title: Molecular structure and conformations of para-methylbenzene sulfonamide and ortho-methylbenzene sulfonamide: gas electron diffraction and quantum chemical calculations study.
abstract: The molecular structure and conformational properties of para-methylbenzene sulfonamide (4-MBSA) and ortho-methylbenzene sulfonamide (2-MBSA) have been studied by gas electron diffraction (GED) and quantum chemical methods (B3LYP/6-311+G** and MP2/6-31G**). Quantum chemical calculations predict the existence of two conformers for 4-MBSA with the S-N bond perpendicular to the benzene plane and the NH2 group either eclipsing or staggering the S-O bonds of the SO2 group. Both conformers possess CS symmetry. The eclipsed form is predicted to be favored by DeltaE = 0.63 kcal/mol (B3LYP) or 1.00 kcal/mol (MP2). According to the calculations, the S-N bond in 2-MBSA can possess planar direction opposite the methyl group (phi(C2C1SN) = 180 degrees ) or nonplanar direction (phi(C2C1SN) approximately 60 degrees ). In both cases, the NH2 group can adopt eclipsed or staggered orientation, resulting in a total of four stable conformers. The nonplanar eclipsed conformer (C1 symmetry) and the planar eclipsed form (CS symmetry) are predicted to be favored. According to the GED analysis, the saturated vapor over solid 4-MBSA at T = 151(3) degrees C consists as mixture of the eclipsed (78(19) %) and staggered (22(19) %) forms. The saturated vapor over solid 2-MBSA at T = 157(3) degrees C consists as a mixture of the nonplanar eclipsed (69(11) %) and planar eclipsed (31(11) %) forms.
authors.affiliation: Ivanovo State University, Ivanovo 153460, Russia, Ivanovo State University of Chemistry and Technology, Ivanovo 153460, Russia.
authors.forename: Vjacheslav M
authors.initials: VM
authors.lastname: Petrov
authors.forename: Georgiy V
authors.initials: GV
authors.lastname: Girichev
authors.forename: Heinz
authors.initials: H
authors.lastname: Oberhammer
authors.forename: Valentina N
authors.initials: VN
authors.lastname: Petrova
authors.forename: Nina I
authors.initials: NI
authors.lastname: Giricheva
authors.forename: Anna V
authors.initials: AV
authors.lastname: Bardina
authors.forename: Sergey N
authors.initials: SN
authors.lastname: Ivanov
mesh_terms: D006860:Hydrogen Bonding; D007536:Isomerism; D013058:Mass Spectrometry; D008956:Models, Chemical; D008958:Models, Molecular; D008968:Molecular Conformation; D044367:Phase Transition; D011789:Quantum Theory; D017550:Spectroscopy, Fourier Transform Infrared; D013449:Sulfonamides / Q000737:chemistry*; D014050:Toluene / Q000031:analogs & derivatives* / Q000737:chemistry; D000096926:Benzenesulfonamides
chemical_list: D013449:Sulfonamides; D014050:Toluene; C025417:4-toluenesulfonamide; D000096926:Benzenesulfonamides; C013307:2-toluenesulfonamide