Propyne

Propyne exists in equilibrium with propadiene, the mixture of propyne and propadiene being called MAPD:

:{{chem2|H3C\sC\tCH ⇌ H2C\dC\dCH2}}

The coefficient of equilibrium K_eq is 0.22 at 270 °C or 0.1 at 5 °C.

MAPD is produced as a side product, often an undesirable one, by cracking propane to produce propene, an important feedstock in the chemical industry. MAPD interferes with the catalytic polymerization of propene.

Propyne can also be synthesized on laboratory scale by reducing 1-propanol,{{cite journal|author1=Keiser, Edward |author2=Breed, Mary |name-list-style=amp |title=The Action of Magnesium Upon the Vapors of the Alcohols and a New Method of Preparing Allylene|journal=Journal of the Franklin Institute|year=1895|volume=CXXXIX|issue=4 |pages=304–309|url=https://books.google.com/books?id=jn-VkwcIt5QC&q=allylene+franklin+magnesium&pg=PA309|access-date=20 February 2014|doi=10.1016/0016-0032(85)90206-6}} allyl alcohol or acetone{{cite journal|last=Reiser, Edward II.|title=The preparation of Allylene, and the Action of Magnesium upon Organic Compounds|journal=The Chemical News and Journal of Industrial Science|year=1896|volume=LXXIV|pages=78–80|url=https://books.google.com/books?id=TxgAAAAAMAAJ&q=allylene+magnesium+preparing&pg=PA78|access-date=20 February 2014}} vapors over magnesium.

European space companies have researched using light hydrocarbons with liquid oxygen, a relatively high performing liquid rocket propellant combination that would also be less toxic than the commonly used MMH/NTO (monomethylhydrazine/nitrogen tetroxide). Their research showed{{citation needed|date=September 2013}} that propyne would be highly advantageous as a rocket fuel for craft intended for low Earth orbital operations. They reached this conclusion based upon a specific impulse expected to reach 370 s with oxygen as the oxidizer, a high density and power density—and the moderate boiling point, which makes the chemical easier to store than cryogenic fuels that must be kept at extremely low temperatures.{{Cite web |last1=Valentian |first1=Dominique |last2=Sippel |first2=Martin |last3=Grönland |first3=Tor-Arne |last4=Baker |first4=Adam |last5=van Den Meulen |first5=Jaap |last6=Fratacci |first6=Georges |last7=Caramelli |first7=Fabio |date=2004 |title=Green propellants options for launchers, manned capsules and interplanetary missions |url=http://www.la.dlr.de/ra/sart/publications/pdf/esa02-2004.pdf |url-status=dead |archive-url=https://web.archive.org/web/20060110171612/http://www.la.dlr.de/ra/sart/publications/pdf/esa02-2004.pdf |archive-date=2006-01-10 |website=la.dlr.de |publisher=DLR Lampoldshausen}}

Propyne is a convenient three-carbon building block for organic synthesis. Deprotonation with n-butyllithium gives propynyllithium. This nucleophilic reagent adds to carbonyl groups, producing alcohols and esters.{{OrgSynth | author1 = Michael J. Taschner|author2=Terry Rosen|author3=Clayton H. Heathcock | title = Ethyl Isocrotonate | collvol = 7 | collvolpages = 226| year = 1990 | prep = CV7P0226}} Whereas purified propyne is expensive, MAPP gas could be used to cheaply generate large amounts of the reagent.{{US patent reference | number = 5744071 | y = 1996 | m = 11 | d = 19 | inventor = Philip Franklin Sims, Anne Pautard-Cooper | title = Processes for preparing alkynyl ketones and precursors thereof }}

Propyne, along with 2-butyne, is also used to synthesize alkylated hydroquinones in the total synthesis of vitamin E.{{cite journal|author1=Reppe, Walter |author2=Kutepow, N |author3=Magin, A |name-list-style=amp |title=Cyclization of Acetylenic Compounds|journal=Angewandte Chemie International Edition in English|year=1969|volume=8|issue=10|pages=727–733|doi=10.1002/anie.196907271}}

The chemical shift of an alkynyl proton and propargylic proton generally occur in the same region of the ¹H NMR spectrum. In propyne, these two signals have almost exactly the same chemical shifts, leading to overlap of the signals, and the ¹H NMR spectrum of propyne, when recorded in deuteriochloroform on a 300 MHz instrument, consists of a single signal, a sharp singlet resonating at 1.8 ppm.{{Cite book|title=Organic chemistry|first1=Marc|last1=Loudon|first2=Jim|last2=Parise|others=Parise, Jim, 1978-|isbn=9781936221349|edition= Sixth|location=Greenwood Village, Colorado|publisher=W. H. Freeman|oclc=907161629|date = 2015-08-26}}

