Spectral and thermophysical properties of some novel deep eutectic solvent based on l-menthol and their mixtures with ethanol

Abstract

The three novel l-menthol based deep eutectic solvents (DESs) with some hydrogen bond donors, salicylic acid (SA), (1S)-(+)-camphor-10-sulfonic acid (CSA), and ethylene glycol (EG) were prepared for the first time and characterized using thermophysical and spectral properties. Major advantage of these types of DESs is hydrophobic feature which lead to formation biphasic media with water at room temperature. In this study, the physical properties of DESs were investigated by density, speed of sound, DSC, TGA, FTIR and NMR analysis and interpreted in terms of hydrogen bond intermolecular interactions. Measurement of density and speed of sound were also performed at T = (288.15 to 308.15) K for their pure state, and their binary mixtures with ethanol. From these data, the excess molar volumes (VE), isentropic compressibility deviation (Δκs), speed of sound deviation (Δu) were calculated at the experimental temperatures. The obtained values were satisfactorily fitted to the Redlich-Kister equation. It was found that excess molar volumes and isentropic compressibility deviations are decreased with increasing the temperature. These results were discussed in terms of various molecular interactions occurring between the components.