(352ab) Thermodynamic and Spectroscopic Properties of Binary Mixtures of Ionic Liquid Sec-butylammonium Methanoate with Alcohols

Ionic liquids are defined as salts, which have melting point below 100°C whereas room temperature ionic liquids (RTIL) are liquids. Many of these compounds have good solubility in organic and inorganic solvents, low volatility, good chemical and thermal stability and are normally green solvents. Over the past decades, ionic liquids have received a great amount of attention from scientific communities because of these special properties.

Our previous studies have focused on the binary liquid mixtures containing varied protic ionic liquids with alcohols [1; 2; 3]. This work is a continuation of thermodynamic and spectroscopic studies of the mixtures of ionic liquid {sec-butylammonium methanoate (S4Met) + ethanol or 1-propanol or 1-butanol} in the whole concentration range at different temperatures T = (293.15 – 313.15) K under ambient pressure p = 92.3 kPa. The experimental data of density and speed of sound were used to calculate excess molar volume and deviation in isentropic compressibility, which were correlated to the Redlich-Kister polynomial equation. S4Met was synthesized in our laboratory by neutralization reaction, using s-butylamine and methanoic acid. S4Met was characterized by using ¹H-NMR, ¹³C-NMR and FTIR spectroscopy techniques and presented a purity over 99 %. A Karl Fischer titration was used to determine the water amount. The densities and speed of sound of pure components and their solutions were measured using a commercial density and speed of sound analyzer manufactured by Anton Paar (model DSA 5000). The analyses of ¹H-NMR and ¹³C-NMR were obtained in an Avance III 600 HD Bruker spectrometer operating at 600 MHz for protons and 150 MHz for carbon. The IR spectra were obtained in a Fourier transform infrared spectroscopy Nicolet with attenuated total reflectance (FTIR-ATR) (model 6700).

For all systems studied, the values of excess molar volumes and isentropic compressibility deviation were negative over the entire composition range. The results obtained were discussed in terms of intermolecular interactions, particularly hydrogen-bonding interactions between like and unlike molecules.

[1] S.S. Bittencourt, H.E. Hoga, R.B. Torres, J.V.H. D’Angelo, J. Chem. Thermodyn. 105 (2017) 238-252.

[2] S.S. Bittencourt, H.E. Hoga, R.B. Torres, J.V.H. D’Angelo, J. Therm. Anal. Calorim. (2018).

[3] G.V. Olivieri, C.S. da Cunha, L.D. Martins, P.A.M. Paegle, S.D. Nuncio, A.D. Morandim-Giannetti, R.B. Torres, J. Therm. Anal. Calorim. 131 (2018) 2925-2942.