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Eschenmoser's salt

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Eschenmoser's salt
Eschenmoser's salt
Names
Preferred IUPAC name N,N-Dimethylmethaniminium iodide
Identifiers
CAS Number
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.046.968 Edit this at Wikidata
PubChem CID
UNII
CompTox Dashboard (EPA)
InChI
  • InChI=1S/C3H8N.HI/c1-4(2)3;/h1H2,2-3H3;1H/q+1;/p-1Key: VVDUZZGYBOWDSQ-UHFFFAOYSA-M
  • InChI=1/C3H8N.HI/c1-4(2)3;/h1H2,2-3H3;1H/q+1;/p-1Key: VVDUZZGYBOWDSQ-REWHXWOFAW
SMILES
  • C(C)=C.
  • .(=C)(C)C
Properties
Chemical formula C3H8NI
Molar mass 185.01 g/mol
Appearance colorless hygroscopic crystals
Melting point 116 °C (241 °F; 389 K)
Solubility in water decomposes
Hazards
GHS labelling:
Pictograms GHS07: Exclamation mark
Signal word Warning
Hazard statements H315, H319, H335
Precautionary statements P261, P264, P271, P280, P302+P352, P304+P340, P305+P351+P338, P312, P321, P332+P313, P337+P313, P362, P403+P233, P405, P501
Except where otherwise noted, data are given for materials in their standard state (at 25 °C , 100 kPa). ☒N verify (what is  ?) Infobox references
Chemical compound

In organic chemistry, Eschenmoser's salt (named for Albert Eschenmoser) is the ionic, organic compound [(CH3)2NCH2]I. It is the iodide salt of the dimethylaminomethylene cation [(CH3)2NCH2].

The dimethylaminomethylene cation is a strong dimethylaminomethylating agent, used to prepare derivatives of the type RCH2N(CH3)2. Enolates, silyl enol ethers, and even more acidic ketones undergo efficient dimethylaminomethylation. Once prepared, such tertiary amines can be further methylated and then subjected to base-induced elimination to afford methylidenated ketones. 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 of the carbocation and an iminium cation:

( CH 3 ) 2 N − CH 2 + ↽ − − ⇀ ( CH 3 ) 2 N + = CH 2 {\displaystyle {\ce {(CH3)2N-CH2+ <=> (CH3)2N+=CH2}}}

The C3N atoms are coplanar. The cation is isoelectronic with isobutene.

Preparation

Pyrolysis of iodomethyltrimethylammonium iodide affords the desired salt:

[ ( CH 3 ) 3 N − CH 2 I ] I ⟶ [ ( CH 3 ) 2 NCH 2 ] I + CH 3 I {\displaystyle {\ce {I -> I + CH3I}}}

An alternative route starts with bis(dimethylamino)methane:

[ ( CH 3 ) 2 N ] 2 CH 2 + ( CH 3 ) 3 SiI ⟶ [ ( CH 3 ) 2 NCH 2 ] I + ( CH 3 ) 3 SiN ( CH 3 ) 2 {\displaystyle {\ce {2CH2 + (CH3)3SiI -> I + (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)

See also

References

  1. ^ E. F. Kleinman in "Dimethylmethyleneammonium Iodide and Chloride" in Encyclopedia of Reagents for Organic Synthesis (Ed: L. Paquette) 2004, J. Wiley & Sons, New York. doi:10.1002/047084289X.rd346
  2. Horst Böhme; Eberhard Mundlos; Otto-Erich Herboth (1957). "Über Darstellung und Eigenschaften α-Halogenierter Amine". Chemische Berichte. 90 (9): 2003–2008. doi:10.1002/cber.19570900942.
  3. ^ Jakob Schreiber; Hans Maag; Naoto Hashimoto; Albert Eschenmoser (1971). "Dimethyl(methylene)ammonium Iodide". Angewandte Chemie International Edition in English. 10 (5): 330–331. doi:10.1002/anie.197103301.
  4. Gaudry, Michel; Jasor, Yves; Khac, Trung Bui (1979). "Regioselective Mannich Condensation with Dimethyl(Methylene)Ammonium Trifluoroacetate: 1-(Dimethylamino)-4-Methyl-3-Pentanone". Organic Syntheses. 59: 153. doi:10.15227/orgsyn.059.0153.
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