Trimethyloxonium tetrafluoroborate

Trimethyloxonium tetrafluoroborate

Names
IUPAC name Trimethyloxonium tetrafluoroborate
Other names Trimethyloxonium fluoborate
Identifiers
CAS Number	420-37-1 Y
3D model (JSmol)	Interactive image
ChemSpider	2016863
ECHA InfoCard	100.006.360
PubChem CID	2735153
InChI InChI=1S/C3H9O.BF4/c1-4(2)3;2-1(3,4)5/h1-3H3;/q+1;-1 Key: CZVZBKHWOFJNCR-UHFFFAOYSA-N
SMILES F[B-](F)(F)F.[O+](C)(C)C
Properties
Chemical formula	C3H9BF4O
Molar mass	147.91 g·mol−1
Melting point	179.6–180 °C (355.3–356.0 °F; 452.8–453.1 K)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Trimethyloxonium tetrafluoroborate is the organic compound with the formula Me₃OBF₄. It is sometimes called the "Meerwein salt" after Hans Meerwein.) This salt is a strong methylating agent, being a source of CH₃⁺. It is a white solid. Triethyloxonium tetrafluoroborate is a closely related reagent.

The compound is prepared by the reaction of boron trifluoride with dimethyl ether and epichlorohydrin:

The salt hydrolyzes readily:

Trimethyloxonium tetrafluoroborate is often ranked as the strongest reagent for the electrophilic methylation.