Molecular structure and conformations of benzenesulfonamide: gas electron diffraction and quantum chemical calculations.

The molecular structure and conformational properties of benzenesulfonamide, C6H5SO2NH2, were studied by gas electron diffraction (GED) and quantum chemical methods (MP2 and B3LYP with different basis sets). The calculations predict the presence of two stable conformers with the NH2 group eclipsing or staggering the SO2 group. The eclipsed form is predicted to be favored by about 0.5 kcal/mol. According to GED, the saturated vapor over solid benzenesulfonamide at a temperature of 150(5) degrees C consists of the eclipsed conformer. The GED intensities, however, possess a very low sensitivity toward the vapor composition, and contributions of the anti conformer of up to 75% (at the 0.05 level of significance) or up to 55% (at the 0.25 level of significance) cannot be excluded. The molecule possesses C(sS) symmetry with the S-N bond perpendicular to the ring plane.