Molecular structure and conformations of 2-nitrobenzenesulfonyl fluoride: Gas-phase electron diffraction and quantum chemical calculations study

The molecular structure and conformational properties of 2-nitrobenzenesulfonyl fluoride, 2-NO 2-C 6H 4SO 2F, have been studied by gas-phase electron diffraction (GED) and quantum chemical methods (B3LYP/6-311+G∗∗ and MP2/6-31G∗∗). Quantum chemical calculations predict the existence of three conformers for 2-NO 2-C 6H 4SO 2F each of them possesses C 1 symmetry. Conformer I, in which the S–F bond of the SO 2F group is nearly perpendicular to the plane of benzene ring, is predicted to be most favored. Conformer II, in which the S–F bond is situated in opposite direction with reference to the NO 2 group, possesses intermediate energy (Δ Е 1–2 = 0.73 kcal/mol (B3LYP), or 0.71 kcal/mol (MP2)), and conformer III with the S–F bond tilted to the NO 2 group possesses the higher energy (Δ Е 1–3 = 1.58 kcal/mol (B3LYP), or 1.47 kcal/mol (MP2)). The analysis of the GED intensities was carried out assuming the vapour consists of three conformers. In was obtained the conformer I dominates in vapour over solid 2-NO 2-C 6H 4SO 2F at T = 383(5) K. The conformer III concentration was found to be negligible. In dominant conformer I the S–F bond is bent slightly towards the nitro group ( ϕ(C–C–S–F) = 84(8)°), and the torsional angle of the nitro group with respect to the benzene ring ϕ(C–C–N–O) equals 125(4)°. The conformation properties were determined by the potential energy surface analysis. The relative stability of conformers is discussed.