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{{Short description|Chemical compound of lithium and carbon, an acetylide}} |
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{{About||the chemical Li<sub>4</sub>C|Tetralithium carbide}} |
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{{Chembox |
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{{Chembox |
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| verifiedrevid = 443924409 |
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| Watchedfields = changed |
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| ImageFile = lithium carbide.png |
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| verifiedrevid = 450703945 |
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| ImageSize = 120px |
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| ImageName = Wireframe model of lithium carbide |
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| ImageFile = lithium carbide.png |
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| ImageSize = 120px |
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| PIN = Lithium carbide |
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| ImageName = Wireframe model of lithium carbide |
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| SystematicName = Dilithium(1+) ethyne |
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| OtherNames = Dilithium acetylide<br /> |
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| PIN = Lithium acetylide |
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| SystematicName = Lithium ethynediide |
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Lithium dicarbon<br /> |
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Lithium percarbide |
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| OtherNames = {{ubl|Dilithium acetylide|Lithium dicarbon|Lithium percarbide}} |
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| Section1 = {{Chembox Identifiers |
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| Section1 = {{Chembox Identifiers |
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| InChI1 = 1/C2.2Li/c1-2;;/q-2;2*+1 |
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| InChI1 = 1/C2.2Li/c1-2;;/q-2;2*+1 |
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| InChIKey1 = ARNWQMJQALNBBV-UHFFFAOYAB |
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| InChIKey1 = ARNWQMJQALNBBV-UHFFFAOYAB |
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| CASNo_Ref = {{cascite|correct|??}} |
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| CASNo = 1070-75-3 |
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| CASNo = 1070-75-3 |
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| UNII_Ref = {{fdacite|correct|FDA}} |
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| ChemSpiderID = 59503 |
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| UNII = GZ7TQ3WG5P |
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| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}} |
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| ChemSpiderID = 59503 |
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| EINECS = 213-980-1 |
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| StdInChI_Ref = {{stdinchicite|correct|chemspider}} |
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| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}} |
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| EINECS = 213-980-1 |
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| PubChem = 66115 |
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| StdInChI_Ref = {{stdinchicite|correct|chemspider}} |
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| StdInChI = 1S/C2.2Li/c1-2;;/q-2;2*+1 |
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| StdInChI = 1S/C2.2Li/c1-2;;/q-2;2*+1 |
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| StdInChIKey_Ref = {{stdinchicite|correct|chemspider}} |
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| StdInChIKey_Ref = {{stdinchicite|correct|chemspider}} |
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| StdInChIKey = ARNWQMJQALNBBV-UHFFFAOYSA-N |
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| StdInChIKey = ARNWQMJQALNBBV-UHFFFAOYSA-N |
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| SMILES = ..# |
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| SMILES = ..# |
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| InChI = 1S/C2.2Li/c1-2;;/q-2;2*+1 |
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| InChI = 1S/C2.2Li/c1-2;;/q-2;2*+1 |
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| InChIKey = ARNWQMJQALNBBV-UHFFFAOYSA-N}} |
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| InChIKey = ARNWQMJQALNBBV-UHFFFAOYSA-N}} |
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| Section2 = {{Chembox Properties |
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| Section2 = {{Chembox Properties |
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| Formula = Li<sub>2</sub>C<sub>2</sub> |
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| Formula = {{chem2|Li2C2}} |
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| MolarMass = 37.9034 g/mol |
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| MolarMass = 37.9034 g/mol |
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| Appearance = Powder |
