organic chemistry Organic chemistry is a subdiscipline within chemistry involving the 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.Clayden, J.; ...

, Eschenmoser's salt (named for

Albert Eschenmoser Albert Jakob Eschenmoser (born 5 August 1925) is a Swiss organic chemist, best known for his work on the synthesis of complex heterocyclic natural compounds, most notably vitamin B12. In addition to his significant contributions to the field of ...

) 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. The ...

. 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 quantitie ...

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 convent ...

. 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 ...

silyl enol ether Silyl enol ethers in organic chemistry are a class of organic compounds that share a common functional group composed of an enolate bonded through its oxygen end to an organosilicon group. They are important intermediates in organic synthesis. Syn ...

s, 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 bo ...

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 a ...

s can be further

methyl In organic chemistry, a methyl group is an alkyl derived from methane, containing one carbon atom bonded to three hydrogen atoms, having chemical formula . In formulas, the group is often abbreviated as Me. This hydrocarbon group occurs in many ...

ated and then subjected to base-induced elimination to afford methylidenated

s. The salt was first prepared by the group of

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 encountere ...

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 al ...

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. Productio ...

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