Microwave spectrum, structure and dipole moment of 3-fluorophenylacetylene (3FPA)

The 6-18 GHz rotational spectrum of 3-fluorophenylacetylene (3FPA) was measured by chirped-pulse Fourier-transform microwave (CP-FTMW) spectroscopy. Rotational constants and quartic centrifugal distortion constants based on a Watson-A reduction were determined with 89 transitions; A = 3383.73821 (33) MHz, B = 1180.97617 (16) MHz, C = 875.26172 (12) MHz, ΔJ = 0.0382 (13) kHz, ΔK = 1.316 (21) kHz, δJ = 13.93 (56) Hz, and δK = 180.3 (60) Hz. An additional 12-13 transitions for each of eight 13C isotopic species and Stark effects to determine dipole moment components were observed by Balle-Flygare FTMW spectroscopy. Gas phase molecular structures of 3FPA were derived via the least-square fitting (r0) and substitution (rs) methods using the moments of inertia of the isotopic species. The ring geometry is discussed and compared with previous studies of structures of monosubstituted benzene and crystalline solid structures of 3FPA.