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| Density = 1.3 g/cm³<ref>{{cite journal | title = Zur Kenntnis des Lithiumacetylids | author = R. Juza; V. Wehle; H.-U. Schuster | journal = ] | year = 1967 | volume = 352 | pages = 252 | doi = 10.1002/zaac.19673520506}}</ref> |
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| Density = 1.3 g/cm<sup>3</sup><ref>{{cite journal | title = Zur Kenntnis des Lithiumacetylids |author1=R. Juza |author2=V. Wehle |author3=H.-U. Schuster | journal = ] | year = 1967 | volume = 352 | pages = 252 | doi = 10.1002/zaac.19673520506 | issue = 5–6}}</ref> |
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| Solvent = |
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| Solubility = Reacts |
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| SolubleOther = |
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| SolubleOther = insoluble in organic solvents |
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| MeltingPt = > 550°C |
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| MeltingPt = 452°C<ref>{{cite journal | title = Thermal properties of lithium carbide and lithium intercalation compounds of graphite |author1=Savchenko, A.P. |author2= Kshnyakina, S.A. |author3=H.-Majorova, A.F. | journal = ] | year = 1997 | volume = 33 | pages = 1305–1307 | issue = 11}}</ref> |
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| BoilingPt = }} |
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| BoilingPt = }} |
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| Section9 = {{Chembox Related |
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| OtherCompounds = {{ubl|]|]|]|]|]|]}} |
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'''Lithium carbide''', Li<sub>2</sub>C<sub>2</sub>, often known as '''dilithium acetylide''', is a chemical compound of ] and ], an ]. It is an intermediate compound produced during ] procedures. Li<sub>2</sub>C<sub>2</sub> is one of an extensive range of lithium-carbon compounds which include the lithium-rich Li<sub>4</sub>C, Li<sub>6</sub>C<sub>2</sub>, Li<sub>8</sub>C<sub>3</sub>, Li<sub>6</sub>C<sub>3</sub>, Li<sub>4</sub>C<sub>3</sub>, Li<sub>4</sub>C<sub>5</sub>, and the ]s LiC<sub>6</sub>, LiC<sub>12</sub>, and LiC<sub>18</sub>.<br /> Li<sub>2</sub>C<sub>2</sub> 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 ], in 1896<ref>H. Moissan Comptes Rendus hebd. Seances Acad. Sci. 122, 362 (1896)</ref> who reacted coal with ]. The other lithium-rich compounds are produced by reacting lithium vapor with ]s, e.g. ]. |
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'''Lithium carbide''', {{chem2|Li2C2}}, often known as '''dilithium acetylide''', is a chemical compound of ] and ], an ]. It is an intermediate compound produced during ] procedures. {{chem2|Li2C2}} is one of an extensive range of lithium-carbon compounds which include the lithium-rich ], {{chem2|Li6C2}}, {{chem2|Li8C3}}, {{chem2|Li6C3}}, {{chem2|Li4C3}}, {{chem2|Li4C5}}, and the ]s {{chem2|LiC6}}, {{chem2|LiC12}}, and {{chem2|LiC18}}. |
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{{chem2|Li2C2}} is the most thermodynamically-stable lithium-rich carbide<ref name=rev1>{{cite journal|last1=Ruschewitz|first1=Uwe|title=Binary and ternary carbides of alkali and alkaline-earth metals|journal=Coordination Chemistry Reviews|date=September 2003|volume=244|issue=1–2|pages=115–136|doi=10.1016/S0010-8545(03)00102-4}}</ref> and the only one that can be obtained directly from the elements. It was first produced by ], in 1896<ref>H. Moissan Comptes Rendus hebd. Seances Acad. Sci. 122, 362 (1896)</ref> who reacted coal with ]. |
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Lithium carbide is sometimes confused with the drug ], Li<sub>2</sub>CO<sub>3</sub>, because of the similarity of its name. |
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:{{chem2|Li2CO3 + 4 C → Li2C2 + 3 ]}} |
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==Structure== |
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Li<sub>2</sub>C<sub>2</sub> is a salt formulated 2Li<sup>+</sup>C<sub>2</sub><sup>2−</sup>. It has a similar structure to that of ] and ]. At high temperatures Li<sub>2</sub>C<sub>2</sub> transforms reversibly to a cubic anti-fluorite structure.<ref>{{cite journal | author = U. Ruschewitz, R. Pöttgen | title = Structural Phase Transition in Li<sub>2</sub>C<sub>2</sub> | journal = ] | volume = 625 | issue = 10 | pages = 1599–1603 | doi = 10.1002/(SICI)1521-3749(199910)625:10<1599::AID-ZAAC1599>3.0.CO;2-J | year = 1999}}</ref> |
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The other lithium-rich compounds are produced by reacting lithium vapor with ]s, e.g. ]. Lithium carbide is sometimes confused with the drug ], {{chem2|Li2CO3}}, because of the similarity of its name. |
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==Preparation and chemistry== |
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==Preparation and chemistry== |
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In the laboratory samples may be prepared by treating ] with a solution of ] in ], on −40°C, with creation of ] of {{chem2|Li2C2*]*2]}} that decomposes in stream of ] at room temperature giving white powder of {{chem2|Li2C2}}. |
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To prepare pure samples in the laboratory molten lithium + ] are reacted at high temperature. Li<sub>2</sub>C<sub>2</sub> can also be prepared by reacting CO<sub>2</sub> with molten lithium. It is reactive and hydrolyses very readily to form ] gas, C<sub>2</sub>H<sub>2</sub>, and ]. |
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:{{chem2|C2H2 + 2 ] → Li2C2 + ]}} |
