New natural deep eutectic solvents based on aromatic organic acids

Figures & data

Figure 1. The predicted solid–liquid equilibrium phase diagrams (full line) by COSMO-RS, the ideal liquidus diagrams (dashed line) and the experimental eutectic points at different mole fractions (▪).

Table 1. Compounds used for the preparation of deep eutectic solvents and their melting properties.

Compound	Structure	CAS	Abbreviation	Tm (K)	Δmh (kJ·mol^−1)
trans-Cinnamic acid		140-10-3	Cin	323.28	19.00
p-Coumaric acid		7400-08-0	Coua	486.90	24.78
trans-Ferulic acid		537-98-4	Fer	481.02	28.17
Benzoic acid		65-85-0	Ben	395.70	13.61
p-Hydroxybenzoic acid		99-96-7	Hyd	489.35	19.40
Salicylic acid		69-72-7	Sal	432.20	19.40
4-Anisic acid		100-09-4	Ani	457.80	17.00
Vanillic acid		121-34-6	Van	483.00	22.79
Mandelic acid		90-64-2	Man	392.00	16.77
Coumarin		91-64-5	Cou	343.00	18.63

T_m, melting (fusion) point; Δ_mh, Enthalpy of fusion.

Figure 2. FTIR spectra for pure sources (A) and the obtained eutectic solvent systems (B). Aromatic organic acids/coumarin molar ratio 1:3.

Figure 3. ¹H NMR chemical shifts of starting materials (A) and the obtained eutectic solvent systems (B). Aromatic organic acids/coumarin molar ratio 1:3.

Figure 4. Binding energy and its physical components calculated at SAPT2+/aug-cc-pVDZ level in the pure substances (A) and the eutectic solvent systems (B).

Table 2. Total mean interaction energy (E) obtained by COSMO-RS.

DES	EHBD	Epure HBD	EHBA	Epure HBA	ΔE
Man-Cou	−7.88	−8.43	−6.61	−5.90	−0.16
Sal-Cou	−7.36	−6.97	−6.71	−5.90	−1.20
Ben-Cou	−7.03	−7.65	−6.57	−5.90	−0.05
Hyd-Cou	−9.48	−10.04	−7.10	−5.90	−0.64
Cin-Cou	−8.42	−8.95	−6.49	−5.90	−0.07
Coua-Cou	−10.64	−11.83	−6.99	−5.90	0.09
Fer-Cou	−9.83	−10.95	−6.65	−5.90	0.38
Ani-Cou	−7.72	−8.51	−6.48	−5.90	0.20
Van-Cou	−8.74	−9.58	−6.71	−5.90	0.03

Values are given in kcal mol⁻¹.