- Organosodium chemistry
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Organosodium chemistry is the chemistry of organometallic compounds containing a carbon to sodium chemical bond.[1][2] The application of organosodium compounds in chemistry is limited in part due to competition from organolithium compounds in the same group 1 elements row of the periodic table. Yet several important compounds exist.
Organometal bonds in group 1 are characterised by high polarity and high nucleophilicity on carbon (compare electronegativity of carbon (2.55) to that of lithium 0.98, sodium 0.93 potassium 0.82 rubidium 0.82). The principal organosodium compound of importance is sodium cyclopentadienide that is prepared from sodium metal and cyclopentadiene:
- 2 Na + 2 C5H6 → 2 NaC5H5 + H2
The higher alkali metals are known to metalate even some unactivated hydrocarbons and are known to self-metalate
- 2 NaC2H5 → C2H4Na2 + C2H6
Some organosodium compounds degrade by beta-elimination:
- NaC2H5 → NaH + C2H4
The carbanionic nature of organosodium compounds can be minimized by resonance stabilization. For instance in Ph3CM compounds is rather stable and is even used as a reagent.[3]
Sodium also react with polycyclic aromatic hydrocarbon via one-electron reduction. With solutions of naphthalene, it forms the deeply coloured radical sodium naphthalenide.
- C10H8 + Na → Na+[C10H8]-•
In the Wanklyn reaction (1858) [4][5] sodium replaces magnesium in a Grignard type reaction with carbon dioxide:
- C2H5Na + CO2 → C2H5CO2Na
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:[6] [7]
- (C2H5)2Hg + 2Na → 2C2H5Na
Industrial applications
Although organosodium chemistry has been described to be of "little industrial importance", it once was central to the production of tetraethyllead.[8] A similar Wurtz coupling-like reaction is the basis of the current industrial route to triphenylphosphine:
- 3 PhCl + PCl3 + 6 Na → PPh3 + 6 NaCl
Organic derivatives of the heavier alkali metals
The higher alkali metals, organopotassium, organorubidium and organocaesium, are even more reactive than organosodium compounds and of limited utility. A notable reagent is Schlosser's base, a mixture of n-butyllithium and potassium tert-butoxide. This reagent reacts with propene to the compound allyl potassium (KCH2CHCH2). cis-2-Butene and trans-2-butene equilibrate when in contact with alkali metals. Whereas isomerization is fast with lithium and sodium, it is slow with the higher alkali metals. The higher alkali metals also favor the sterically congested conformation.[9]
References
- ^ Synthesis of Organometallic Compounds: A Practical Guide Sanshiro Komiya Ed. 1997
- ^ C. Elschenbroich, A. Salzer Organometallics : A Concise Introduction (2nd Ed) (1992) from Wiley-VCH: Weinheim. ISBN 3-527-28165-7
- ^ W. B. Renfrow, Jr and C. R. Hauser (1943), "Triphenylmethylsodium", Org. Synth., http://www.orgsyn.org/orgsyn/orgsyn/prepContent.asp?prep=CV2P0607; Coll. Vol. 2: 607
- ^ J. A. Wanklyn, Ann. 107, 125 (1858)
- ^ The Merck index of chemicals and drugs: an encyclopedia for chemists, Paul G. Stecher
- ^ P. Schorigin, Ber. 40, 3111 (1907)
- ^ P. Schorigin, Ber. 41, 2711, 27l7, 2723 (1908)
- ^ Rolf Ackermann, Ludwig Lange "Sodium Compounds, Organic" in Ullmann's Encyclopedia of Industrial Chemistry, 2005 Wiley-VCH, Weinheim. doi:10.1002/14356007.a24_341
- ^ Manfred Schlosser (1988). "Superbases for organic synthesis". Pure and Appl. Chem. 60 (11): 1627–1634. doi:10.1351/pac198860111627.
CH He CLi CBe CB CC CN CO CF Ne CNa CMg CAl CSi CP CS CCl CAr CK CCa CSc CTi CV CCr CMn CFe CCo CNi CCu CZn CGa CGe CAs CSe CBr CKr CRb CSr CY CZr CNb CMo CTc CRu CRh CPd CAg CCd CIn CSn CSb CTe CI CXe CCs CBa CHf CTa CW CRe COs CIr CPt CAu CHg CTl CPb CBi CPo CAt Rn Fr Ra Rf Db Sg Bh Hs Mt Ds Rg Cn Uut Uuq Uup Uuh Uus Uuo ↓ CLa CCe CPr CNd CPm CSm CEu CGd CTb CDy CHo CEr CTm CYb CLu Ac Th Pa CU Np Pu Am Cm Bk Cf Es Fm Md No Lr Chemical bonds to carbon Core organic chemistry Many uses in chemistry Academic research, but no widespread use Bond unknown / not assessed Categories:- Organosodium compounds
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