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Propadiene
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<h2 id="production-and-equilibrium-with-methylacetylene">Production and equilibrium with methylacetylene</h2> <p>Propadiene exists in equilibrium with <a href="/facts/Methylacetylene/GJpDzkBj">methylacetylene</a> (propyne) and the mixture is sometimes called MAPD for methylacetylene-propadiene: </p> H3C−C≡CH ⇌ H2C=C=CH2 <p>for which <i>K</i>eq = 0.22 at 270 °C or 0.1 at 5 °C. </p><p>MAPD is produced as a side product, often an undesirable one, of <a href="/facts/Dehydrogenation/vwFAAqzp">dehydrogenation</a> of <a href="/facts/Propane/E0b23KGh">propane</a> to produce <a href="/facts/Propene/5eLDmPvm">propene</a>, an important <a href="/facts/Feedstock/cthCpclF">feedstock</a> in the <a href="/facts/Chemical_industry/3M6gfHer">chemical industry</a>. MAPD interferes with the <a href="/facts/Ziegler%25E2%2580%2593Natta_catalyst/bkDSDf9d">catalytic</a> <a href="/facts/Polymerization/1hmBz7Ur">polymerization</a> of propene.<a class="footnote-ref" id="fnref:2" href="#fn:2"><sup>2</sup></a> </p> <h2 id="occurrence-in-space">Occurrence in Space</h2> <p>In 2019 it was announced that propadiene had been detected in the atmosphere of Saturn's moon <a href="/facts/Titan_(moon)/lg0l9PCH">Titan</a> using the <a href="/facts/NASA_Infrared_Telescope_Facility/J6moYhjV">NASA Infrared Telescope Facility</a>.<a class="footnote-ref" id="fnref:3" href="#fn:3"><sup>3</sup></a> This was the first time that propadiene had been detected in space, and the second <a href="/facts/Isomer/PXlvDVdg">structural isomeric</a> pair (paired with <a href="/facts/Propyne/GJpDzkBj">propyne</a>) detected in Titan's atmosphere, after <a href="/facts/Hydrogen_cyanide/vNtA0Mxe">HCN</a>-<a href="/facts/Hydrogen_isocyanide/gfnqSpKo">HNC</a>.<a class="footnote-ref" id="fnref:4" href="#fn:4"><sup>4</sup></a><a class="footnote-ref" id="fnref:5" href="#fn:5"><sup>5</sup></a> </p> <h2 id="references">References</h2> <ol> <li id="fn:1"><p>IUPAC, Compendium of Chemical Terminology, 2nd ed. (the "Gold Book") (1997). Online corrected version: (2006–) "allenes". doi:10.1351/goldbook.A00238 <a href="/wiki/International_Union_of_Pure_and_Applied_Chemistry" target="_blank">/wiki/International_Union_of_Pure_and_Applied_Chemistry</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></p></li> <li id="fn:2"><p>Klaus Buckl, Andreas Meiswinkel "Propyne" in Ullmann's Encyclopedia of Industrial Chemistry, 2008, Wiley-VCH, Weinheim. doi:10.1002/14356007.m22_m01 <a href="/wiki/Doi_(identifier)" target="_blank">/wiki/Doi_(identifier)</a> <a href="#fnref:2" class="footnote-back-ref">↩</a></p></li> <li id="fn:3"><p>Lombardo, Nicholas A; Nixon, Conor A; Greathouse, Thomas K; Bézard, Bruno; Jolly, Antoine; Vinatier, Sandrine; Teanby, Nicholas A; Richter, Matthew J; G Irwin, Patrick J; Coustenis, Athena; Flasar, F Michael (2019-08-20). "Detection of Propadiene on Titan". The Astrophysical Journal Letters. 881 (2): L33. arXiv:1908.07424. doi:10.3847/2041-8213/ab3860. ISSN 2041-8205. <a href="https://doi.org/10.3847%2F2041-8213%2Fab3860" target="_blank">https://doi.org/10.3847%2F2041-8213%2Fab3860</a> <a href="#fnref:3" class="footnote-back-ref">↩</a></p></li> <li id="fn:4"><p>Moreno, R.; Lellouch, E.; Lara, L. M.; Courtin, R.; Bockelée-Morvan, D.; Hartogh, P.; Rengel, M.; Biver, N.; Banaszkiewicz, M.; González, A. (December 2011). "First detection of hydrogen isocyanide (HNC) in Titan's atmosphere". Astronomy & Astrophysics. 536: L12. doi:10.1051/0004-6361/201118189. ISSN 0004-6361. <a href="http://www.aanda.org/10.1051/0004-6361/201118189" target="_blank">http://www.aanda.org/10.1051/0004-6361/201118189</a> <a href="#fnref:4" class="footnote-back-ref">↩</a></p></li> <li id="fn:5"><p>Hébrard, E.; Dobrijevic, M.; Loison, J. C.; Bergeat, A.; Hickson, K. M. (May 2012). "Neutral production of hydrogen isocyanide (HNC) and hydrogen cyanide (HCN) in Titan's upper atmosphere". Astronomy & Astrophysics. 541: A21. doi:10.1051/0004-6361/201218837. ISSN 0004-6361. <a href="http://www.aanda.org/10.1051/0004-6361/201218837" target="_blank">http://www.aanda.org/10.1051/0004-6361/201218837</a> <a href="#fnref:5" class="footnote-back-ref">↩</a></p></li> </ol>