Design of Deep Eutectic Systems: A Simple Approach for Preselecting Eutectic Mixture Constituents.

Ahmad Alhadid,Mirjana Minceva,Liudmila Mokrushina

doi:10.3390/molecules25051077

Ahmad Alhadid, Mirjana Minceva + Show 1 more

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https://doi.org/10.3390/molecules25051077

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Abstract

Eutectic systems offer a wide range of new (green) designer solvents for diverse applications. However, due to the large pool of possible compounds, selecting compounds that form eutectic systems is not straightforward. In this study, a simple approach for preselecting possible candidates from a pool of substances sharing the same chemical functionality was presented. First, the melting entropy of single compounds was correlated with their molecular structure to calculate their melting enthalpy. Subsequently, the eutectic temperature of the screened binary systems was qualitatively predicted, and the systems were ordered according to the depth of the eutectic temperature. The approach was demonstrated for six hydrophobic eutectic systems composed of L-menthol and monocarboxylic acids with linear and cyclic structures. It was found that the melting entropy of compounds sharing the same functionality could be well correlated with their molecular structures. As a result, when the two acids had a similar melting temperature, the melting enthalpy of a rigid acid was found to be lower than that of a flexible acid. It was demonstrated that compounds with more rigid molecular structures could form deeper eutectics. The proposed approach could decrease the experimental efforts required to design deep eutectic solvents, particularly when the melting enthalpy of pure components is not available.

Highlights

Eutectic systems are mixtures of two or more compounds that exhibit partial immiscibility or negligible mutual solubility in the solid phase [1]
The lowest predicted melting entropy was for cyclohexanecarboxylic acid with a flexibility number Φ equal to zero
If the melting enthalpy is not available, it can be estimated from the melting entropy, which is correlated with the molecular structure, using the simple non-group contribution model proposed by Jain et al [44]

Summary

Introduction

Eutectic systems are mixtures of two or more compounds that exhibit partial immiscibility or negligible mutual solubility in the solid phase [1]. These advantages have led to the recent increase in applications of DESs, for example, as solvents in diverse separation methods [4,5,6,7,8], media for chemical [9,10,11,12,13,14], electrochemical [15,16,17,18,19], and biological reactions [20,21], in polymer chemistry [22,23,24], and for increasing the solubility of active pharmaceutical ingredients [25,26,27,28] Their preparation may be easier than that of ILs, DESs are more difficult to design.

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