Thermodynamic Properties of 1-Butyl-3-methylpyridinium Tetrafluoroborate and Its Mixtures with Water and Alkanols

In this article, we study the behavior of an ionic liquid (IL) derived from pyridinium, 1-butyl-3-methylpyridinium tetrafluoroborate [b3mpy][BF 4 ], in mixtures with water and with the first alkanols of the series from methanol to butan-1-ol, at the temperatures of (298.15 and 318.15) K. First, the miscibility regions with the alkanols were established at these two temperatures, determining experimentally the liquid−liquid equilibria and the upper critical solution temperature (UCST) for each binary mixture, confirming the quasiexponential variation of the UCST with the alkanol chain. The enthalpies were determined experimentally with a newly designed calorimetric cell, and the excess molar volumes were determined from densities, at (298.15 and 318.15) K. In all cases, the are positive with ( d / dT ) p > 0, whereas the are negative for mixtures with alkanols but positive for the mixture of IL + water. The thermal coefficient ( d / dT ) p > 0 was also positive in all cases. All data were correlated with a suitable polynomial equation, and the area and volume parameters of [b3mpy][BF 4 ] were calculated. Finally, we give an interpretation of the results and of the behavior of the mixtures.