Propyne has been detected in multiple astrophysical objects following its first observation in 1973 in the galactic center giant molecular cloud Sgr B2 using radio astronomy techniques.{{Cite journal |last1=Snyder |first1=L. E. |last2=Buhl |first2=D. |date=May 1973 |title=Interstellar Methylacetylene and Isocyanic Acid |url=https://www.nature.com/articles/physci243045a0 |journal=Nature Physical Science |language=en |volume=243 |issue=125 |pages=45–46 |doi=10.1038/physci243045a0 |issn=2058-1106|url-access=subscription }} Propyne has been proposed to act as a precursor molecule to the formation of PAHs in space, such as indene.{{Cite journal |last1=Abplanalp |first1=Matthew J. |last2=Góbi |first2=Sándor |last3=Kaiser |first3=Ralf I. |date=2019-03-06 |title=On the formation and the isomer specific detection of methylacetylene (CH3CCH), propene (CH3CHCH2), cyclopropane (c-C3H6), vinylacetylene (CH2CHCCH), and 1,3-butadiene (CH2CHCHCH2) from interstellar methane ice analogues |url=https://pubs.rsc.org/en/content/articlelanding/2019/cp/c8cp03921f |journal=Physical Chemistry Chemical Physics |language=en |volume=21 |issue=10 |pages=5378–5393 |doi=10.1039/C8CP03921F |issn=1463-9084|url-access=subscription }}

Propyne has been detected by infrared spectroscopy in the chemically reducing atmospheres of the outer planets in the Solar System, including on Jupiter in 2000 {{Citation |last1=Fouchet |first1=T. |title=Jupiter's hydrocarbons observed with ISO-SWS: vertical profiles of C2H6 and C2H2, detection of CH3C2H |date=2000 |last2=Lellouch |first2=E. |last3=Bezard |first3=B. |last4=Feuchtgruber |first4=H. |last5=Drossart |first5=P. |last6=Encrenaz |first6=T.|arxiv=astro-ph/0002273 }} and on Saturn in 1997,{{Cite journal |last1=de Graauw |first1=T. |last2=Feuchtgruber |first2=H. |last3=Bezard |first3=B. |last4=Drossart |first4=P. |last5=Encrenaz |first5=T. |last6=Beintema |first6=D. A. |last7=Griffin |first7=M. |last8=Heras |first8=A. |last9=Kessler |first9=M. |last10=Leech |first10=K. |last11=Lellouch |first11=E. |last12=Morris |first12=P. |last13=Roelfsema |first13=P. R. |last14=Roos-Serote |first14=M. |last15=Salama |first15=A. |date=1997-05-01 |title=First results of ISO-SWS observations of Saturn: detection of CO_2_, CH_3_C_2_H, C_4_H_2_ and tropospheric H_2_O. |url=https://ui.adsabs.harvard.edu/abs/1997A&A...321L..13D/abstract |journal=Astronomy and Astrophysics |volume=321 |pages=L13–L16 |bibcode=1997A&A...321L..13D |issn=0004-6361}} both using the Infrared Space Observatory; on Titan in 1981 using Voyager's IRIS instrument;{{Cite journal |last1=Maguire |first1=W. C. |last2=Hanel |first2=R. A. |last3=Jennings |first3=D. E. |last4=Kunde |first4=V. G. |last5=Samuelson |first5=R. E. |date=August 1981 |title=C3H8 and C3H4 in Titan's atmosphere |url=https://www.nature.com/articles/292683a0 |journal=Nature |language=en |volume=292 |issue=5825 |pages=683–686 |doi=10.1038/292683a0 |issn=1476-4687}} and on the ice giants Uranus in 2006 {{Cite journal |last1=Burgdorf |first1=Martin |last2=Orton |first2=Glenn |last3=van Cleve |first3=Jeffrey |last4=Meadows |first4=Victoria |last5=Houck |first5=James |date=2006-10-01 |title=Detection of new hydrocarbons in Uranus' atmosphere by infrared spectroscopy |url=https://www.sciencedirect.com/science/article/abs/pii/S001910350600203X |journal=Icarus |volume=184 |issue=2 |pages=634–637 |doi=10.1016/j.icarus.2006.06.006 |issn=0019-1035|url-access=subscription }} and on Neptune in 2008 {{Cite journal |last1=Meadows |first1=Victoria S. |last2=Orton |first2=Glenn |last3=Line |first3=Michael |last4=Liang |first4=Mao-Chang |last5=Yung |first5=Yuk L. |last6=Van Cleve |first6=Jeffrey |last7=Burgdorf |first7=Martin J. |date=2008-10-01 |title=First Spitzer observations of Neptune: Detection of new hydrocarbons |url=https://linkinghub.elsevier.com/retrieve/pii/S0019103508002273 |journal=Icarus |volume=197 |issue=2 |pages=585–589 |doi=10.1016/j.icarus.2008.05.023 |issn=0019-1035|url-access=subscription }} using the Spitzer space telescope.

• [http://webbook.nist.gov/cgi/cbook.cgi?ID=C74997 NIST Chemistry WebBook page for propyne]
• [https://web.archive.org/web/20060110171612/http://www.la.dlr.de/ra/sart/publications/pdf/esa02-2004.pdf German Aerospace Center]
• [https://web.archive.org/web/20070928144135/http://www.novachem.com/ProductServices/docs/CrudePropylene_MSDS_EN.pdf Nova Chemicals]
• [https://www.cdc.gov/niosh/npg/npgd0392.html CDC - NIOSH Pocket Guide to Chemical Hazards]

{{Alkynes}}

{{Molecules detected in outer space}}

{{Hydrides by group}}

{{Authority control}}

Category:Alkynes

Category:Fuel gas

Category:Rocket fuels