Triethyloxonium tetrafluoroborate is the

organic Organic may refer to: * Organic, of or relating to an organism, a living entity * Organic, of or relating to an anatomical organ Chemistry * Organic matter, matter that has come from a once-living organism, is capable of decay or is the product ...

oxonium compound with the formula CH₃CH₂)₃OF₄. It is often called Meerwein's reagent or Meerwein's salt after its discoverer

Hans Meerwein Hans Meerwein (May 20, 1879 in Hamburg, Germany – October 24, 1965 in Marburg, Germany) was a German chemist. Several reactions and reagents bear his name, most notably the Meerwein–Ponndorf–Verley reduction, the Wagner–Meerwein rearran ...

. Also well known and commercially available is the related

trimethyloxonium tetrafluoroborate Trimethyloxonium tetrafluoroborate is the organic compound with the formula . (It is sometimes called "Meerwein's salt" after Hans Meerwein.Meerwein's salt classically referred to triethyloxonium tetrafluoroborate. However, in recent years, the t ...

. The compounds are white solids that dissolve in polar organic solvents. They are strong alkylating agents. Aside from the salt, many related derivatives are available.

Synthesis and reactivity

Triethyloxonium tetrafluoroborate is prepared from

boron trifluoride Boron trifluoride is the inorganic compound with the formula BF3. This pungent, colourless, and toxic gas forms white fumes in moist air. It is a useful Lewis acid and a versatile building block for other boron compounds. Structure and bondin ...

, diethyl ether and

epichlorohydrin Epichlorohydrin (abbreviated ECH) is an organochlorine compound and an epoxide. Despite its name, it is not a halohydrin. It is a colorless liquid with a pungent, garlic-like odor, moderately soluble in water, but miscible with most polar organi ...

: : 4 Et₂O·BF₃ + 2 Et₂O + 3 C₂H₃(O)CH₂Cl → 3 Et₃O⁺ + B OCH(CH₂Cl)CH₂OEtsub>3 The trimethyloxonium salt is available from

dimethyl ether Dimethyl ether (DME; also known as methoxymethane) is the organic compound with the formula CH3OCH3, (sometimes ambiguously simplified to C2H6O as it is an isomer of ethanol). The simplest ether, it is a colorless gas that is a useful precursor ...

via an analogous route. These salts do not have long shelf-lives at room temperature. They degrade by hydrolysis: : CH₃CH₂)₃Osup>+ + H₂O → (CH₃CH₂)₂O + CH₃CH₂OH + HBF₄ The propensity of trialkyloxonium salts for alkyl-exchange can be advantageous. For example, trimethyloxonium tetrafluoroborate, which reacts sluggishly due to it low solubility in most compatible solvents may be converted in situ to higher alkyl/more soluble oxoniums, thereby accelerating alkylation reactions.

Structure

The structure of triethyloxonium tetrafluoroborate has not been characterized by X-ray crystallography, but the structure of triethyloxonium hexafluorophosphate has been examined. The measurements confirm that the cation is pyramidal with C-O-C angles in the range 109.4°–115.5°. The average C–O distance is 1.49 Å.

Safety

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.

References

{{Tetrafluoroborates Reagents for organic chemistry Tetrafluoroborates Ethylating agents Oxonium compounds