Tetramethylammonium hydrogen sulfate monohydrate is widely used in organic synthesis as a phase-transfer catalyst. It facilitates the transfer of reactants between immiscible phases, enhancing reaction rates and yields. It is particularly effective in alkylation and polymerization reactions. Additionally, it serves as an electrolyte in electrochemical applications, including batteries and sensors, due to its ionic conductivity. In analytical chemistry, it is employed as a reagent for ion-pair chromatography, aiding in the separation and detection of various compounds. Its stability and solubility in water make it a versatile choice in these applications.