Tetrabutylammonium hydrogen sulfate, referred to as TBAHS, is a quaternary ammonium salt used as a phase-transfer catalyst and reagent. It facilitates the transport of ions between the aqueous and organic phases, enhancing the progress of reactions in heterogeneous systems.
The presence of the hydrogen sulfate anion can influence the product's behavior in the reaction environment, distinguishing it from bromide or chloride PTC catalysts.