View source for Propyne

{{Short description|Alkyne hydrocarbon compound with three carbon atoms}}
{{distinguish|propane|propene}}
{{chembox
| Verifiedfields = changed
| verifiedrevid  = 406858995
| Name           = Propyne
| ImageFile      = PROPYNE.png
| ImageSize      = 120px
| ImageName      = Methylacetylene
| ImageFile1     = Propyne-3D-vdW.png
| ImageSize1     = 180px
| PIN            = Propyne<ref name=iupac2013>{{cite book | title = Nomenclature of Organic Chemistry. IUPAC Recommendations and Preferred Names 2013 (Blue Book) | chapter = Characteristic (Functional) and Substituent Groups | publisher = [[Royal Society of Chemistry|The Royal Society of Chemistry]] | date = 2014 | location = Cambridge | page = 374 | doi = 10.1039/9781849733069-00372 | isbn = 978-0-85404-182-4}}</ref><ref group="note">"Prop-1-yne" mistake fixed in the [https://www.qmul.ac.uk/sbcs/iupac/bibliog/BBerrors.html errata] {{Webarchive|url=https://web.archive.org/web/20190801093648/https://www.qmul.ac.uk/sbcs/iupac/bibliog/BBerrors.html |date=2019-08-01 }}. The locant is omitted according to P-14.3.4.2&nbsp;(d), p.&nbsp;31 for propene and P-31.1.1.1, Examples, p.&nbsp;374 for propyne.</ref>
| SystematicName = 
| OtherNames     = Methylacetylene<br />Methyl acetylene<br />Allylyne
| IUPACName      = 
| Section1       = {{Chembox Identifiers
| CASNo = 74-99-7
| CASNo_Ref = {{cascite|correct|CAS}}
| UNII_Ref = {{fdacite|correct|FDA}}
| UNII = 086L40ET1B
| ChEMBL_Ref = {{ebicite|changed|EBI}}
| ChEMBL = 116902
| SMILES = CC#C
| EINECS = 200-828-4
| PubChem = 6335
| ChemSpiderID = 6095
| InChI = 1/C3H4/c1-3-2/h1H,2H3
| InChIKey = MWWATHDPGQKSAR-UHFFFAOYAI
| StdInChI = 1S/C3H4/c1-3-2/h1H,2H3
| StdInChIKey = MWWATHDPGQKSAR-UHFFFAOYSA-N
| RTECS = 
| MeSHName = C022030
| ChEBI = 48086
| ChEBI_Ref = {{ebicite|correct|ebi}}
| Beilstein = 878138
  }}
| Section2       = {{Chembox Properties
| Formula = {{chem2|CH3C\tCH}}
| MolarMass = 40.0639 g/mol
| Density = 0.53 g/cm<sup>3</sup>
| MeltingPtC = -102.7
| BoilingPtC = -23.2
| Appearance = Colorless gas<ref name=NIOSH/>
| Odor = Sweet<ref name=NIOSH/>
| VaporPressure = 5.2 [[Standard atmosphere (unit)|atm]] (20°C)<ref name=NIOSH/>
  }}
| Section3       = {{Chembox Hazards
| PEL = TWA 1000 ppm (1650 mg/m<sup>3</sup>)<ref name=NIOSH>{{PGCH|0392}}</ref>
| ExploLimits = 1.7%-?<ref name=NIOSH/>
| IDLH = 1700 ppm<ref name=NIOSH/>
| REL = TWA 1000 ppm (1650 mg/m<sup>3</sup>)<ref name=NIOSH/> 
}}
| Section4       = 
| Section5       = 
| Section6       = 
}}

'''Propyne''' ('''methylacetylene''') is an [[alkyne]] with the [[chemical formula]] {{chem2|CH3C\tCH}}.  It is a component of [[MAPP gas|MAPD gas]]—along with its [[isomer]] [[propadiene]] (allene), which was commonly used in [[gas welding]]. Unlike [[acetylene]], propyne can be safely [[Condensation|condensed]].<ref name=Ullmann>Peter Pässler, Werner Hefner, Klaus Buckl, Helmut Meinass, Andreas Meiswinkel, Hans-Jürgen Wernicke, Günter Ebersberg, Richard Müller, Jürgen Bässler, Hartmut Behringer, Dieter Mayer, "Acetylene" in Ullmann's Encyclopedia of Industrial Chemistry Wiley-VCH, Weinheim 2007 ({{doi|10.1002/14356007.a01_097.pub2}}).</ref>

==Production and equilibrium with propadiene==
Propyne exists in equilibrium with [[propadiene]], the mixture of propyne and propadiene being called MAPD:
:{{chem2|H3C\sC\tCH ⇌ H2C\dC\dCH2}}
The [[Chemical equilibrium|coefficient of equilibrium]] ''K''<sub>eq</sub> is 0.22 at 270&nbsp;°C or 0.1 at 5&nbsp;°C.
MAPD is produced as a side product, often an undesirable one, by [[cracking (chemistry)|cracking]] [[propane]] to produce [[propene]], an important [[feedstock]] in the [[chemical industry]].<ref name=Ullmann/>  MAPD interferes with the [[Ziegler–Natta catalyst|catalytic]] [[polymerization]] of propene.

