Tetramethylammonium fluoride is the

quaternary ammonium salt In chemistry, quaternary ammonium cations, also known as quats, are positively charged polyatomic ions of the structure , R being an alkyl group or an aryl group. Unlike the ammonium ion () and the primary, secondary, or tertiary ammonium cation ...

with the formula (CH₃)₄NF. This hygroscopic white solid is a source of “naked fluoride", that is fluoride ions not connected to a metal atom in a complex. Most other soluble salts of

fluoride Fluoride (). According to this source, is a possible pronunciation in British English. is an inorganic, monatomic anion of fluorine, with the chemical formula (also written ), whose salts are typically white or colorless. Fluoride salts ty ...

are in fact bifluorides, HF₂^–. Historically, there has been two main approaches to prepare TMAF: (i) Via neutralization of tetramethylammonium hydroxide (TMAOH) with HF, and (ii) through the metathesis reaction of different ammonium salts with inorganic sources of fluoride, such as KF or CsF. Due to the high

basicity In chemistry, there are three definitions in common use of the word base, known as Arrhenius bases, Brønsted bases, and Lewis bases. All definitions agree that bases are substances that react with acids, as originally proposed by G.-F. R ...

of the fluoride

anion An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by conve ...

, the salt reacts slowly with

acetonitrile Acetonitrile, often abbreviated MeCN (methyl cyanide), is the chemical compound with the formula and structure . This colourless liquid is the simplest organic nitrile ( hydrogen cyanide is a simpler nitrile, but the cyanide anion is not clas ...

, inducing its

dimerization A dimer () ('' di-'', "two" + ''-mer'', "parts") is an oligomer consisting of two monomers joined by bonds that can be either strong or weak, covalent or intermolecular. Dimers also have significant implications in polymer chemistry, inorganic che ...

to CH₃C(NH₂)=CHCN, which co-crystallizes.

Related salts

* Tetramethylphosphonium fluoride (CH₃)₄PF forms stable solutions in acetonitrile. It is prepared by reaction of the

ylide An ylide or ylid () is a neutral dipolar molecule containing a formally negatively charged atom (usually a carbanion) directly attached to a heteroatom with a formal positive charge (usually nitrogen, phosphorus or sulfur), and in which both atoms ...

with potassium bifluoride: :(CH₃)₃P=CH₂ + KHF₂ → (CH₃)₄PF + KF :In the gas phase, tetramethylphosphonium fluoride exists as the phosphorane, but in acetonitrile solution, it dissociates into ions. A more elaborate phosphazenium salt ( CH₃)₂N)₃Psub>2N⁺F⁻) is also known. *Anhydrous

Tetrabutylammonium fluoride Tetra-''n''-butylammonium fluoride, commonly abbreviated to TBAF and ''n''-Bu4NF, is a quaternary ammonium salt with the chemical formula (CH3CH2CH2CH2)4N+F−. It is commercially available as the white solid trihydrate and as a solution in tetra ...

has been prepared by the reaction of

hexafluorobenzene Hexafluorobenzene, HFB, , or perfluorobenzene is an organic, aromatic compound. In this derivative of benzene all hydrogen atoms have been replaced by fluorine atoms. The technical uses of the compound are limited, although it is recommended as ...

and tetrabutylammonium cyanide.{{cite journal , author1=Haoran Sun , author2=Stephen G. DiMagno , name-list-style=amp , title= Anhydrous Tetrabutylammonium Fluoride , journal=

Journal of the American Chemical Society The ''Journal of the American Chemical Society'' is a weekly peer-reviewed scientific journal that was established in 1879 by the American Chemical Society. The journal has absorbed two other publications in its history, the ''Journal of Analyti ...

, year= 2005 , volume= 127 , pages= 2050–1, doi=10.1021/ja0440497 , pmid= 15713075 , issue= 7

References

Tetramethylammonium salts Fluorides Nonmetal halides Reagents for organic chemistry