Organosodium chemistry
Organosodium chemistry is the
The principal organosodium compound of commercial importance is sodium cyclopentadienide. Sodium tetraphenylborate can also be classified as an organosodium compound since in the solid state sodium is bound to the aryl groups.
Organometal bonds in group 1 are characterised by high
Synthesis
Transmetallation routes
In the original work the alkylsodium compound was accessed from the dialkylmercury compound by transmetallation. For example, diethylmercury in the Schorigin reaction or Shorygin reaction:[3][4][5]
- (C2H5)2Hg + 2 Na → 2 C2H5Na + Hg
The high solubility of lithium alkoxides in hexane is the basis of a useful synthetic route:[6]
- LiCH2SiMe3 + NaO–t–Bu → LiOt–Bu + NaCH2SiMe3
Deprotonation routes
For some acidic organic compounds, the corresponding organosodium compounds arise by deprotonation. Sodium cyclopentadienide is thus prepared by treating sodium metal and cyclopentadiene:[7]
- 2 Na+ 2 C5H6 → 2 Na+ C5H5− + H2
Sodium acetylides form similarly. Often strong sodium bases are employed in place of the metal. Sodium methylsulfinylmethylide is prepared by treating DMSO with sodium hydride:[8]
- CH3SOCH3 + NaH → CH3SOCH−
2Na+ + H2
Metal-halogen exchange
Trityl sodium can be prepared by sodium-halogen exchange:[9]
- Ph3CCl + 2 Na → Ph3C− Na+ + NaCl
Electron transfer
Sodium also reacts with
- C10H8 + Na → Na+[C10H8]−•
Structural studies show however that sodium naphthalene has no Na-C bond, the sodium is invariably coordinated by ether or amine ligands.[10] The related anthracene as well as lithium derivatives are well known.
Structures
Simple organosodium compounds such as the alkyl and aryl derivatives are generally insoluble polymers. Because of its large radius, Na prefers a higher coordination number than does lithium in
3 groups with Na–C distances ranging from 2.523(9) to 2.643(9) Å.[6]
Reactions
Organosodium compounds are traditionally used as strong bases,[9] although this application has been supplanted by other reagents such as sodium bis(trimethylsilyl)amide.
The higher alkali metals are known to metalate even some unactivated hydrocarbons and are known to self-metalate:
- 2 NaC2H5 → C2H4Na2 + C2H6
In the Wanklyn reaction (1858)[14][15] organosodium compounds react with carbon dioxide to give carboxylates:
- C2H5Na + CO2 → C2H5CO2Na
Grignard reagents undergo a similar reaction.
Some organosodium compounds degrade by
- NaC2H5 → NaH + C2H4
Industrial applications
Although organosodium chemistry has been described to be of "little industrial importance", it once was central to the production of
- 3 PhCl + PCl3 + 6 Na → PPh3 + 6 NaCl
The polymerization of butadiene and styrene is catalyzed by sodium metal.[3]
Organic derivatives of the heavier alkali metals
Organopotassium, organorubidium, and organocaesium compounds are less commonly encountered than organosodium compounds and are of limited utility. These compounds can be prepared by treatment of alkyl lithium compounds with the potassium, rubidium, and caesium alkoxides. Alternatively they arise from the organomercury compound, although this method is dated. The solid methyl derivatives adopt polymeric structures. Reminiscent of the
A notable reagent that is based on a heavier alkali metal alkyl is Schlosser's base, a mixture of n-butyllithium and potassium tert-butoxide. This reagent reacts with toluene to form the red-orange compound benzyl potassium (KCH2C6H5).
Evidence for the formation of heavy alkali metal-organic intermediates is provided by the equilibration of
See also
- Alkynation
References
- ^ Synthesis of Organometallic Compounds: A Practical Guide Sanshiro Komiya Ed. 1997
- ISBN 3-527-28165-7
- ^
- .
- ^
- ^ Iwai, I.; Ide, J. (1988). "2,3-Diphenyl-1,3-Butadiene". Organic Syntheses; Collected Volumes, vol. 6, p. 531.
- ^ .
- .
- PMID 29897357.
- ^
- .
- J. A. Wanklyn, Ann. 107, 125 (1858)
- ^ The Merck index of chemicals and drugs: an encyclopedia for chemists, Paul G. Stecher
- .