Solubilities of Benzene, Toluene, and Ethylbenzene in Deep Eutectic Solvents

In this work, choline chloride/urea (1:2), choline chloride/oxalic acid (1:1), choline chloride/ethylene glycol (1:2), benzyltriphenylphosphonium chloride/ethylene glycol (1:11), tetrabutylammonium bromide/ethylene glycol (1:4), tetrabutylammonium bromide/diethylene glycol (1:4), and tetrabutylammonium bromide/triethylene glycol (1:4) were examined as deep eutectic solvents (DESs). The melting points and dynamic viscosities of these solvents were determined, and the solubilities of benzene, toluene, and ethylbenzene in each were assessed using the cloud point method between T = 303.15 and 353.15 K at atmospheric pressure. The solubilities of each of these three aromatic compounds in these DESs were found to increase with increases in temperature. Both the hydrogen bond acceptors and hydrogen bond donors in the DESs were also shown to affect solubility, with the former having a greater effect and this effect decreasing in the order of tetrabutylammonium bromide > benzyltriphenylphosphonium chloride > choline chloride. The simplified dual-parameter equation and the Apelblat empirical equation were used to correlate the experimentally determined solubilities of benzene, toluene, and ethylbenzene in the seven DESs, and the latter equation generated higher correlations.