Strontium carbide

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Strontium carbide (also more precisely known as ... acetylide or ... dicarbide) is a salt with chemical formula SrC2. It was first synthesized by Moissan in 1894.[1]

Strontium carbide can be formed in an electric arc furnace from strontium carbonate and a reductant, such as a reducing sugar[1][2] or magnesium metal.[3] Alternatively, carbothermal reduction of strontium oxide with graphite begins around 150 °C and is catalyzed by calcium oxide.[4] Classical organic chemistry syntheses include transmetallation from mercury acetylide or an acid-base reaction between dibenzylstrontium and acetylene, although these techniques often produce complexes with the solvent.[5] Direct formation from the elements has a notional enthalpy of -20 kcal/mol.[6]

Nevertheless, strontium carbide may be only metastable when encapsulated in a fullerene.[7] It slowly hydrolyzes in air to acetylene.[1]

The material is polymorphic, forming a monoclinic crystal structure akin to calcium carbide II[2] and a black[1] tetragonal phase. Heated to 370 °C, it reversibly converts to a face-centered cubic (fcc) lattice.[2] Yttrium carbide retains the fcc lattice down to room temperature; the difference is a 3eg orbital that strontium lacks the electrons to fill.[8] Cyanamide impurities stabilize one other strontium carbide polymorph, just as they do for calcium carbide. The stabilized calcium carbide polymorph is triclinic, and the strontium carbide polymorph is believed to be so as well.[9]

At roughly 1800 °C, strontium carbide melts.[6] It forms a solid solution with europium carbide, as Eu2+ has an almost identical ionic radius to Sr2+.[10]

Strontium carbide is a chemical intermediate in an archaic carbon-14 dating technique: burning the material to be dated releases carbon dioxide, trapped as strontium carbonate. Magnesium then reduces the carbonate to strontium carbide and hydrolysis releases acetylene.[3][11] The radioactive decay of the acetylene can then be observed directly[11] or heating to 600 °C polymerizes the acetylene to benzene for a liquid scintillator.[3]

Solid state metathesis of strontium carbide and a (complex) metal oxide gives the corresponding metal carbide and strontium oxide. The latter washes away easily in pure water.[12]

References[edit]

  1. ^ a b c d Moissan, Henri (27 March 1894). "Étude des acetylures crystallisés de baryum et de strontium" [Study on crystalline acetylides of barium and strontium]. Comptes rendus de l'Académie des Sciences (in French): 684. Text available at Gallica.
  2. ^ a b c Bredig, M. A. (5 June 1942). "The polymorphism of calcium carbide". The Journal of Physical Chemistry. 46 (8): 801–819. doi:10.1021/j150422a003.
  3. ^ a b c Tamers, M. A.; Stipp, J. J.; Collier, J. (1961) [22 Nov 1960]. "High sensitivity detection of naturally occurring radiocarbon I: Chemistry of the counting sample". Geochimica et Cosmochimica Acta. 24 (3–4). Northern Ireland: Pergamon: 266–276. Bibcode:1961GeCoA..24..266T. doi:10.1016/0016-7037(61)90022-9.
  4. ^ Prell, Laurie J.; Styris, David L.; Redfield, David A. (May 1990) [6 Nov 1989]. "Mechanisms controlling atomisation of strontium and associated interferences by calcium in electrothermal atomic absorption spectrometry". Journal of Analytical Atomic Spectroscopy. 5 (3): 233. doi:10.1039/JA9900500231. 9/04815D.
  5. ^ Alexander, Jacob S.; Ruhlandt-Senge, Karin (2002). "Not just heavy 'Grignards'". European Journal of Inorganic Chemistry. Weinheim: Wiley-VCH: 2763. doi:10.1002/1099-0682(200211)2002:11<2761::AID-EJIC2761>3.0.CO;2-2. I02148.
  6. ^ a b Flowers, R. H.; Rauh, E. G. (1966) [13 Aug 1965]. "Studies of the equilibrium metal vapor pressures over the alkaline earth carbides". Journal of Inorganic Nuclear Chemistry. 28 (6–7). Northern Ireland: Pergamon: 1355–1366. doi:10.1016/0022-1902(66)80167-7.
  7. ^ Saito Y.; Matsumoto T. (1998) [28 Oct 1997]. "Hollow and filled rectangular parallelopiped carbon nanocapsules catalyzed by calcium and strontium". Journal of Crystal Growth. 187 (3–4). Elsevier: 406–408. Bibcode:1998JCrGr.187..402S. doi:10.1016/S0022-0248(98)00013-X.
  8. ^ Zhukov, V. P.; Novikov, D. L.; Medvedeva, N. I.; Gubanov, V. A. (July–August 1989) [25 December 1987]. "Electronic structure and chemical bonding in yttrium dicarbide and strontium dicarbide". Zhurnal Strukturnoi Khimii. 30 (4). Plenum (published 1990): 27–32. doi:10.1007/BF00751445. UDC 541.19.
  9. ^ Vannerberg, Nils-Gösta (1962) [8 Nov 1961]. "The crystal structure of calcium carbide II and IV" (PDF). Acta Chimica Scandinavica. 16 (5): 1219.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  10. ^ Link, Pascal; Wandner, Dirk; Schellenberg, Inga; Pöttgen, Rainer; Paulus, Michael; Sahle, Christoph J.; Sternemann, Christian; Ruschewitz, Uwe. "EuxSr1-xC2 (0 ≤ x ≤ 1): A dicarbide solid solution with perfect Vegard behavior" (PDF). Zeitschrift für anorganische und allgemeine Chemie. 636 (12). Wiley-VCH: 2276–. doi:10.1002/zaac.201000206. HAL hal-00583554.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  11. ^ a b Mitamura Muneki (Mar 1991) [3 Dec 1990]. "Radiocarbon measurement and 14C ages of holocene deposits in the eastern margin of the West Osaka area, Southwest Japan" (PDF). Journal of Geosciences. 34. Osaka City University: 77–80. ISSN 0449-2560.
  12. ^ Nartowski, Artur M.; Parkin, Ivan P.; Mackenzie, Maureen; Craven, Alan J. (18 Sep 2001) [19 June 2001]. "Solid state metathesis: synthesis of metal carbides from metal oxides". Journal of Materials Chemistry. 11 (12). Royal Society of Chemistry: 3116–3119. doi:10.1039/b105352n – via CiteSeerX.
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