The Microwave Spectrum of Furan

Chirped-Pulse Fourier Transform Millimeter-Wave Spectroscopy of Furan, Isotopologues, and Vibrational Excited States

“…In addition, we include two sets of previous observations: five high-resolution measurements of low- J transitions below 5 GHz and 150 mmW rotational transitions between 130 and 260 GHz . These observations were weighted according to their reported uncertainties: 25–50 Hz for the 5 GHz data from Tomasevich et al and 50 kHz for the mmW data from Wlodarczak et al An additional data set of 26 transitions observed in the K band by Stark modulation spectroscopy was not included in the new fit because the residuals for these points were found to be much larger than the quoted 100 kHz uncertainty of the measurements; for completeness, these frequencies are included in the linelist, found in the Supporting Information, with a fit weight of zero.…”

“…Ground State. Furan is a planar, near oblate asymmetric top (κ = 0.9161) with a dipole moment of approximately 0.661 D 25 oriented along the inertial a axis and the C 2v symmetry axis (see Figure 5). The C 2v symmetry of furan produces a characteristic intensity alternation as a result of the nuclear spin statistics of the four hydrogen atoms.…”

The heavy atom structures and 33S quadrupole coupling constants of 2-thiophenecarboxaldehyde: insights from microwave spectroscopy

“…In the syn-conformer, it conjoins with the dipole moment of the aldehyde group (2.33 D in formaldehyde [62]), pointing from the oxygen atom towards the carbon atom and stabilize this form, while in the anti-conformer, the dipoles repel each other. In both molecules, furfural (2) and 2TPC (1), the dipole moment of 0.661(6) D and 0.55(1) D of the furan [63] and the thiophene ring [64], respectively, directs from the ring center towards the heteroatom and repels the dipole moment of the aldehyde group in the syn conformation. The dipole-dipole interaction may account for the destabilization of the syn-form in furfural…”

Microwave Rotational Spectra of 2-Bromofurane and 3-Bromofurane and Bromine Nuclear Quadrupole Coupling Tensors

“…In addition each spectrum actually consists of two, one arising from the interaction of the electric field vector of the incident microwave radiation with the a-component of the permanent molecular electric dipole moment and a second arising from its interaction with the 6-component (c-axis perpendicular to the molecular plane). From vector addition of the experimental electric dipole moments of Furane [3] and Bromobenzene [4] see Figure 1, the a-type spectra may be estimated to be stronger by a factor on the order of 20 if compared to the 6-type transitions. Thus the assignment of the spectra was accomplished in a two step procedure.…”