Exploring the Molecular Interactions of 1,3-Dimethylimidazolium Methyl Sulfate Ionic Liquid in Aqueous and Aqueous l‑Alanine Solutions at Various Temperatures

The present study employed volumetric and compressibility methods to investigate the intermolecular interactions of 1,3-dimethylimidazolium methyl sulfate, i.e., [MMIm][MeSO₄] ionic liquid in both aqueous and aqueous l-alanine solutions. Density (ρ) and sound velocity (<i>c</i>) for [MMIm][MeSO₄] in two different systems such as the binary system ([MMIm][MeSO₄] in water) and the ternary system ([MMIm][MeSO₄] in 0.05 mol kg^–1 aqueous l-alanine solution) were measured within a temperature range of 288.15–318.15 K at intervals of 5 K over the concentration range of 0.03–0.15 mol kg^–1. We calculated various parameters such as the apparent molar volume of solute (<i>V</i>_ϕ), the limiting apparent molar volume of solute (<i>V</i>_ϕ^ο), the experimental slope (<i>S</i>_v), the isobaric thermal expansion coefficient (α), the transfer limiting apparent molar volume of solute (Δ_tr<i>V</i>_ϕ⁰), the isentropic compression of solution(κ_S), the apparent molar isentropic compression of solute (<i>K</i>_S,ϕ), the partial molar isentropic compression of solute (<i>K</i>_S,ϕ⁰), the transfer partial molar isentropic compression of solute (Δ_tr<i>K</i>_S,φ⁰), and Hepler’s constant (∂²<i>V</i>_ϕ⁰/∂<i>T</i>²) by using the experimental ρ and <i>c</i> data. The outcomes are elucidated in terms of interactions between the solute–solute and solute–solvent in the studied systems.