Tetrabutylammonium bromide is widely used as a phase transfer catalyst in organic synthesis. It facilitates the transfer of reactants between immiscible phases, enhancing reaction rates and yields. This compound is particularly effective in nucleophilic substitution reactions, where it helps in the transfer of anions from the aqueous phase to the organic phase. It is also employed in the preparation of ionic liquids and in the synthesis of pharmaceuticals, where it aids in the formation of complex molecules. Additionally, it finds application in the purification of proteins and nucleic acids, acting as a stabilizing agent during extraction and separation processes.