In Competition for Water: Hydrated Choline Chloride:Urea vs Choline Acetate:Urea Deep Eutectic Solvents

Pietro, Maria Enrica Di; Tortora, Mariagrazia; Bottari, Cettina; Dugoni, Greta Colombo; Pivato, Roberto Vittorio; Rossi, Barbara; Paolantoni, Marco; Mele, Andrea

doi:10.1021/acssuschemeng.1c03811

Cited by 36 publications

(25 citation statements)

References 73 publications

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“…This behavior was predicted from MD simulations and ascribed to a more heterogeneous environment of the NH 2 groups and stronger hydrogen bonds involving the water molecules [11]. Pietro et al [21], also relate the red shift of the NH 2 rocking band observed in Raman spectra with new hydrogen bond interactions of urea with water. In the second region (2,700-3,800 cm −1 , Figure 6B), there are two main broad features, assigned to the CH and NH + OH stretching modes, centered at ca.…”

Section: Effect Of Water In Chcl:urea Desmentioning

confidence: 76%

“…A matter that emerges from a large number of experimental reports is the effect of water on the properties of DES. It has become evident that the effect of water on the physicochemical properties and on the structural features of DES has important practical implications [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24]. Water addition promotes structural changes on DES at the microscopic level and these changes are not yet fully understood.…”

Section: Introductionmentioning

confidence: 99%

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Water in Deep Eutectic Solvents: New Insights From Inelastic Neutron Scattering Spectroscopy

et al. 2022

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The effect of water on the physicochemical properties of deep eutectic solvents (DES) is a trending research topic. In this work, inelastic neutron scattering (INS) spectroscopy, was used to probe intermolecular interactions in the water-deep eutectic solvent mixtures for the cases of choline chloride (the hydrogen bond acceptor) and three different hydrogen bond donors, with different degrees of acidity: urea, glycerol and lactic acid. It was found that quenching samples in liquid nitrogen is a procedure that may retain the liquid phase morphology of DES at the low temperatures required by INS spectroscopy. The three studied systems share the preference of water molecules to bind to chloride anion, as predicted by numerous molecular dynamics simulations. Despite this similarity, the three systems present several distinct INS features upon water addition that are related to their unique properties and structure at the molecular level. In the choline chloride:urea system, water molecules promote a strengthening of hydrogen bonds with the NH and OH donors, while for the choline chloride:lactic acid system INS probed the existence of solvated DES clusters instead of specifically interfering water molecules. This study takes advantage from the unique capabilities of INS and paves the way for future studies in these systems.

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Section: Effect Of Water In Chcl:urea Desmentioning

confidence: 76%

Section: Introductionmentioning

confidence: 99%

Water in Deep Eutectic Solvents: New Insights From Inelastic Neutron Scattering Spectroscopy

et al. 2022

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“…[22] Based on our previous findings that DESs can behave as non-innocent reaction media in catalyzing the cyclization/aromatization of nitrogen heterocycles, [15,16] we next turned our attention towards a different DES, namely choline acetate (ChOAc)/urea (1 : 2 mol mol À 1 ), whose components are both basic, and in which protons are more easily exchanged. [23] To our delight, using up to 2 equiv. of base, not only the range of yields increased up to 77-98 % with 7 educts (3 a-e, 3 g,h) now isolated in 98 % yield, but the reaction time, in some cases, also shortened up to 2-4 h (3 a-c, 3 g) (Scheme 2).…”

Section: Resultsmentioning

confidence: 97%

“…This is based on a cycloaddition‐elimination cascade reaction between aryl azides and enol ethers to access either 1,4‐ or 1,5‐disubstituted triazoles [22] . Based on our previous findings that DESs can behave as non‐innocent reaction media in catalyzing the cyclization/aromatization of nitrogen heterocycles, [15,16] we next turned our attention towards a different DES, namely choline acetate (ChOAc)/urea (1 : 2 mol mol −1 ), whose components are both basic, and in which protons are more easily exchanged [23] . To our delight, using up to 2 equiv.…”

