An in-depth study of the hydrophobic eutectic mixturesformed by l-menthol (MEN) with the butylated hydroxytoluene(BHT), 2-tert-butyl-p-cresol (TBC),and p-cresol (PC) compounds has been carried out,where TBCand PC are analogous to the BHT species but with a different degreeof steric hindrance around the hydroxyl group. Thermal characterizationevidenced that the BHT/MEN system can be classified as an ideal eutectic,while the TBC/MEN and PC/MEN mixtures behave as type V deep eutecticsolvents (DESs) for a wide range of compositions around the eutecticpoint. As shown by an array of experimental and theoretical methods,in the BHT/MEN mixtures the establishment of hydrogen-bond (H-bond)interactions between the components is dramatically hampered becauseof the steric hindrance in the BHT molecule, so that the achievementof a liquid phase at room temperature for the eutectic compositionis driven by apolar-apolar attractions among the alkyl functionalgroups of the constituents. Differently, the TBC-MEN donor-receptorH-bond is the main driving force for the formation of a type V DESand derives from a concurrence of electronic and steric factors characterizingthe TBC molecule. Finally, the absence of steric hindrance aroundthe hydroxyl group allows the self-association among PC moleculesthrough H-bonded networks already in the pristine compound, but thereplacement with the more favorable PC-MEN H-bond provides a typeV DES upon mixing of these components. Our combined approach, togetherwith the peculiarity of the inspected systems, delivered an archetypalstudy able to shed light onto the various contributions ruling thestructure-properties relationship in DESs and possibly deepeningthe currently accepted view of these inherently complex media.l-Menthol mixtures with butylatedhydroxytoluenederivatives unveiled the complex contributions driving the formationof sustainable type V hydrophobic deep eutectic solvents.
The Complex Story Behind a Deep Eutectic Solvent Formation as Revealed by l-Menthol Mixtures with Butylated Hydroxytoluene Derivatives
Capocefalo, A;
2023-01-01
Abstract
An in-depth study of the hydrophobic eutectic mixturesformed by l-menthol (MEN) with the butylated hydroxytoluene(BHT), 2-tert-butyl-p-cresol (TBC),and p-cresol (PC) compounds has been carried out,where TBCand PC are analogous to the BHT species but with a different degreeof steric hindrance around the hydroxyl group. Thermal characterizationevidenced that the BHT/MEN system can be classified as an ideal eutectic,while the TBC/MEN and PC/MEN mixtures behave as type V deep eutecticsolvents (DESs) for a wide range of compositions around the eutecticpoint. As shown by an array of experimental and theoretical methods,in the BHT/MEN mixtures the establishment of hydrogen-bond (H-bond)interactions between the components is dramatically hampered becauseof the steric hindrance in the BHT molecule, so that the achievementof a liquid phase at room temperature for the eutectic compositionis driven by apolar-apolar attractions among the alkyl functionalgroups of the constituents. Differently, the TBC-MEN donor-receptorH-bond is the main driving force for the formation of a type V DESand derives from a concurrence of electronic and steric factors characterizingthe TBC molecule. Finally, the absence of steric hindrance aroundthe hydroxyl group allows the self-association among PC moleculesthrough H-bonded networks already in the pristine compound, but thereplacement with the more favorable PC-MEN H-bond provides a typeV DES upon mixing of these components. Our combined approach, togetherwith the peculiarity of the inspected systems, delivered an archetypalstudy able to shed light onto the various contributions ruling thestructure-properties relationship in DESs and possibly deepeningthe currently accepted view of these inherently complex media.l-Menthol mixtures with butylatedhydroxytoluenederivatives unveiled the complex contributions driving the formationof sustainable type V hydrophobic deep eutectic solvents.Pubblicazioni consigliate
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