物理化学学报 >> 2000, Vol. 16 >> Issue (01): 15 -21 .doi: 10.3866/PKU.WHXB20000104

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1,2-二硫方酸的气相酸性和芳香性

周立新, 莽朝永, 章永凡   

  1. 福州大学化学系,福州 350002
  • 收稿日期:1999-04-05 修回日期:1999-06-01 发布日期:2000-01-15
  • 通讯作者: 周立新

Gas-phase Acidity and Aromaticity of 1,2-dithiosquaric Acid

Zhou Li-Xin, Mang Chao-Yong, Zhang Yong-Fan   

  1. Department of Chemistry,Fuzhou University,Fuzhou 350002
  • Received:1999-04-05 Revised:1999-06-01 Published:2000-01-15
  • Contact: Zhou Li-Xin

摘要:

在RHF/6-311G**、RHF/6-311+G**和B3LYP/6-311+G**水平,优化得到1,2-二硫方酸(3,4.二羟基-3-环丁烯-1,2-二硫酮)三种平面构象异构体的平衡几何构型.进一步用MPZ(full)/6-311+G**//RHF/6-311+G**方法计算三种异构体的单点能量,发现ZZ型异构体是能量最低构象,且ZZ和ZE型能量非常接近.用优化的最稳定构象ZZ型异构体,在RHF/6-311G**//RHF/6-311G**、RHF/6.311+G**//RHF/6-311+G**、MPZ(full)/6.311+G**//RHF/6-311+G**和B3LYP/6-311+G**和B3LYP/6-311+G**水平,计算其气相酸性(△G_298_Θ),并用同键反应方法在同样水平计算其芳香性稳定化能.用基团加和法(group increment approach)在RHF/6.311+G**//RHF/6-311+G**和B3LYP/6-311+G**//B3LTh/6-311+G**水平计算其磁化率增量(Λ).计算结果指出,标题合物的键长发生了平均化,芳香性稳定化能和磁化率增量均为负值,表明它具有芳香性,实现了标题化合物芳香.

关键词: 1,2-二硫方酸, 从头算, 密度泛函理论, 芳香性, 气相酸性

Abstract:

The conformation, aromaticity and gas--phase acidity (free energy of deprotonation, ΔGΘ ) of 1, 2- dithiosquaric acid (3, 4 - dihydroxy - 3 -cyclubutene- 1, 2 - dithione ) were calculated at the SCF and MP_2 and B3LYP levels using 6-311G(d, p) and 6-311 + G(d, p) basis sets. The global minimum found on the potential energy surface of 1, 2-dithiosquaric acid presents a planar conformation. The ZZ isomer was found to be the most stable one of the three planar conformers. The aromatic stabilization energy (EAS,) and magnetic susceptibility exaltation(Λ) were also computed by using the homodesmotic reaction and RHF-CSGT (Continue set of Gauge Transformations) (IGAIM, a slight varation on CSGT) and B3LYP-CSGT(IGIAM) methods at the 6-311 + G(d, p) level. The calculated EAS and were more negative values, indicating that 1, 2-dithiosqaric acid is aromatic. Thus the titled compound fulfilled the geometrical, energetic and magnetic criteria of aromaticity. The most reliable theoretical gas-phase acidity are C _298.1Θ,=1278. 2 kJ• mol -1 and G_298.1Θ= 1648. 5 kJ• mol-1.

Key words: 1,2-dithiosquaric acid, Ab initio, Density functional theory(DFT), Aromaticity, Gas-phase acidity