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| Names | |
|---|---|
| Preferred IUPAC name Lithium carbide | |
| Systematic IUPAC name Dilithium(1+) ethyne | |
| Other names
Dilithium acetylide Lithium dicarbon | |
| Identifiers | |
| CAS Number | |
| 3D model (JSmol) | |
| ChemSpider | |
| ECHA InfoCard | 100.012.710 
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| EC Number |
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InChI
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SMILES
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| Properties | |
| Chemical formula | Li2C2 |
| Molar mass | 37.9034 g/mol |
| Density | 1.3 g/cm³ |
| Melting point | > 550°C |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C , 100 kPa).
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Infobox references
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Lithium carbide, Li2C2, often known as dilithium acetylide, is a chemical compound of lithium and carbon, an acetylide. It is an intermediate compound produced during radiocarbon dating procedures. Li2C2 is one of an extensive range of lithium-carbon compounds which include the lithium-rich Li4C, Li6C2, Li8C3, Li6C3, Li4C3, Li4C5, and the graphite intercalation compounds LiC6, LiC12, and LiC18.
Li2C2 is the thermodynamically-stable lithium-rich compound and is the only one of them that can be obtained directly from the elements. It was first produced by Moissan, in 1896 who reacted coal with lithium carbonate. The other lithium-rich compounds are produced by reacting lithium vapor with chlorinated hydrocarbons, e.g. CCl4.
Lithium carbide is sometimes confused with the drug lithium carbonate, Li2CO3, because of the similarity of its name.
Structure
Li2C2 is a salt formulated 2LiC2. It has a similar structure to that of Rb2O2 and Cs2O2. At high temperatures Li2C2 transforms reversibly to a cubic anti-fluorite structure.
Preparation and chemistry
To prepare pure samples in the laboratory molten lithium + graphite are reacted at high temperature. Li2C2 can also be prepared by reacting CO2 with molten lithium. It is reactive and hydrolyses very readily to form acetylene gas, C2H2, and LiOH.
Use in radiocarbon dating
Main article: Radiocarbon datingThere are a number of procedures employed, some that burn the sample producing CO2 that is then reacted with lithium, and others where the carbon containing sample is reacted directly with lithium metal. The outcome is the same: Li2C2 is produced, which can then be used to create species easy to mass, like acetylene and benzene. Note that lithium nitride may be formed and this produces ammonia when hydrolyzed, which contaminates the acetylene gas.
References
- R. Juza; V. Wehle; H.-U. Schuster (1967). "Zur Kenntnis des Lithiumacetylids". Zeitschrift für anorganische und allgemeine Chemie. 352: 252. doi:10.1002/zaac.19673520506.
{{cite journal}}: CS1 maint: multiple names: authors list (link) - H. Moissan Comptes Rendus hebd. Seances Acad. Sci. 122, 362 (1896)
- U. Ruschewitz, R. Pöttgen (1999). "Structural Phase Transition in Li2C2". Zeitschrift für anorganische und allgemeine Chemie. 625 (10): 1599–1603. doi:10.1002/(SICI)1521-3749(199910)625:10<1599::AID-ZAAC1599>3.0.CO;2-J.
- Swart E.R. (1964). "The direct conversion of wood charcoal to lithium carbide in the production of acetylene for radiocarbon dating". Cellular and Molecular Life Sciences. 20: 47. doi:10.1007/BF02146038.
- University of Zurich Radiocarbon Laboratory webpage