Mixing thermodynamic properties of 1-butyl-4-methylpyridinium tetrafluoroborate [b4mpy][BF4] with water and with an alkan-1ol (methanol to pentanol)

This article presents a study of the behaviour in solution of 1-butyl-4-methylpyridinium tetrafluoroborate [b4mpy][BF4] in water and in the first five alkanols of the series methanol to pentan-1-ol. The excess enthalpies, HmE and volumes, VmE were determined at the temperatures (298.15 and 318.15) K. At these temperatures, the [b4mpy][BF4] was completely miscible in water, methanol, and ethanol, but only partially miscible in the other alkanols. A solubility study was carried out and the (liquid + liquid) equilibria of the ([b4mpy][BF4] + alkanol) systems were experimentally determined, evaluating zones of complete miscibility and determining the UCST in each case. The mixtures with water gave positive values of HmE and VmE, being also positive the changes of these quantities with temperature. The mixtures with alkanols gave values of HmE>0 and VmE<0, and for these binary mixtures (dHmE/dT)p>0 and (dVmE/dT)p<0. For all cases, results were interpreted and compared with data obtained in mixtures with another isomer [b3mpy][BF4]. Excess properties were correlated with a suitable equation and the area and volume parameters were calculated for [b4mpy][BF4].