Within the framework of green chemistry,
solvents occupy a strategic
place. To be qualified as a green medium, solvents should meet a few
important standards such as availability, nontoxicity, biodegradability,
recyclability, flammability, and low price among others. Deep eutectic
solvents (DESs) are the type of solvents that can meet these conditions.
In this work, we performed experimental and computational studies
on the DESs, type III group, which are mixtures of xylitol and sorbitol
with choline chloride at eutectic composition. The mentioned DESs
were compared with commonly used DESs of sugar alcohols: ethylene
glycol and glycerol. Moreover, the key factor for choosing these solvents
is that their freezing points are below 293.15 K, and so, they are
all liquids at room temperature. With the growing interest in this
field, there is an urgent need for a deep understanding on the formation
and functioning of these solvents at the molecular level. Besides,
complementarity of theoretical and experimental studies can be helpful
in further designing novel DESs. Thus, in this work, we report the
physicochemical properties of the mentioned DESs, which include density,
viscosity, electrical conductivity, molar volume, refractive index,
molar refraction, and free molar volume in temperatures ranging from
293.15 to 353.15 K. The reported properties were fitted to appropriate
linear or polynomial equations with very satisfactory correlation
coefficients (R
2). Moreover, the density
functional theory (DFT) method and molecular dynamics (MD) simulations
have been used to probe DESs at the molecular level. Molecular dynamic
simulations confirmed that hydrogen bonds between sorbitol, xylitol,
and choline chloride play a fundamental role in the observed properties
of these DESs.
