Gas electron diffraction and quantum chemical Studies of THE Molecular structure of 2-nitrobenzenesulfonic acid
A combined gas electron diffraction and quantum chemical (B3LYP/6-311+G**, B3LYP/cc-pVTZ) study of the molecular structure of 2-nitrobenzenesulfonic acid (2-NBSA) is performed. Quantum chemical calculations show that the 2-NBSA molecule has five conformers, and the Gibbs energy of one of them is lower by more than 4.5 kcal/mol than the energy of the other conformers. It is found experimentally that the saturated vapor of 2-NBSA at <i>Т</i> = 394(5) K contains only the low-energy conformer that has an intramolecular hydrogen bond between the H atom of the hydroxyl group and one of the О atoms of the NO<sub>2</sub> group. The C-C-S-O(Н) torsion angle determining the position of the S-O(Н) bond is -72(7)°, while the NO<sub>2</sub> group is substantially turned relative to the benzene ring plane (C1-C2-N-O = 40(5)°). The following experimental values of the internuclear distances are obtained for this conformer (Å): <i>r</i><sub><i>h</i>1</sub>(C-H)<sub>av</sub> = 1.07(2), <i>r</i><sub><i>h</i>1</sub>(C-C)<sub>av</sub> = 1.401(4), <i>r</i><sub><i>h</i>1</sub>(C-S) = 1.767(6), <i>r</i><sub><i>h</i>1</sub>(S=O)<sub>av</sub> = 1.412(4), <i>r</i><sub><i>h</i>1</sub>(S-O) = 1.560(6), <i>r</i><sub><i>h</i>1</sub>(N-O)<sub>av</sub> = 1.217(5), <i>r</i><sub><i>h</i>1</sub>(C-N) = 1.461(8), <i>r</i><sub><i>h</i>1</sub>(O-H) = 0.99(3).