Theoretical and experimental study of a new thiosulfonate derivative: Methyl trifluoromethanethiosulfonate, CF3SO2SCH3. Conformational transferability in CX3SO2S-R compounds

Abstract

Methyl trifluoromethanethiosulfonate, CF3SO2SCH3, was synthesized and characterized by 13C NMR, 19F NMR, and vibrational spectroscopy. This structural study was supported by MP2 and DFT (B3LYP and MPW1PW91) calculations, which revealed a strong dependence of the theoretical structure on the polarization of the basis set. Theoretical data indicate that only one conformer, gauche, is predicted by rotating around the S–S bond. This conformational preference was studied using the total energy scheme and natural bond orbital partition scheme. These results evidence that electron delocalization and especially LP S → σ∗ C(1)-S interactions play an interesting role in the reactivity-structure connection of oxoesters and thioesters. Gas and liquid infrared and liquid Raman spectra were recorded and assigned. The experimental vibrational data along with theoretical force constants (B3LYP) were used to define a scaled quantum mechanical force field, which enabled the reproduction of the measured frequencies with a final root-mean-square deviation of 8.06 cm−1.