===Laboratory methods===
Propyne can also be synthesized on laboratory scale by reducing [[1-propanol]],<ref>{{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 |bibcode=1895FrInJ.139..304K }}</ref> [[allyl alcohol]] or [[acetone]]<ref>{{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}}</ref> vapors over magnesium.

==Use as a rocket fuel==
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 orbit]]al operations. They reached this conclusion based upon a [[specific impulse]] expected to reach 370 [[second|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 fuel]]s that must be kept at extremely low temperatures.<ref>{{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=[[German Aerospace Center|DLR]] Lampoldshausen}}</ref>

==Organic chemistry==
Propyne is a convenient three-carbon building block for [[organic synthesis]]. Deprotonation with [[n-Butyllithium|''n''-butyllithium]] gives [[propynyllithium]]. This [[nucleophilic]] reagent adds to [[carbonyl]] groups, producing [[Alcohol (chemistry)|alcohol]]s and [[ester]]s.<ref>{{OrgSynth | author1 = Michael J. Taschner|author2=Terry Rosen|author3=Clayton H. Heathcock | title = Ethyl Isocrotonate | collvol = 7 | collvolpages = 226| year = 1990 | prep = CV7P0226}}</ref>  Whereas purified propyne is expensive, MAPP gas could be used to cheaply generate large amounts of the reagent.<ref>{{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 }}</ref>

Propyne, along with [[2-butyne]], is also used to synthesize [[alkylated]] [[hydroquinone]]s in the [[total synthesis]] of [[vitamin E]].<ref name=Cyclization>{{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}}</ref>

The chemical shift of an alkynyl proton and propargylic proton generally occur in the same region of the [[Proton nuclear magnetic resonance|<sup>1</sup>H NMR]] spectrum.  In propyne, these two signals have almost exactly the same chemical shifts, leading to overlap of the signals, and the <sup>1</sup>H NMR spectrum of propyne, when recorded in deuteriochloroform on a 300&nbsp;MHz instrument, consists of a single signal, a sharp singlet resonating at 1.8 ppm.<ref>{{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}}</ref>

== In Astrophysics ==
Propyne has been detected in multiple astrophysical objects following its first observation in 1973 in the [[Galactic Center|galactic center]] [[Molecular cloud|giant molecular cloud]] [[Sagittarius B2|Sgr B2]] using [[radio astronomy]] techniques.<ref>{{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 |bibcode=1973NPhS..243...45S |issn=2058-1106|url-access=subscription }}</ref> Propyne has been proposed to act as a precursor molecule to the formation of [[Polycyclic aromatic hydrocarbon|PAHs]] in space, such as [[indene]].<ref>{{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 (CH<sub>3</sub>CCH), propene (CH<sub>3</sub>CHCH<sub>2</sub>), cyclopropane (c-C<sub>3</sub>H<sub>6</sub>), vinylacetylene (CH<sub>2</sub>CHCCH), and 1,3-butadiene (CH<sub>2</sub>CHCHCH<sub>2</sub>) 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 |pmid=30221272 |bibcode=2019PCCP...21.5378A |issn=1463-9084|url-access=subscription }}</ref>

Propyne has been detected by [[infrared]] [[spectroscopy]] in the [[Redox|chemically reducing]] [[atmosphere]]s of the [[Solar System|outer planets]] in the [[Solar System]], including on [[Jupiter]] in 2000 <ref>{{Citation |last1=Fouchet |first1=T. |title=Jupiter's hydrocarbons observed with ISO-SWS: vertical profiles of C<sub>2</sub>H<sub>6</sub> and C<sub>2</sub>H<sub>2</sub>, detection of CH<sub>3</sub>C2H |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 }}</ref> and on [[Saturn]] in 1997,<ref>{{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<sub>2</sub>, CH<sub>3</sub>C<sub>2</sub>H, C<sub>4</sub>H<sub>2</sub> and tropospheric H<sub>2</sub>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}}</ref> both using the [[Infrared Space Observatory]]; on Titan in 1981 using [[Voyager program|Voyager's]] [[Infrared interferometer spectrometer and radiometer|IRIS]] instrument;<ref>{{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=C<sub>3</sub>H<sub>8</sub> and C<sub>3</sub>H<sub>4</sub> 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 |bibcode=1981Natur.292..683M |issn=1476-4687|url-access=subscription }}</ref> and on the [[ice giant]]s [[Uranus]] in 2006 <ref>{{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 |bibcode=2006Icar..184..634B |issn=0019-1035|url-access=subscription }}</ref> and on [[Neptune]] in 2008 <ref>{{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 |bibcode=2008Icar..197..585M |issn=0019-1035|url-access=subscription }}</ref> using the [[Spitzer Space Telescope|Spitzer]] space telescope.

==Notes==
<references group="note" />

==References==
<references/>

==External links==
* [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]]