Tetramethylammonium fluoride tetrahydrate (TMAF) is a quaternary ammonium salt. TMAF is commonly used as a weak base and a source of fluoride ions in various organic reactions, including nucleophilic substitution, functional group deprotection, and ring-opening polymerization. Unlike other fluoride sources, TMAF is compatible with many functional groups, making it a versatile tool in synthetic chemistry. Functional reagents, In addition, TMAF has been used as a fluorinating agent in medicinal chemistry, for the preparation of radiotracers and protein modification in biochemistry, and the tetrahydrate form of TMAF is more stable and easier to handle than the anhydrous form.