Studies of the tautomeric equilibrium of 1,3-thiazolidine-2-thione: Theoretical and experimental approaches

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• 作者：Camilla Abbehausen ; Raphael E.F. de Paiva ; André ; L.B. Formiga ; ^{formiga@iqm.unicamp.br} ; Pedro P. Corbi
• 关键词：1 ; 3-Thiazolidine-2-thione ; Tautomeric equilibrium ; 1H NMR ; DFT
• 刊名：Chemical Physics
• 出版年：2012
• 出版时间：26 October, 2012
• 年：2012
• 卷：408
• 期：Complete
• 页码：62-68
• 全文大小：4432 K

文摘

The tautomeric equilibrium of the thione/thiol forms of 1,3-thiazolidine-2-thione was studied by nuclear magnetic resonance, infrared and ultraviolet-visible spectroscopies. Density functional theory was used to support the experimental data and indicates the predominance of the thione tautomer in the solid state, being in agreement with previously reported crystallographic data. In solution, the tautomeric equilibrium was evaluated using ¹H NMR at different temperatures in four deuterated solvents acetonitrile, dimethylsulfoxide, chloroform and methanol. The equilibrium constants, K = (thiol)/(thione), and free Gibbs energies were obtained by integration of N bonded hydrogen signals at each temperature for each solvent, excluding methanol. The endothermic tautomerization is entropy-driven and the combined effect of solvent and temperature can be used to achieve almost 50 % thiol concentrations in solution. The nature of the electronic transitions was investigated theoretically and the assignment of the bands was made using time-dependent DFT as well as the influence of solvent on the energy of the most important bands of the spectra.