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Eschenmoser's salt

Ionic compound with the formula [(H3C–)2N–CH2]I From Wikipedia, the free encyclopedia

Eschenmoser's salt

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]+.

Quick Facts Names, Identifiers ...
Eschenmoser's salt
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Eschenmoser's salt
Names
Preferred IUPAC name
N,N-Dimethylmethaniminium iodide
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.046.968
UNII
  • InChI=1S/C3H8N.HI/c1-4(2)3;/h1H2,2-3H3;1H/q+1;/p-1 Y
    Key: VVDUZZGYBOWDSQ-UHFFFAOYSA-M Y
  • InChI=1/C3H8N.HI/c1-4(2)3;/h1H2,2-3H3;1H/q+1;/p-1
    Key: VVDUZZGYBOWDSQ-REWHXWOFAW
  • C[N+](C)=C.[I-]
  • [I-].[N+](=C)(C)C
Properties
C3H8NI
Molar mass 185.01 g/mol
Appearance colorless hygroscopic crystals
Melting point 116 °C (241 °F; 389 K)
decomposes
Hazards
GHS labelling:
GHS07: Exclamation mark
Warning
H315, H319, H335
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 [77 °F], 100 kPa).
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The dimethylaminomethylene cation is a strong dimethylaminomethylating agent, used to prepare derivatives of the type RCH2N(CH3)2.[1][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[3] after whom the reagent is named.

Structure and bonding

Dimethylaminomethylene cation is described as a resonance hybrid of the carbocation and an iminium cation:

(CH3)2N−CH+2 ⇌ (CH3)2N+=CH2

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

Preparation

Pyrolysis of iodomethyltrimethylammonium iodide affords the desired salt:[3]

[(CH3)3N+−CH2I]I− → [(CH3)2N+=CH2]I− + CH3I

An alternative route starts with bis(dimethylamino)methane:

[(CH3)2N]2CH2 + (CH3)3SiI → [(CH3)2N+=CH2]I− + (CH3)3SiN(CH3)2

Related salts

Other salts of the dimethylaminomethylene cation:

  • Dimethyl(methylidene)ammonium trifluoroacetate.[4][1]
  • Dimethyl(methylidene)ammonium chloride (Böhme's salt[1], after Horst Böhme)

See also

References

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