Abstract: Solutions serve as a common reaction environment across various fields such as chemistry, materials science, and biology. Understanding the relationship between the structure and properties of solutions is of significant importance; however, undergraduate laboratory courses often lack experiments that focus on solution structure. This study employs nitrile compounds as infrared spectral probes to investigate molecular-ion interactions in solution using Attenuated Total Reflection-Fourier Transform Infrared Spectroscopy (ATR-FTIR). By varying the solute concentration and modulating the solvent’s induction effect, steric hindrance, and coordination, we analyze their impact on the solvation structure. This experiment integrates knowledge from instrumental analysis, physical chemistry, and organic chemistry, while also expanding the applicability of infrared spectroscopy. Moreover, the straightforward experimental procedures enhance students’ investigative skills and creative thinking, making it a valuable addition to innovative undergraduate laboratory courses.

Key words: Solution structure, Infrared absorption spectroscopy, Probes, Molecular-ion interactions