Tetra-N-Hexylammonium Iodide is primarily used as a phase-transfer catalyst in organic synthesis. It facilitates the transfer of reactants between immiscible phases, such as aqueous and organic layers, enhancing reaction efficiency. This compound is particularly valuable in nucleophilic substitution reactions, where it helps in the smooth generation and transfer of anions. It is also employed in the synthesis of ionic liquids and as a stabilizer in electrochemical applications. Additionally, it finds use in the preparation of nanoparticles and in polymerization processes, where it aids in controlling the reaction environment and improving product yields.