Section: Resultsmentioning

confidence: 99%

1,3‐Dipolar Cycloaddition of Alkanone Enolates with Azides in Deep Eutectic Solvents for the Metal‐Free Regioselective Synthesis of Densely Functionalized 1,2,3‐Triazoles

et al. 2022

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Dedicated to Professor Cesare Gennari on the occasion of his 70th birthday.An eco-friendly metal-free protocol was developed for the regioselective synthesis of densely functionalized 1,2,3-triazoles through a 1,3-dipolar cycloaddition reaction of alkanone enolates with azides performed in the environmentally responsible choline chloride/urea or choline acetate/urea eutectic mixture. This approach displays a broad substrate scope, straightforwardly furnishing the desired triazoles (including the challenging phenolic derivatives) in yields of up to 98 %, while working at room temperature and under aerobic conditions. The practicability of the method is exemplified by the sustainable synthesis of some pharmaceutically relevant triazole derivatives carried out via telescoped, one-pot cycloaddition/ reduction processes in the same eutectic mixture without any halfway isolation/purification step of intermediates.

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“…Further features in the fingerprint region cannot be assigned and could also be the result of subtle modifications in the spectra caused by varying water concentrations in NADES. It has been reported in the literature that molecular interactions can be affected by water concentrations in NADES, associated with a weakening of the hydrogen bonding between HBD-HBA, H 2 O-HBD and H 2 O-HBA, which can be observed by Raman spectroscopy [ 85 , 86 , 87 ]. However, the OH scissoring bending band from water at ~1633 cm −1 is weak compared to the other bands and, due to the overlap with the L-Proline band at 1624 cm −1 , its contribution to the PLSR model is not significant.…”

Section: Resultsmentioning

confidence: 99%

Comparison of Vibrational Spectroscopic Techniques for Quantification of Water in Natural Deep Eutectic Solvents

et al. 2022

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Vibrational spectroscopic techniques, i.e., attenuated total reflectance infrared (ATR-IR), near infrared spectroscopy (NIRS) and Raman spectroscopy (RS), coupled with Partial Least Squares Regression (PLSR), were evaluated as cost-effective label-free and reagent-free tools to monitor water content in Levulinic Acid/L-Proline (LALP) (2:1, mol/mol) Natural Deep Eutectic Solvent (NADES). ATR-IR delivered the best outcome of Root Mean Squared Error (RMSE) of Cross-Validation (CV) = 0.27% added water concentration, RMSE of Prediction (P) = 0.27% added water concentration and mean % relative error = 2.59%. Two NIRS instruments (benchtop and handheld) were also compared during the study, respectively yielding RMSECV = 0.35% added water concentration, RMSEP = 0.56% added water concentration and mean % relative error = 5.13% added water concentration, and RMECV = 0.36% added water concentration, RMSEP = 0.68% added water concentration and mean % relative error = 6.23%. RS analysis performed in quartz cuvettes enabled accurate water quantification with RMECV = 0.43% added water concentration, RMSEP = 0.67% added water concentration and mean % relative error = 6.75%. While the vibrational spectroscopic techniques studied have shown high performance in relation to reliable determination of water concentration, their accuracy is most likely related to their sensitivity to detect the LALP compounds in the NADES. For instance, whereas ATR-IR spectra display strong features from water, Levulinic Acid and L-Proline that contribute to the PLSR predictive models constructed, NIRS and RS spectra are respectively dominated by either water or LALP compounds, representing partial molecular information and moderate accuracy compared to ATR-IR. However, while ATR-IR instruments are common in chemistry and physics laboratories, making the technique readily transferable to water quantification in NADES, Raman spectroscopy offers promising potential for future development for in situ, sample withdrawal-free analysis for high throughput and online monitoring.

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In Competition for Water: Hydrated Choline Chloride:Urea vs Choline Acetate:Urea Deep Eutectic Solvents

Cited by 36 publications

References 73 publications

Water in Deep Eutectic Solvents: New Insights From Inelastic Neutron Scattering Spectroscopy

Water in Deep Eutectic Solvents: New Insights From Inelastic Neutron Scattering Spectroscopy

1,3‐Dipolar Cycloaddition of Alkanone Enolates with Azides in Deep Eutectic Solvents for the Metal‐Free Regioselective Synthesis of Densely Functionalized 1,2,3‐Triazoles

Comparison of Vibrational Spectroscopic Techniques for Quantification of Water in Natural Deep Eutectic Solvents

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