Raman and Infrared Spectra, Barrier to Internal Rotation, Vibrational Assignment and Ab Initio Calculations of 2,3,3,3-Tetrafluoropropionitrile

The Raman (3100 to 10 cm−1) and infrared (3100 to 400 cm−1) spectra of 2,3,3,3‐tetrafluoropropionitrile, CF3CHFCN, were recorded for the gas, liquid and solid phases. Additionally, the far‐infrared (370 to 60 cm−1) spectrum of the gas was recorded. The CF3 torsional fundamental was observed at 67 cm−1 with a ‘hot band’ at 66.5 cm−1. From these data, the three‐fold barrier to internal rotation is found to be 1433±5 cm−1 (4.10±0.01 kcal mol−1). The structure, infrared intensities, Raman activities and vibrational wavenumbers were determined from ab initio calculations using the RHF/3–21G, RHF/6–31G* and MP2/6–31G* basis sets. These results are compared with those obtained for some related molecules.