Effect of Alcohol Structure on Heat Capacity Behavior of Choline Chloride-Based Deep Eutectic Solvents

Abstract: This study investigates the molar heat capacities (Cp) of three choline chloride-based deep eutectic solvents (DESs)—Reline, Ethaline, and Glyceline—and their binary mixtures with two structurally distinct alcohols: 1-butanol (linear) and 2-butanol (branched). Cp measurements were carried out under standard pressure using a differential scanning calorimeter (DSC) across a temperature range of 303.2 K to 353.2 K at various compositions. Results show that Cp increases with both temperature and DES concentration. The temperature dependence of pure DESs was well described using a second-order empirical model, with an average absolute deviation (AAD%) of 0.05. The binary mixtures exhibited predominantly negative excess molar heat capacities (Cpᴱ), indicating non-ideal mixing behavior due to altered hydrogen-bonding interactions. The Redlich–Kister polynomial equation effectively correlated the Cpᴱ values with temperature and composition. The comparative analysis of mixtures with linear and branched alcohols highlights the significant impact of molecular structure on thermal behavior, providing valuable insights for designing sustainable solvents for heat-sensitive and green chemical processes.

Chemistry

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