Acta Phys. -Chim. Sin. ›› 2016, Vol. 32 ›› Issue (1): 267-273.doi: 10.3866/PKU.WHXB201510303

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Thermodynamic Properties and Predicting the Surface Tension of Pyridinium-Based Ionic Liquids of [C6py][DCA] Using a New Eötvös Equation

Xiao-Xue BU1,Ben-Han FAN1,Jie WEI1,Nan-Nan XING1,2,Xiao-Xue MA1,Wei GUAN1,*()   

  1. 1 College of Chemistry, Liaoning University, Shenyang 110036, P. R. China
    2 College of Chemistry and Chemical Engineering
  • Received:2015-09-09 Published:2016-01-13
  • Contact: Wei GUAN
  • Supported by:
    the National Natural Science Foundation of China(21173107);Liaoning Excellent Talents in University, China(2015025)


The pyridinium-based ionic liquids [C6py][DCA] (N-hexyl-pyridinium dicyanamide) was prepared and characterized using [1]H and [13]C nuclear magnetic responancec (NMR) spectroscopies, Fourier transform infrared (FT-IR) spectroscopy, and differential scanning calorimetry (DSC). The density (ρ), surface tension (γ), and refractive indices (nD) were measured at the temperature range from 288.15 to 338.15 K. Molecular volume (Vm), energy of surface (Ea), molar polarization (Rm), and polarization coefficient of [C6py][DCA] (αp) were calculated from the experimental data. Ea, Rm, and αp were approximately temperature-independent. The concept of molar surface Gibbs free energy (gs) was conceived, for which a new Eötvös equation was derived. The gs, critical temperature (Tc), and Eötvös empirical parameter related to polarity (kE) were also obtained. The new Eötvös equation was used to predict the surface tension and the predicted values of [C6py][DCA] are in close agreement with the corresponding experimental ones.

Key words: Pyridinium-based ionic liquid, Density, Surface tension, Molar surface Gibbs free energy, Eötvös equation


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