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) °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 CsS symmetry
with the S−N bond perpendicular to the ring plane.