Shah Dhawal, Mansurov Ulan, Mjalli Farouq S
Department of Chemical and Materials Engineering, Nazarbayev University, Kazakhstan.
Petroleum and Chemical Engineering Department, Sultan Qaboos University, Oman.
Phys Chem Chem Phys. 2019 Aug 21;21(31):17200-17208. doi: 10.1039/c9cp02368b. Epub 2019 Jul 25.
Reline, a typical type III Deep Eutectic Solvent (DES), composed of urea and choline chloride, is widely used and highly investigated for its thermo-physical properties and intermolecular interactions. The formation of hydrogen bonds between urea and chloride ions and a strong suppression in the hydrogen bonds between the urea molecules lead to a significantly low melting point of reline. Considering commercial applications, aqueous solutions of reline have been extensively analyzed; however, water, being a protic solvent, strongly affects the hydrogen bond network in reline and disrupts its structure. A mixture of reline with aprotic solvent has not been systematically investigated in the literature. To this end, we herein explore the intermolecular interactions between reline and dimethylsulfoxide (DMSO), a commonly used industrial solvent, which unlike water, does not have labile hydrogen. Our experiments revealed that a decrease in the density of the mixture with increasing DMSO amount is less significant as compared with water. Furthermore, molecular dynamics simulation results, as analyzed in terms of the hydrogen bonds between the components and interaction energies, suggest a very limited effect on urea-urea, urea-chloride, and urea-choline interactions in the presence of DMSO. Moreover, DMSO preferentially interacts with urea in the mixture; whereas in the case with water, the chloride ion was preferentially hydrated. Radial distribution analysis indicates that reline, while getting diluted by DMSO, maintains its structure up to 0.7-mole fraction of DMSO. Taken together the results reveal that DMSO reserves intermolecular interactions of reline better than water.
雷尼林是一种典型的III型深共熔溶剂（DES），由尿素和氯化胆碱组成，因其热物理性质和分子间相互作用而被广泛应用并受到深入研究。尿素与氯离子之间形成氢键，同时尿素分子间的氢键受到强烈抑制，导致雷尼林的熔点显著降低。考虑到商业应用，人们对雷尼林的水溶液进行了广泛分析；然而，水作为质子溶剂，会强烈影响雷尼林中的氢键网络并破坏其结构。雷尼林与非质子溶剂的混合物在文献中尚未得到系统研究。为此，我们在此探究雷尼林与二甲基亚砜（DMSO，一种常用的工业溶剂）之间的分子间相互作用，与水不同，DMSO没有不稳定的氢。我们的实验表明，与水相比，随着DMSO含量增加，混合物密度的降低不太显著。此外，根据各组分之间的氢键和相互作用能进行分析的分子动力学模拟结果表明，在DMSO存在下，对尿素 - 尿素、尿素 - 氯化物和尿素 - 胆碱相互作用的影响非常有限。此外，在混合物中DMSO优先与尿素相互作用；而在与水混合的情况下，氯离子优先被水化。径向分布分析表明，雷尼林在被DMSO稀释时，在DMSO的摩尔分数达到0.7之前仍能保持其结构。综合这些结果表明，DMSO比水能更好地保留雷尼林的分子间相互作用。
