物理化学学报 >> 2018, Vol. 34 >> Issue (8): 927-932.doi: 10.3866/PKU.WHXB201801112

所属专题: 绿色化学

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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

魏杰,董贺新,陈霞,杨宇轩,房大维*(),关伟*(),杨家振   

  • 收稿日期:2017-12-25 发布日期:2018-04-03
  • 通讯作者: 房大维,关伟 E-mail:davidfine@163.com;guanweiy@sina.com
  • 基金资助:
    国家自然科学基金(21673107);国家自然科学基金(21373005);国家自然科学基金(21703090)

Physicochemical Properties of 1-Methoxyethyl-3-Methylimidazolium Glycine

Jie WEI,Hexin DONG,Xia CHEN,Yuxuan YANG,Dawei FANG*(),Wei GUAN*(),Jiazhen YANG   

  • Received:2017-12-25 Published:2018-04-03
  • Contact: Dawei FANG,Wei GUAN E-mail:davidfine@163.com;guanweiy@sina.com
  • Supported by:
    The project was supported by the National Natural Science Foundation of China(21673107);The project was supported by the National Natural Science Foundation of China(21373005);The project was supported by the National Natural Science Foundation of China(21703090)

摘要:

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298.15–338.15 K,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Eötvös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Eötvös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Eötvös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。

关键词: 1-甲氧乙基-3-甲基咪唑甘氨酸, 密度, 表面张力, 摩尔表面Gibbs自由能

Abstract:

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, ρ, and surface tension, γ, 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, α, was also obtained based on the density values. In terms of the molar surface Gibbs free energy, gs for [MOEMIM][Gly], the traditional Eötvös equation is improved so that it has physical significance, that is, the intercept C0 represents molar surface enthalpy, h, which is a temperature-independent constant and the slop C1 = −($\partial $gs/$\partial $T)p is molar surface entropy, s, it shows that modified Eötvös equation is not only an empirical equation, but also a strict thermodynamic one. In addition, by a combination of gs and the modified Eötvös 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.

Key words: 1-Methoxyethyl-3-methy limidazolium glycine, Density, Surface tension, Molar surface Gibbs free energy

MSC2000: 

  • O642