Used as a phase-transfer catalyst in organic synthesis, facilitating reactions between reagents in different phases by transferring ions into organic solvents. Commonly employed in nucleophilic substitutions, esterifications, and polymerizations. Also utilized in electrochemistry as a supporting electrolyte due to its good solubility and stability in polar solvents. Plays a role in the preparation of quaternary ammonium-based ionic liquids and surfactants. In biological research, it acts as a cholinergic agent to study ion channels and nerve signaling, mimicking acetylcholine effects in some systems.