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Samples prepared in this manner generally are poorly ]. Crystalline samples may be prepared by a reaction between molten lithium and ] at over 1000 °C.<ref name=rev1 /> {{chem2|Li2C2}} can also be prepared by reacting ] with molten lithium. |
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:{{chem2|10 Li + 2 CO2 → Li2C2 + 4 ]}} |
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Other method for production of {{chem2|Li2C2}} is heating of metallic lithium in atmosphere of ]. |
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:{{chem2|6 Li + C2H4 → Li2C2 + 4 ]}} |
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Lithium carbide ] readily to form acetylene: |
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:{{chem2|Li2C2 + 2 H2O → 2 ] + C2H2}} |
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] reacts with graphite at 400°C forming lithium carbide. |
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:{{chem2|2 LiH + 4 C → Li2C2 + C2H2}} |
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Also {{chem2|Li2C2}} can be formed when ] compound ] reacts with acetylene in ] or ] used as a solvent, reaction is rapid and highly ]. |
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:{{chem2|C2H2 + 2 CH3CH2CH2CH2Li → Li2C2 + 2 CH3CH2CH2CH3}} |
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Lithium carbide reacts with acetylene in liquid ammonia rapidly to give a clear solution of lithium hydrogen acetylide. |
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:{{chem2|Li+Li+ + HC\tCH → 2 Li+}} |
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Preparation of the reagent in this way sometimes improves the yield in an ethynylation over that obtained with reagent prepared from lithium and acetylene. |
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==Structure== |
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{{chem2|Li2C2}} is a ] compound and exists as a ], with the formula {{chem2|2}}. Its reactivity, combined with the difficulty in growing suitable ]s, has made the determination of its crystal structure difficult. It adopts a distorted ], similar to that of ] ({{chem2|Rb2O2}}) and ] ({{chem2|Cs2O2}}). Each ] atom is surrounded by six ] atoms from 4 different ] ], with two acetylides co-ordinating side -on and the other two end-on.<ref name=rev1 /><ref>{{cite journal|last1=Juza|first1=Robert|last2=Opp|first2=Karl|title=Metallamide und Metallnitride, 24. Mitteilung. Die Kristallstruktur des Lithiumamides|journal=Zeitschrift für anorganische und allgemeine Chemie|date=November 1951|volume=266|issue=6|pages=313–324|doi=10.1002/zaac.19512660606|language=German}}</ref> The observed relatively short C-C distance of 120 ] indicates the presence of a C≡C ]. At high temperatures {{chem2|Li2C2}} transforms reversibly to a cubic anti-fluorite structure.<ref>{{cite journal |author1=U. Ruschewitz |author2=R. Pöttgen | title = Structural Phase Transition in {{chem|Li|2|C|2}} | journal = ] | volume = 625 | issue = 10 | pages = 1599–1603 | doi = 10.1002/(SICI)1521-3749(199910)625:10<1599::AID-ZAAC1599>3.0.CO;2-J | year = 1999}}</ref> |
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==Use in radiocarbon dating== |
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==Use in radiocarbon dating== |
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{{main|Radiocarbon dating}} |
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{{main|Radiocarbon dating}} |
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There are a number of procedures employed, some that burn the sample producing ] that is then reacted with lithium, and others where the carbon containing sample is reacted directly with lithium metal.<ref>{{cite journal | author = Swart E.R. | title = The direct conversion of wood charcoal to lithium carbide in the production of acetylene for radiocarbon dating | journal = ] | doi = 10.1007/BF02146038 | year = 1964 | volume = 20 | pages = 47}}</ref> The outcome is the same: Li<sub>2</sub>C<sub>2</sub> is produced, which can then be used to create species easy to mass, like acetylene and benzene.<ref></ref> Note that ] may be formed and this produces ] when hydrolyzed, which contaminates the acetylene gas. |
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There are a number of procedures employed, some that burn the sample producing ] that is then reacted with lithium, and others where the carbon containing sample is reacted directly with lithium metal.<ref>{{cite journal | author = Swart E.R. | title = The direct conversion of wood charcoal to lithium carbide in the production of acetylene for radiocarbon dating | journal = ] | doi = 10.1007/BF02146038 | year = 1964 | volume = 20 | pages = 47–48| s2cid = 31319813}}</ref> The outcome is the same: {{chem2|Li2C2}} is produced, which can then be used to create species easy to use in mass ], like ] and ].<ref> {{webarchive|url=https://web.archive.org/web/20090801100716/http://www.geo.unizh.ch/c14/ |date=2009-08-01}}</ref> Note that ] may be formed and this produces ] when ], which contaminates the acetylene gas. |
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==References== |
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==References== |
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{{Lithium compounds}} |
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{{Carbides}} |
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