MD simulations explain the excess molar enthalpies in pseudo-binary mixtures of a choline chloride-based deep eutectic solvent with water or methanol
The addition of molecular liquid cosolvents to choline chloride (ChCl)-based deep eutectic solvents (DESs) is increasingly investigated for reducing the inherently high bulk viscosities of the latter, which represent a major obstacle for potential industrial applications. The molar enthalpy of mixin...
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Frontiers Media S.A.
2022-11-01
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| Series: | Frontiers in Chemistry |
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| Online Access: | https://www.frontiersin.org/articles/10.3389/fchem.2022.983281/full |
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| author | Leon de Villiers Engelbrecht Xiaoyan Ji Carlo Maria Carbonaro Aatto Laaksonen Aatto Laaksonen Aatto Laaksonen Aatto Laaksonen Aatto Laaksonen Francesca Mocci |
| author_facet | Leon de Villiers Engelbrecht Xiaoyan Ji Carlo Maria Carbonaro Aatto Laaksonen Aatto Laaksonen Aatto Laaksonen Aatto Laaksonen Aatto Laaksonen Francesca Mocci |
| author_sort | Leon de Villiers Engelbrecht |
| collection | DOAJ |
| description | The addition of molecular liquid cosolvents to choline chloride (ChCl)-based deep eutectic solvents (DESs) is increasingly investigated for reducing the inherently high bulk viscosities of the latter, which represent a major obstacle for potential industrial applications. The molar enthalpy of mixing, often referred to as excess molar enthalpy HE—a property reflecting changes in intermolecular interactions upon mixing—of the well-known ChCl/ethylene glycol (1:2 molar ratio) DES mixed with either water or methanol was recently found to be of opposite sign at 308.15 K: Mixing of the DES with water is strongly exothermic, while methanol mixtures are endothermic over the entire mixture composition range. Knowledge of molecular-level liquid structural changes in the DES following cosolvent addition is expected to be important when selecting such “pseudo-binary” mixtures for specific applications, e.g., solvents. With the aim of understanding the reason for the different behavior of selected DES/water or methanol mixtures, we performed classical MD computer simulations to study the changes in intermolecular interactions thought to be responsible for the observed HE sign difference. Excess molar enthalpies computed from our simulations reproduce, for the first time, the experimental sign difference and composition dependence of the property. We performed a structural analysis of simulation configurations, revealing an intriguing difference in the interaction modes of the two cosolvents with the DES chloride anion: water molecules insert between neighboring chloride anions, forming ionic hydrogen-bonded bridges that draw the anions closer, whereas dilution of the DES with methanol results in increased interionic separation. Moreover, the simulated DES/water mixtures were found to contain extended hydrogen-bonded structures containing water-bridged chloride pair arrangements, the presence of which may have important implications for solvent applications. |
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| institution | Directory Open Access Journal |
| issn | 2296-2646 |
| language | English |
| last_indexed | 2024-04-11T08:07:43Z |
| publishDate | 2022-11-01 |
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| series | Frontiers in Chemistry |
| spelling | doaj.art-12408e50221e49d9aef4c825d5e1f4532022-12-22T04:35:29ZengFrontiers Media S.A.Frontiers in Chemistry2296-26462022-11-011010.3389/fchem.2022.983281983281MD simulations explain the excess molar enthalpies in pseudo-binary mixtures of a choline chloride-based deep eutectic solvent with water or methanolLeon de Villiers Engelbrecht0Xiaoyan Ji1Carlo Maria Carbonaro2Aatto Laaksonen3Aatto Laaksonen4Aatto Laaksonen5Aatto Laaksonen6Aatto Laaksonen7Francesca Mocci8Department of Chemical and Geological Sciences, University of Cagliari, Cagliari, ItalyDivision of Energy Science, Energy Engineering, Luleå University of Technology, Luleå, SwedenDepartment of Physics, University of Cagliari, Cagliari, ItalyDepartment of Chemical and Geological Sciences, University of Cagliari, Cagliari, ItalyDivision of Energy Science, Energy Engineering, Luleå