Thermophysical Properties of Propaline + 1-Alcohols: An Experimental and Molecular Insight

Abstract

In this work, we measure density, speed of sound, and viscosities of Propaline [Choline Chloride:Propylene Glycol (1:2)] with methanol, ethanol, and 1-propanol at temperatures from (288.15 to 343.15) K at atmospheric pressure. A. vibrating tube densimeter and a microviscometer are used to obtain these physical properties. Propaline crystallizes at low temperatures. Derived properties (excess molar volumes, viscosity deviations, speed of sound deviations, and isentropic compressibility deviations) are obtained from experimental measurements. The derived properties are negative at all temperatures except for speed of sound deviations which are negative and positive. Derived properties are represented with the Redlich–Kister equation. Kinematic viscosities are correlated with the McAllister and the Nava-Rios equations. The average absolute relative deviation is (2.01 and 1.47)% for the McAllister and Nava-Rios equations, respectively. Density Functional Theory (DFT) simulations reveal weak hydrogen bonding interactions between Propaline components and ethanol molecules, characterized by electron density (ρ) and Laplacian values (∇²ρ) near the lower bound of hydrogen bonding criteria. Molecular dynamics (MD) simulations demonstrate the reinforcement of intermediate-range molecular ordering at lower ethanol concentrations, which gradually transitions into disorder at higher ethanol concentrations due to thermal disruption of the hydrogen bond network.