Measurement Of Thermodynamic Properties Of Lactic Acid Ionic Liquid And Estimates

Since imidazole-based Ionic liquids(ILs) gain more interest in many fields such as life sciences, pharmaceutics, environment and even national defense due to the peculiar properties of green and designed, it provides an important scientific research value for green chemistry.1-alkyl-3-methyl imidazole lactic acid salts [Cnmim][Lact](n = 2,3,4,5) were prepared based on the materials of imidazole bromides, the structures were characterized by 1H NMR and differential scanning calorimetry(DSC).The water contents were measured by Karl Fischer moisture titrator(ZSD-2 type), a solution-reaction isoperibol calorimeter(SRC-100) was used to determine the molar enthalpies of solution for different molalities of the ILs in the temperature range of(288.15 to 308.15 ± 0.01) K with an interval of 5 K. According to Archer et al., in terms of a Debye-Hückel limiting equation, the standard molar enthalpies of solution for [Cnmim][Lact](n = 2,3,4,5), ΔsolHmθ, can be obtained at the given temperature, Plotting M against Y, some good straight lines were obtained, with the slopes of the lines being the standard molar enthalpies of solution, then the apparent relative molar enthalpy, ?LB, for these four ILs were obtained in the temperatures.Plotting ΔsolHmθ against(T – 298.15) K, the standard molar heat capacity of dissolution process, ΔCp,mθ, was obtained and then the values of ΔCpθ, were obtained. According to Paulechka et al., molar heat capacity, Cp, of ILs can be estimated with the molar volume(V/cm3·mol-1). According to the values of standard molar enthalpies of solution, ΔsolHmθ, in infinite dilution aqueous and lattice energy, UPOT, the hydration enthalpies of cation and anion,(ΔH+ + ΔH–), for ILs [Cnmim][Lact](n = 2,3,4,5) were estimated, the hydration enthalpies of lactic acid anion, ΔH–([Lact]-), were also calculated by using the values of the hydration enthalpy of cation, ΔH+([C2mim]+), ΔH+([C4mim]+), ΔH+([C5mim]+).