Insights into the Chloride versus Bromide Effect on the Formation of Urea-Quaternary Ammonium Eutectic Solvents

Abstract

The intermolecular interactions of urea and quaternary ammonium salts relevant to their thermodynamic nonideality were here investigated by measuring the solid–liquid equilibria of their binary mixtures. The experimental data revealed that the anion transfer between the quaternary ammonium salt and urea increases with increasing alkyl chain lengths, leading to negative deviations from ideality in the urea-rich side for [N4,4,4,4]-based systems. However, the use of bromides instead of chlorides dampens the nonideality of urea because of larger size and lower electronegativity of the anion. The behavior of urea when mixed with ChCl or ChBr was found to be remarkably different, indicating that its nonideality in the ChCl/urea eutectic solvent is governed by urea–chloride rather than hydroxyethyl–urea interactions. The conclusions presented highlight the contribution of charge delocalization in the formation of deep eutectic solvents of type III.

Exploring asymmetry induced entropy in tetraalkylammonium–urea DES systems: what can be learned from inelastic neutron scattering?

“…4. The melting points of pure salts (considered with the caveats discussed earlier) 9 are higher for the smaller systems. The comparison for tetramethylammonium bromide vs. chloride:urea systems was reported elsewhere, 9 concluding that both components behave closer to thermodynamic ideality, in spite of small differences on the overall interactions present.…”

“…4B) is sufficient to define the behaviour of the mixture. In fact, since the melting temperatures of alkylammonium salts are typically above 500 K 9,31 and the salt : urea ratio for the ideal eutectic point is expected to be between ca. 1 : 1–1 : 3, the temperature of the ideal eutectic point must fall within the 360 ± 30 K interval of the urea SLE ideal line.…”

“…4A) has been reported to decrease the non-ideality of the bromide salt, leading to near-ideal behaviour. 9 On the other hand, Fig. 4B evidences the different behaviour between the symmetrical [N 2,2,2,2 ]Cl and the asymmetrical [N 2,2,2,1 ]Cl systems, with a strong deviation from ideality of urea for the asymmetrical compound.…”

“…Depending on the physical state of the final mixture, a capillary melting point apparatus or an oil bath was used to measure its melting point. The solid mixtures of all systems were firstly ground in the glove box and the temperatures were measured following the melting point capillary method described previously by Martins et al 9 For the mixtures presenting a pasty consistency ( x (urea) = 0.5 to 0.8 of the [N 2,2,2,1 ]Cl:urea system), samples were heated in an oil bath under stirring until completely melting. The melting temperatures were measured using a Pt100 probe (±0.1 K) corresponding to the last solid disappearance.…”

Experimental and Mechanistic Analysis of Chlorinated Volatile Organic Compound Capture by Quaternary Ammonium-Based Deep Eutectic Solvents

“…Quaternary ammonium salts are commonly used as surfactants and disinfectants. Moreover, they can combine with most polyols and acids to create DESs with a eutectic point well below room temperature, ensuring stability in both physical and chemical properties. , This type of DES is very beneficial as an absorbent, and many researchers have conducted such studies. For instance, Cheng and Qi.…”