Tetrabutylammonium hydroxide is a chemical compound with the formula (C<sub>4</sub>H<sub>9</sub>)<sub>4</sub>NOH, abbreviated Bu<sub>4</sub>NOH with the acronym TBAOH or TBAH. This species is employed as a solution in water or alcohols. It is a common base in organic chemistry. Relative to more conventional inorganic bases, such as KOH and NaOH, Bu<sub>4</sub>NOH is more soluble in organic solvents.
Solutions of Bu<sub>4</sub>NOH are usually prepared in situ from butylammonium halides, Bu<sub>4</sub>NX. For example, by reacting them with silver oxide or using an ion exchange resin. Attempts to isolate Bu<sub>4</sub>NOH induces Hofmann elimination, leading to Bu<sub>3</sub>N and 1-butene. Solutions of Bu<sub>4</sub>NOH are typically contaminated with Bu<sub>3</sub>N for this reason.
Treatment of Bu<sub>4</sub>NOH with a wide range of acids forms water and other tetrabutylammonium salts:
Bu<sub>4</sub>NOH is a strong base that is often used under phase-transfer conditions to effect alkylations and deprotonations. Typical reactions include benzylation of amines and generation of dichlorocarbene from chloroform.
Bu<sub>4</sub>NOH can be neutralized with a variety of mineral acids to give lipophilic salts of the conjugate base. For example, treatment of Bu<sub>4</sub>NOH with disodium pyrophosphate, Na<sub>2</sub>H<sub>2</sub>P<sub>2</sub>O<sub>7</sub>, gives (Bu<sub>4</sub>N)<sub>3</sub>[HP<sub>2</sub>O<sub>7</sub>], which is soluble in organic solvents. Similarly, neutralization of Bu<sub>4</sub>NOH with hydrofluoric acid affords a relatively water-free Bu<sub>4</sub>NF. This salt dissolves in organic solvents and is useful in desilylation.