Molecular Structure and Conformations of para-Methylbenzene Sulfonamide and ortho-Methylbenzene Sulfonamide: Gas Electron Diffraction and Quantum Chemical Calculations Study

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• 作者：Vjacheslav M. Petrov ; Georgiy V. Girichev ; Heinz Oberhammer ; Valentina N. Petrova ; Nina I. Giricheva ; Anna V. Bardina ; Sergey N. Ivanov
• 刊名：Journal of Physical Chemistry A
• 出版年：2008
• 出版时间：April 3, 2008
• 年：2008
• 卷：112
• 期：13
• 页码：2969 - 2976
• 全文大小：239K
• 年卷期：v.112,no.13(April 3, 2008)
• ISSN：1520-5215

文摘

The molecular structure and conformational properties of para-methylbenzene sulfonamide (4-MBSA) andortho-methylbenzene sulfonamide (2-MBSA) have been studied by gas electron diffraction (GED) and quantumchemical methods (B3LYP/6-311+G** and MP2/6-31G**). Quantum chemical calculations predict theexistence of two conformers for 4-MBSA with the S-N bond perpendicular to the benzene plane and theNH₂ group either eclipsing or staggering the S-O bonds of the SO₂ group. Both conformers possess C_Ssymmetry. The eclipsed form is predicted to be favored by E = 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 themethyl group ((C2C1SN) = 180) or nonplanar direction ((C2C1SN) 60). In both cases, the NH₂group can adopt eclipsed or staggered orientation, resulting in a total of four stable conformers. The nonplanareclipsed conformer (C₁ symmetry) and the planar eclipsed form (C_S symmetry) are predicted to be favored.According to the GED analysis, the saturated vapor over solid 4-MBSA at T = 151(3) C consists as mixtureof the eclipsed (78(19) %) and staggered (22(19) %) forms. The saturated vapor over solid 2-MBSA at T =157(3) C consists as a mixture of the nonplanar eclipsed (69(11) %) and planar eclipsed (31(11) %) forms.