millimeter-Wave and High-Resolution Infrared Spectroscopy of 2-Furonitrile─A Highly Polar Substituted Furan.

The rotational spectrum of 2-furonitrile (2-cyanofuran) has been obtained from 140 to 750 GHz, capturing its most intense rotational transitions at ambient temperature. 2-Furonitrile is one of two isomeric cyano-substituted furan derivatives, both of which possess a substantial dipole moment due to the cyano group. The large dipole of 2-furonitrile allowed over 10 000 rotational transitions of its ground vibrational state to be observed and least-squares fit to partial octic, A- and S-reduced Hamiltonians with low statistical uncertainty (σ = 40 kHz). The high-resolution infrared spectrum, obtained at the Canadian Light Source, allowed for accurate and precise determination of the band origins of its three lowest-energy fundamental modes (ν, ν, and ν). Similar to other cyanoarenes, the first two fundamental modes (ν A″, and ν, A', for 2-furonitrile) form an - and -axis Coriolis-coupled dyad. More than 7000 transitions from each of these fundamental states were fit to an octic A-reduced Hamiltonian (σ = 48 kHz), and the combined spectroscopic analysis determines fundamental energies of 160.1645522 (26) cm and 171.9436561 (25) cm for ν and ν, respectively. The least-squares fitting of this Coriolis-coupled dyad required 11 coupling terms, , , , , , , , , , , and . Using both the rotational and high-resolution infrared spectra, a preliminary least-squares fit was obtained for ν, providing its band origin of 456.7912716 (57) cm. The transition frequencies and spectroscopic constants provided in this work, when combined with theoretical or experimental nuclear quadrupole coupling constants, will provide the foundation for future radioastronomical searches for 2-furonitrile across the frequency range of currently available radiotelescopes.