TY - JOUR
T1 - Structural properties and stability of the Betaine-Urea natural deep eutectic solvent
AU - Nava Ocampo, Maria F.
AU - Al Fuhaid, Lamya
AU - Santana, Adriano
AU - Bucs, Szilard
AU - Verpoorte, Robert
AU - Hae Choi, Young
AU - Witkamp, Geert Jan
AU - Vrouwenvelder, Johannes S.
AU - Farinha, Andreia S.F.
N1 - KAUST Repository Item: Exported on 2021-09-29
Acknowledgements: The authors thank King Abdullah University of Science and Technology (KAUST) for funding this research project. This research used the resources of the Supercomputing Laboratory at King Abdullah University of Science and Technology (KAUST) in Thuwal, Saudi Arabia. The authors thank Dr. Nuno M. M. Moura for the insights given in the NMR discussion.
PY - 2021/9/25
Y1 - 2021/9/25
N2 - This work focuses on the stability and supramolecular structure of the betaine-urea-water (B:U:W) natural deep eutectic solvent. Solutions spanning a range of molar ratios of betaine, urea, and water were prepared, varying the temperature and preparation times, and were analyzed by attenuated total reflection Fourier-transform infrared spectroscopy and Nuclear Magnetic Resonance. Density Functional Theory and the Natural Bond Orbital analysis were employed to obtain the most stable conformations for each mixture. The experimental results show that, in non-anhydrous conditions, betaine:urea (1:1), a minimum of two moles of water are needed to form a metastable transparent liquid, and a minimum of three moles of water is required to have a stable NADES. Comparison of the 13C-NMR spectra of B:U:W 1:1:2 and 1:1:3 shows for the latter that the carbonyl groups of betaine and urea form stronger hydrogen bonds with water, and that the CH3 group of betaine becomes more deprotected by the addition of the extra water molecule, making 1:1:3 a more stable solution. Our experimental and computational results show that water is of crucial importance to the NADES supramolecular structure and stability. A better understanding of the structural characteristics of NADES can lead to better envisage applications for these green solvents.
AB - This work focuses on the stability and supramolecular structure of the betaine-urea-water (B:U:W) natural deep eutectic solvent. Solutions spanning a range of molar ratios of betaine, urea, and water were prepared, varying the temperature and preparation times, and were analyzed by attenuated total reflection Fourier-transform infrared spectroscopy and Nuclear Magnetic Resonance. Density Functional Theory and the Natural Bond Orbital analysis were employed to obtain the most stable conformations for each mixture. The experimental results show that, in non-anhydrous conditions, betaine:urea (1:1), a minimum of two moles of water are needed to form a metastable transparent liquid, and a minimum of three moles of water is required to have a stable NADES. Comparison of the 13C-NMR spectra of B:U:W 1:1:2 and 1:1:3 shows for the latter that the carbonyl groups of betaine and urea form stronger hydrogen bonds with water, and that the CH3 group of betaine becomes more deprotected by the addition of the extra water molecule, making 1:1:3 a more stable solution. Our experimental and computational results show that water is of crucial importance to the NADES supramolecular structure and stability. A better understanding of the structural characteristics of NADES can lead to better envisage applications for these green solvents.
UR - http://hdl.handle.net/10754/672012
UR - https://linkinghub.elsevier.com/retrieve/pii/S0167732221023801
U2 - 10.1016/j.molliq.2021.117655
DO - 10.1016/j.molliq.2021.117655
M3 - Article
SN - 0167-7322
SP - 117655
JO - Journal of Molecular Liquids
JF - Journal of Molecular Liquids
ER -