Acta Phys. -Chim. Sin. ›› 2000, Vol. 16 ›› Issue (01): 15-21.doi: 10.3866/PKU.WHXB20000104

• ARTICLE • Previous Articles     Next Articles

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

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