Natural Eutectic Solvent Mixture of l‐Menthol/Malonic acid (4 : 1) and Its Ibuprofen Solution: Thermal and Physical Characterizations and NMR Studies of Molecular Interaction

Abstract

A eutectic mixture of L-menthol and malonic acid, Me/MA (4 : 1), was characterized by calorimetry and other physical measurements. The new deep eutectic solvent (m.p. 6 °C) solvates 338 mg of ibuprofen per mL, and the solution is stable in a wide temperature range. Strategies of NMR titration used in supramolecular chemistry were employed to explore binding forces between the eutectic constituents as well as solutesolvent interaction in ibuprofen solution. Even in acetonitrile, Me 4 MA is formed through a hydrogen-bonding network, where the constituents act as hydrogen donors and acceptors at the same time. The estimated association constant is around 30 M À 1 ; the binding forces are enough to build the eutectic mixture at high concentrations. The aggregate Me 4 MA forms a molecular complex with ibuprofen in acetonitrile as a result of the cooperative effect of the constituents. In addition, van der Waals interactions are operative between ibuprofen and menthol in the saturated IB-Me/MA (4 : 1) solution.

Study of the chlorogenic acid extraction with choline chloride‐based deep eutectic solvents and its non‐covalent interactions analysis

“…DES were prepared in a glove box (LABCONCO 5060110) under a nitrogen atmosphere according to the already published procedure 32 . Briefly: the starting materials were dried in a vacuum pump for two hours; then, the appropriate amounts of choline chloride and the corresponding hydrogen donor were placed in a 250‐ml flask with a stir bar and the mixtures were heated at 80°C for 40 min until a homogeneous liquid was obtained.…”