Lithium amide
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| Lithium amide | |
|---|---|
| IUPAC name | Lithium amide |
| Other names | Lithamide |
| Identifiers | |
| CAS number | [] |
| Properties | |
| Molecular formula | LiNH2 |
| Molar mass | 22.96 g/mol |
| Appearance | white solid |
| Density | 1.178 g/cm3 |
| Melting point |
380 - 400 °C |
| Solubility in water | Reacts vigorously in water |
| Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox disclaimer and references |
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Lithium amide is an inorganic compound with the chemical formula Li+NH2-, i.e. it is composed of a lithium cation, and the conjugate base of ammonia. It is a white solid with a tetragonal crystal structure.
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[edit] Lithium amides
The anionic conjugate bases of amines are known as amides. Thus lithium amide may also refer to lithium salts of amines e.g. Li+NR2-. An example of a lithium amide is lithium diisopropylamide (LDA), which is quite commonly used.
Lithium amide can be made by adding lithium metal to liquid ammonia:
- Li + NH3 → LiNH2 + 0.5 H2
Lithium amides in general can be similarly formed, substituting ammonia with the appropriate amine:
- Li + R2NH → LiNR2 + 0.5 H2
Lithium amides are very reactive compounds and can act as strong bases. Unless the nitrogen atom is hindered, as in the case of LDA, they can also act as nucleophiles.
[edit] Examples
The lithium salt of 2,2,6,6-tetramethylpiperidine has been crystalised as a tetramer:
On the other hand, the lithium derivative of di-(1-phenylethyl)amine crystallises as a trimer:
It is also possible to make mixed oligomers of metal alkoxides and amides. [3] These are related to the super bases which are mixtures of metal alkoxides and alkyls. The cyclic oligomers form when the nitrogen of the amide forms a sigma bond to a lithium while the nitrogen lone pair binds to another metal centre.
Other organolithium compounds (such as BuLi) are generally considered to exist in and function via high-order, aggregated species.
[edit] See also
[edit] References
- ^ M.F. Lappert, M.J. Slade, A. Singh, J.L. Atwood, R.D. Rogers and R. Shakir (1983). "Structure and reactivity of sterically hindered lithium amides and their diethyl etherates: crystal and molecular structures of [[Li{N(SiMe3)2}(OEt2)]]2 and tetrakis(2,2,6,6-tetramethylpiperidinatolithium)". Journal of the American Chemical Society 105 (2): 302-304. DOI:10.1021/ja00340a031.
- ^ D.R. Armstrong, K.W. Henderson, A.R. Kennedy, W.J. Kerr, F.S. Mair, J.H. Moir, P.H. Moran and R. Snaith, Dalton Transactions, 1999, 4063.
- ^ K.W. Henderson, D.S. Walther and P.G. Williard (1995). "Identification of a Unimetal Complex of Bases by 6Li NMR Spectroscopy and Single-Crystal Analysis". Journal of the American Chemical Society 117 (33): 8680-8681. DOI:10.1021/ja00138a030.
- Merck Index, 11th Edition, 5398.
[edit] External links
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