1-甲氧基乙基-3-甲基咪唑甘氨酸离子液体的物理化学性质的研究（英文）

Physicochemical Properties of 1-Methoxyethyl-3-Methylimidazolium Glycine

由于氨基酸基的独特性质,我们以甘氨酸作为阴离子,醚基咪唑基团作为阳离子合成了一种新型离子液体1-甲氧乙基-3-甲基咪唑甘氨酸[MOEMIM][Gly],并经过核磁共振氢谱、核磁共振碳谱和差示扫描量热进行表征。由于离子液体和水之间形成氢键导致传统的方法不能去除水的影响,所以在实验测定中,选用标准加入法在温度范围为298.15–338.15K,每隔5 K测定离子液体[MOEMIM][Gly]的密度和表面张力。利用密度数据,计算得到离子液体[MOEMIM][Gly]的摩尔体积,并且摩尔体积随着温度的升高而增加,同时得到了热膨胀系数。根据离子液体[MOEMIM][Gly]的摩尔表面Gibbs自由能,改进了传统的E?tv?s经验方程,使得方程具有更明确的物理意义,即截距C0代表摩尔表面焓,它是一个与温度无关的常数,斜率则为摩尔表面熵,这表明改进的E?tv?s方程不仅是一个经验方程,而且还是严格的热力学方程。另外,结合摩尔表面Gibbs自由能和改进的E?tv?s方程,估算了离子液体的[MOEMIM][Gly]的表面张力,并与实验值进行比较,发现两者很好的一致。

Because of the unique acid-base behavior of amino acids, we combined glycine as the anion with an ether group as the cation and prepared a novel ionic liquid （IL）, 1-methoxyethyl-3-methylimidazolium glycine [MOEMIM][Gly]. The formation of this IL was confirmed by 1H-NMR, 13C-NMR, differential scanning calorimetry （DSC） and thermogravimetry （TG） analyses. The density, p, and surface tension, y of the ILs were measured in the temperature range from 298.15 K to 338.15 K at intervals of 5 K using the standard addition method, because the strong hydrogen bonds between the IL [MOEMIM][Gly] and trace amounts of water made it, extremely difficult to remove water by convention methods. The calculated molar volume, Vm, of [MOEMIM][Gly] increased with increasing temperature. The thermal expansion coefficient, a, was also obtained based on the density values. In terms of the molar surface Gibbs free energy, gs for [MOEMIM][Gly], the traditional Eotv6s equation is improved so that it has physical significance, that is, the intercept Co represents molar surface enthalpy, h, which is a temperature-independent constant and the slop C1 =-（αgslαT）p is molar surface entropy, s, it shows that modified Eotvos equation is not only an empirical equation, but also a strict thermodynamic one. In addition, by a combination of gs and the modified Eotvos equation, the surface tension values of [MOEMIM][Gly] were estimated and compared with the experimental values; both sets of data were in good accordance with each other.