Triethyloxonium tetrafluoroborate is the organic compound with the formula [(CH3CH2)3O]BF4. It is often called Meerwein's reagent after its discoverer Hans Meerwein. Also well known and commercially available is the related trimethyloxonium tetrafluoroborate (CAS#
420-37-1). The compounds are exceptionally strong alkylating agents. Aside from the BF4- salt, many related derivatives are available with varying solubilities and stabilities.
Triethyloxonium tetrafluoroborate is prepared from boron trifluoride
, diethyl ether
, and epichlorohydrin
. The trimethyloxonium salt is available from dimethyl ether
via an analogous route. These salts do not have long shelf-lives at room temperature. These salts degrade by hydrolysis:
- [(CH3CH2)3O]BF4 + H2O → (CH3CH2)2O + CH3CH2OH + HBF4
The compound features pyramidal oxonium cation and a tetrahedral fluoroborate anion. Reflecting its ionic character, the salt dissolves in polar but inert solvents such as dichloromethane
, sulfur dioxide
, and nitromethane
Triethyloxonium tetrafluoroborate is a strong alkylating agent, although the hazards are diminished because it is non-volatile. It releases strong acid upon contact with water. The properties of the methyl derivative are similar.