1-乙基-3-甲基咪唑丙氨酸离子液体热力学性质的研究

用中和法合成了氨基酸离子液体1-乙基-3-甲基咪唑丙氨酸(C₂mim]Ala]),并利用恒温环境的溶解反应热量计,在(288.15±0.01) K-(308.15±0.01) K温度范围内每隔5 K,测定不同质量摩尔浓度离子液体在水中的溶解焓(Δ_solH_m^θ).根据Archer的方法,通过线性拟合得到了该离子液体的标准摩尔溶解焓(Δ_sol),并计算了其相对表观摩尔溶解焓(^ΦL).在298.15 K下,根据Glasser经验方法得到了格子能U_POT = 566 kJ·mol^-1,并计算了其阴阳离子水化焓值(ΔH⁺ + ΔH^-) = -620 kJ·mol^-1及阴离子水化焓ΔH^-(Ala]^-) = -387 kJ·mol^-1.此外,估算了C₂mim]Ala]水溶液的热容(C_p(sol))和表观摩尔热容(^ΦC_p).

Study on Thermodynamic Properties of Ionic Liquid 1-Ethyl-3-methylimidazolium Alanine

We synthesized the alanine-based ionic liquid C₂mim]Ala] (1-ethyl-3-methylimidazolium alanine) by using the neutralization method and characterized it. Using a solution-reaction isoperibol calorimeter, we determined the molar enthalpies of the solution (Δ_solH_m) at various molalities in water from (288.15±0.01) to (308.15±0.01) K in intervals of 5 K. Using Archer's method, we obtained the standard molar enthalpy of solution for C₂mim]Ala] (Δ_solH_m^θ) and calculated its apparent relative molar enthalpy (^ΦL). Using Glasser's theory of lattice energy, we obtained the lattice energy, U_POT = 566 kJ·mol^-1, the hydration enthalpy of the cation and anion, (ΔH⁺ + ΔH^-) = -620 kJ·mol^-1, and the hydration enthalpy of an anion, ΔH^-(Ala]^-) = -387 kJ·mol^-1 at 298.15 K. Finally, we obtained the heat capacity of aqueous C₂mim]Ala] (C_p(sol)) and its apparent molar heat capacity (^ΦC_p) at various specific molalities.