organic chemistry Organic chemistry is a subdiscipline within chemistry involving the science, scientific study of the structure, properties, and reactions of organic compounds and organic materials, i.e., matter in its various forms that contain carbon atoms.Clay ...

, Eschenmoser's salt (named for Albert Eschenmoser) is the ionic,

organic compound In chemistry, organic compounds are generally any chemical compounds that contain carbon- hydrogen or carbon-carbon bonds. Due to carbon's ability to catenate (form chains with other carbon atoms), millions of organic compounds are known. Th ...

. It is the iodide

salt Salt is a mineral composed primarily of sodium chloride (NaCl), a chemical compound belonging to the larger class of salts; salt in the form of a natural crystalline mineral is known as rock salt or halite. Salt is present in vast quanti ...

of the dimethylaminomethylene

cation 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 dimethylaminomethylene cation is a strong dimethylaminomethylating agent, used to prepare

derivatives The derivative of a function is the rate of change of the function's output relative to its input value. Derivative may also refer to: In mathematics and economics *Brzozowski derivative in the theory of formal languages *Formal derivative, an ...

of the type .E. F. Kleinman in "Dimethylmethyleneammonium Iodide and Chloride" in Encyclopedia of Reagents for Organic Synthesis (Ed: L. Paquette) 2004, J. Wiley & Sons, New York.

Enolate In organic chemistry, enolates are organic anions derived from the deprotonation of carbonyl () compounds. Rarely isolated, they are widely used as reagents in the synthesis of organic compounds. Bonding and structure Enolate anions are electr ...

s, silyl enol ethers, and even more acidic

ketone In organic chemistry, a ketone is a functional group with the structure R–C(=O)–R', where R and R' can be a variety of carbon-containing substituents. Ketones contain a carbonyl group –C(=O)– (which contains a carbon-oxygen double bon ...

s undergo efficient dimethylaminomethylation. Once prepared, such

tertiary amine In chemistry, amines (, ) are compounds and functional groups that contain a basic nitrogen atom with a lone pair. Amines are formally derivatives of ammonia (), wherein one or more hydrogen atoms have been replaced by a substituent such ...

s can be further methylated and then subjected to base-induced

elimination Elimination may refer to: Science and medicine * Elimination reaction, an organic reaction in which two functional groups split to form an organic product *Bodily waste elimination, discharging feces, urine, or foreign substances from the bo ...

to afford methylidenated

s. The salt was first prepared by the group of Albert Eschenmoser after whom the reagent is named.

Structure and bonding

Dimethylaminomethylene cation is described as a

resonance hybrid In chemistry, resonance, also called mesomerism, is a way of describing bonding in certain molecules or polyatomic ions by the combination of several contributing structures (or ''forms'', also variously known as ''resonance structures'' or ...

of the

carbocation A carbocation is an ion with a positively charged carbon atom. Among the simplest examples are the methenium , methanium and vinyl cations. Occasionally, carbocations that bear more than one positively charged carbon atom are also encoun ...

and an

iminium In organic chemistry, an iminium cation is a polyatomic ion with the general structure . They are common in synthetic chemistry and biology. Structure Iminium cations adopt alkene-like geometries. The central C=N unit is nearly coplanar with a ...

cation: :(CH3)2N-CH2+ <=> (CH3)2N+=CH2 The atoms are coplanar. The cation is isoelectronic with

isobutene Isobutylene (or 2-methylpropene) is a hydrocarbon with the chemical formula . It is a four-carbon branched alkene (olefin), one of the four isomers of butylene. It is a colorless flammable gas, and is of considerable industrial value. Producti ...

Preparation

Pyrolysis of iodomethyltrimethylammonium iodide affords the desired salt: : CH3)3N-CH2I -> CH3)2NCH2 + CH3I An alternative route starts with bis(dimethylamino)methane: : CH3)2NCH2 + (CH3)3SiI -> CH3)2NCH2 + (CH3)3SiN(CH3)2

Related salts

Other salts of the dimethylaminomethylene cation: *Dimethyl(methylidene)ammonium trifluoroacetate. *Dimethyl(methylidene)ammonium chloride (''Böhme's salt'', after Horst Böhme)

References

{{reflist Reagents for organic chemistry Iodides Quaternary ammonium compounds

Structure and bonding

Preparation

Related salts

See also

References