Catalytic behavior, electronic structure and spectroscopic (FT-IR, Raman, UV–vis) properties for the new ionic liquid imidazolium hydrogen sulfate

• Published in: Journal of molecular structure 2025-02, Vol.1322, p.140445, Article 140445
• Main Authors: Tankov, Ivaylo, Yankova, Rumyana
• Format: Article
• Language: English
• Subjects: Catalytic behavior; Esters production; Imidazolium ionic liquids; Reaction kinetics; Spectroscopic properties; Theoretical study
• ISSN: 0022-2860
• DOI: 10.1016/j.molstruc.2024.140445

•Catalytic, electronic and spectroscopic behavior for [H–Im]+[HSO4]– was studied.•O3···H12 and O2···H10 bonds manage the structural stability of [H–Im]+[HSO4]–.•O2···H10 bond (477.98 kJ/mol) is notably stronger than O3···H12 one (7.25 kJ/mol).•H8/O6 atom is the most electrophilic/nucleophilic site in [H–Im]+[HSO4]–.•The positive charge on H8 dictates the catalytic performance of [H–Im]+[HSO4]–. Catalytic performance, chemical reactivity, vibrational modes and electronic transitions of the ion pair [H–Im]+[HSO4]– were investigated in the current paper. Hence, a combined experimental (Hammett acidity function, infrared, Raman and ultraviolet-visible spectroscopies) and theoretical (molecular electrostatic potential surface, reduced density gradient, frontier molecular orbital analysis, quantum theory of atoms in molecules, net atomic charges, global and local reactivity descriptors) study was conducted. In terms of the catalytic performance, the acetic acid esterification with butanol was evaluated. Important kinetic (rate constant, activation energy, pre-exponential factor) and thermodynamic (enthalpy, entropy, Gibbs free energy barrier) factors for ester production as a function of the temperature and catalyst loading have been determined. Results revealed intensive electron density distribution in [H–Im]+[HSO4]– due to chemical interactions between the cationic and anionic moieties. These bonds were established as electrostatic in nature. The pronounced charge transfers within [H–Im]+[HSO4]– managed the title compound acidity (H0) and its catalytic behavior towards butyl acetate synthesis. Using the thermodynamic and kinetic measurements, a mechanism for acetic acid esterification with butanol in the presence of imidazolium hydrogen sulfate ionic liquid was offered. [Display omitted]