The criterion to distinguish a simple eutectic mixture from
a deep eutectic solvent (DES) lies in the deviations to thermodynamic
ideality presented by the components in the system. In this work, the
current knowledge of the molecular interactions in types III and V DES is
explored to liquefy a set of three fatty acids and three fatty alcohols, here
used as model compounds for carboxyl and hydroxyl containing solid
compounds. This work shows that thymol, a stronger than usual hydrogen
bond donor, is able to form deep eutectic solvents of type V with the fatty
alcohols studied. This is particularly interesting, since these DES formed
are hydrophobic. Regarding type III DES, the results suggest that the
prototypical DES hydrogen bond acceptor, cholinium chloride, is unable
to induce negative deviations to ideality in the model molecules studied.
By substituting choline with tetramethylammonium chloride, it is shown that the choline hydroxyl group is responsible for the
difficulty in forming choline-based deep eutectic solvents and that its absence induces strong negative deviations to ideality in the
alkylammonium side. Finally, it is demonstrated that tetrabutylammonium chloride acts as a chloride donning agent, causing
significant negative deviations to ideality in both fatty acids and alcohols and leading to the formation of deep eutectic solvents of
type III.This work was developed within the scope of the projects
CICECO-Aveiro Institute of Materials, UIDB/50011/2020 and
UIDP/50011/2020, financed by national funds through the
Portuguese Foundation for Science and Technology/MCTES,
and CIMO-Mountain Research Center, UIDB/00690/2020,
financed by national funds through the FCT/MEC and when
appropriate cofinanced by FEDER under the PT2020 Partnership
Agreement. L.P.S. acknowledges FCT for her PhD grant
SFRH/BD/135976/2018.info:eu-repo/semantics/publishedVersio