University of Technology, Luleå, SwedenDivision of Physical Chemistry, Arrhenius Laboratory, Department of Materials and Environmental Chemistry, Stockholm University, Stockholm, SwedenCenter of Advanced Research in Bionanoconjugates and Biopolymers, “Petru Poni” Institute of Macromolecular Chemistry, Iasi, RomaniaState Key Laboratory of Materials-Oriented and Chemical Engineering, Nanjing Tech University, Nanjing, ChinaDepartment of Chemical and Geological Sciences, University of Cagliari, Cagliari, ItalyThe addition of molecular liquid cosolvents to choline chloride (ChCl)-based deep eutectic solvents (DESs) is increasingly investigated for reducing the inherently high bulk viscosities of the latter, which represent a major obstacle for potential industrial applications. The molar enthalpy of mixing, often referred to as excess molar enthalpy HE—a property reflecting changes in intermolecular interactions upon mixing—of the well-known ChCl/ethylene glycol (1:2 molar ratio) DES mixed with either water or methanol was recently found to be of opposite sign at 308.15 K: Mixing of the DES with water is strongly exothermic, while methanol mixtures are endothermic over the entire mixture composition range. Knowledge of molecular-level liquid structural changes in the DES following cosolvent addition is expected to be important when selecting such “pseudo-binary” mixtures for specific applications, e.g., solvents. With the aim of understanding the reason for the different behavior of selected DES/water or methanol mixtures, we performed classical MD computer simulations to study the changes in intermolecular interactions thought to be responsible for the observed HE sign difference. Excess molar enthalpies computed from our simulations reproduce, for the first time, the experimental sign difference and composition dependence of the property. We performed a structural analysis of simulation configurations, revealing an intriguing difference in the interaction modes of the two cosolvents with the DES chloride anion: water molecules insert between neighboring chloride anions, forming ionic hydrogen-bonded bridges that draw the anions closer, whereas dilution of the DES with methanol results in increased interionic separation. Moreover, the simulated DES/water mixtures were found to contain extended hydrogen-bonded structures containing water-bridged chloride pair arrangements, the presence of which may have important implications for solvent applications.https://www.frontiersin.org/articles/10.3389/fchem.2022.983281/fulldeep eutectic solventcholine chloridecosolventsexcess propertiespseudo-binary solvent mixtureMD simulations |
| spellingShingle | Leon de Villiers Engelbrecht Xiaoyan Ji Carlo Maria Carbonaro Aatto Laaksonen Aatto Laaksonen Aatto Laaksonen Aatto Laaksonen Aatto Laaksonen Francesca Mocci MD simulations explain the excess molar enthalpies in pseudo-binary mixtures of a choline chloride-based deep eutectic solvent with water or methanol Frontiers in Chemistry deep eutectic solvent choline chloride cosolvents excess properties pseudo-binary solvent mixture MD simulations |
| title | MD simulations explain the excess molar enthalpies in pseudo-binary mixtures of a choline chloride-based deep eutectic solvent with water or methanol |
| title_full | MD simulations explain the excess molar enthalpies in pseudo-binary mixtures of a choline chloride-based deep eutectic solvent with water or methanol |
| title_fullStr | MD simulations explain the excess molar enthalpies in pseudo-binary mixtures of a choline chloride-based deep eutectic solvent with water or methanol |
| title_full_unstemmed | MD simulations explain the excess molar enthalpies in pseudo-binary mixtures of a choline chloride-based deep eutectic solvent with water or methanol |
| title_short | MD simulations explain the excess molar enthalpies in pseudo-binary mixtures of a choline chloride-based deep eutectic solvent with water or methanol |
| title_sort | md simulations explain the excess molar enthalpies in pseudo binary mixtures of a choline chloride based deep eutectic solvent with water or methanol |
| topic | deep eutectic solvent choline chloride cosolvents excess properties pseudo-binary solvent mixture MD simulations |
| url | https://www.frontiersin.org/articles/10.3389/fchem.2022.983281/full |
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