CF3CF2NS(F)CF3: Vibrational spectra and conformational properties

• CF3CF2NS(F)CF3 exists in the gas phase as a mixture of anticlinal and syn forms.
• Theoretical calculations predict the anticlinal form as the global minimum.
• Steric effects govern the conformational preferences showed by CF3CF2NS(F)CF3.

The structural, conformational, and configurational properties of 1,1,1-trifluoro-N-(1,1,2,2,2-pentafluoroethyl) methanesulfinimidoyl fluoride, CF3CF2NS(F)CF3 have been studied by vibrational spectroscopy [IR (vapor) and Raman (liquid)] and quantum chemical calculations [B3LYP, MP2 and B3PW91 levels of theory (using the 6-311+G(d) and 6-311+G(2df) basis sets). According to these theoretical approximations, CF3CF2NS(F)CF3 might be found in the gas phase as a mixture of a favoured anticlinal form (CN bond anticlinal with respect to the CSF bisector angle) and a less abundant syn conformer showing C1 symmetry as well (ΔG° ≈ 1.5 kcal mol−1). However, corresponding vibrational modes for these conformers show only small shifts which would not allow confidently detecting the rather small contribution of this second form in the experimental spectra.

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