Microwave Spectrum and Conformation in 2-Fluorophenylisothiocyanate

The microwave rotational spectra of 2-fluorophenylisothiocyanate have been investigated in the frequency region of 26.0–38.0 GHz. Analysis of a-type R-branch transitions confirmed the existence of two conformers: cis and trans. Rotational and centrifugal distortion constants for both conformers have been derived. The observed inertial defect values demonstrate their planarity. From the relative intensity ratio the cis form was shown to be more stable than the trans form by about 208 cm−1. Finally, molecular geometries for both conformers have been proposed.